tcason avatar image
tcason asked

Gel batteries cannot handle high loads

My bank of 4 GEL 220ah batteries has lost its ability to absorb high amp loads through my Victron inverter. This occurs after only a 10% discharge. I have performed a very slow, deep discharge/recharge protocol suggested by my dealer over the winter and this worked for about 30 days but after a period where mainly on shore power the problem reoccurred when on battery only. Is there a fix for this issue.


battery chargingbattery capacity
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2 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi Tcason,

Off the top of my head, some ways to maintain a battery bank for a long life is:

Good solid connections, inspected regularly.

Consistent temperature control around 25 degrees

Limit charge and discharge currents to 10% of their Ah capacity - 100Ah battery, limit to 10A.

Return to float as soon as possible after deep cycling.

Minimise deep cycles.

Slow charging speed as much as possible and maintain consistent charging voltages, currents and schedules.

Monitor individual cell voltages and balance the battery bank when necessary.

Don’t use cells in parallel arrangements where an imbalance can cause uneven cycling across the bank.

Any of those will contribute to damage of the lead battery, reducing usable capacity, and leading to further damage.

Some are manageable, others are not possible for various reasons in some circumstances.

Once a cell is badly damaged, it is unlikely to recover. Identify the specific cell with a multi meter under load, and make the appropriate correction.

A qualified Victron dealer should be able to assist with next steps back towards acceptable performance.

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tcason avatar image tcason commented ·

I am running this bank as a 24 volt system with two pairs of batteries in parallel. When I check the voltage on each battery independently I get one of the two pairs at 12.7 and the other at approximately 9.1 with a system voltage of 21.7 for both Paris after multi hour discharge. One negative terminal with most of the external ground wires attached had crud built up on the terminal and end of the wires. I cleaned this off.

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JohnC avatar image JohnC ♦ tcason commented ·

If you can't find a string midpoint V close to half your overall V, your bank (or part of it) is likely cactus. You could try moving the two high-V batts to the same string, hence the two low-V ones together as well.

In practice, under charge, one string may well get much hotter than the other. That's the one passing the current, and is likely (but not necessarily) the faulty one.

After a good charge, lift the midpoint connector of each string (one at a time will do) and test each batt for V. The ones that can't hold it are likely done for.

This procedure can be onerous and usually ends up heartbreaking. But you may be able to salvage half your batts for a little more time.

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Something is clearly terribly wrong now with the 9.1V cell. BEST CASE it is just flat, and will recover somewhat with a recharge, but depending how long it has been like that, more likely there is permanent damage.

You must now recharge each cell individually with a 12V charger to full, before resuming normal operation to make sure that they are all balanced.

Ideally, you would discharge and then recharge each of the batteries in a controlled fashion and monitor how much energy they are able to absorb before they are full. They should all be very similar, and if one is much lower, it should be replaced.

There are many ways to incorrectly wire a parallel bank that could lead to this situation. I'd suggest contacting a nearby professional with experience, if you are not able to do so, please read these two references for further understanding:

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tcason avatar image
tcason answered ·

Mr. Stuart..

I am attempting to contact Philippe DeLance who was the Victron expert with Blanquart marine where I purchased the batteries in SJDL France. He is very knowledgeable and assisted me on the install of the batteries as well as an isolation transformer.

Before I received your response I connected the Victron Multi 24 inverter back to the battery bank and charged it without separating the batteries. After an overnight charge the voltages are:

Number 1 - 14.3

Number 2 - 13.7

Number 3 - 13.7

Number 4 - 14.1

Numbers 1-2 are in parallel

Numbers 3-4 are in parallel

Batteries 1-3 are from 7/14

Battery 4 is from 8/17

In current set up all negative system connections run to battery 1 and all positive system connections run to battery 3. I do not have a buss bar set up at this time as is recommended on page 16 of your wiring manual.

When I opened up the battery box for inspection, I found the system negative terminal of battery one with significant corrosion built up. None of the other terminals had any buildup.

I have cleaned that terminal. At this point, would it still make sense to separate and charge each one separately and reconnect?



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You really want to get all those cells as close in voltage as possible to each other.

Then solve the issue for why they were so far apart in the first place.

So yes, I would still recommend individual cell charging and balancing.

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tcason avatar image tcason commented ·


I am in the process of charging each cell individually as you recommended. The first two 12v cells that make up 24v bank #1 came out 13.1 and 13.0 after charge and rest. Should have the other 2 completed today. I have identified proper busbars for the battery set up in your manual. And I will reconfigure the cabling when we return to home port in a few weeks.

I have a question or two on the details of this new configuration.

On the positive side, I have three charging sources (victron, solar, alternator) and 2 load circuits to a switch and the main 24v breaker panel. I have a shunt on the negative side for your amp monitor with a similar number of ground circuits running to the panel and alternator ground.

Should all of these be routed to the positive or negative busbar with only a single main cable going to each of the 2 banks positives or negatives?

Finally, the run for the main busbar to battery connecting cables will be about .5m. What size cable would you recommend? I have 25 square battery cable on hand.

Sorry for the 20 questions. Phillipe DeLance has retired so I really appreciate your assistance on this.



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Hi @tcason,

To set a good example, we should return to the community guidelines.

Please create new posts for these new questions, and give the community another opportunity to answer them. We are now quite off the original topic.

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tcason avatar image tcason commented ·


My apologies. New to the process.

Will do.


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