diy solar

diy solar

BMS Alternative

etuini

New Member
Joined
Jan 10, 2022
Messages
4
Location
Houston, Tx
Newbie question... I'm building a 6s2p 12v 40ah pack from Toshiba 20ah LTO cells from Battery Hookup. So far, everything has gone well except for the BMS. I got an ANT bms and fried it within an hour or so. It wouldn't come on so I tried various things to activate it and given the smell it put off, I'm pretty sure I burned it out. I can order another one and be more careful, but I'm wondering if I actually need to. My understanding is that a BMS serves 4 functions:
  1. High voltage disconnect
  2. Low voltage disconnect
  3. High/low temperature disconnect
  4. Cell balancing and/or disconnect if one cell gets too high
I think I have 1, 2, and 3 satisfied:
  1. High voltage disconnect: I have a Victron 75/30 charge controller programmed to disconnect the pack when it reaches 15.8 volts
  2. Low voltage disconnect: I have a Victron battery protector (https://www.amazon.com/gp/product/B01N6ATT8C) that will disconnect the pack when it reaches 12v
  3. I plan to have this outside in the winter, which is why I'm going with LTO cells (also, I just want to experiment with LTO cells). So temperature is not a factor.
That leaves cell balancing. I top balanced the cells initially, but need a way to keeping them balanced. I was initially planning to order another BMS and be more careful and then had another idea. I was thinking of something like a Heltec cell balancer attached to a switch. I guess I could run it all the time, but that seems like overkill. It seems like that would satisfy all the functions a BMS serves and be at least as reliable as the less expensive BMS models I've been looking at.

Other than the additional redundancy a BMS would add, is there any reason that approach wouldn't work? Am I missing anything?
 
Man can't do anything right the first time. So now on to the BMS. What model bms and some pictures. Where you got it. Can you see the componints on the board. Shoud be able to figure out what went wrong.

What battery size and voltage and the cutoff voltages?
What application is the battery going to serve?

Can you run the cells in a battery without a BMS, sure. If the cells are good and new you probably won't need to balance them for 100's of cycles.
 
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