oldswamm wrote:I'm confused. What are you going to do with the pic on the mains side? Are you going to measure something there?
Measure the voltage of the pack.
The solid state relays are already isolated, and that's all I figured on having on the mains side.
My board would be at Batt-, and there's no practical way to isolate it that I can see.
I would ground the case, and the only thing not enclosed would be the battery.
The battery leads are connected to the mains, but heck, the battery is dangerous at 24s or more even without this.
<edit> Do you have a plan to isolate the battery from the mains? Because the battery is dangerous,it should be totally isolated, and well insulated whether using this charger or not. <endedit>
Here's the path that I see:
1. Mains is connected to the caps via the SCRs.
2. The caps are connected to the bridge.
3. The bridge is connected to Batt+ and Batt-
None of these are isolated. So that means that the pack is connected to mains voltage. And if it so happens that that the hot and neutral are swapped on the plug/socket, that the ground is in fact connected to the Hot side of the mains.
Now the control board.
1. Mains is isolated from the board via the xformer power supply.
2. Control board is using optoisolators to throw the SCRs.
So far the control board is isolated. Now here's the kicker:
* Connect the ground of the control board to Batt- !!!
All the isolation goes poof! The control board is now directly connected to both the pack and the mains with no isolation. And if that ground is connected to the hot side, then the potential of that connection can by up to mains voltage. It sabotoges all of the isolation that you're trying to accomplish.
Throw up a sketch, so we can see what the extra processor is for. It would be nice if we could come up with a cooperative design. The way things usually work on ES is there's discussion, then everybody does their own design. If you have a better way than I can come up with, and it's not to expensive, I'm fine with going with your design.
First Sketch. Hope it comes out OK.
The objective is to maintain the carefully constructed isolation of the control board. The only purpose of that ground connection is to measure the pack voltage. The extra processor's job is to measure voltages/currents on the mains/pack side, then communicate that information to the isolated control board via an optoisolated interface.
The point is that any connection between the control board and the pack/mains needs to be isolated. The power supply is. The SCRs are. The measurement needs to be too.
P. S. for those of you who want one of these chargers, but don't want to build one, you can buy it here.
I don't think I would want to be their insurance provider, though.
And the price!!
My P.S. from the diyelectriccar thread. This site: http://stores.directhvacsupply.com/StoreFront.bok sells the caps ultra cheap. I just purchased ten 80 MFD 440V run capacitors from them for $60 including shipping. Show be good enough to get the charger in the 30A range.