The Offshore Voyaging Reference Site

Q&A—Are Battery Desulphators a Good Idea?


From member Conner:

I was wondering if there is any instance or reason you are aware of where a continuous battery maintainer/desulphator would be bad for AGM batteries? Unfortunately we live on shore power a lot right now, and I wanted to buy a maintainer for our AGM starting batteries to live on, such as this one. [A combined desulphator and charger.]

The distributor said I did not need it, and actually said to not get it. Do you know of any reason why a maintainer/desulphater for AGM batteries, hooked up full time to AGMs, would be harmful? (Full River AGM batteries)

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Conor Smith

Thank you John for the great follow-up information!




Well, I installed one of those desulphators 7 years ago. Have not had one electrical failure on instruments etc. which indicates that the spikes do not harm the electronics.

My first set of LifeLines lasted 6 seasons. I never did a equalizing charge. But they had a comfortable marina life most of the time as I was still working and only had 4 weeks vacation + weekend sailing. The first set of batteries was exchanged prematurely. Would probably lasted another season or two.

The curent set of Lifelines have been in the boat 3 season. These batteries are cycled much harder as we are cruising full time 6 month/year. They are still going strong.

If the desulphator do any good I can not say. But I´m pretty sure it is not doing any damage to batteries or instruments. I totally agree that it can not replace the fact that batteries need to fully charged as often as possible.

As I wrote I have never done a equalizing charge. But what I do is to run the battery charger on absorption voltage 14.4V for 16 hours if the batteries have been discharged a longer period. (More than 2-4 days) I believe this might be why I have been successful not having to do the equalizing charge.

When I had open ventilated batteries I learned quickly by measuring the acid that it take much longer time to charge the batteries 100% than what the manufacturer expected. Battery chargers tend to have absorption time between 4-6 hours. This is many times to short to charge the battery to 100 %. My Mastervolt charger can be programmed to max. 8 hours. Even that is to short if the batteries have been discharged for several day between 50-70%. It takes time to charge a battery properly.

Sorry for derailing a little bit:-)



A friend of mine purchased one of these that was solar powered. He connected it to the battery
on his wife’s brand new jeep grand cherokee ( not sure why ). It destroyed the cars E.C.M. She was
not amused. This is just anecdotal but it does give evidence that electronics can be damaged by
the high voltage pulses from these devices even with the battery acting as a buffer.

Chris Phillips

I ran a couple of Pulsetech PowerPulse desulphators on our last boat, which had a pair of Odyssey 2150s and a single Odyssey 1500 for the starter. I used one unit for both the house batteries and a separate unit for the starter. After 4 years of use the batteries seemed strong without any significant degradation. Its worth reviewing the testing that Pulsetech has done, it seems scientific (to me).


Hi John,
thank you for the deep insights (again). Regarding concerns about the voltage spikes – couldn’t a voltage stabilizer help to reduce the danger? I’m thinking of a separate DC ring for electronics (and other possibly sensitive devices) only that don’t draw a lot of power, a DC ring that is guarded by a stabilizer such as this:

Steven D'Antonio


I’ve always been suspicious of these devices, it seems that every time I worked the boat show circuit a new brand had popped up, and an old one had fallen by the wayside. Not scientific I agree, but also not encouraging.

On a related subject I’ve faced a vexing problem, what to do about a vessel living dockside and running AC loads on inverters, i.e. a 60 Hz boat in Europe, wherein the chargers are often providing significant current (and necessarily higher, bulk voltage) to keep up with inverter demand, yet the batteries are always 100% charged. Over time this leads to chronic over charging that seems unavoidable, and shortened battery life.

Marc Dacey

Since I’ve installed my new house bank and charger/inverter, I turn off the charging when I’m not there as I have no DC loads (save the bilge pump which doesn’t cycle due to the PSS). When I show up, I go to “float” within 15-30 minutes, and that’s just on a 15 amp breaker to the charger. I feel this is, even with my set points, a better way to stay close to 100% SOC.

Of course, we will be using onboard charging sources once underway and will rarely be on shorepower, European or otherwise, so that’s not an issue, per se.

Tony St. Amant

New to cruising and needing to desulfate my batteries for the first time and running into many logistical issues. After reading your article I figured I would to a Google search to see what products I could find that might help me out. Ran across this device and would like to hear your opinion. It almost looks too good to be true as it would definitely solve all my logistical issues including allowing me to desulfate my batteries at anchor. Given it’s price point compare to most things boat one would want to buy a dozen just to feel right about it. :)

Geir ove

i know many ho have used them for years on normal LEAD, batts, and they work fine, makes the batts live much longer, but havend heard about any using them on AMG .

Terje M

Let’s go sailing!

I want all systems (mechanical and electrical) to work all the time without fails or break downs. Few components are more important than others. I also like to be able to fix all things myself when it goes wrong.

Desulphators – I can’t even spell it!

We now got Rolls AMG batteries on-board. When installed, the battery bank was extended, re-located and all critical wiring redone. Then it was chargers, inverters, isolators, control panels and desulphators……

Sorry, I have looked it up, and I know what it is.

I went for a Struder Xtender 2000. A Swiss quality product first made for homes in the Swiss Alps without any power supply. I can tell you – it was expensive but it works. It is now almost 1500 days since it was installed, according to the control panel.

The yacht is in frequent use. The power system has never failed. With 560 amp AMG batteries I only need to keep an eye on % charged. If it goes down to 60% charged, I like to do something, read start the engine and get it charged up too minimum 85%. Job done. I can focus on sailing.

Some benefits:
– Got 240v on-board all the time.
– If shore power is unstable or we use more than what the marina can gives us, I got a steady supply.
– No need to think of any switches when plugging in the shore power.
– Acts like a UPS, good for computers and other stuff.
– Charges the batteries quickly, in the right order.
– A very good battery monitor.
– Can control generators, el-panels, hydro and more.
– It monitors the state of the AMG batteries, including battery temperature.

I would not install the product myself. It is complex.

This sound like an advert – I paid for the product in full and will recommend it to anyone.
Terje M
Yacht Maud

RC Collins


I have been testing desulphators now for well in excess of 6 years, and have compiled lots and lots of data. Unfortunately none of the data I have collected paints a good light on these products for actually “desulfating”.

I have tested multiple products including the PulseTech a BLS and even a Sterling Power model desulfator. I can’t talk to the actual data, because PS has asked me for it, but suffice it to say I have looked at this every way from Sunday and I have never seen any sort of “desulfating” occurring nor seen any measurable changes in terms of restoring lost capacity, internal resistance changes or better cranking abilities..

I have tested these using:

-Baseline Ah capacity (Array 3721A) then moving forward Ah capacity changes
-Baseline internal resistance (Argus) then moving forward internal resistance changes
-Baseline CCA/MCA (Midtronics EXP-1000HD) then moving forward changes
-Baseline CCA (Argus 500WP) then moving forward changes
-Baseline peak deliverable in-rush current (Fluke 376) to starter then moving forward changes
-Baseline peak in-rush low voltage (Fluke 289) to starter motor then moving forward changes.

Each battery I have tested has had no less than 6 months on a desulfator product. All batteries chosen for testing have come from quite freshly abused banks and none have exceeded 2 years old. Most are less than 18 months old and suffering from chronic undercharging and sulfation. I use and look for batteries that came from “parallel banks or from contiguously wired banks. This gives me a similar battery to run other conditioning protocols on. In every single situation standard equalizing procedures has beat the desulfator and done so in a matter of hours as opposed to 6+ months.

I really hate to just bash a whole class of products so have not yet decided whether to publish or not but from where I sit, having done huge amounts of testing using lab grade tools, I would advise saving your money if you expect a desulfator to actually desulfate a sulfated battery or to restore lost performance.

I can’t comment on what would happen if they were used from new as this data would take multiple A/B testing scenarios and 8-10 years to complete. I suspect the manufacturers of these devices know this so they know it is also very difficult to prove they don’t work when used from new. As for desulfating a sulfated battery that is pretty easy to test for and they simple answer is no, I’ve not seen them do anything measurable in terms of improving a sulfated battery.

My testing has been frustrating because it was first intended for myself because I do need a reliable way to recover abused batteries. I spent my hard earned dough on all of them and none have done what I need, expect or was told they could do..

-RC Collins
Compass Marine Inc.


Hello John
I have a large GEL battery 12 V/1’500 Ah capacity. The battery is charged/discharged via a combined charger/inverter (true sine). I also installed a battery desulphator. I noted strange behaviours in the AC system and hooked up an oscilloscope to check the wave form that came out of the inverter – the wave form was totally distorted and did not resemble a sine wave at all. After I removed the desulphator from the battery everything was back to what it should be with a regular sine wave showing on the instrument – apparently the desulphator was the trouble maker.