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BQ35100: BQ35100

Part Number: BQ35100
Other Parts Discussed in Thread: BQ76920, BQ40Z50


I have a product using an Alkaline battery pack, I'm interested to monitor/ measure the current and voltage. I found this reference design on your website

but it's for automotive industry is possible to use the same design for Alkaline/lithium batteries, or is there any other reference design you recommend for this purpose that can be used with DAQ .


  • Hello Sam,

    bq35100 is typically used  with Lithium primary batteries. You can use automotive designs in regular applications. For non-lithium batteries, check the list of Chemistry IDs and see if your cell model is listed.

  • Hello, Thanks for your reply. Could you please clarify more what you mean by regular applications? What I have is an end-user product powered by a non-rechargeable battery pack of (5-10V) AA Alkaline and Lithium, every single battery is 1.5v, do you recommend any reference design that can be used for at least for AA alkaline liFeS2, do you recommend automotive designs, or BQ76920 or bq35100 or...

  • Automotive products typically have higher operating temperature ranges and undergo additional tests compared to consumer products.

  • Please check all the specifications and ratings to make sure bq35100 can operate reliably for your application.

  • Hello Sam,

    We recommend choosing voltage correlation mode rather then resistance correlation for alkaline chemistry.

  • Hello Shirish, Thanks, so you recommend bq35100, I will check all the specifications, and if I can use it with Bus-Powered Multifunction DAQ USB Device.

  • Hello Sam,

    You are welcome. Note that bq35100 can provide battery voltage and current readings through I2C interface.

  • Thanks, I have more questions if possible just before I start the design:

    If I use bq35100, is it possible to read voltage/current measurements for 4 batteries as one block and at same time the readings for every cell in this block? 

    I checked some of Ti resources, and found BQ76920 can be used for monitoring, is it possible to use this to monitor the current/voltage of Alkaline instead of Guage bq35100?

    Any other options that can be used to extract battery voltage/current readings without using bq35100?

  • Hello Sam,

    bq35100 is for a single cell. You may want to look at bq40z50 which supports 4 series cells. This is an SMBus gauge. Voltage and current can also be read out.

    You can use bq76920 if you do not want gauging.

  • Thanks! yes I see bq40z50  "Fully Integrated 1-Series, 2-Series, 3-Series, and 4-Series Li-Ion or Li-Polymer Cell Battery Pack Manager and Protection. I'm wondering if it supports AA  Alkaline battery?

    What is the recommendation for mixing parallel/ series battery back (e.g. a pack of 6 cells every three connected in series, then output two series-connected in parallel)?
    Note: interested in readings for every individual cell, 3 series cells and for the whole pack.

  • Assuming that end goal is to read individual cell voltages:

    bq40z50 can operate above 2.2V and can provide individual cell voltages for the pack. It can take a mix of parallel and series cells. It can provide cell voltage and pack voltage readings. As long as pack voltage stays above 2.2V (which is half the voltage output of this pack), bq40z50 is a good choice.

    The type of battery only matters for gauging purposes. It does not impact voltage and current readings.

  • Good, so the threshold 2.2V just for pack, not for every cell? since the voltage level for cell is less than 2.2V. 

    The designed board will be used with Bus-Powered Multifunction DAQ USB Device, at which interface can I get battery voltage and current reading? is it SMBD/SMBC?

  • Hello Sam,

    Yes. You can get voltage and current reading through SMBC/SMBD

  • Thanks for the help Shirish, will start designing using bq40z50 . at the same time will design another board for the same purpose without using bq40z50 to compare the results from both boards, for the second case( without using bq40z50 ) the board I will design includes batteries holder, the product will be connected with these batteries as load, so will measure the voltage of these batteries direct individually and as a pack through having test points connected with DAQ. I have a question regarding current readings, I think there is a need to use voltage to a current converter or current sensing amplifier, do you have any recommendations or reference designs for this purpose?

  • Hello Sam,

    The bq40z50 uses an external sense resistor to measure current. The amplifier is integrated.

    For your other circuit you can check the different types of current sense amplifiers at this link

  • Thanks, I checked the link you sent, there are many options, its tricky to select, maybe you can redirect me to the correct option, I think I need a high-side sensing option, I have 6 batteries (1.2V each) for every 3 cells connected in series, another cell also connected in the same way, and by the end, I have a parallel connection which will feed the product with power(4.6-5V). The maximum current for this product could reach 900mA and the minimum 50mA. So will connect the shunt resistor and diode in series with the first 3 cells which are connected in series and check the current at this point through using the prober amplifier. The same thing for the other 3 cells, the same when the 2 series rails are connected in parallels, so I think I will need 3 amplifiers. Do you have any recommended amplifier for this scenario?

  • Hello Sam,

    This forum is for gauging and is not monitored by amplifier experts. Please post on the amplifiers forum for questions related to amplifiers. The people on that forum are more knowledgeable about amplifiers.