DC leccy problem HEEEEEELP

[bobgoode]

Clearly a problem somewhere...I suspect that the batteries are not wired as you state. I would start by careful checking of this aspect. A more likely scenario is two in parallel for the domestic comsumption and a third wired as an engine start. ote the parallel pair and the engine start should not be linked.

 

[rhumlady]

Quote "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. " Unquote

If this is the case and the two parallel batteries are not getting fully charged then the fully charged on may be topping them up. Just a thought. But the original post says it worked fine until recently I believe. Strange. If Vic's drawing is correct then It is a bit strange although you would be able to tap off 12V at the centre point for the services.

 

[William_H]

@4V Batteries

Clearly there is some confusion about the battery connections. It is conceivable that the 2 batteries in parallel are connected negative to the earth side with the single battery connected in series to give 24v to earth. This would be arranged so that 12v could be tapped off to feed domestic requirements while 24v is available for engine start. However the arrangement would need 2 charging sources one at 12v to charge the greater demand at 12v and another at 24v for the engine start. This would have to be reproduced boith for engine driven alternator and shore charging.
The best arrangement for a 24v system is to run everything possible on 24v and use a voltage converter to provide 12v for those services demanding 12v.
If indeed you have the battery connections as described by you with no tappings off the 12v then best practice would be to remove one parallel battery or add another to make each 12v part of the 24v symetrical. But yes the 3 batteries could have functioned in an apparently satisfactory manner for a long time.(as a 110AH battery

Regardless of the above. One advantage of a 24v system is that the connection between the batteries in series is available. So if your 24v system reads low you can use a multimeter to check which of the 12v batteries is down. If it is genuine discharge they should both be equal voltage ie 11v each. But if one battery has died or been discharged on its own then you will read low voltage on one 12v battery and normal on the other.
If you have the 3 batteries connected as you describe then you would expect the one 12v in series to be discharged first however it is also likely that the 2 in parallel are not being fully charged while the single battery is so there may or may not be a difference.

So it is all very confusing. You describe it as the starboard battery set up. Does that mean there is a similar port battery set up. If so is it wired the same with similar 3 batteries. Yikes!!!!

I think an ideal set up would be 2 X12v batteries in series for each engine start. One set could suffice.
A 24v domestic bank of 2X12 in series or 4x12v in series paralell for domestic with diodes from each engine battery system to provide charge from the engine alternators and a 24 to 12v converter for 12v domestic systems. You need provision for jump start from the domestic batteries to either engine battery bank if needed.

I wonder if there are 3 batteries in each side for weight distribution symetry that are connected in a more conventional style.
So it is all very difficult without seeing the system (and refraining from redesign) good luck olewill

 

[gonfishing]

I have now removed the third battery and have 2 batteries connected in series to give me the 24 volt engine start and domestics requiring 24 volt I also have a 24 to 12 volt dropper to supply the 12 volt electrics fitted, I now have a potential 220amp hour bank, both batteries have been removed and independantly charged and both are showing 13.8 volts each and 27 volts in series. Stll no eveidence of anything getting hot so will keep you all posted.
grr this is frustrating.

 

[VicS]

I now have a potential 220amp hour bank,

Sorry but 2 x 12 volt, 110Ah batteries connected in series to give 24 volts only gives you a capacity of 110 Ah!

In parallel they'd give you 220 Ah but of course only 12volts.

To get 24 volts and 220Ah capacity you will need 4 x 12volt, 110Ah batteries connected in a series - parallel configuration.

 

[markdj]

If you are willing to fly us out, we can look at your system and can guarantee competitive rates and that we can most definitely fix your problem. I don't know what the problem is currently but you definitely need help.

Mark
www.boatdoctorni.com

 

[hightech]

You either to lose a battery or gain a battery.

For 24v systems basedon 12v batteries, you need them to be in pairs, batteries in the configuration you have will give you the problem you describe.

 

[grumpy_o_g]

Victron Argo FET uses FET's so doesn't have the barrier voltage of a conventional semi-conductor diode to overcome.

In a normal diode with a p-n junction you will need about .6 volts to "breakdown" the barrier at the junction before current can flow freely acroos the diode. Obviously, if you try putting voltage across it the other way it won't allow any significant current through.

 

[markdj]

Having only one set of batteries for your domestic and engine is very bad practice and even running down your domestic battery bank to anything lower than 24.4volts is going to seriously reduce your battery life expectancy.