Battery woes...

[jacob]

Morning all,

 

I'm having a bit of a headache with my batteries, wondering if you could help me diagnose the issue. For context, we're liveaboards at a marina, so we're almost always plugged in to a shoreline

 

Around 3 months ago one of our batteries started offgassing pretty badly - I assumed it was just a knackered battery, so took it out the circuit. Then a second battery started offgassing a day later. I did some fault finding and reckoned that the old dusty battery charger was the issue. I got another new battery and a shiny 12V 30A Victron blue smart charger. I set that all up and everything was working flawlessly...

 

...until last night - at around midnight I noticed the smell again and another battery was offgassing. I disconnected everything from the circuit and this morning inspected everything. The dead battery is another of the old ones that came with the boat. Looking at the victron app (pictures attached) it seems the last cycle lasted 50 days and the vast amount of this was in storage mode. I've also attached a picture of the batteries, the duff one is the second from the bottom (although the bottom one has also lost its green 'healthy' indicator)

 

Any ideas what's going on? My plans for temporarily fixing this is to either remove the old battery from the circuit, or to go all the way and set up the charger as a power source, with no batteries connected. A long term fix would be much appreciated as I don't have the funds to replace my battery setup every 3months...

 

Thanks

Edited November 26, 2022 by jacob

[nicknorman]

Likely the old batteries are all the same age, so it can’t be too surprising that they are dying at much the same time. I would just get rid of the old batteries and keep whatever new ones you have in circuit.

[mrsmelly]

Ive said this many times before. The first thing I do when buying a boat new to me, is replace all the leisure/service batteries. You dont know how old or how good they are. Batteries are like diesel, use and replace. Dodgy batteries can cause all manner of peculiar problems with the electrics. Having seen one after it exploded on a commercial boat I am licensed for you wouldnt believe the devastation one can cause, and that was one we knew and maintained and it still went bang whilst on charge.

[jacob]

Cheers both, have removed the two old batteries from the circuit

 

 

[David Mack]

53 minutes ago, jacob said:

 

I assume the top one is the engine start battery and the bottom three are the domestics. When you go back to more than one domestic battery it would be better to connect to the opposite corners of the battery bank like this:

 

http://smartgauge.co.uk/batt_con.html

 

[Tony Brooks]

The gassing, especially if you get the dangerous rotten egg smell, in the circumstances you describe is almost certainly caused by internal shorts developing in a cell or cells. First the cells gas, then as they dry out produce hydrogen sulphide, eventually they dry out, spark internally and ignite the hydrogen being produced.  At that pint the cell lid splits, the case may fracture and the acid in other cells sprays all over the place.

 

If any individual cells get hotter than the rest, are dryer than the rest, the charge time gets longer and the discharge time gets shorter all indicate shorting cells, as is a higher charging rate maintained for longer than usual. All indicate the battery or ideally the whole bank needs replacing ASAP.

 

Not caused by short circuits but by sulphation that results in a loss of capacity, if you see the ends of the battery case bowing it is time to start saving for new ones before they start shorting in the cells.

[ditchcrawler]

On 26/11/2022 at 09:40, jacob said:

Cheers both, have removed the two old batteries from the circuit

 

 

If you are on shore supply 24/7 you don't require a big battery bank, one good one should do the job OK