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BQ34110: Gas gauge chip selection for 64v lead acid battery

David Prince
Prodigy 185 points
Part Number: BQ34110

Good morning,

I am looking for suggestions for a gas gauge IC to report State of health for the following application. I have a 64V 32 cell lead acid battery at 550 AH. The battery is used to start a diesel engine and operate the stand by system when the engine is off. The battery is charged by the diesel engine.

It takes roughly 250,000 AH for 10 seconds to start the engine and during stand by the current draw is a constant 10-20A for 2-4 hours. I don't have any control over when the engine is started, the loads on the battery, or the battery charger. The engine is stated 2-8 times a day. Unfortunately I don't control the battery either, so the customer uses 550 to 650 AH FLA and maybe VRLA.

What chip would be suitable to give a State of Health for the battery?

  • 0
    TI__Mastermind 24870 points
    What are your typical currents here? I'm worried for sense resistor value selection.
  • 0 in reply to Kang Kang
    Prodigy 185 points
    Cranking current can peak to 1200A at the beginning of cranking. I plan on using a 1200A or 1500A hall effect sensor and scaling it down to the mV range for the shunt input of the chip using an opamp. Typical battery discharge currents are 1200A to 500A for cranking, 10-20A during stand by, and the battery charger seems to be limited to 120A bulk charge, with absorption and float being constant voltage.
  • 0 in reply to David Prince
    TI__Mastermind 24870 points
    This is very high. The first thing I would look at is the sense resistor value. We can support down to 5 mOhm on this part. I'm not sure what the output of the hall effect sensor will be. We report in terms of mA, so we will need to do some scaling to our current.

    I suggest looking at non-coulomb counting based devices.
  • 0 in reply to Kang Kang
    Prodigy 185 points
    I have read the documentation on voltage and current scaling for the gas gauge chips and i feel confident i can get the correct voltages fro the chip. With my heave short discharges and light long discharges along with a three stage battery charger, which gas gauge chip or technology would be best?