Recent content by markb

Replying to myself, here, in case anyone comes across this post with the same question. So the way this works is: 1) You need to set a reasonable amp-hour value for OAH. This is is used the the percent calculation. You can dial in a more exact value later. 2) Either charge the battery to what...

I have meter #2 above. I've had it a while, and it's showing current and voltage correctly. But it always shows the battery SOC as 100%. How do I get this to work? Any hints?

Not yet. Once it's a complete BMS, I might do that, but right now, it's more like a proof of concept. And really all I've done is taken the original code (linked in my previous message) and made a few hacks to it.

I have the teensy talking to the battery module and logging the cell voltages and temperature. It should be a simple matter to connect and control a relay, which is the next step. After that, I will have it control the charger and the inverter. It’s all pretty straightforward. I just need to...

I'm working on a DIY BMS using a Teensy 3.2 to talk to the board that's built into the battery module and control a relay to disconnect/reconnect the battery. This is dirt cheap. It can also instruct the board to balance at whatever SoC I choose. I'm basing it on the code from here...

BTW, can you post a photo of the potentially damaged BMS wires?

To determine which side is positive and which is negative, you can just use a multimeter in voltage mode. If you connect it backwards, it will show a negative voltage. Another way is to try to decipher my ASCII art! When viewed from the top: +--------+ | | | | | | |...

No HOA, I hope! I'm pretty sure I wouldn't be allowed to attach to the wall like that, at my house.

I can't find the user manual for that one, here's the user manual for the PIP-HSP/MSP: http://www.mppsolar.com/manual/PIP-HSP,MSP%2024V/PIP-HSP_MSP%2024V%20manual.pdf Starting on page 17, it gives these voltage ranges: Bulk charging (CV): 24.0-29.2V Float charging: 24.0-29.2V Low voltage...

Doesn't the 24V MPP all-in-one system that @Will Prowse has talked about in his videos have configurable voltages that would make it compatible with a 6S Tesla module? If so, it would be awesome if Will could revisit his Tesla module in a video!

Yeah, that's true. 78W is a decent amount of power. What's the Victron's on resistance?

The largest I see in a cursory Digikey search is 80A for $32. But you could put smaller ones in parallel. For instance, you could use six 36A current limiters in parallel for a total of 216A and a cost of $15: https://www.digikey.com/product-detail/en/ametherm/SL32-0R536/570-1057-ND/749897

What about using a thermistor-based current limiter? These initially provide resistance to limit current, but as they heat up, the resistance drops to practically nothing. The disadvantage is they need cool-down time between sessions.

I would think so. It’s just like using two multimeters simultaneously to measure the voltage drop across the shunt.

This is an excellent point. If the primary low voltage protection is in the inverter, I have no concerns about the relay failing closed. Unfortunately, the inverter that I want to use for my project has fixed low voltage cutoff that is too low, so I need to figure out a switching solution that I...