24v Inverter off 12v battery bank

[Zero]

I need to run a 24v Inverter off of my 12v battery bank, what is the best way to do this without creating uneven charging?

Thanks,

Z.

[veewee77]

unless there is a way to connect those batteries in an even method and get 24 volts, there isn't a way that won't wase a lot of power. . .

Why do you have to keep the batteries at 12V?

[zmoz]

The ONLY practical way is to rewire the batteries for 24v.

[ghurd]

Why not get a 12v inverter?

G-

[RobD]

You can run a 24 volt inveter off a 12 volts pack but you will have to split the batteries to supply your 12 volts needs. When you do make sure you balance the legs so that the 12 volt legs each have the same current draw on each leg. (Do this with balanced loads on  each one)

Run the batts in series to make the 24 volts then tap your 12 volts off each leg.

RobD

[Zero]

My system generates at 12v, and I have a nice old APC1250 UPS with dead batteries but it is 24v and I want to run it from my batery bank, so how can I charge at 12v and take off 24v to the UPS without creating an imballance in the bank?

Dan, can you clarify that abit for me, I'm not sure what you mean but it sounds good.

Z.

[Zero]

RobD, sorry dont know why I called you Dan...

Is there no edit button in this forum?

Z.

[Opera House]

I assume you have an even number of batteries to place them in series.  If the charging system is 12 volt, you could build an alternating relay that connected the charger to one set of batteries for 5 minutes and switched to the other set for 5 minutes.  This could easily be done with a MC14541 timer chip and a DPDT relay.  If solar, this could be run off the panel power so it "sleeps" at night.  One thing people don't think about is that relays have a life of about 500K.  If you count the number of cycles in a year, that adds up fast. The timer could be set up for periods of hours for less cycles.  The charger electronics should keep the batteries balanced.

[RobD]

If you are not running anything off the batteries but your 24 volt inverter you can run them in series ( 2 batteries to make the 24 volts)

You will need a way to charge the two 12 volt batteries independently of each other, which means two charges or one that alternates between the two. Cheap chargers can be had at Electronics Goldmine for about $15.00 each and you can tie the ends that go to the solar cells together and run the independent ends to each battery. This will charge the batteries evenly and supply your UPS.

RobD

[Opera House]

I wouldn't tie he inputs of two seperate chargers together unless you want to see a lot of smoke.  That would short out one of the batteries.

[ghurd]

I think he means with a battery isolator.

[ghurd]

Now that I think of it, the isolators I've used would make majic smoke. Not good for this.