DPDT for series/parallel battery? AC->DC translation?

[dirtdad]

I am looking for a DPDT switch that can handle 72VDC 50A for doing a series/parallel battery reconfig. It seems switches are all rated for AC. So are fuses, breakers and other components. 2 questsions:

1) Can anyone recommend a switch ? I dont plan to do a relay. I plan to pull over, disconnect and switch manually.

2) All the switches I find on line are rated for AC, mostly household, like 120VAC 15A. But they are just switches, they don't care about AC vs DC as far a function goes. Looking at them and the wire gauge are made for, they look like they could handle the job. Is there some kind of conversion for VAC to VDC specs for simple components like switches, fuses, wire gauge, etc.? I am thinking just convert to total watts would be a good guideline. So for the above switch, 120VAC 15A is 18KW. If I want that to handle 72VDC, that would be 25A.

 

[frodus]

higher current DC contacts we wetted... and no, that doesn't mean water. They're made of different material, and coated with something to help extinguish the arc. They're also rated differently because the voltage no longer crosses 0, like in AC. You may be able to use a switch, but the life is greatly decreased. Just keep that in mind. 120VAC contacts do not = 120VDC contacts.

If you close the contacts under load, you're hurting the contacts.... just make sure there's no load while you're switching the bats. Also, realize, they you've got to switch all the batteries all at once to switch from s to p. It would be wise to have an on off on switch... that way you can turn all of the batteries off, then switch one at a time to series (or parallel). I'm not sure how you're wiring all of it up, just be careful not to short things out, or put 24V across a 12V battery.

 

[Drunkskunk]

Doc posted the wiring diagram of how to set up the switch, using a center off. that kills all the power as you're switching.

I'm working on a version with a precharge resistor that also acts as a bleed, so you don't fry the BMS when the capacitors discharge after switching back to parallel.