One battery down , disconnect ?

[billyfish]

I have 2 house batteries and one looks to have failed, black not green in the site thingy, both identical 110 Ah not holding charge should I disconnect it from the one that looks good ie green in the thingy. I seem to remember one will drag the other down. New one ordered but not here till next week and we are one the boat with radio,Giles Peterson, and fridge on.

 

[Refueler]

Yes ... as a fellow sufferer .. I wish I had disconnected my dud battery earlier as it probably caused the reduction of the 'good' one ...

 

[Trident]

Best to remove it form the circuit and then test it separately for voltage etc if you have the tools aboard to do so.

Until the new one arrives just charge the remaining one
more often

 

[Boater Sam]

The green eye is a meaningless thing. Firstly it is only in one cell, secondly it is only checking electrolyte level, not density.
Separate the batteries for an hour and then measure them individually.

 

[Mistroma]

The green eye reference would tend to indicate a battery often sold as maintenance free. i.e. Sealed and no way to top up.

It's possible you might get some more life out of it whilst waiting new batteries. It could be very low on electrolyte and simply adding deionised water then charging is worth a try. You could also check the other battery.

I've yet to see one that's actually sealed. There's usually a sticker and or plastic strip hiding the filling caps. Cells are sometimes dry but this type usually has a reasonable amount of extra electrolyte added when new.

It might give some extra capacity if the other one shows signs of failing. Never a great idea to fit one new battery if both are similar vintage and getting to expected lifespan.

 

[billyfish]

Well, damm it , disconnected the one I thought was down but the remained dropped to 50% overnight with nothing on not even a phone charger. So ordered another. They are 3.5 years old is that what you get for £200. Maybe lithium next time as some suggest

 

[Refueler]

3.5yrs is a bit short in my view ... I would be looking for 4 - 5yrs before losing performance ... unlike a cars where they should last significantly longer.

 

[Trident]

Well, damm it , disconnected the one I thought was down but the remained dropped to 50% overnight with nothing on not even a phone charger. So ordered another. They are 3.5 years old is that what you get for £200. Maybe lithium next time as some suggest

You should get more out of them than that if they are decent deep cycle LA batteries. Lithium will last decades but you'll need a safe way to charge them so probably a DCDC from the start battery and slightly different fuses so its not a straight swap and adds a bit to the price .. pop back to Chi some time if you want to talk it through but unless you're using the boat a lot it may be unnecessary

 

[Mistroma]

Well, damm it , disconnected the one I thought was down but the remained dropped to 50% overnight with nothing on not even a phone charger. So ordered another. They are 3.5 years old is that what you get for £200. Maybe lithium next time as some suggest

Have you looked at the electrolyte levels in both? Useful information to have. Could be overcharging if very dry. Could just be that it's worth checking from time to time and topping up. Might help with extending life of replacements.

 

[Refueler]

Have you looked at the electrolyte levels in both? Useful information to have. Could be overcharging if very dry. Could just be that it's worth checking from time to time and topping up. Might help with extending life of replacements.

Don't do as I did though .... I topped up the 'dead' battery and when I started charging it ... it started to drip out of vent tube ....

Only top up to cover the plates - leaving plenty of space for electrolyte expansion as the cells warm up / try to charge ...

 

[Mistroma]

Don't do as I did though .... I topped up the 'dead' battery and when I started charging it ... it started to drip out of vent tube ....

Only top up to cover the plates - leaving plenty of space for electrolyte expansion as the cells warm up / try to charge ...

Good tip. Many people don't know about this effect. I don't think expansion is primarily due to warming. The casing will also expand to some extent. I think thermal expansion will be around 1-2% and case expansion will reduce the effect to around 1%.

I'd guess it's bubble formation at the plates. There will be many micro bubbles formed, even before gassing is obvious and the gas will displace some liquid. It will get worse when there's vigorous gassing as that will propel some acid from a vent. The level will rise during charging but should subside later, even if none ejected from vents.

The mechanism isn't really important, just knowing it happens is useful.

 

[Refueler]

Only IF the battery charges up and appears to be useful - then top up to usual marks.

Because I have various uses for batterys - low wattage and high ... even near dead batterys have their uses ... as long as power demand is low - they can still deliver power for light load bench services. I try to extract every last bit out of my gear before the final bin !

 

[Mistroma]

Only IF the battery charges up and appears to be useful - then top up to usual marks.

Because I have various uses for batterys - low wattage and high ... even near dead batterys have their uses ... as long as power demand is low - they can still deliver power for light load bench services. I try to extract every last bit out of my gear before the final bin !

I also did that many years ago. I had a garage far from my flat when first married and an old battery worked well there for light and only needed to be charged a few times a year. That was pre-LED days. I imagine it would be a lot better now.

However, I sold my last lot of old boat batteries a couple of years ago as they'd just been sitting in my garage. I couldn't see any use for them in future. I moved to a new house with integral garage, solar and LFP batteries. They weren't even useful for a hut in my garden. I didn't bother running power either as it came with a small solar powered light and battery.

LEDs, battery powered tools, battery packs and falling Li-ion battery prices will probably reduce the need to keep old lead acid batteries to a very low level.

 

[billyfish]

I know i should have done more but needed to be ready to get back from the Dart so got 2 new batteries all working as they should do, got back OK and got the old batteries home. As someone said even though sold as sealed I prized the top off to find acid over the top of the plates,,,just. So going to top them up. Currently on pulse on a mains charger. Then I will trickle charge and see what happens. They are exide so I'm surprised they went down aged 3.5 years.

 

[Refueler]

I know i should have done more but needed to be ready to get back from the Dart so got 2 new batteries all working as they should do, got back OK and got the old batteries home. As someone said even though sold as sealed I prized the top off to find acid over the top of the plates,,,just. So going to top them up. Currently on pulse on a mains charger. Then I will trickle charge and see what happens. They are exide so I'm surprised they went down aged 3.5 years.

As long as plates are covered ... then that's ok.

There are 'pulsators' that can recover batterys - but they must be batterys that are so close to good that the pulsator can help. But usually when the battery fails - they do not recover sufficiently to be reasonable power source again.
You can often use them for low power things ...

 

[Mistroma]

I was pretty certain you'd be able to open the cells for filling. I have seen ones with little electrolyte left due to prolonged overcharging and you might have been able to get a little life back by filling. However, they usually have a fair amount of extra electrolyte as designed to be low maintenance, Approx.3.5 years normal use shouldn't have reduced the level below the top of the plates. Worth checking as it's an easy job.