Drained LA Batteries

[MaasGuy]

Hello all....We've had our 36' Albin at a boatyard for the past month or so....bottom paint, prop shafts etc. Problem is apparently the house bank of batteries (8 ea 6v LA) were completely drained. They have them on a charger now, but is there a way I can test them for future use? Or just pay attention to how fast they'll drain now? Thanks for any advice.

Guy
1999 36' Albin Express trawler

 

[O C Diver]

How old are the batteries?

Ted

 

[MaasGuy]

We think PO replaced them about 2 years ago....we've had the boat for about 6 months.

 

[Fleming]

I would slowly charge them up, then check the water level. Then perform an equalizing charge. After that the only way to truly know the capacity is to discharge them at the 20 hour discharge rate. https://marinehowto.com/under-load-battery-voltage-vs-soc/

 

[Don L]

We think PO replaced them about 2 years ago....we've had the boat for about 6 months.

They are going to be history!!!!!

No matter what happens after you recharge them and cycle them again to test, they are history. The thing you have to decide if it is OK for them to die in a month or 2, or 4, on THEIR schedule or whether it is best to replace now on your schedule.

I base this having been through it.

BUT

It you want you can fully recharge till they only accept 0.5% charge (so for 8 wired as series parallel into 12V that is 22amps) at 14.6-14.8V. And you can consider an equalization charge of 15.2V for a couple of hours. Then do a discharge capacity test and see where they are.

But if you are an off grid type needing those batteries I wouldn't go far from a supply choice.

- if a 24V system double the volts above and half the amps

 

[MaasGuy]

Thanks for the input…..sounds like it may be time to replace along with replacing the inverter/charger that doesn’t seem to be inverting.

 

[utclmjmper]

It certainly won't invert if the batteries are dead..>>>Dan

 

[BruceK]

At 2yo, it`s worth a try, but they could be toast,? sulphation from long term undercharge. Charge them as suggested and invest $10 or so in a hydrometer to check the specific gravity they reach. It should come with instructions, if not, check a Calder or other electrical manual for how they should read.

 

[Don L]

Btw bad lead acid are normally still usable during their death match and provide clues before completely dying

 

[PM]

Better replace them. They might take a charge but they are on their last legs. If you use the boat a lot they will last longer. With occasional use you will be disappointed.

pete

 

[BruceK]

This stuff is good for desulphating LA unsealed batteries. Obviously you can`t get it into sealed versions. Saved 2 of 3 for me years ago. Costs less per battery in larger pack.

 

[mvweebles]

Why did the batteries drain-down in a month? If you had a parasitic load that took them down to <6v? (I don't know what the flat-dead number is), they are likely dead. Many devices such as fridges etc. have auto-cutout at around 10.5v so do not take the battery to zero. There is some damage, but should be recoverable from there. If they had sat for 6-months or so, I'd be less optimistic due to the inherent 5%/mo loss typical of FLA batteries

Fingers crossed for you....

Peter