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I'm thinking about creating a BMS for my Battery Bank. The bank consists of 12 VRLA Batteries connected in 4 series and 3 parallel configuration to get a 48V system.

For this bank I wanted to monitor if a battery goes bad or drifts away.

I had several thoughts about it:

  1. Creating a wired system with simple voltage dividers and maybe a muxed thing into one adc on a µC which sends the data to internet.
  2. Creating for each battery a small µC system like a esp8266 and send the data
  3. Upon research I stumbled upon this chip: BQ78412 (https://www.ti.com/product/BQ78412) which seems quite cool, offers a temp sensor and also a UART interface to get data from it.

Option 2 and 3 should be powered from the single battery itself.

Hooked on option 3, adding a Arduino based µC and maybe a NRF24 to create a sensor network with one master which will query the battery sensors was my plan.

But because I have not studied electronics I'm concerned about the monitoring in the parallel part of the bank. The batteries as far as I know will come down to a common voltage and so my 78412 or any other thing can't read the actual State of Charge or anything from the single battery or am I wrong?

What are your thoughts about a BMS for my 12 Batteries?

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  • \$\begingroup\$ Keep in mind that you can not access individual cells, only batteries of 6 cells each. \$\endgroup\$
    – Elliot Alderson
    Commented Jun 22, 2021 at 12:15
  • \$\begingroup\$ Aww, sorry every time I mentioned cell I mean a single battery in my bank. I'll edit my post. \$\endgroup\$
    – fork
    Commented Jun 22, 2021 at 12:43

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You will need a separate BQ78412 for each battery. It is designed to be used with a single 12 V lead-acid battery. If are determined to use this device, and you want to detect the failure of an individual battery, then you need to actually monitor each battery individually.

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  • \$\begingroup\$ Yes using a single BQ78412 for each battery was also my idea. But what is about the batteries in the parallel configuration part? Their Voltage will form a common voltage across all batteries in the parallel part. I don't think that the BQ78412 will work then on a single battery? \$\endgroup\$
    – fork
    Commented Jun 23, 2021 at 8:30
  • \$\begingroup\$ I assumed that you would connect them in series first, then in parallel. \$\endgroup\$
    – Elliot Alderson
    Commented Jun 23, 2021 at 10:05
  • \$\begingroup\$ Ah okay. My batteries are in a rack with 3 floors and the original plan was to connect each floor in parallel and the floors in series at the edge battery of the floor. So because I've space left on the floor can add more batteries to the floor to increase the capacity. Would it be a bad idea? \$\endgroup\$
    – fork
    Commented Jun 23, 2021 at 10:47

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