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I'm living in an off-grid house with battery power storage. Batteries are one of the most expensive and problem prone aspects of off-grid power. I have a battery bank in which some of the batteries are experiencing positive terminal growth. This is when the positive terminal literally grows longer and starts to push its way out of the battery case.

The batteries are 2v 460 A/hr Gel Batteries (sealed lead acid). I have 24 batteries running in series.

I have not had much luck finding out exactly what causes this and how to avoid further worsening of the batteries.

Does anyone know the exact causes of this, or whether it's possible to reverse it?

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    This question probably belongs over on electronics.SE. Also, it would be helpful if you provide the specs of your batteries, and maybe a picture or two. – LShaver Aug 25 '16 at 1:15
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    I'm posting here because I'm living in an off-grid house with battery power storage. Batteries are one of the most expensive and problem prone aspects of off-grid power. Area 51 has a renewable energy SE, but it's not in beta yet. – Henry Aug 25 '16 at 1:18
  • My own experience is limited, but from what I've read this may be sulfation - however this typically occurs on the negative terminal, not the positive: batteryuniversity.com/learn/article/… – LShaver Aug 26 '16 at 18:57
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    @LShaver many larger lead-acid systems have single cell batteries. It's generally more efficient to have fewer, larger cells where possible, but a 6-cell battery is unwieldy above a few hundred amp-hours. Building and maintaining a complex series-parallel setup is expensive, even when (or especially when) some of the series connections are hidden inside the batteries. How do you deal with a single cell failing in a 200kg, 12V battery? – Móż Jan 6 '17 at 23:21
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    @LShaver - yes they are 2V cells. There are 24 of them making and 48V bank. – Henry Jan 8 '17 at 1:10
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I've read somewhere that this occurs because over time the positive plates of lead acid batteries corrode. The plates grow and start pushing at the weakest point which usually is the pole.

This article briefly describes the process and mentions that you cannot prevent it, but you can take measures to avoid rapid corrosion:

Limiting the depth of discharge, reducing the cycle count, operating at a moderate temperature and controlling overcharge are preventive measures to keep corrosion in check....... [prolonged overcharge] is especially damaging to sealed lead acid systems.

It may be too late for your current batteries, but I've read here that you can keep lead acid batteries in good condition if you

apply a fully saturated charge lasting 14 to 16 hours. If the charge cycle does not allow this, give the battery a fully saturated charge once every few weeks.

More do's and don'ts can be found here.

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