Why is my battery boiling dry?

[stuartwineberg]

Over the years I am reasonably comfortable discussing that noisy diesel guzzling lump of metal under my feet but the electrical side is still a bit of a mystery so I need some help.

My Hardy 25 has what seems to be simple set up. One domestic battery, one engine battery each on a separate breaker. There is one charger, a CTEK M200. Both batteries were new in 2010. I have always left the batteries on continuous charge on my boats. The problem is that the domestic battery is constantly boiling dry. Every time I check (about once a week) I am having to put over 2 litres of DW in there and the battery is quite warm. The engine battery is in the same box and seems fine - levels are OK and plenty of grunt when needed. What is happening?

 

[[2068]]

I'd start by using a digital voltmeter across each battery when they are charging.
It could be that the charger is faulty, and is overcharging the domestic battery.

 

[rogerboy]

+1

I'd start by using a digital voltmeter across each battery when they are charging.
It could be that the charger is faulty, and is overcharging the domestic battery.

 

[NoIllusion]

Get rid of the battery if it is getting warm/hot..........before it does some serious damage........it's goosed!!!

 

[stuartwineberg]

I'd start by using a digital voltmeter across each battery when they are charging.
It could be that the charger is faulty, and is overcharging the domestic battery.

Thanks - I can do that easily - what should be the right voltage? Also I assumed that the charger woud be pumping the same charge into both batteries - is that not the case?

 

[NoIllusion]

It could be a charger or alternator problem........or you could be simply overfilling it, but I'm guessing you know the correct levels. Boiling batteries can be very dangerous.........have it checked by a pro.

 

[volvopaul]

Stuart, the bad battery will have a duff cell, 2010 must be previous owner fit. Get a new one before it explodes.

 

[Firefly625]

Stuart, the bad battery will have a duff cell, 2010 must be previous owner fit. Get a new one before it explodes.

+1

 

[sarabande]

charging voltage of the M200 is like most chargers about 14.4V.

It sounds as if the charger is connected simultaneously to both batteries, yes ? Is it set up in parallel or series charge ?

If a single output from the charger then the hot battery has something seriously wrong with it. When you replace it, the new battery should be as near the same capacity and other characteristics as possible so that both batteries are 'balanced' when being charged. If you don't do this then the intelligence in the charger cannot cope with batteries which are significantly different.

Max capacity of both batteries for the M200 should be ~300AHr

 

[Spi D]

Agreed. The M200 charger isn't ideally suitable for two battery charging but if used for it, the two should be identical for them to be charged the same, when the charger treats them as one.

A charger with one 'channel' for each connected battery would cope better, but that's a different cup..

 

[stuartwineberg]

Thanks All. I've turned the charger off for the time being so at least it wont cook any more and will check out the size and type when I get down here but will certainly look at the voltages from the charger first. Now I have the fun job of wrestling the battery out from the lazarette