Stupid Alternator Regulators Get Smarter…Finally

If an alternator voltage regulator is not connected to a shunt, it's not smart.

One of the biggest snow jobs in boat gear sales is the myth of the smart three-stage alternator regulator. In fact, the alternator voltage regulators that have been available to us cruisers for about the last 15 years are not that bright...OK, they're downright stupid.

They're so stupid that they can't even perform their primary function of charging our batteries properly until full.

I know what you're thinking:

John is saying that a piece of gear with tens of thousands of units installed (that's a guess) in boats, and thousands more sold every year, that's so fundamental to comfortable live-aboard life, does not even work. Clearly he has lost his grip.

I totally get your scepticism. Heck, when our old, and sadly no longer made, Link 2000-R regulator died—the last cruiser's alternator regulator that was actually smart—I bought the then, and now, most popular "smart three-stage regulator" thinking that it would work, too.

I settled down and read the whole manual looking for the fundamental capability that would make it usable on a liveaboard cruising boat, and got to the end to find...nada. So I figured there were pages missing...nope.

What Matters in Alternator Regulators

What's that fundamental capability? The ability to measure when our batteries are full and reduce the voltage output by the alternator to float.

Lead acid (liquid-filled, gel, AGM, whatever) batteries are fully charged when the current (amps) they are accepting at their specified acceptance voltage—typically about 14.4 volts at 70˚F (20˚C)—has dropped to about 0.5% of their total capacity measured in amp hours. (Check with the battery manufacturer, since these two numbers vary between brands, though not by much.)

Sounds pretty simple, right? And it is. All you need is a shunt in a cable to the house battery to measure that current—often already there on a cruising boat to support a battery monitor—and a bit of simple logic in the regulator to turn the charge voltage down to float (typically 13.4 volts) when the above threshold is reached, but not before.

Easy peasy. But since the death of the Link 2000-R, and a rather complicated regulator from Ample Power (no longer in business), there has been no alternator regulator available, at least that I have found, that could do that simple fundamental thing.

How Could This Be?

Why? Beats the crap out of me. Maybe because few boat owners really understand how batteries charge and, even more distressingly, very few technicians in boatyards do, either, so the industry got away with selling stupid regulators for years, and they even had the nerve to call stupid smart—the power of marketing.

Stupid Is As Stupid Does

Rather than making that simple required measurement, these stupid regulators guesstimate using a combination of time and how much the regulator needed to juice the alternator field coil to maintain the acceptance voltage. That's bad enough, since different alternators have different relationships between field and output current (amperage) and, of course, how long a battery will take to charge will depend on how much it was discharged...duh.

But gets worse. These stupid regulators have no way to understand how much of the alternator's output is charging the battery and how much is supplying loads—they truly operate blind.

Making Stupid Worse

The way the manufacturers of stupid regulators get around this fundamental weakness is by shipping the regulator factory programmed to chronically undercharge the batteries, to the point that the regulator will typically cut the charge current back to float in less than two hours, even though a lead acid battery bank discharged even just 25% will typically take at least four hours to fully recharge, no matter how big the alternator—if you don't believe that, see Further Reading.

Now this can be kind of fixed, in a klugy way, by reprogramming the regulator, which is what I did, and then wrote an article about it to help others, recently deleted since this new regulator makes it obsolete.

At Last, Real Smarts

But now, finally, we have, once again, a truly smart regulator. Let's take a look:

  1. Why Most New-To-Us Boat Electrical Systems Must Be Rebuilt
  2. One Simple Law That Makes Electrical Systems Easy to Understand
  3. How Batteries Charge (Multiple Charging Sources Too)
  4. 5 Safety Tips For Working on Boat DC Electrical Systems
  5. 7 Checks To Stop Our DC Electrical System From Burning Our Boat
  6. Cruising Boat Electrical System Design, Part 1—Loads and Conservation
  7. Cruising Boat Electrical System Design, Part 2—Thinking About Systems
  8. Cruising Boat Electrical System Design, Part 3—Specifying Optimal Battery Bank Size
  9. Balancing Battery Bank and Solar Array Size
  10. The Danger of Voltage Drops From High Current (Amp) Loads
  11. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 1
  12. Should Your Boat’s DC Electrical System Be 12 or 24 Volt?—Part 2
  13. Battery Bank Separation and Cross-Charging Best Practices
  14. Choosing & Installing Battery Switches
  15. Cross-Bank Battery Charging—Splitters and Relays
  16. Cross-Bank Battery Charging—DC/DC Chargers
  17. 10 Tips To Install An Alternator
  18. Stupid Alternator Regulators Get Smarter…Finally
  19. WakeSpeed WS500—Best Alternator Regulator for Lead Acid¹ and Lithium Batteries
  20. Smart Chargers Are Not That Smart
  21. Do You Need A Generator?
  22. Efficient Generator-Based Electrical Systems For Yachts
  23. Battery Bank Size and Generator Run Time, A Case Study
  24. Battery Options, Part 1—Lithium
  25. Battery Options, Part 2—Lead Acid
  26. A Simple Way to Decide Between Lithium or Lead-Acid Batteries for a Cruising Boat
  27. Why Lithium Battery Load Dumps Matter
  28. 8 Tips To Prevent Lithium Battery Load Dumps
  29. Building a Seamanlike Lithium Battery System
  30. Lithium Ion Batteries Explained
  31. 11 Steps To Better Lead Acid Battery Life
  32. How Hard Can We Charge Our Lead-Acid Batteries?
  33. How Lead Acid Batteries Get Wrecked and What To Do About It
  34. Equalizing Batteries, The Reality
  35. Renewable Power
  36. Wind Generators
  37. Solar Power
  38. Hydro Power
  39. Watt & Sea Hydro Generator Review
  40. Battery Monitors, Part 1—Which Type Is Right For You?
  41. Battery Monitors, Part 2—Recommended Unit
  42. Battery Monitors, Part 3—Calibration and Use
  43. Battery Containment—Part 1
  44. Q&A—Are Battery Desulphators a Good Idea?
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Robert Muir

John, I have a Victron shunt already installed. Can I piggy-back on it for this application?

Michael Beemer

Bob, I think the shunt will work just fine, it’s a standard 500 amp, 50 MV, great regulator

Michael Beemer

These are great! I installed and tested a prototype 2 years ago at Skagit Valley College, now the programming is easier! Any battery type, AGM, FireFly, lithium. We are installing 2 more this summer, one on my own boat.

Steve D

I’ve been spec’ing them for the last year, primarily for lithium ion systems; I’m a fan. They are collaborating closely with Lithionics of Clearwater FL, the industry’s only UL Listed LFP battery manufacturer, yet another feather in their cap.

(In Taiwan)

John Carroll

When I suggested putting 2 LiFePO4 batteries on my J boat, I was told that the yard’s experience with these batteries was negative. Even with J installations on new boats. Is this perhaps due to a regulator not being programmed to LiFePO4?


Thats’ likely a factor, albeit not the only one. You can’t just swap in LiFePO4 without also replacing or reprogramming the controllers for all the charging sources. The performance curves are totally different, and a regulator configured for Pb-H2SO4 is virtually guaranteed to cause a spectrum of problems with lithium.

LiFePO4 is now a mature technology, and properly installed & configured setups are proving to be quite reliable (albeit still expensive).

Stein Varjord

Hi John C,
That’s a question with many possible answers, some well founded, most not so. Most likely they were just using other less obvious words for “We are not competent”. Incompetent people, including the majority of professional boat techs, not admitting to their incompetence, is definitely the most normal reason for problems with lithium.

The second most normal reason, which is mostly related to greed and poor morale, but also the above reason, is that inferior batteries are chosen. Drop-in batteries look like normal batteries and are often marketed as being ready for, as the name says, just dropping them in where the lead batteries were. This is a flat out lie, a scam to sell more. The systems MUST be adapted, most likely changed significantly. Since a large number of installations fail at this point, bad customer experiences pile up.

Drop-in type batteries can be made almost as good as Prismatic cell type systems, but most are far from it! In general, prismatic cell systems last more than twice as long, are far more efficient and handle several times as much power, Amps, both in and out. The price, including a (real) pro to do the setup, is often even lower than equivalent drop-in, with the same service. Read what the guru Rod Collins say about drop-ins. This is a great but very (!) long article. You can scroll a bit down to the title “What about drop-ins?”

Steve D

Rod’s Marine How To article is very interesting, I’ve referred clients to it on several occasions. As always he does a great job with thoroughly testing this technology.

It believe it was written in 2017. In the world of lithium ion batteries that’s a very long time, and much has changed.

You say, “Drop-in batteries look like normal batteries and are often marketed as being ready for, as the name says, just dropping them in where the lead batteries were. This is a flat out lie, a scam to sell more.”

Today that’s not only an overly-broad statement, it’s also incorrect, or at least dated, and I know a few LI battery manufacturers who would even say it’s a lie. Yes, there may be some drop-in LI manufacturers who are unscrupulous, but that’s true of externally regulated LI battery manufacturers as well.

I sit on the ABYC Project Technical Committee tasked with writing the new, soon to be released, LI battery standard, TE13. My fellow committee member are among the most learned in the industry when it comes to LI batteries.

The Standard requires the use if a BMS, “A BMS should be tested and constructed to recognized or accepted standards. A BMS should be designed and tested to manage overcharging and over-discharging.”

Nowhere in the standard does it indicate that the BMS must be external to the battery. If a drop-in battery has a BMS that, “meets recognized or accepted standards”, it’s compliant.

One of the issues with LI batteries, or any new technology, is it changes rapidly, and as such there will always be a (larger) contingent of people whose information is outdated. That’s understandable, however, where LI is concerned it can be dangerous, as errors can lead to failures, loss of vessel power and fires.

Finally, Marine How To not only approves of drop in LI batteries, they sell them. Here’s what they say…
“With drop-in style LiFePO4 batteries gaining in popularity, and our customers asking us for them on a near daily basis, we examined nearly every drop-in LFP battery option available for our customers over a 13 month period. Hands down the Lithioncs 12V125A-G31-5CND-LRB was the clear winner on every front. This is a 125Ah G-31 (actually 1/2″ shorter than a typical 13″ long G-31) format battery that is capable of engine cranking and includes a Bluetooth Interface. It is also made here in the USA (with the exception of the prismatic LiFePO4 cells).
The internal construction of this battery is the best we’ve seen including massively thick nickel plated busbars and the proprietary Lithionics NEVERDIE® BMS which is designed and built here, in the USA. The battery even features an ON/OFF switch for storage, and for use during hook up to minimize errors and arcing during installation. Another unique feature of the NEVERDIE® BMS offers Power Reserve. This means the battery will self protect, at a safe level, but for an emergency you can re-boot it and have emergency level energy available.”

I’m a fan of Lithionics batteries, and as I noted earlier they work closely with Wakespeed. I’ve been to their very impressive manufacturing facility in Clearwater FL. Knowing, and seeing, all that goes into their products, I trust them to make a safe LFP battery, internal or external BMS. But, they are not alone, there are other reputable manufacturers making internally-regulated LFP batteries.

Steve D


Yes, the definition of “drop in” is not entirely standardized, that’s for certain. Many of the requirements you describe are necessary for external BMS batteries as well, so no real difference there, although I’d argue you don’t necessarily need a complete rewiring; but that depends a great deal on the robustness of the original design. The distinction between the systems is really the lack of an external BMS, and the associated wiring.

I’ve encountered, in the last two years, several seemingly successful drop in scenarios, although these were modern vessels that were somewhat LFP ready. They required reprogramming of chargers and regulators, but little else. I’m not advocating this necessarily, all of the large new build projects I’m now working on (I’m in Taiwan now working on two of them) are getting external BMS LFP systems, and at the moment that remains my preference.

From what I’m seeing, the biggest issue with LFP systems, new and refit, is the strain they place on the wiring, as it’s now being loaded heavier and for longer than with AGMs, which is leading to overheating issues, of connections and alternators, and even chargers in some cases. The batteries on the other hand, have been nearly trouble free.

“None of this is to say that lithium is not a good alternative for some, particularly new builds, but it’s also not a “drop in” panacea as some vendors would have the unwary believe—I stood and listened at the booth of one of these vendors at the US Sailboat show and over 10 minutes heard some real woppers being told.” And you hear those only about drop in LI batteries;-)? Seriously, I hear those carnival barkers too, and I cringe.

To hold all drop in integral LI batteries up as frauds, using material from RC, when RC currently sells them, seemed outdated at best, and the “it’s a lie” claim struck me as overly broad, you can design a system to accept LI batteries that have integral BMS, and it can be safe and successful. However, I agree they can’t be swapped with conventional LA batteries without modifications, the extent of which depends entirely on the vessel.

Stein Varjord

Hi Steve,
I think we agree on most of these issues. The reason I use the strong words “lie” and “scam”, is that this is still very much the actual reality an uneducated customer will find. There’s no doubt that “drop-in” batteries can be made very good and that it’s probably what will eventually be the standard for most users. Still, large prismatic cells are arguably a better choice than hundreds of 18650 cells with loads of connections and enclosed electronics. Even if the latter is done well, just mechanics will be an issue, plus heat management, etc.

The trouble with lithium drop-in isn’t the good stuff, though. Not even that there is still a lot of obviously poor products being offered. The main problem seems to be the quantity of deeply flawed information available to potential users. Even a great product will fail if the info is wrong. The comment I reacted to is describing how he got turned off using lithium at all, because the “professional” opinion he was given was that they had bad experiences with it, probably meaning they had no experience at all and no competence. That seems to be the norm among leisure marine “tech” people, with a few bright stars of competence like you, here and there. Customers using Facebook posts and forums as their primary information source is a problem. “Professionals” doing the same is worse.

I’m not a professional on this, but quite competent for an amateur. I’m in contact with a lot of people about this and other boat related issues, partly as the admin of a 10 k member Facebook group, no less. 🙂 The amount of misinformation there has been limited because I hammer down on it and marketing is not allowed, but I notice how much shit is out there and how hard it is for normal boaters to find reliable good info on lithium. Very hard!

Rods article I agree is from around 2017, which absolutely does mean a lot has changed, but the article is being constantly revised and kept up to date with his current view on the issues. I also direct people there all the time. Frequently I read parts or the whole again, to be sure I don’t claim something wrong. Less than two months ago there must have been a major revision. Some passages were removed and others added. Probably more than I would notice. He’s been using a 400 Ah lithium house bank in his own boat for about 12 years (?) now, which due to frequent testing has been run way harder than most would do in a boat. It still gives more than 100% of the rated capacity. Winston prismatic cells. He’s got a LOT of experience.

Lithionics seem to have the right competence and attitude for great products. Victron seem similarly good. Battleborn mostly likewise. Probably many more good brands. These are most likely very good choices for the normal user, provided that they also have an actually competent installer to change the boat systems as needed. The latter seems to be very rare among the normal budget boaters. For nerds like me, I really think there are significantly better options at far lower prices than the mentioned brands, but that does need a different level of understanding.

When it comes to Wakespeed, I really like their thinking and product. I haven’t bought it yet, but probably will. By the way, I talked about the WS500 with a very nice guy in Balmar at METS Amsterdam last autumn. He said that they are working with connecting the smart shunt from their SG200 monitor to their regulators. In the future, they will have the same functionality as the WS500. Probably not this year…

Stein Varjord

One more issue: I criticise “drop-in” batteries and glorify prismatic cells. I may exaggerate the judgement on some issues, and as mentioned, false info is a bigger problem than poor products. Still, when looking at the alternative to drop-in; prismatic cells, there are some fundamental reasons why this is a better solution.

I already mentioned the very high number of cell and other connections in drop-ins, that can’t be serviced, and the issues with poor cooling of equally unserviceable electronics inside the same box. Even when this is done as well as possible, it’s still an inherently weaker solution than prismatic cells, giving far less performance. There is another problem, however, that I’m far less comfortable with:

The integrated nature of drop-in batteries and the large number of components means that the user has very little control over the system. We will have to trust the electronics to take care of the system. The system has automatic balancing of the cells. For this to work properly, we have to charge the battery full quite frequently and leave it on charge for some time so the BMS balancing feature has time to distribute the current slowly to the right cells.

This is a major problem, since lithium cells should be kept operating around half full and rarely be discharged too low or charged too full. Also, if we need the full capacity, we can charge it all the way up, but then we should absolutely never let it rest there. We need to start using it immediately. A pack that is mostly kept around 50% and almost always between 20% and 90% full, SOC, seems to triple its life, compared to the same system run to 100% on most cycles.

A system with prismatic cells can be easily programmed to stop at any level. It doesn’t need automatic balancing systems. The cells can easily be run at lower charge Voltage, like 13,8, without any reduction in speed. This stresses the cells far less than what drop-in cells live with. The cells in both systems are just as good, but the drop-in layout gives some unfixable problems. The only “benefit” they give is an illusion of a simpler to install and simpler to use system. None of those are true. As I see it, the only true benefit of drop-in batteries is that they are easier to buy. There are fewer items to buy.

Edit: I notice that I’m going too far into detail on an essentially off topic issue. This comment probably belongs in another thread…

Chris Daly

Hi John,
? Not necessary to connect temperature sensor to alternator?

Philip Streat

Another regulator which may offer the same functionality (control by amperage sensing at the shunt) is the Mastervolt Alpha Pro III regulator in combination with a MasterShunt at the batteries. Section 6.3.11 of the Alpha pro manual states: “The MasterShunt ….. measures the actual current that goes into the battery. When only a
small percentage of current is measured, the Alpha Pro III considers the battery to be full and switches to maintenance charging (float)”.

The same may apply to the Chargemaster battery chargers.

I say “may” because their manuals are maddeningly vague about what actually happens when their charging devices are connected to the MasterShunt.

Petter Mather Simonsen

I also have the MV Alpha Pro regulator. Via a free piece of windows software (mastervolt) and a somewhat costly USB interface this regulator can be heavily programmed and monitored to suit just about any configuration. The same regulator may be used on either a 12 or 24v system by flipping a switch.

Scott Halpern

I went to the site and didn’t find information about dual alternator control with 1 house bank. Does anyone know ?

Two 120 amp Balmar with one 660ah Firefly house

David Huck

Hi Scott, the data sheet says it can be used for single engine dual alternator set ups by splitting the field connection. I’ve written to ask them for more details, will share here if/when I get an answer.

Rick Jones

Hey Scott,
One of the big benefits of the CAN is the WS500’s ability to connect with other WS500 regulators in the system via a simple CAT5e cable when multiple alternators are used to charge a single battery bank. When two (or more) WS500 regulators are connected via the CAN in a twin (or multiple) engine application, each regulator will act independently (if only one engine is running). When subsequent engines are started, one of the regulators will be dominant, and the other(s) will act based on the charging decisions of the dominant regulator. No special switching devices or complicated wiring are required. Each regulator is only responsible for delivering the field current required to drive its respective alternator — so charging remains well balanced.

Robbie Wilderspin

One thing I’ve never understood is how its possible to separate the charge current from load current. Given that, once the charge current is getting into the 0.5-1% of capacity you’re into territory where you really cant differentiate between charge and load – or can you.

Anyway, I’d agree that this method of using current should give most a much better chance of fully charged batteries without too much fiddling around

Robbie Wilderspin

Thanks John,
I read as much detail as I could find on the product website and I have previously read your book. I dont understand how its possible to differentiate charge from load current without some very clever circuitry which the product documentation doesnt even hint at. In its way its not dissimilar to what RC describes as the Link 2000 ‘gotcha’, where that device could be fooled that the batteries were charged. I’ve also read Panbos summary and can visualise his overcharge problem.

I have a Link 2000, so I’m used to a current counting system. To really differentiate between charge and load you’d need two shunts, one on each line and a comparator circuit, wouldnt you?

So, I’m not knocking this charger, I think it adds a lot of value for the ‘average’ boater. But there is this area that I cant visualise, sorry.

Robbie Wilderspin

Fair enough, got it – thanks

Richard Ritchie

The point about this regulator seems to be not that it does anything special to separate the charge going to the battery from the load, but that it bothers to USE the current actually going to the battery as a way of controlling the alternator power. The shunt setup looks totally normal.
John, Can you please confirm my understanding that it can just SHARE the same existing shunt that is already feeding the battery monitor ( if the right specification)?

Ernest E Vogelsinger

Actually you cannot really tell them apart – as soon as you put a load on the system this will reduce the “amperage” going into the battery. An example: a 200Ah bank would, at a given moment, accept 1A of inrush current, which makes it for the 0.5% acceptance, and the smart regulator would switch from bulk to float. Lets assume however that the fridge had activated and is currently drawing 3A, so the sum that the shunt (and the regulator) sees is 4A and the regulator would continue to feed bulk voltage. Which doesn’t hurt at all, the fridge would be fed by the charger and the battery bank would still only draw 1A. As soon as the fridge stops, the current will drop to 1A and the regulator would switch to float voltage.

Ernest E Vogelsinger

Thinking a bit more about my post I need to correct the assumption that the shunt “will see the sum of charge plus house load”. If it did it would be wired incorrrectly. So please disregard my above post as it is plain wrong.

The correct position for the shunt is directly on the battery, with nothing being connected in between, so that every current going in AND out will always have to pass the shunt.
So the correct sequence as seen from the regulator would be regulator – house load negative – shunt – battery.

And if wired correctly it is now clear that the shunt will only see the 1A that goes into the battery so the regulator would indeed switch to float voltage, regardless if the assumed fridge would draw 3A or not. And since the float voltage is still above the nominal battery voltage (it wouldn’t charge at all if it weren’t) the 3A for the assumed fridge will still be delivered from the regulator instead of the batteries. The regulator would deliver 4A, but if it depends on the shunt and not “own” or “built-in” measurements it would do this at float voltage, not at bulk voltage.

Colin Speedie

Hi John
these new regulators sound like a valuable development, definitely to be welcomed.
One word of caution for anyone thinking of installing one with a new(ish) boat, where the engine warranty is intact – do check that installing one would not affect your engine warranty. Some engine manufacturers can be awfully picky about ‘smart’ regulators.

Rob Gill

Hi John,
Not sure that’s an entirely fair criticism, as Volvo do not preclude other alternators being used (though I can’t comment on warranty issues). Volvo sell an engine mount / adaptor kit (including new serpentine drive belt) for our 17 year old Volvo D2 55, specifically for mounting a MasterVolt 130 Amp alternator (the factory fitted unit was only 60 Amp on our engine). The MV alternator then uses their own “Alpha-Pro” smart regulator that regulates the battery charging regime. So the MV alternator is not only approved by Volvo, they actively support it as a “system” tested alternative, for upgrading their older engines. Can’t comment on new engines – but our model comes standard with 120A alternators now I believe.
Br. Rob

Steve D

Indeed, good advice, but it goes beyond the warranty. The truth is, virtually every engine manufacturer has a limit to how much HP/kW you can pull off a crankshaft, the smaller the engine, the lower that threshold, and with good reason. In two cases I’ve seen broken crankshafts as a result of alternator over-loading.

Michael Beemer

Colin & Steve,
If I hadn’t lost lab time with students(C-19), we’d have finished our alternator testing project.

The WakeSpeed regulator can also monitor engine load and reduce output of the alternator when the engine hits 80% (user defined) – that test was great, and worked perfectly! It’ll really be helpful when putting a large alternator on a small sailboat auxiliary.

What we didn’t finish, but will, is actual load on the engine. We’re setting an alternator up on a shaft that can rotate and attaching a digital force gauge to get actual HP on the engine crank. Stay tuned this fall for results.


Steve D


Re. lithium ion batteries, agreed.

Robert Andrew

About 3 years ago I replaced the original controller on my Betamarine engine with a Balmar programmable one (considered to be “smart” at that time as I recall). I set it up per Rod Collins and it was a big improvement. How much of an improvement is this new regulator design over the Balmar?

Paulo Reisdorfer

Great content as always!

Very timely as we have decided to (finally) have an external regulator installed to our Yanmar 4JH45 Common Rail engine’s alternator. For that, the WS500 seems like the ideal solution (until a better one comes along at least!)

However, our main issue now is that it’s a Valeo 125a 12V internally regulated super dumb unit, and in order for it to accept external regulation it will require:

1. Modification to a P-type
2. A ready-to-install kit such as the Balmar 30-SR12-02 Internal Smart Ready® Regulator Conversion Kit (not sure if it will work with the WS500 though)

Has anyone experience with either option?

Ideas and suggestions are highly appreciated!

Thank you!


Stein Varjord

Hi Paolo,
I’m no specialist and have not installed this unit, but have from the horse’s mouth that the WS500 is ready for both P and N type. No need to modify the alternator in that respect. That job would also be relatively easy. You just have to change which brush goes to earth and which you bring out. You also need no extra units to disconnect the internal regulator and connect the external one. You open it up and connect the wires. The hassle involved varies between alternator models, but it isn’t too hard.

The WS500 has a temperature sensor to prevent overheating. If your transition to external regulator is because you move to lithium, it’s still considered smart to use the WS500 software to tune down the alternator power perhaps 20-30%. That is probably smart with other battery types too, if your battery bank is big. The alternator will live longer and charge smoother. It’s not made for running full speed for a long time, which it will with big banks, especially lithium. They have so low charge resistance that they can swallow any power given to them, but that means the alternator has to supply that power. With small lead battery banks, the resistance will increase quickly so the charge speed goes down and the alternator load does the same.

Steve D

This stock alternator is almost certainly not suited for external regulation, and the heat load that this will place on it. Just because it’s high output, over 100 amps, does not mean it’s designed to maintain that output for extended time periods, while charging a house bank for instance. This article covers the subject, and includes a photo of a stock alternator that was externally regulated, and the results.

If you can confirm with the manufacturer that it is capable of sustained high output, then it would be a different story.

Paulo Reisdorfer

Hi John, Steve and Stein,

Many thanks for the feedback. Excellent points and I have contacted Balmar and got some additional info about their Internal Smart Ready kit’s capabilities:

“I am not aware of any alternator model or brand that acts any different when externally regulated on internally regulated. There have been thousands of internally regulated alternators converted. You need to install the alternator temp sensor to protect the alternator incase of an over temperature should occur.”

I believe Balmar did enough research on this specific Valeo 125aA alternator to determine that it was capable of doing the heavy work and worth the effort to convert it. Having temperature compensation is certainly an important part of this of course.

Temperature regulation is indeed provided with the WS500 as John and Stein pointed out.

As for the WS500 being ready for both P and N type alternators, it does seem so according to it’s data sheet:

I did get SOME limited response directly from Wakespeed regarding what modifications are required:

“The Valeo 125A alternator will require modification to disable the internal regulator and allow external connection between the positive brush and the regulator’s field output wire. We do recommend converting the alternator for P-type regulation.”

In short, as far as I understand, I would need to get my Valeo modified somehow, and thus I’m looking at the Balmar Conversion Kit (less hassle and chances to messing up?), but have not been able to hammer out a clear response from Balmar if their kit will work with ANY other external regulator other than their MC-614. I understand their reluctance for a straight yes as naturally they would prefer for customers to purchase their not-so-smart regulator…

Steve D

External regulation conversion is relatively easy, but unless you are a savvy DIYer, take it to an alternator shop for the conversion. They should not charge more than $50. It is literally no more than disabling the internal regulator by disconnecting the field and bringing that wire outside the alternator. Ideally, this should be done using a stud rather than a wire, as the stud is more secure and reduces the likelihood of the wire breaking from vibration.

I remain somewhat skeptical that the Valeo is ready for continuous duty, but you don’t have much to lose by trying other than the cost of its conversion. Frankly, the “I am not aware of any alternator model or brand that acts any different when externally regulated on internally regulated.” statement shocks me, there is a decided difference between intermitent and continuous duty alternators, that is irrefutable.

Paulo Reisdorfer

Hi John and Steve,

Thank you for the great insights!

I totally agree on stock alternators not being up to the task or even intended for high continuous output, and exchanging it for a truly rated unit would be ideal. However, at least in my case, not living onboard full time or spending more than 7-10 days at anchor every couple of months away from shorepower, and thus not demanding as much from my charging system, perhaps taking advantage of the gear I have currently and setting it up for regulation with as much protections as possible (house battery bank temperature sensing, alternator temperature sensing, belt load managing, alternator downrating, advanced charging profile setting) could be an option.

Also as we are jumping over to a REAL full-time liveaboard cruiser within 2-3 years from now, investing more than the necessary in a proper new heavy-duty alternator and it’s accessories might not be the best use of resources. There’s also the issue of voiding the engine manufacture’s warranty when changing the stock alternator to a new one, which I’m not 100% certain about, but have read and heard this might be an issue specifically with Yanmar engines.

Steve D

You’ll find out pretty quickly if this alternator is up to the task, the overheated example in the article I shared lasted less than a season of heavy battery charging.

Regarding the warranty, I suspect you’ll void that by altering the stock alternator, changing it all together won’t make a difference.

As an aside, on warranties, I hear fear mongering from folks in the industry from time to time, i.e. anything you change leaves the owner with no coverage what so ever. Changing or altering the alternator means of course the engine manufacturer is no longer responsible for it, but it does not mean the engine’s warranty overall is voided, if a piston fails unless it can be demonstrated that occurred because you changed the alternator, the warranty remains valid.

Under the terms of the Moss Magnusson Act (in the US), engine manufacturers cannot force customers to use their filters for instance, unless they provide them for free, which of course they never do. I have nothing against stock filters, but many are exorbitantly priced, and high quality after market alternatives may exist.

Carl Johanson

Thank you all for very valuable inputs. The WS500 seem to be the perfect.
Please forgive me if you have already covered it but I have not found suggestions on how to charge the engine’s starter battery. Of course you can skip the separate starter battery and use the house bank for that purpose too. If the house bank is well charged and maintained there should always be enough energy in it to start the engine. However, if I like to have a separate starter battery, how do I charge it with a WS500 alternator regulator? A separate DC-DC charger like Sterling Battery to Battery Charger BB1230 DC DC?

Frans Botman

Hello John,

Reading through the articles and in the process of upgrading my charging system I am a bit confused about what to do. On one hand we have the Sterling type alternator regulators ( ) that claim that as the batteries get charged towards 80-90% the internal resistance increases hence the amps go down on a conventional type alternator regulator. By increasing the voltage towards the end of the charge cycle Sterling proclaims you can charge your batteries much faster to 100% by doing so. On the other hand there is the wakespeed that keeps charging, although at a much lower pace, by measuring the amps going into the batteries till they reach 0.5-1.0% of the battery capacity. If I get this right the combination of the 2 would be the ideal world?



Stein Varjord

Hi Frans,
I’m no electrician or such, so see my words as coming from an amateur having looked into these issues quite a bit.

The short answer to your last question is: No. That combination is not at all usable. If you have the WakeSpeed, the Sterling A2B charger is redundant. Using it will only sabotage the Wakespeed regulator.

An A2B (alternator to battery) charger is a shortcut to a somewhat better charge output from the alternator. It works by letting the alternator see a low resistance (low voltage) so it keeps putting out max amperage. Then the voltage is transformed in the A2B to what the batteries need.

Just to avoid confusion, there is also something called a B2B charger. Battery to battery. This is far more different from an A2B than the name would indicate. A B2B is a very nice and useful item in many cases, like keeping secondary battery banks charged, but is of course not used between an alternator and a battery.

This method will often give a better charging curve than the internal regulator of the alternator would alone, mostly because the A2B is usually better at giving the correct voltage at the correct time, but will normally lead to on/off charging. The reason being that the internal regulator is still operative in the alternator. It normally has a overheating protection circuit that will reduce its output to reduce the heat. The A2B will often push the alternator to higher output until the charging is turned off, until the alternator is cooled down, and then this is repeated. Not very efficient and not good for the alternator.

A smart regulator, like the WS500, (there are many other good ones, but probably not quite as good) is the real solution that takes no shortcuts and gets the maximum output your alternator can supply without getting damaged. You can adjust the output. It will also give a perfect charge cycle and take the best care of both batteries and alternator. The downside of a smart regulator is that you have to bypass the stupid regulator that is in most alternators. The bypassing consists of disconnecting and reconnecting a couple of wires. It’s a bit different depending on which alternator. You can find descriptions for yours online. It’s totally doable for an amateur.

Just to make it absolutely clear. Do not use both an A2B charger and a smart regulator in the same system.

Frans Botman

Hello Stein,

Thank you for your in depth answer. Already thought it to be that way but very glad I got confirmation. Reading further on the Sterling site they do seem to have an A2B charger in which you have to bypass the internal Alternator regulator. Guess the wake speed is the one to go for. As it outputs only for one battery which bank splitter do you use if I may ask? The argofet from Victron? At least that one does not have the 0,7V drop. Cheers Frans

John Michaels

Just found out that Balmar has come out with the MC618, that along with the SG200 battery monitor/shunt, it supposedly offers similar capabilities as the Wakespeed WS500 unit in terms of battery charging, and maintenance based on voltage, current, and temperature. In the not too near future, I foresee boaters satisfying their electric/electronic needs based on platforms and not individual products. For example, the Wakespeed WS500 very shortly will be fully integrated with the Victron platform.

Stein Varjord

Hi John,
I have no more news, but I can confirm that Balmar had plans already 2 years ago. I spoke with one of the core guys a the METS trade show. He said as mentioned here, that they will have an updated version of their alternator regulator that according to them would do everything that the WS500 can do.

He said the updated product would come in two stages. The first stage would be the 618 and be connected to the SG200 battery monitor. This would not do the full WS500 job, but would make it possible to read and control both items via their smartphone app. The next development stage he said would be about now, and be the full on WS500 competitor. He meant that the regulator could have significant advantages over the WS500 from having access to the smarts of the SG200 monitor. Just as a reminder, this is statements from 2 years back. They are probably not accurate.

The Balmar SG200, seems the be the very best battery monitor on the market. It even gets a reliable state of charge level with lithium cells and even then manages better than 2% precision and never needs to be reset, even after unlimited partial charge cycles. To do this it uses some secret software magic that made Rod Collins almost not believe his own test results. Obviously this is on my “must have” list. Even more so if it can work with an updated regulator.

One very important advantage of Wakespeed is that they are very active with integrating their system with other systems. They communicate with Victron systems as if it was a Victron product. Same with the REC BMS for lithium cells. I don’t know if Balmar is as good at this, but it might be.

Richard Cordovano

John, I just bought the Balmar SG200 battery monitor based on Rod Collins involvement in its development and his endorsement of it. In fact, I bought it from Rod’s web store.

I talked to Balmar today about a few installation instructions I wanted to clarify, and they tried to upsell me from the MC-614 alternator regulator I have to the new MC-618. The MC-618 does interface with the SG200, which allows you to program it via a Bluetooth connection, if you buy the Bluetooth module for the SG200. However, it is otherwise the same as the MC-614, so it is not equivalent to the WS500 you have written up so well here.

Which brings me to my point. Now that I have read Rod’s articles and bought the SG200, I figured I was set to program the MC-614. I contacted my battery manufacturer (East Penn) for charging parameters and got some help, but not quite enough to satisfy me. Remembering your article on the MC-614, I came looking and well…hello, WS500!

The WS500 sounds great, but I feel like I have sort of already committed. I suppose I could install an additional shunt in series with the Balmar shunt and scrap my MC-614, but I hesitate to do so, and have steeled myself to the notion of not having the best regulator. That said, can I get a copy of that excellent guidance I remember from the pre-WS500 version of this chapter?

Stein Varjord

Hi Richard,
As I mentioned in the comment just above yours here, I spoke to an informed person from Balmar at the METS trade show a couple of years ago, who said that the next model after the 618 would have all the functionality of the WS500, using the SG200 shunt. My impression (not reliable) was that this would be about a year after the 618, so not too soon, but perhaps worth waiting for?

Anyway, there is an article on Marinehowto that contains detailed instructions on how to program any Balmar regulator. Rod Collins is extremely competent on this type of stuff, so I’d just follow that:

Stein Varjord

Hi John,
I totally agree on buying the WakeSpeed regulator. I think it’s a great product and they have now even had some time to develop the details. If Balmar is leaking info about future products to reduce the sales of WakeSpeed, they might hurt their own sales more, as those considering a 618 would then rather wait, and while waiting, might come across the WS500…. That’s what killed Commodore Computers company back in the day, as you may remember. They were easily the best in their niche, (80ies home/gaming computers) but then they said the next model would be a revolution. That totally stopped all sales of their current models, of course, and they ran out of cash.

The WS500 communicates natively with Victron equipment, which is more useful than it might seem, as several other companies implement the same communication standard. One example is REC BMS, one of the best for those who want to go into lithium with separate cells and not use the always lower quality and more expensive assembled batteries (“drop-in” type). That means the WS500 communicates smartly with the BMS and they can do pretty important stuff together. They can also both use Victron shunts, and their own shunts can feed the Victron BMV 712, and most other items. Also, Victrons superior Bluetooth platform can be used to gather info from the WS500. I don’t think it can be used for programming yet, but that might come. WakeSpeed also have their own Bluetooth platform, but reportedly not as smooth yet.

My guess is that when Balmar, in a year or probably more, come with a product that can compete better with the WS500, it might not immediately be a smoothly working item, and it might take time until it’s communicating well with other items in the same system. Also the Bluetooth platform, again, seems to be not on par with the competition, but I have no experience with it, so that’s just what I hear.

Steven Bibula

What about those who are designing a house bank essentially from scratch, find all this technically out of their league, live a few towns over from Rod Collin’s business but cannot use his services because he is booked out 18 months, and simply want someone to design a complete and PROPER AGM (leaning toward Oasis CF) system so I (okay, I am in fact talking about myself, as was obvious all along) can buy the parts and have my AYB electrician install them to according to plan? Who do you respect, who, for example, actually agrees with the conclusions in this article, and is available for paid consult? Perhaps even a knowledgable cruiser who wants to help a fellow and earn some clams doing so…

Terence Thatcher

I write to find out if anyone has installed the Wakespeed or has any information on its reliability/ durability. Winter approaches, bringing winter projects. I currently use a Balmar, programmed using advice from Compass Marine. Thanks.

Stein Varjord

Hi Terence,

I have not tried the WakSpeed myself. Since it’s not been on the market more than a couple of years, no proper long term experience exists. However, I have communicated with several who have the device and they are more than happy with it. We should always beware of confirmation bias, the urge to defend our own position, but the owners seem enthusiastic, not defensive. I’ve also not heard of a single complaint yet, which is pretty impressive. Even a hypothetical perfect item will get haters sooner or later. Since they seem to be absent so far, we can only assume the product is pretty good.

Scott Halpern

Hi John,
I wanted to report that I did install the WS500 Nov 2020 (Outbound 46 with two 120A alternators mounted on a single Yanmar).

Splitting the field output & installing a millivolt sensor line on the existing shunt was straight forward. When dual regulators are involved, it’s important to NOT also split the red power and black ground but to simply choose one alternator (the closest one). It’s also important to get the polarity right on the shunt (use a multimeter and label pos)

While there is just one temperature sensor, it’s a well engineered product and the difference in the Absorption phase is remarkable. Those with Firefly carbon foam AGM house batteries who periodically ‘reset’ by discharging to 10.5v and attempting to push 35-40 amps per battery will notice a big difference in time to complete the process.

While the online documentation isn’t clear about the dual installation wiring points made above, I received great phone support. It really is the only smart regulator on the market.

Dave Meindl

We are upgrading our entire electrical system this winter. I recently spoke with one of the partners at Wakespeed (who used to work for Balmar) and he told me that Wakespeed has entered a partnership with Victron and has provided Victron with data on the WS500. They are working towards having a firmware update to the Victron BMV712 that will allow you to view data on the 712 showing what the regulator is doing. They are also working towards releasing a Dongle so you can easily program the Wakespeed using bluetooth (currently you can plug a laptop in to the unit via USB but depending on location that can be a pain). The WS500 is the only regulator I’m aware of that actually uses current flow, voltage, battery temp, and alternator temp to tweak the charging regimen. As you’ve mentioned, sometimes getting different components to play together nicely can be a challenge. The fact that Wakespeed is working with and sharing data with Victron settles it for us; we are going to get the WS500 and the BMV712.

Dan Tisoskey


I recently rewired my Downeast 32 and re-powered with a Beta 35, 120 amp alternator and serpentine belt. (love the Beta 35 and a great choice for the Adventure 40)

During this refit, I decided to go with one lead acid starting battery and one lithium ion, 300 amp hour house battery.

I use a Balmar regulator to charge the house bank and a Victron 30 amp DC to DC charger to charge the starting battery.

Everything worked well except the house bank did not want the charge the Balmar was sending (seems like the house was fully charged and the Balmar was still sending. After many re-programs of the Balmar, I reached out to the company for support. They told me I would have to use a different model Balmar (I am using the one that supports Lithium) but the model they suggested was one I could shut down the charge once I found my battery fully charged.

I am going to give Wake Speed a call this week to see if their product can solve this problem – from reading your article, seems like it will as it is SMART.


Matt Boney

I’ve read all your online articles on batteries and commented on many.

The bottom line here is that any external regulator will dramatically improve battery charging – but why do you need an even smarter regulator because you should never use an engine to try and fully charge your batteries on a cruising boat. It’s a noisy, expensive and very inefficient use of fuel, as well as putting unnecessary wear and tear on the engine. A 5 HP auxiliary generator can charge a very large battery bank, so a 50 HP main engine is complete overkill.

It’s easy, and fairly quick, to get batteries up to about 80% of their maximum capacity, above this the battery’s ability to accept charging current reduces dramatically, so the last 20% can take a very long time.