DC leccy problem HEEEEEELP

[gonfishing]

the starboard battery bank of 3 x 110amp batteries are only lasting 4/5 hrs before voltage drops below 18 volts. These are all new and have been swapped out with a proven set of batteries with the same result. I have had a DC clamp meter on the system and with everything on, that would be on at anchor we draw a maximum of 11 amps,when the fridge compressor is running, average current draw is 5amps otherwise. With everything switched of there is no current draw,so apparently no leakage. I have checked the terminals to the starter motor and alternator and they are all clean and making good contact. This set up has worked perfectly in the past 3 years but now all of a sudden this problem has popped up. I am now at a loss as to what the problem can be, so any ideas out there I would be most grateful, I have spent dys on this and it is driving me mad!!!! I cannot use the boat with this problem so would like to get it sorted asap so that IF and When the weather breaks here in Wales I may get to use the boat!!!!
Look forward to the replies.
Regards
Jules

 

[NorthUp]

Check the charging system- your batteries are not being fully charged.

 

[billcole]

Maybe an internal short in one of the batteries. Try un-paralleling them and see if one of them discharges itself. Often caused by bits falling off the plates forming a pile at the bottom of the battery which then shorts across the bottom edges of two adjacent plates

 

[seamaster30]

the starboard battery bank of 3 x 110amp batteries are only lasting 4/5 hrs before voltage drops below 18 volts.

Can you clarify? If you have 3 batteries I would have guessed a 12v system, but you quote 18v as being low.

If you have 3 batteries giving 36V (unlikely) you would only have a capacity of (at best) 50ah, so 10 hours at 5ah draw.
Given your fridge and other items - that would probably be about right with older batteries?
5ah draw is a lot for 'normal draw' - What on earth have you got running?

 

[VicS]

Yes agree check the charging.

To run a 330Ah battery bank flat in 5 hours is going to take a pretty substantial current ( 66 amps in theory) and you could not fail to detect that sort of current. or notice the heat it would produce!

 

[gonfishing]

These are brand new batteries and we swapped them out with another complete set o 3 batteries, just in case we used a different brand in case of a bad batch.The system is 24 volt, general overnight loading is
Anchor light
TV maybe 3 hrs 4.5 amp draw
VHF overnight
Depth Sounder.
GPS for anchor drag alarm
Water pump
Fridge 5amp when compressor running.

Will be checking the charging system but I have had shore power on with the charger trickle charging the batteries

 

[Nigelhg]

How can you use 3x 12v batteries in a 24v system? Do you mean 3 sets of 2 12v batteries or just 3 batteries? It sounds more like you may not have found all the batteries in your boat...

 

[sarabande]

does the configuration you have quoted mean that you have 2 batts in series, and one in parallel with one of the others? If so then the "220 aHr" battery will not be charged as fully as the single 110 aHr, and that will drag the whole system down.

How is the charging arranged ? Is it 12v into each of the batteries, a mixed 12/24v, or a full 24 v. ?

 

[paulrae]

Do you have a diode splitter?

I have a similar problem with my engine start battery. On the output of the alternator there's a diode splitter (Victron Argofet) which takes the output and separates it for the engine start battery and the domestic battery.

A while back I noticed that starting was a bit laboured, so charged the engine start battery directly from the shore power. Over the next couple of weeks of frequent use (both starting and motoring - hence charging) I noticed the laboured starts again. 'Battery's obviously jiggered' thought I. Replaced and binned the old 'un.

Now the problem's occurring again. Checked the circuit and there's an appreciable volt-drop across one of the diodes (0.6V). Spoke to Victron who weren't very helpful, but advised that 'it is probably broken'. As some current is getting through, and I'm based on a pontoon, so can charge from shore power, I can put up with it for the moment.

I'd suggest that you work your way round your charging circuit, ensuring that there's no large volt-drops across any joints of components. You could also check the current into the battery by switching off all of your loads and using a clamp meter (one that's suitable for dc!) on the cable.

Charging the bank from shore power should provide a useful datum to compare discharge time when compared to alternator charging.

Good luck finding the source of your problem.

 

[VicS]

there's an appreciable volt-drop across one of the diodes (0.6V).

That's normal and is the snag with using a diode splitter

There are two common solutions. One is to use a battery sensing alternator, which will then increase its output voltage to compensate for the drop across the diodes. The other is to use a voltage sensitive relay (VSR) in place of the diode splitter. That allows one battery , usually arranged to be the starter battery, to charge to a preset level before the connecting and charging the other. No diodes so no volts drop! (There are electronic gadgets that do much the same with very little volts drop too, eg X-split)

HOWEVER The Victron Argo Fet is not it seems an ordinary diode splitter. They dont say what it is exactly (something similar to the X-split maybe??) You should not see 0.6 volts drop across it. It should be only 0.02v to 0.1 v depending on current flow.

Yours is either defective or you have a bad connection on one terminal.

 

[VicS]

How is the charging arranged ? Is it 12v into each of the batteries, a mixed 12/24v, or a full 24 v.

I originally assumed this was 3 x 110Ah 24 volt batteries but I now realise that is rather unlikely.

Possible explanation is 3 x 110Ah x 8 volt batteries in series (EG Trojans)

If that is the case then the capacity of the bank is 110Ah not 330 Ah. That would begin to put a different slant on things but would still require a substantial current to run the bank flat from fully charged on 5 hours ... something like 20 amps.
You still could not fail to measure or notice that going to waste somewhere. 20 amps at 24 volts is best part of half a kilowatt!

 

[griff191]

Hi, I have just joined this forum, and came across your post.

I have held a senior position as an electrical engineering manager with one of the major boat manufactures for many years, before retiring this year.

In my time I have come across many atrocious fixes for electrical problems and installations.
Your post worries me with regards to safety at sea.
Please seek profession help from a suitable qualified marine electrician. Not cheap but neither is your life or someone else’s.

However, two 6volt 100ah batteries connected in series =12volt 100ah
Two 12 volt 100ah batteries connected in parallel =12volt 200ah
Two 12volt 100ah batteries connected in series=24volt 100ah.
Please employ a qualified engineer to check your system.

 

[gonfishing]

I am at the mercy of the electricians that have had a look and they are baffled as well(one of them is a DC wizz by all accounts) The bit I do not understand is that exactly the same configuration of batteries has not altered, nothing has been added or taken away from the system, except the mastervolt charging system which managed to fry 6 batteries, I am using the original onboard shore charger, which I have assumed is a 24 volt charger supplied at time of manufacturer. I think I will investigate the charging circuit further. Will keep ypu all posted.

 

[seamaster30]

I am at the mercy of the electricians that have had a look and they are baffled as well(one of them is a DC wizz by all accounts) The bit I do not understand is that exactly the same configuration of batteries has not altered, nothing has been added or taken away from the system, except the mastervolt charging system which managed to fry 6 batteries, I am using the original onboard shore charger, which I have assumed is a 24 volt charger supplied at time of manufacturer. I think I will investigate the charging circuit further. Will keep ypu all posted.

The bottom line, is if the batteries are starting full charged, and going flat, they are either knackered, or the power is going somewhere.

You need to double check there is no possibility of anything else drawing power that is not going through the cable you have your clamp meter on.

You need to confirm the battery condition, charge and capacity, and if the power is being measured correctly and you are not getting the expected capacity out of the batteries then they are dead.

You need to check the charger is set correctly and not cooking the batteries. - It sounds like that's happened in the past, so would be my first port of call.

Were the new batteries connected up exactly as the old ones were? - If you got some connections wrong I would have thought it would be obvious in the voltage readings, but may be worth a double check.

Do you have an inverter connected directly to the batteries that you are not measuring the power consumption from?

 

[bobgoode]

More info needed:
are any of the batteries dedicated to engibne start?
are you sure it's a 24 v system?
if so likely only two are for the board and the other is engine start
Twin engines, two start batts???

 

[nimbusgb]

You really do need to find out how those batteries are wired together to give you 24v

 

[gonfishing]

A real conumdrum.
3 x 12v brand new batteries fitted this afternoon @ 110 amp each 2 in parralell one in series this has been the case for 4 years, no previous problem. DC amp meter showing no current draw from distribution board. Consumption as previosly stated at max 11 amps when fridge compressor working, have gone around the boat cannot find anything getting hot, batteries showing 26.9 volts on test meter when fitted, after 3 hrs down to 24.6 volts, have checked terminals to both starter motor and alternator all are clean no apparent arcing. Voltage will drop quicker now over the next hour or so and fall to 18volts if things have not changed. Will keep you all posted

 

[halcyon]

I am at the mercy of the electricians that have had a look and they are baffled as well(one of them is a DC wizz by all accounts) The bit I do not understand is that exactly the same configuration of batteries has not altered, nothing has been added or taken away from the system, except the mastervolt charging system which managed to fry 6 batteries, I am using the original onboard shore charger, which I have assumed is a 24 volt charger supplied at time of manufacturer. I think I will investigate the charging circuit further. Will keep ypu all posted.

If you start the engine what voltage is shown on engine voltmeters at the helm ?

If you have 24 volt, you may have a fourth battery tucked away, if so this will kill the three new ones you fitted.

The 0.6 volt drop may not mean a fault, a number of FET splitters state 0.1 volt drop at float charge, this means at a very low current, so it could be higher with a load. MOSFET's have a known resistance, so more current equals more volt drop, you improve the situation by fitting multiple FETs, but you still get varying volt drop.

You need to sort out facts before throwing money at the problem.

Brian

 

[VicS]

A real conumdrum.
3 x 12v brand new batteries fitted this afternoon @ 110 amp each 2 in parralell one in series

Thats got me totally puzzeld, others too I supect.

Are you saying the batteries are connected like this?
Is this because you have both 12 volt and 24 volt equipment on board?

 

[sarabande]

the only thing I can think of is that you have in effect two batteries of different sizes; one of 220 aHr, and one of 110 aHr.

If you charge the all three, the 220 aHr batt will not reach its full charge as soon as the 110aHr one It may be that the charger is reading the 110 as 'full', and so shuts down to float charge.

But if everything is shut down, and there is no flow from them, I cannot see where the juice is disappearing to. Have you tried charging, then disconnecting all three at the terminals and then see if the batts drain ?

Where do the charger to battery cables connect ? Am I correct in understanding that you have two chargers connected - ah, could there be a current flow from the batts back into one of the chargers/inverter. Sounds exciting if there is.

Have you disconnected the chargers in turn to see if the batts fail ?