dead batteries

[Alf Roberts]

this one is slightly out of my experience.

 

A pair of 6v us2200 copies, so 232Ah. Left on a boat for 3 months this winter with 80W of solar, commoned with a start battery 664 type.

 

I returned to the boat to find a 2W LED light had been left on and both batteries flat* - though the light was still on. They've been on charge for a couple of weeks, being gently cycled with 3 equalisation charges.

 

*flat = the 664 at 10.6V the 2200s at 7.4V

 

The 664 has recovered fine, is now sat at 12.8V and after being left a couple of days starts the engine easily.

 

the other two are behaving a little strangely. they seem to charge OK, take them off and they run low power loads fine, seeming to have capacity. As soon as I put a medium load - theoretically around 10A on them they just die, going down to a terminal voltage of 4V (!)

 

now my feeling is they are dead. so far so simple.

but they have had an easy life up until now, 3.5 years old, landline, easy loads, constant solar so it seems a little odd they should 'just' die.

 

what is going on in the battery that causes the death? is it extremely heavy sulphation? have they shed their lead?

 

any ideas as to a revival programme or shall I just junk them?

[bizzard]

this one is slightly out of my experience.

 

A pair of 6v us2200 copies, so 232Ah. Left on a boat for 3 months this winter with 80W of solar, commoned with a start battery 664 type.

 

I returned to the boat to find a 2W LED light had been left on and both batteries flat* - though the light was still on. They've been on charge for a couple of weeks, being gently cycled with 3 equalisation charges.

 

*flat = the 664 at 10.6V the 2200s at 7.4V

 

The 664 has recovered fine, is now sat at 12.8V and after being left a couple of days starts the engine easily.

 

the other two are behaving a little strangely. they seem to charge OK, take them off and they run low power loads fine, seeming to have capacity. As soon as I put a medium load - theoretically around 10A on them they just die, going down to a terminal voltage of 4V (!)

 

now my feeling is they are dead. so far so simple.

but they have had an easy life up until now, 3.5 years old, landline, easy loads, constant solar so it seems a little odd they should 'just' die.

 

what is going on in the battery that causes the death? is it extremely heavy sulphation? have they shed their lead?

 

any ideas as to a revival programme or shall I just junk them?

I'd wheel them to a garage that has a powerful boost starter of about 100 amp or so. Give em a good oomph, fast boil for a while, but keep an eye on them in case they get too hot. Might desulphate them. Worked at my garage many time.

Edited February 24, 2015 by bizzard

[Keeping Up]

Without the solar charger, 2 watts = ¹/₆ amps = 4 amp-hours per day = 120 amp-hours per month, which would definitely flatten the batteries. But I would have thought the solar panels would keep pace with that, even in winter.

[Alf Roberts]

My feeling is that the solar was 'almost' keeping up hence the light being on when I arrived but over the months it had gradually drained the batteries.

 

I was assuming sulphation hence a few 15.5V equilisation charges. I have an old fashioned Sealey charger with boost charge so I might replace them and then see if, disconnected from the system I can jolt them into life.

 

I am curious as to what would he the chemical process of 'battery death'

[Tony Brooks]

My feeling is that the solar was 'almost' keeping up hence the light being on when I arrived but over the months it had gradually drained the batteries.

 

I was assuming sulphation hence a few 15.5V equilisation charges. I have an old fashioned Sealey charger with boost charge so I might replace them and then see if, disconnected from the system I can jolt them into life.

 

I am curious as to what would he the chemical process of 'battery death'

 

The only chemical process is sulphation but other causes are teh plates shedding material cause by old age or abuse, filling the sediment wells and shorting out the plates, or the plates or a chunk of shed materials rubbing through the separators and gain causing an internal short.

 

Then we come to potential corrosion or mechanical failure of the plates where they join the posts or interlinks.

[matty40s]

some useful advice here Alf

 

I don't understand why you think it needs to be 12V trojans (or the US Battery equivalents). Buy sets of 2 6V US2200 or Trojan T105 batteries, 2 is 220Ah at around £230 so although a bit more expensive than leisure batteries well worth it a. for the extra cycles and b. for the fact you can take them to a deeper DOD.

The above about truck batteries is, in my opinion, rubbish.


eta: 110Ah Numax from tayna £90
232 AH US2200 £121

I know which i'd choose

[dmr]

Are you measuring voltage at the battery terminals? If not, and this is a long shot, just check that the isolator switch is not too blame.

 

............Dave

[Alf Roberts]

a little too long.... yes battery terminals when load is applied. they recover their voltage pretty quickly once the load is removed and there is no fault with the load.

 

I'm pretty sure they've had it, I'm just a little surprised at the behaviour of semi-traction batteries ( versus a starter battery) under these circumstances.