Help! Batteries not holding charge

[rallantando]

I'm a novice boater and recently acquired a narrowboat. She was running completely smoothly, including two cruises, until this weekend when the batteries have stopped working. Everything works fine when the engine is running, but as soon as it shuts off everything (including the inverter, charger and 12V system) turns off.

Looks to me that the batteries are not holding charge but not sure why this would be. I did accidentally run the batteries completely flat, but have since run the engine for about 10 hours to fully charge but they're not taking. Any help?

Specs:
- 5 x 200Ah Victron GEL Deep Cycle Batteries
- 3Kva Victron Phoenix MultiPlus 12/3000 Inverter Charger
- Victron 3600W 230v Isolating Transformer

[Alan de Enfield]

It very much sounds like the batteries are totally 'goosed' and have no 'capacity' left they can still be 12v when charged but instead of having 200 ah capacity they are now dead and may only have a 'few' ah.

 

Get them as fully charged as you can.

Find a known load (an old 50watt headlight bulb is ideal)

Connect the bulb to each battery individually (with nothing else connected) and see how long it takes for the voltage to go down to around 12.2 volts.

 

It is very rough and ready but will indicate if the batteries are any good.

 

12.2 volts is the reading for a battery at 50% charge.

50 watt bulb will draw ~4 amps

If your battery goes down to 12.2 volts after (say) 4 hours then you know that your capacity is :

 

4 amps x 4 hours x 2 (you have only used 50% of capacity) = 32Ah battery capacity remaining.

 

Do the batteries separately as one of them may be very poorly and dragging down the others.

 

When you are charging the batteries do the get VERY hot (untouchable), - maybe just one of them gets hot.

Are any of the batteries misshapen (ends distorted) ?

 

Report back when you have done the tests.

 

 

37 minutes ago, rallantando said:

I did accidentally run the batteries completely flat, but have since run the engine for about 10 hours to fully charge but they're not taking.

 

10 hours is unlikely to be sufficient to recharge 1000Ah of batteries via an alternator

 

How many amps rating is your battery charger ?

(there should normally be another number after the 12/3000/ ??)

Can you not go onto a mains hook-up for a couple of days ?

Edited February 12 by Alan de Enfield

[Tony Brooks]

Is the alternator(s) charging the batteries? Is the alternator belts) properly tensioned? What is the battery voltage when revving at (say) 1200 to 1500 rpm.

 

There is a lot of difference between charging for 10 hours on idle and 10 hours at (say) 1200 rpm so what revs do you charge at, and is the 10 hours in one hit, or made up of several shorter time periods.

 

While charging, feel all the cell tops to see if you have any local hot spots indicating an internal cell short circuit, because after 10 hours of charging the batteries should have lasted a few hours unless you also do something daft like running a mains heating device from the inverter. A cell short circuit will vastly extend the charging period required and will also start discharging the batteries as soon as charging stops.

 

 

 

 

[nicknorman]

Electricity is invisible and we are not able to smell it from this distance! In other words, the only option for resolving this is to take some measurements. You have a very large battery bank, perhaps the charging system has never worked and you have only now flattened the batteries. Or perhaps the charging did work but now doesn't.

You need to measure the voltage across the battery terminals with the engine running, to see if the problem is that it is not charging, or whether it is that the batteries are knackered ( the former is the more likely because it is unlikely, though not impossible, that the batteries are suddenly completely knackered).

What engine? What alternator arrangement? What is the behaviour of the alternator warning light(s) on the panel (should be on when you turn the ignition on, and go out after the engine starts)

 

One easy answer could be that the domestic battery isolator has either been turned off by accident, or is faulty (high resistance, melted plastic) and the 12v systems are being run directly from the alternator. What sort of battery isolator is installed and is it on? If it has a red plastic key it has probably melted and disconnected the batteries

[Midnight]

Have you accidently knocked the battery isolater switch off? It's easy done.

 

 

 

12 minutes ago, nicknorman said:

One easy answer could be that the domestic battery isolator has either been turned off by accident, or is faulty (high resistance, melted plastic) and the 12v systems are being run directly from the alternator. What sort of battery isolator is installed and is it on? If it has a red plastic key it has probably melted and disconnected the batteries

 

Or is the red plastic key lying on the floor?

Edited February 12 by Midnight