• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 227 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Gas gauge for 13S removable battery

Don Goodman-Wilson
Prodigy 10 points
Other Parts Discussed in Thread: BQ34Z100, EV2400

Hey all!

I'm looking for help in figuring out if there is a suitable chip for my use case. I have an electric bicycle with a removable 13S 47.45V Li-Ion battery, and a fixed 2.14mOhm low-side shunt resistor. I basically have access to Vbatt (41-54V), the two sides of the shunt, and GND. The battery is removed for charging. These are pretty much fixed constraints—but there might be some flexibility, depending.

Is there a solution in the TI catalog for calculating gas gauge / battery life remaining given these signals and constraints?

  • 0
    Genius 3970 points

    Hello, and welcome to the forums!


    The bq34z100 looks like a good choice for your needs; it only needs access to Vbat, SRP/SRN for the shunt, and a thermistor. It uses TI's Impedance Track algorithm which is very good at measuring battery capacity, runtime and can keep accuracy even as the battery pack ages over time.

    That said, I have a few questions for you (sorry for the wall of text below!).

    1. When you say that the battery is removed for charging, do you intend to put the fuel gauge in the electric bike, or do you intend to attach it to the battery pack directly? The bq34z100 is one of TI's "pack-side" fuel gauges, which means it's supposed to be always connected to the battery pack.
    2. Do you have one of TI's EV2300 or EV2400 USB-to-I2C adapters? The chip is much easier to work with if you have a PC interface to the chip, as TI has software that can perform the required steps in configuring and programming the fuel gauge.
    3. What particular chemistry or cell part # does your pack have, like LiCoO2 (lithium cobalt oxide, the most common type), LiMnO4 (Li-Mn as it's sometimes called out there) or LiFePO4 (Lithium Phosphate)? TI's chips can work with all of these types, but accuracy is greatly improved if the exact cell characteristics are known. For example, say you have the Samsung SDI INR18650-5Q, a NiCoMn (nickel-cobalt-manganese) cell with 1500 mAh capacity. TI has a specific profile that can be programmed into the chip, which will greatly improve the fuel gauge's accuracy. If you don't know, there are ways to use the software to log the battery's discharge cycle to find a profile to fit the cells in your battery pack.