24V to 12V series / parallel battery switch

AntronX

I have 2000W 12V input inverter, but 24V battery system. For a while I have been using 600W 24V input inverter for all my needs. I am planning to get into surface mount circuit board prototyping at home, and I want to run everything from my solar system. I would need to power laser printer and small reflow soldering setup. I do not want to switch from 24V system back to 12V, neither I want to buy another inverter. I also have 15 of 75Ah 12V used UPS batteries currently not in use.

My idea is to make two 12V banks using 7 of those batteries in each bank connected in parallel. Then I would switch those two banks from series to parallel using 3 A/B switches ganged together. I need help finding such switch. I think I could use heavy duty AC 3-phase A/B transfer switch, but where can I buy one?

I will switch to 24V when I need to charge those batteries from my solar system. At the same time, they will share the work with my main 24V bank. When I need to use my 2KW inverter, I will switch them over to 12V configuration. I am aware of large inrush currents that I may have to deal with.

I attached the diagram I drew using Gschem in Linux. Does anyone know of better drawing program for Linux or Windows?

niel

Re: 24V to 12V series / parallel battery switch

this 3 switch idea does not seem to be a good idea to me. i don't see you physically ganging them first of all. even if you manage to gang them the odds of all of them switching at the same moment is very iffy and there would be a high probability of a short occurring. finding a switch with your requirements in a single package would be a challenge. 3pdt high current.

AntronX

Re: 24V to 12V series / parallel battery switch

I was thinking about those heavy duty mechanical knife switches, like the ones used of electrical service disconnect. But for this, I would need dual position single throw type, instead of just single position ones.

niel

Re: 24V to 12V series / parallel battery switch

the heavy knife switch would allow for a neutral position avoiding a possible short circuit. i'm not sure who might still make them, but i think it would be possible to get this in the proper high current 3pdt you need.
if you find such a heavy duty knife switch manufacturer with reasonable costs, please share it with us.

AntronX

Re: 24V to 12V series / parallel battery switch

Found beautiful knife switches made by Filnor. I won't bother asking their prices, just by looking how nice they are they must be out of my reach. http://www.filnor.com/html/products/knife-switch.php But now by looking at them, I got few ideas how to homebrew a switch for myself.