Wet cell battery bubbling slowly with no charge or draw.

[nmuir]

I am interested in learning what can cause a battery to bubble hydrogen when it is not being charged and there is no draw on it. It is happening with 2 different batteries.

Now I accept the batteries likely need replacement so please don't worry about pointing this out. I am however puzzled as to what could cause this and want to learn more.

The batteries in question were charged days ago and were entirely removed from the battery bank - they have nothing connected to the terminals. I noticed that 2 of them are bubbling slowly - days later. I am not 100% sure but think it may be from only some of the cells. Is it something like a cell is trying to equalize with another that is cooked?

I do not have a hydrometer so cannot check across the individual cells.

These are 6V Trojan deep cycle wet cell batteries. Voltages are about 6.5V

Can anyone shed any light on what is happening here?

[Wolfe10]

As you already mentioned, you need to buy a battery hydrometer-- should be under $10.


Everything else would just be speculation.

[nmuir]

Originally Posted by Wolfe10

As you already mentioned, you need to buy a battery hydrometer-- should be under $10.


Everything else would just be speculation.

Thanks Wolfe10. I am in a remote location so no hydrometers nearby.
Knowedgeable speculation is fine.

[SailingHarmonie]

This could be caused by a shorted cell.

You can test it by disconnecting the bubbling battery from the bank, and check the voltage across the terminals. If it is closer to 10V than 12V it has a shorted cell and should NOT be returned to service.

[boatpoker]

Originally Posted by SailingHarmonie

This could be caused by a shorted cell.

You can test it by disconnecting the bubbling battery from the bank, and check the voltage across the terminals. If it is closer to 10V than 12V it has a shorted cell and should NOT be returned to service.

Yup !
Internal short. It is unsafe to charge these batteries or this can happen ...

[Pete7]

Originally Posted by SailingHarmonie

If it is closer to 10V than 12V it has a shorted cell and should NOT be returned to service.

Be a bloody good battery if its got 10v in it

Pete

[cal40john]

Originally Posted by SailingHarmonie

This could be caused by a shorted cell.

You can test it by disconnecting the bubbling battery from the bank, and check the voltage across the terminals. If it is closer to 10V than 12V it has a shorted cell and should NOT be returned to service.

From OP's original message -

were entirely removed from the battery bank

These are 6V Trojan deep cycle wet cell batteries

[Jim Cate]

Originally Posted by boatpoker

Yup !
Internal short. It is unsafe to charge these batteries or this can happen ...

But the OP says that the voltage on both batteries is around 6.5 V and this isn't far off normal for a charged T-105. Don't see how that voltage is consistent with a shorted cell.

Jim

[Pete7]

Originally Posted by nmuir

I noticed that 2 of them are bubbling slowly - days later. I am not 100% sure but think it may be from only some of the cells.

I think you are on the right lines, its just a couple of plates in the odd cell that are shorted by a mix of the crud that forms at the bottom of batteries over time. The good news is Trojans have deep sumps to allow for this, up to a point.

Either way, weigh the batteries in with a nearby scrap yard. Lead acid batteries are 60p a Kg in England at the moment and its good for the planet to recycle stuff too.

Some 4 decades ago, I used to watch the vehicle electricians take old batteries off a vehicle or tank into the battery shop. Pour the contents down the large Belfast sink and flush out the rest of the muck with a hose pipe, then leave to drain over night. Following day fill with new electrolite and connect them to the big copper bars running around the shop for several days. Once checked by the hydrometer and if fit for purpose they would go back into service for another couple of years.

[donradcliffe]

Are the bubbling cells warmer than the rest of the batteries? If so, take those batteries out of service.