In the last post we wrote about the very poor service life that we have been getting from AGM batteries on Morgan’s Cloud—typically just a year or so.
Justin Gobar at Lifeline, who provided us with new batteries, is advising us on how to care for them. Put broadly, there are four ways that will yield different lifetimes based on daily 50% deep cycles:
- Fully charge after each discharge. (We understand that is not feasible [in our case].) Estimated life: 6-9 Years.
- Fully Recharge at least once a week and equalize once a month. Estimated life: 4-6 Years.
- Only recharge to 85% and equalize once a month. Estimated life: 2-4 years.
- Only charge to 85% and never equalize. Estimated life: 1 year.
A Big Surprise
The big surprise in Justin’s recommendations is that he actually wants you to equalise his batteries, and puts it in writing too. This is contrary to much of the “accepted wisdom” around AGM batteries, particularly that expounded in the yachting press. This misconception is so wide spread that many battery chargers actually prevent you from starting an equalisation cycle if you have them configured for AGM batteries and some of Justin’s competitors specifically forbid equalisation.
Cost Per Cycle
The spread sheet above calculates cost per cycle for each of Justin’s scenarios using a price of US$1800 for two 8D Lifeline AGM batteries with a combined capacity of 510 amp/hours at 12 volts; our configuration. Sadly, our experience to date with AGM batteries has been very much scenario 4.
As you can see, the key to reasonable cost is equalisation. Bottom line, according to what Justin says and backed up by our own experience on Morgan’s Cloud, a lead-acid battery of any type from a manufacturer that forbids equalisation is cost prohibitive on a voyaging boat.
Our Plan
Our plan is to aim somewhere between scenarios 2 and 3, which should give us a daily cost of about $1.35—acceptable to us to get the advantages of AGM batteries detailed in the last post. In fact, the fuel and maintenance savings that we will get on the generator from faster charge times and better loading should help offset the additional cost of the AGM batteries over liquid acid.
However, if none of this works in actual service on our boat, we will be going back to liquid acid batteries, or possibly gel cells.
OK, now we know that we need to equalise at least once a month, how do we do that with off-the-shelf charging equipment and fit it into the life and times of a live-aboard voyaging sailboat? It’s not as easy as it might sound., but it is doable. That will be for the next post.
By the way, Justin claims that there is really no difference in the care required for his AGM batteries and traditional liquid filled batteries. In other words, he is saying that the latter will fail just as quickly as the former if not regularly fully charged and equalised.
Does anyone have any thoughts? If so, leave a comment.
Further Reading
- Other posts in this series
- Also, check out the great, and very educational, thread of comments on the first post, including a must read from Justin.
{ 19 comments… read them below or add one }
I have an issue with the comment that equalisation is essential for any battery. I previously had sonnescheim gells and only changed to Northsatr AGM’s for capacity/space reasons, howver my gells still live today some 8 years on, but AGM’s have failed twice in 4 years. No equalisation for either bank!!!
Hi Michael,
Interesting, we too, on Morgan’s Cloud had very good service from gells before switching to AGM. However our usage was different and much lower than today, so we have hesitated to draw any conclusions.
Also, I think you are right about not equalizing gells since, as I understand it, the draw back of them is that they are very sensitive to higher voltages.
Keep in mind that our intent with this series is not to debate which of the three lead acid battery technologies is the best, but rather to come up with, if possible, a care scenario that will make AGM batteries cost effective on a voyaging boat for those users that want the particular benefits of AGM.
If we can’t do that, then we for one, will be abandoning AGM batteries and trying something else.
I think you have to find a way to fully charge at least once a week. Why can’t you do that? This is very important and to do this after some days at anchor your generating method needs to be around 200 amps. I use 200a 24v per day with 700a forktruck batteries. The typical forktruck driver does not care about battery charging regimes and will happily crawl his completely discharged forktruck back to the charger before smoko. What could be worse for a battery? I bulk charge at 29.6volts. Once a week I leave the generator on for another hour to fully charge. It’s annoying and also does not completely fully charge. Extended anchoring is the weakness in my systems so I am fitting solar which will give me 100amps per day to help the batteries get back to fully charged. I have a propshaft alternator, so I can fully charge while sailing at over 5 kts. Charging while sailing is also important.
Hi John,
All good points. The problem is the time it takes to get to full charge–an extra hour of generator time just does not do it.
Full charge is usually defined as the point where the battery is accepting less than 1% of its capacity when being charged at its acceptance voltage (about 14.4 for a 12 volt bank). In our case it takes 5-6 hours to get from 90% charge to full charge. We are just not willing to run our generator at very light load (very bad for it) to accomplish that.
Solar is a good idea if you have enough room, without compromising sail handling (we like to stand on our hard dodger and bimini) to install enough panels in a seamanlike way (that won’t fail in heavy weather) to really make a difference–we don’t.
Making power with a towed or shaft alternator is interesting. However, we are great believers in not hanging too much stuff off the main engine, which is for us, in the north, a mission critical system.
Conversely, and probably in contradiction to what I just said, we love to sail fast, and so are not willing to use a non-feathering propeller, which can cost as much as 20 miles a day.
Bottom line, we all pick and live with our own compromises. Sounds like yours are working great for you. Now we just have to get ours sorted out!
One recommendation I had followed from an experienced cruising couple was to supplement your offshore battery charging arsenal to include one of the newer inverter style generators that run quieter and will self regulate their speed to economize fuel. Well, I bought one only to find out that inverter generators are very limited in what you can run off them, including our Xantrex battery charger which is NOT compatible with square wave generators. Yikes.
Many electrical appliances that run on 120VAC will not work well, or at all, if it’s inverter square wave AC that powers them. Before you run out and buy that nice, portable, quiet generator make darn sure it’s going to be able to run the intended appliances including your battery charger you hope to use while away from shorepower!!
Hi Allan,
Wow, that’s worth knowing, I certainly would not have thought of that gotcha. When you say “inverter style generators” I assume that you are referring to a generator like those made by Honda?
That last 10 to 15% can be a real bugger….
One solution I’ve seen mentioned now and then is a small CHP (combined heat/power) unit to either supplement or replace the usual genset and heater. Whispergen makes one, based on a Stirling engine, that puts out 800 W (about 60 A on a 12 V system) for battery charging and 19,000 btu/h for space/water heating. I like the concept- simple, reliable, nearly silent and doesn’t have the diesel’s underloading issues- but I’ve yet to try the thing myself, and last I checked they were (inexplicably) quite expensive.
CHP would make little sense in the tropics, but at higher latitudes where the “H” becomes more important, it may be an appealing option if the capital costs can be brought down. The ability to produce a bit of current to top off the batteries, without burning any extra fuel (you’d burn it in a heater otherwise) or running an underloaded diesel, could be quite useful in a high-latitude boat.
Hi Matt,
Yes, the Wispergen does seem to to be very interesting technology. I saw one at the London boatshow in 2008, but since then have not heard much. At first glance, the specifications look near ideal for our application. However, we have a rule on Morgan’s Cloud that we don’t install technology until it is tried, proven and widely available. It’s hard enough to maintain an offshore voyaging sailboat that goes to remote places without the challenges of new technology added in. Of course, sadly, it is just this sort of policy that makes it difficult for innovative products like this to become mainstream.
It’s Justin Godber again from Lifeline Batteries.
Very interesting comments everyone has made. Matt Marsh, great idea about the Whispergen. The more efficient that last 10-15% gets the more likely everyone would do it, resulting in very long battery life.
As far as splitting the banks in two. Well, first off this is not a terrible idea, however these types of battery banks can be tricky to maintain. I would say this. If you are a full time sailor then this might be a good solution because you can make it part of your daily regimen. If you do not sail all year long then make sure you tie the batteries back together when in storage or plugged into shore power. This will help make sure the batteries are equal and last the same amount of time.
Short example of a system that doesn’t work: We had a builder that uses 8 batteries in a 24 volt system. They use a equalizer (not to be confused with equalizing) to bring 12 volts out of the 24 volt bank evenly. That’s a good idea, however, they only hook the equalizer to 4 batteries. Now, the 12 volt tap is for all the lighting and any other small 12 volt loads. They have an automatic generator start system on board. The problem is if they are not using anything at night except for lighting then there was huge differences in the banks. The 12 volt lights would bring the 4 batteries down to 22 volts and the other four were still full. The problem is the automatic generator start would see that the battery banks were only 45% discharged as it was looking at the bank as a whole. One side gets fully discharged and the other side barely gets used.
Just wanted to give that example so you could see the importance of keeping separate battery banks equal. It can be done with a simple battery switch. The kind that has battery 1, battery 2, or both. If you wire everything into that, you can manage charging battery 1, while using bank 2, and vice versa.
To close, you can do it either way. Managing two battery banks is a little more work but the end results could be much longer battery life, assuming that bank will be fully recharged.
Does anyone use the AMPAIR water/wind generator? Just curious if we could get some real world feedback.
I recently bought a new boat. The previous owner has six 8D AGM batteries on it. Double the amperage that I have ever carried on a boat. We use under 200 amps per day so our daily discharge as a percentage of total capacity is very small. Any idea how this will effect the longevity and thereby the daily cost of electricity from a larger battery bank? If my calculations are correct I would need to get over 12 years out of these batteries to get the daily cost down to your $1.35 target…seems unlikely.
Hi Chris,
Sounds to me that you are in great shape since battery life tends to go up exponentially as the percentage depth of cycle goes down. The only thing you might consider would be splitting this very large bank in two, as another commenter suggested. This way, by alternating usage daily, each bank could get two days of charging after each discharge and be re-charged to a level closer to 100%.
Of course such a change will substantially increase the complexity of your installation and will result in each bank being discharged twice as much. Therefore the question becomes, will the higher percentage of recharge outweigh the deeper discharge? I will see if Justin has an answer to that.
I’ve been following the battery discussion and thought it about time I threw in my two cents. First of all I was amazed at the myth that I couldn’t equalize AGM’s. I always thought they were sealed sufficiently to cause harm if heated by equalization. Quite a revelation, thanks Justin.
Like John, I have had less than stellar service from my AGM’s although they are still the battery of choice here aboard “Sea Return”, our Pearson 530 and winter home for twenty years now.
We alternate the scenery between Maine in the summer and Bahamas/Caribbean each winter. The boat is usually anchored or moored out and is loaded with all the power hungry creature comforts. “Battery of choice” because adding batteries over the years required stacking and you haven’t had a workout until you have added water to a stacked battery bank.
My first AGM’s were indeed Lifelines, they went five years before showing signs of diminished capacity. They were never equalized and deep cycled to 50% charge almost daily.
I do have a system similar to an earlier commenter where I lead/lag the house bank with two 4D batteries in each of two house banks. Each battery bank as well as the the two house banks have their own dedicated 40 amp Statpower charger set to AGM mode. There are four identical chargers plus a spare aboard. The house bank battery switch is toggled between the two house banks daily allowing the resting bank full benefit of the 40 amp charge if on AC power, gen or shore.
We also have a 90 amp (soon to be two) alternator off the main engine run through the same battery switch after an electronic battery isolator by Mastervolt. This amazing device allows the full 14.2 VDC to reach whatever bank needs charging. When motoring the switch is placed at the “all” position so both house banks are on line as well as the furler/windlass bank/thruster bank, engine start and generator start batteries. The older diode style isolators used to sap a half volt or so to punch through each diode.
Even with this bullet proof system we have had similar issues to John. Our last set of AGM’s were not Lifelines but Dekas. The house banks both failed after ten months, all four batteries were bulging with distorted cases. Deka replaced them free of charge so we were sucked into another go around, this time two years. We were having issues all along with these Dekas so we were running the switch on “all ” to supply adequate ship’s power at a proper voltage. Consequently we did not lead/ lag after the first few months when they first started giving up storage capacity. Even the brand literature cautioned that these less expensive batteries were only good for a few hundred cycles.
Now to the present and a fresh set of Lifelines ($$$$). I’m back to my lead/lag practice with plans to equalize monthly. Equalization is much easier with my setup John because I use one bank while equalizing the second when off line. Having dedicated chargers allows for the 15+ volts without concern for other on board appliances. The gen set gets a workout however.
Now I should be complete and note that all other AGM’s on board are five years old or older and have no signs of giving in. Of course they are always in a topped up condition. They are a mixture of brands (not in the same bank) with none by Lifeline, all 4Ds because my 59 yr old body is done with 8Ds. That’s my two cents worth on batteries.
Like John, on my way to Billings Diesel for my new M92B install along with a new Sea Frost refrigeration system. The present system is a (still running great) Grunnet Versimatic vintage 1983. I hate to part with this piece of the boat but parts are becoming difficult to find now that RParts is no longer. I also have to check out this new found efficiency everyone is talking about with the Danfoss 12VDC sealed compressors. You don’t get something for nothing but reports are they got close.
Bob Tetrault S/V Sea Return, Gulf of Maine headed East.
Hi Bob,
Thanks for a great comment sharing your experience.
I have some questions for Justin regarding how to get the most out of a battery. Which is better for the battery: fewer recharge cycles, or less discharge? For example, say I use 25% of my battery capacity each day, and can fully recharge any time I want. Which would be better: recharging every day (limiting the discharge to 25% of capacity, but using twice the cycles), or recharging every 2 days (using half the cycles, but discharging down to 50%)? What about recharging twice a day? How is this choice effected by only recharging to 85%, with a weekly or monthly 100% recharge? Thanks for your input to this great discussion.
Ahoy John
Very interesting post. I have Lifeline AGMs on Doolittle and after 6 years they are still as good as new. My secret is to never, NEVER let the volts drop below 12.2. So they have never been fully discharged. There is a lot spoken about how to look after batteries and I’ve tried all the advice and have got through a ridiculous amount of batteries over the years. Never discharging the batteries more than 50% seems to work for me. I also have a Balmar charger. We cruise for about half the year and for the other half are plugged in and the batteries are kept topped up by a charger. During the summer the batteries are rarely fully charged just kept above 12.2 volts.
I have two 105 amp/hr batteries and they have always been paralleled (effectively making one battery). Seems to work for me. I wonder how much longer they will last?
Hi Benjy,
I think you are right, it is really important not to discharge the batteries more than 50%, or at least not often. But keep in mind that voltage is a lot about load in relation to battery size as well as percentage discharge. For example, our bank of two 8Ds in parallel will read about 12.0 when about 45% discharged if the load is say 25 amps, not an unusual amount for us. Put the toaster on through the inverter and that will drop to a bit below 12 volts. In these cases, these lower voltages do not indicate any abuse.
I’m also guessing that the very good service you have received from your batteries is a lot about the six months a year they spend fully charged while alongside. That will go a long way to removing sulfates from the plates.
Hi John,
Just inquiring about your Lifeline experience so far? I went ahead with Lifeline, with the help of Justin I have hopefully got the right setup. I have also now managed to get my Victron Inverter/Chargers to run equalization, so I am set for that too at the end of the season, which is Justin’s recommendation. Early warning from you would be appreciated.
Thanks
Michael
Hi Michael,
So far our Lifelines are going strong coming up to their one year anniversary. See this report card.
John,
Having similar problems with 2 Lifeline 4DLs using a Xantrex Truecharge and a Link 20. After 4 years 11 months they appear to have died. And I never let them go below 12.2 v. I have a circuit diagram on my charging set up. http://oceanplayground.blogspot.com/
I am trying to equalize now at 15.5 v. on a separate charger. We will see if they come back. I had the Xantrex on, charging pretty much continuously at dock. Trickle charging at 13.2 v (AGM) with temperature sensor. The batteries appeared ok, started engine ok, etc. I decided to disconnect them from the charger and let sit without any draw on either battery. After a couple of weeks, one battery discharged itself. It took a charge but would not hold it. ( I tried to equalize, finally it just would take no charge — last week.)
The second 4DL was ok for about 2 more weeks, it took a charge etc,. and appears to hold it…then after being disconnected from the charger for another week it went dead. I tried to charge it but is only drawing ~ 1 amp. I am trying to bring it back now. But Justin indicates they are getting old. I think the batteries had gone before this time, but because they were on the Xantrex float, they appeared OK. Meanwhile they were sulfating. I guess I should have equalized monthly as a preventive maintenance. I wish I had known this as this is easy to do. I also believe the Xantrex was undercharging them. They charged at 14.2 in bulk only and would pull about 5 amps but went to absorption and float at 13.2 and only pulled 2 amps. The Link 20 said they were 100% but I am not sure. They were reading Full.
My alternator on my engine charges at 14.2. After reading the post I feel like they never were completely charged and could be the reason they failed.
Let me know if the circuit diagram appears OK. I did it to the book.
Thanks