Saturday, February 14, 2015

Sometimes waiting help - a lot...

Look what TI released just last month:

A kind of 'super INA226', it is built upon a small uC and included not only the Vbat and Amps measurement capability, but a column counter as well as a whole host of firmware to monitor and calculate a batteries SOC.  Still interfaced via I2C, and under $5

Am thinking to use this as the foundation for the monitoring portion of the BMS - add an Arduino based uC to provide CAN bus communications and controlling of the cell-management logic (See prior post:  "Central or Distributed") and external alarming - - - -  With some smart power management to reduce overhead..


  1. Just a quick note: As far as I understand, the BQ34Z100-G1 only supports battery capacities up to 29Ahrs (29.000 mAhrs). That might be a little to small for our applications...

    1. Hello, thanks for the comment - as I read the datasheet, it has an optional 'scaled' mode which allows one to support larger capacities. Configuration register 48/30 Design Energy Scale allow a scaling factor of up to 255 - of a 7,395Ah battery - however the datasheet also cautions that one should keep the scaling value to a max of 10x, or 290Ah - so in the end you may be correct...

    2. Ah, I see. So there is still hope. Calculating SOC is a non-trival task and TI seems to have a rather sophisticated algorithm build into this chip.
      From what I understand, you also want to include cell-balancing for LiPos into this BMS. Don't you think this makes the whole project overly complex? There are so many dedicated devices for this task and only very few people are using LiPos on a boat or in an off-grid location anyways...
      BTW, I'm observing your projects for quite a while now. You are really doing a fantastic job, thank you! I'm in an off-grid situation with solar, batteries, an inverter and a 24v generator. A combination of your alternator regulator, bms and possibly also the mppt solar controller would be perfect for me!
      All the best from Germany,

    3. Kai,
      Thanks again for taking the time to read these things, and comment on them!

      Yes, there is perhaps hope - but as I turn back to the BMS, this new TI part may or may not make the cut. I just need to read more about it. As you point out, it uses a rather sophisticated approach to determine SOC - and that might not scale to the larger battery sizes used in house banks.

      As a reminder: The primary reason for for doing this it to have it become part of an integrated charging system, allowing all charging sources to work well together - and extend performance of the house bank. I think marine, and some off-grid applications bring the uniqueness of multiple charging sources - and that is what I want to focus on.

      Cell balancing: See next brog post (just got too long..).

      Thanks again!