Battery Charging

[Castaway]

Having not been to my boat for the last couple of weeks, arriving today I had no 12V leisure power. Engine started like clockwork, but the second alternator doesn't kick in to charge the leisure batteries which have presumably run a little low during a few weeks stood. Having checked all the obvious things (I think!), I found that using a portable inverter/12V power supply to inject 12V ish into my 12V circuit this voltage will trigger the leisure alternator and hey presto dashboard gauge is showing 14V and everything is working ticketyboo?????>.

 

Would it be normal for the leisure batteries to power the trigger to switch on the second alternator? Any possible amendments to improve this scenario?

 

I think the boat was set up to be on shore power, configured with a battery charger from 240V to a trickle into the 12V system.

 

Any thoughts please?

[Phil Ambrose]

Having not been to my boat for the last couple of weeks, arriving today I had no 12V leisure power. Engine started like clockwork, but the second alternator doesn't kick in to charge the leisure batteries which have presumably run a little low during a few weeks stood. Having checked all the obvious things (I think!), I found that using a portable inverter/12V power supply to inject 12V ish into my 12V circuit this voltage will trigger the leisure alternator and hey presto dashboard gauge is showing 14V and everything is working ticketyboo?????>.

 

Would it be normal for the leisure batteries to power the trigger to switch on the second alternator? Any possible amendments to improve this scenario?

 

I think the boat was set up to be on shore power, configured with a battery charger from 240V to a trickle into the 12V system.

 

Any thoughts please?

 

I'm no expert but some alternators are self exciting while others need a 12v input of some sort, this is often provided by the charge warning light circuit, have you ablown bulb maybe.

 

Phil

[by'eck]

Having not been to my boat for the last couple of weeks, arriving today I had no 12V leisure power. Engine started like clockwork, but the second alternator doesn't kick in to charge the leisure batteries which have presumably run a little low during a few weeks stood. Having checked all the obvious things (I think!), I found that using a portable inverter/12V power supply to inject 12V ish into my 12V circuit this voltage will trigger the leisure alternator and hey presto dashboard gauge is showing 14V and everything is working ticketyboo?????>.

 

Would it be normal for the leisure batteries to power the trigger to switch on the second alternator? Any possible amendments to improve this scenario?

 

I think the boat was set up to be on shore power, configured with a battery charger from 240V to a trickle into the 12V system.

 

Any thoughts please?

 

Yes it would be normal for the alternator to be exited by the battery(s) it was feeding.

 

To improve the scenario don't let it happen again. I don't mean to be cynical saying that but in letting them run that low you have probably significantly reduced their life, unless you are using true deep cycle batteries. It could be they are already knackered of course.

 

In any case if leaving the boat for a considerable time, ensure there is no drain on the batteries & arrange a trickle feed from solar panels or if mains available, a smart charger that can be left in float mode. This will offset internal discharge & sulphation.

[Castaway]

Thanks, I did leave the central heating pump on which is undoubtedly the cause for completely flattening the batteries! Since then the opportunity to re-charge has been limited to just a few hours at tickover so I guess I'm nowhere near the full charge state or any kind of strength.

 

The batteries are sealed, when peeking in the viewing window they are showing Green dot's which is suggested as being fine.

[Arthur Brown]

If a fair sized house battery has gone to totally flat in "a couple of weeks" then where is the power going? A working battery should lose less than 1% per day from self discharge. FIND the energy loss route quickly as deeply discharging the batteries will kill them very quickly.

 

Yes it's quite normal for all forms of clever charger to refuse to start a totally flat battery If there is too little voltage the charger doesn't recognise that any battery is connected. The usual work round is to apply power as you did, but a single jump lead linking the +ve terminals on both batteries can work too.

 

I would strongly suggest a small solar installation. A sub £50 cell would keep the batteries topped off against self discharge over the winter. I bigger and betterplanned solar aray would provide useful summer power too. -yes a small solar panel in the window is enough to keep up with natural self discharge, more would be better.

 

Getting your batteries back to 100% SoC is important for their life, at this time of year that means diesel or mains.

[Arthur Brown]

If the batteries were flat to the point where the generator wouldn't start to charge them they are not charged after a "few hours on tickover" more likely they need 10 hours on cruise RPM.

 

Get a good volts reading and watch it change over a few hours. Rapidly it should come up from it's flat stage to 12ish volts then as the generator pushes power in the volts should rise to 14 ish then maybe onto 14.4 after that the auto charge controller should back off to a float voltage in the order of 13.2 - 13.6v After an hour or two at the float stage your batteries are fully charged. How that relates to their original fully charged state is a measure of their place on their life cycle that the batteries are at.

[Castaway]

Thank you. Will be moving the boat to pastures new soon and estimate a good 7-8 hours in transit. I'll take some readings before and after and see how they look! The Aldi boiler is now out so won't be leaving it switched on again!

[by'eck]

Thank you. Will be moving the boat to pastures new soon and estimate a good 7-8 hours in transit. I'll take some readings before and after and see how they look! The Aldi boiler is now out so won't be leaving it switched on again!

 

Don't rely on those battery state indicator thingies either. They are notorious for sticking so always give the battery a shake if you can before checking the colour. Much better to use a hydrometer or even accurate voltmeter of course.