Have I damaged my battery?

[RogerFoxTerrier]

I bought a 12v 105AH leisure battery last summer. Due to solar problems, it completely drained several times on the mooring, though only with a small bilge pump doing tests every 2 mins. This year I've got much better solar, and so far, the battery shows full (on the solar controller) when we get onboard, but dips incredibly quickly. We only have instruments, VHF and cabin lights. No fridge or windlass for any heavy use.

Is it possible I've damaged it? Is there any way I can test its health?

Thanks

 

[Baggywrinkle]

If it has happened several times, and not been recharged immediately with a decent battery charger then there is a good chance it is suffering from sulfation, which means a permanent reduction in capacity and performance.

You could try putting it on a smart charger with a dedicated "desulfation" mode, it might recover.

To find out if it really is dead and not just "pining for the fjords", charge it fully, let it sit for a good few hours and then get it discharge tested.

 

[toothless]

as above. but solar controllers can fib - it might not be anywhere near charged. take it home and give it a go with a proper charger (especially one that can do a pulse repair or whatever). If that doesn't do it, she's dead Jim.

 

[KompetentKrew]

It's definitely been knackered by draining it completely flat multiple times, and the test is the results you're seeing.

Probably even a secondhand battery for £10 or £20 from a breaker's yard (test the resting batteries with a handheld multimeter and select the one with the highest voltage) would prove this to you.

I imagine your battery is going to zero very quickly when you start using the electronics, and any half-decent battery will last hours longer.

 

[Tomaret]

I bought a 12v 105AH leisure battery last summer. Due to solar problems, it completely drained several times on the mooring, though only with a small bilge pump doing tests every 2 mins. This year I've got much better solar, and so far, the battery shows full (on the solar controller) when we get onboard, but dips incredibly quickly. We only have instruments, VHF and cabin lights. No fridge or windlass for any heavy use.

Is it possible I've damaged it? Is there any way I can test its health?

Thanks

A surveyor switched off my solar controller last September. I couldn’t visit the boat until April and 380 amph of domestic and 75amph of starter battery were completely flat. Charging them warmed them up but they wouldn’t hold the charge and had to be replaced. The expenditure hasn’t improved my opinion of the surveyor.

 

[billskip]

Is it not under gtee?..take it back ....

 

[Mark-1]

FWIW I've been lucky and had a battery that sat completely pancake flat for 5 days twice and got away with it. Charged with an old fashioned dumb 6amp charger which I often use as a power supply.

I reckon try a proper charge with a battery charger rather than solar and see how it behaves after that.

 

[Babylon]

Rule of thumb is that lead-acid batteries do not like being discharged below 50% of their capacity. You could probably get away with a slightly higher discharge now and again as long as it is then charged up fairly quickly with good 240v smart-charger with a de-sulphation function etc, but the chances are that you've damaged it beyond normal recovery.

My last set of lead-acid batteries (dedicated engine start battery and two 110Ah domestics in a separate bank) lasted thirteen(!) years, kept charged up on the mooring via the wind-generator, died three years ago when I forgot to turn off the main isolator switches when checking the boat on a cold winter's day, and some residual current somewhere (no electric bilge pump etc) then sucked them by the Spring.

PS: is it normal to leave electric bilge-pumps active when a fully-enclosed boat isn't in use? Why not isolate the battery completely?

 

[Graham376]

PS: is it normal to leave electric bilge-pumps active when a fully-enclosed boat isn't in use? Why not isolate the battery completely?

My bilge pump is connected directly to batteries but with float switch, 20 amp fused. The OP says his runs every 2 minutes to check if any water present, how much current does that draw over days or maybe weeks?