Multi-voltage battery bank?

JSYmartini

JSYmartini

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A question for the panel:

I'm planning to fit a dedicated house battery bank this winter using 4 Trojan T105's connected in series (24V boat).
As with most boats I do have some 12v equipment onboard - car stereo, VHF, accessory sockets etc.
Currently this 12v is supplied via a couple of small 24v-12v convertors.
I'm wondering if it is possible to tap into the battery bank with separate cables in such a way as to get a 12v supply, also without just taking it from 2 of the batteries (best practice to charge & discharge each battery equally I understand)?
All independant of course from the main cables which would carry 24v.

C'est possible?
 
It works whilst using - discharging - the batteries tapping 12 and 24 Volts.
But there is a charging problem. The two batteries used for 12V will supply current both for the 12 V loads and the 24 V loads and will be discharged more than the other two. If they all are charged in series with a 24 V system, these two batteries will never be charged enough.

Hope this helps
Sandro
 
When I had a similar situation, I had a complicated system tapping 12v out of 24v. I involved changing over the two every week. It still gave problems, so I installed a 12v alternator, charging its own 12v battery, for the 12v equipment, and still had the 24v system totally separate. never any trouble after that.
 
Sandro said:
It works whilst using - discharging - the batteries tapping 12 and 24 Volts.
But there is a charging problem. The two batteries used for 12V will supply current both for the 12 V loads and the 24 V loads and will be discharged more than the other two. If they all are charged in series with a 24 V system, these two batteries will never be charged enough.

Hope this helps
Sandro
Click to expand...

Why not wire the 12v as two pairs of 6v series batteries connected in parallel? That should drain all the batteries equally on 12v and 24v.

Richard
 
I think the ideal situation is to either continue to run the 24 to 12v converters or
Set the new house batteries up as a 12v bank. Charge these from the 24v bank via a 24 to 12v converter. Use either manual switching or a VSR to turn on the 12v charging when the 24v is being charged. Thus you have the power of the 24v system for starting, anchor winch and or thrusters but the convenience of 12v for the domestic loads.
good luck olewill
 
RichardS said:
Why not wire the 12v as two pairs of 6v series batteries connected in parallel? That should drain all the batteries equally on 12v and 24v.

Richard
Click to expand...

pvb said:
I think a diagram is called for!
Click to expand...

So do I! I'm looking for the simplest solution, if trying to wire the batteries like this gets complicated and messy then I'll just stick with the convertors. Or swap them for one larger one at least.
 
JSYmartini said:
So do I! I'm looking for the simplest solution, if trying to wire the batteries like this gets complicated and messy then I'll just stick with the convertors. Or swap them for one larger one at least.
Click to expand...

It's probably not possible but I was suggesting wiring two 6v batteries together in series to give a 12v "block" and the other two 6v batteries in series to give another 12v "block". You can then wire the two 12v "blocks" in parallel to give 12v total with all batteries in use. Whether this will interfere with the 24v takeoff without additional switching I know not.

Richard
 
RichardS said:
It's probably not possible but I was suggesting wiring two 6v batteries together in series to give a 12v "block" and the other two 6v batteries in series to give another 12v "block". You can then wire the two 12v "blocks" in parallel to give 12v total with all batteries in use. Whether this will interfere with the 24v takeoff without additional switching I know not.
Click to expand...

I feel a diagram won't be forthcoming! ;)
 
JSYmartini said:
I'm wondering if it is possible to tap into the battery bank with separate cables in such a way as to get a 12v supply, also without just taking it from 2 of the batteries (best practice to charge & discharge each battery equally I understand)?
All independant of course from the main cables which would carry 24v.
Click to expand...

Best to stick with the converters.
 
Richard post#5,

Without a diagram I don't understand well your system.
If I understood the OP question, what I meant - and presents charging problems - is something like this:


IMG_7204.jpg

It looks very simple and practical but, in time, the bottom battery becomes more and more discharged or the top one overcharged.

Sandro
 
Sandro said:
Richard post#5,

Without a diagram I don't understand well your system.
If I understood the OP question, what I meant - and presents charging problems - is something like this:


View attachment 47818

It looks very simple and practical but, in time, the bottom battery becomes more and more discharged or the top one overcharged.

Sandro
Click to expand...

I agree that some switching would be needed to make the system work properly. It sounds as if the OP will need to stick with the current system.

Richard
 
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