DIY open source lithium BMS (battery management system)

[ericbecky]

Thanks for getting this project so far along. It's been a lot of fun and good challenge for my brain.

For now I'm not sure how much farther I'll be going since this fits my needs.

Probably won't think about it until the end of September when I get a bit more free time.

[Daox]

I made some progress on my BMS this weekend. I worked on the electronics up in the front of the car. This mainly just is the SOC meter and on/off switch. The pain is trying to fit everything I want into a blanked out dash insert. I think I have it all laid out so it'll work, but it took some time to put together.

Here is the blanked out dash insert with a hole cut in it for the SOC gauge.








Here is half of the circuit board that will mount up to the dash insert. The other half will have the shift register and voltage regulator on it. The toggle switch is for the plugin kit. The momentary switch is to put the Prius into EV mode.

[Daox]

I've been working on the second board for this section of electronics. Its been interesting trying to cram everything on the board, and I still have a little ways to go...

Here is the second board with most of the components on it.






Here is how it will attach to the first board.

[skeeterb]

It's been a while since I've posted on this thread, but I'm thrilled by the progress that you are making Daox. If I were to convert I'd probably use one of Paul's designs for a motor controller and your BMS to keep the batteries managed, that would probably really keep the costs down. It would mainly be the batteries, the motor, and the few other important bits like the fuses and contactor that would make it pretty costly. Keep up the good work and keep us informed

[shauger]

Great thread! I have quite a few 60 amp-hr LFP large format cells leftover from a school project. They are new - we never used them. Send me a PM if you're interested.

[Daox]

Thanks skeeterb and shauger. I can't wait to get the full system into the car and try it out. There just always seems to be one more thing to do before that can happen!

[skeeterb]

Originally Posted by Daox

Thanks skeeterb and shauger. I can't wait to get the full system into the car and try it out. There just always seems to be one more thing to do before that can happen!

Doesn't it always seem that way?

[Daox]

Haha, yes it certainly does.

The soldering on the display/switch panel is all done except for connecting the wires that go back to the arduino. I also have it mounted in the plastic dash piece. Sorry, I didn't snap any pictures of it yet.

One thing I am questioning is how to attach the wires to the board and stress relieve them. The wires are only phone/ethernet line, so they're probably 28 gauge or so (tiny). I need a way to hold them in place so they don't break over time.

[Daox]

Just a small update. I finally snapped a picture of the mostly done SOC gauge and on/off switch. I still have to pop a hole in it for the EV button switch. The LED bargraph is a bit more inset than I had hoped. I'm contemplating unsoldering it and adding a socket under it to bring it up a bit more, but I'll probably just live with it.

[skeeterb]

Looks pretty good Daox.