Battery woes update...

[Guest]

Following on from This thread I am finally back at the boat.

 

The battery in question that was hotter than the others is showing 11.73 volts (disconnected from the bank of course.

 

I then disconnected another on and it too is showing 11.73, I'm guessing this is because they have all been connected for serveral weeks and if the dodgy one is left unconnected it will fall to 10.5????

 

or

 

Is this pointing more to an over charging issue, in which case how best is it to check what the alternator(s) are putting out, is it just a matter of firing up the motor and checking across the batteries or is it best to leave things running for a short while with the engine running (I don't want to risk the potentially dodgy battery splitting/exploding though).

 

Oh and the Mastervolt combi now starts up in charge mode with no problem (I quickly flicked it on to check now off again)

 

Supplementary question -

 

I've had a good look at the way the batteries are wired today and had a proper look at the wiring diagram for the boat.

 

2 of the batts are served by a +ve lead marked 1 with a pen mark, 3 of them are served with a +ve lead marked 2 in pen and another +ve marked Inverter.

 

All the negs are linked together as per the wiring diagram for the boat. The wiring diagram has a section on it that says -

 

Charging circuit-

 

The starter alternator charges the starter battery and a bank of 2 domestic batteries through a split charge diode, and the domestic alternator charges a bank of 5 domestic batteries. There is now only 3 in this bank after removed one a couple of months ago, preumably at some point the previous owners reduced by 1 too.

 

However what I've noticed is that the positive side of both 'banks' are actually all connected by virtue of a connecting lead connecting the positive terminal in the two battery bank with one in the other. Effectively they are all connected together to form one bank it looks to me which is not what the boat diagram shows - modified by the previous owners perhaps???

 

Thanks for any help in advance.

[by'eck]

Firstly its highly likely all your batteries are knackered now so be prepared for a big bill

 

I assume the battery that was found hotter than the others (shorted cell) has been disconnected and disposed of. Almost certainly this is the root of your problems which I believe triggered the battery overtemp indication. Given the situation & time involved, your previously good batteries will have been fully discharged & left in that state for some time. Its possible some of their remaining life may be recovered with a good charge + equalisation if not sealed/AGM, but it seems doubtful.

 

From your description it appears you have two service battery banks, one serving the inverter plus a start battery. This seems unnecessarily complicated. Having a single larger service bank connected to your Combi would probably serve you better.

 

From your further description it looks as though someone has in fact joined the two (now diminished) banks together anyway. This should have been done with suitable sized cable say at least 70mm². If not then suggest its done correctly, however I would also add back the batteries that have been previously discarded when replacing the bank.

Edited June 14, 2012 by by'eck

[Guest]

Firstly its highly likely all your batteries are knackered now so be prepared for a big bill

 

I assume the battery that was found hotter than the others (shorted cell) has been disconnected and disposed of. Almost certainly this is the root of your problems which I believe triggered the battery overtemp indication. Given the situation & time involved, your previously good batteries will have been fully discharged & left in that state for some time. Its possible some of their remaining life may be recovered with a good charge + equalisation if not sealed/AGM, but it seems doubtful.

 

From your description it appears you have two service battery banks, one serving the inverter plus a start battery. This seem unnecessarily complicated. Having a single larger bank connected to your Combi would probably serve you better.

 

From your further description it looks as though someone has in fact joined the two (now diminished) banks together anyway. This should have been done with suitable sized cable say at least 70mm². If not then suggest its done correctly, however I would also add back the two batteries that have been discarded when replacing the bank.

 

Cheers - the wire connecting the banks is indeed marked 70mm² - I noted that.

 

I'm pretty much resigned to replacing the bank (luckily the tax man has just landed me with a tidy little refund - came at a good time) but I don't want to do this until I'm sure they are not being overcharged by the alternator.

 

How is best to asses what is going into them when the engine is running, after the engine has been running a while or just as soon as it starts up?

 

Ed to add - sorry I should have added - I haven't disconnected or disposed of the 'dodgy' battery - it's actually still in the bank and a bit risky perhaps I've got the charger on but I am visually and physically checking it every 15 minutes. The charger has been running now about 4 hours and I've got no sense of the same issues as I had when it was being charged last with the engine running.

Edited June 14, 2012 by MJG

[by'eck]

Cheers - the wire connecting the banks is indeed marked 70mm² - I noted that.

 

I'm pretty much resigned to replacing the bank (luckily the tax man has just landed me with a tidy little refund - came at a good time) but I don't want to do this until I'm sure they are not being overcharged by the alternator.

 

How is best to asses what is going into them when the engine is running, after the engine has been running a while or just as soon as it starts up?

 

Depends on battery state of charge before you start engine. Probably the simplest check would be to monitor the volts at the batteries. Check the service bank and starter battery with engine off. Lets say they are fully charged and indicate around 12.5 volts (with Combi off). Start engine. After a few minutes of running at a fast idle the service bank should read somewhere between 13 & 14.6 volts and starter battery something similar. Only be concerned if you see voltage approaching 15 volts or more.

 

Having said this I think your concerns of alternator overcharging are unfounded given that you found a clear shorted cell fault with a battery previously, and which explained all the battery boiling.

 

I note you have a split charge diode in the (smaller?) starter alternator. There will be a volt drop across this dependent on current flowing through it, but expect at least half a volt which will impact on the starter volt reading. A solution is to use a zero volt drop splitter or an external sensing alternator regulator, although this can only sense on one or other of the split outputs.

[simon&jan]

You must disconect that battery , it will bring all the others down ,then you might stand a chance of reviving the rest with a good charge .

[Guest]

Cheers all - too late to run the engine now - will do so in the morning and confirm what is happening.

 

Will also disconnect the 'offender'

[Arthur Brown]

Are you in a position to disconnect all the batteries and give them individually a good full mains charge? This MAY enable you to sort out the ones that hold a reasonable voltage from those that don't.

[Roger Crown]

Hi Martin

It looks like the Dog House has a ”dogs breakfast” for a battery set up

You are resigned to a new set of batteries; I would suggest you get back to a simple and basic set up.

1 start battery and a bank of cabin/ house batteries. Charge each set with a designated alternator.

Get rid of the split charge diode. Dependant on the size of your alternators you may wish to link the alternators then I would recommend using a Smartbank, preferably connected to a Smartgauge.

With the poor batteries it’s not going to be possible to ascertain alternator charging rates.

This can quickly be sorted when the new batteries are fitted.

Regards

Roger

[smileypete]

How is best to asses what is going into them when the engine is running, after the engine has been running a while or just as soon as it starts up?

Best way is a panel voltmeter and panel ammeter and a bit of basic know how and experience to interpret what they're saying.

 

Google for 'battery bulk absorption charging' and it'll give quite a few pages that explain these batt charging phases.

 

Once there's some understanding of what should happen normally it should be possible to spot early on when something's going wrong.

 

cheers, Pete.

~smpt~

Edited June 15, 2012 by smileypete

[bizzard]

I don't think you live on your boat Martin,so i think you probably only need 3 cabin batteries and 1 engine battery,cheaper,less connections to fail and easier to maintain and charge.

[Guest]

Update -

 

OK with them charged and the combi off and the engine running at fast idle I get 14.06 volts across the terminals of each battery so I am now much more confident now they are not being over charged with the engine running (noting though comments about being able to asses this correctly above).

 

As to the complexity of the system - yes it does seem overly complicated but it's what we have got. I would love to get it down to a more simple layout, in particular get it as depicted on the smart gauge site but to be honest I don't have the expertise to even begin to contemplate converting what we have got to something more simple.

 

I've already taken the 'offender' out of the bank and I have left the boat with the combi off and will go back in a few days to see what the remaining batteries are doing before I definitely decide what I do next.

 

Thanks everybody.

 

ed to add pic. in an attempt to clarify how the bank is wired at the mo. in case it helps. Nothing is to scale ref cable lengths etc, it just represents how they are connected.

 

The 1,2, and inverter labels relate to how each +ve wire is marked.

 

 

The 'offender' is far right at 90 degrees to the rest.

 

(Note we have a completely separate starter battery not include in the diagram)

Edited June 15, 2012 by MJG