BQ40Z80 Battery Management System

Printed circuit board for my Turtle Rover battery management system, based on TI BQ40Z80 2 to 7 series battery pack manager with impedance track gas gauge.

BQ40Z80 PCB Top

BQ40Z80 PCB Top.

BQ40Z80 PCB Bottom

BQ40Z80 PCB Bottom.

A 4-layer board, where its customized schematic and layout follows as close as possible the reference design of the BQ40Z80EVM-020 evaluation module. Both are available in here.

10 thoughts on “BQ40Z80 Battery Management System

  1. Hi,

    What was the software you used to design the bms? 🙂
    Would you share the files?

    Thank you very much,

    nick

    • In case you mean CAD, it’s Target3001. I will not share CAD files. But the task is not that hard. Just follow the EVM design as close as possible. First take the schematic and remove everything you don’t need. Then, define you board size, place at least the high current components similar to EVM and route signals. A multi-layer board is highly recommended, with a (nothing else) ground layer between high current signals on top and control and measurement signals. Bottom should be a second ground layer. Keep the BQ40Z80 and its surrounding components away from high current loops. Again, see EVM design.

  2. Busy evaluating various BMS IC’s. The BQ40Z80 looks like a good all round solution. Can you please share your experience/evaluation results using the BQ40Z80? Would you recommend using this IC? Like your nice compact layout of the PCB.

    • Comparing with other BQ IC’s, also dual combos, I tried before, the BQ40Z80 is easy to setup and handle when you follow the documentation. I have not played much with hardware design, just copied, simplified and shrunk the evaluation board reference design. You should pay attention to get the chemistry id correct for your cells since this is the base for correct gauging. For configuration of the chip you need to go through each an every parameter, unfortunately. Calibrating your board is a last important step. I can definitely recommend the chip for small battery packs.

  3. Thanks for the info, I plan to replace a DeepCycle Lead Acid battery for my RV with a Li-Ion or Li based cells as the cost of the 16850 cells (2Ah each, 4S20P getting to 40Ah) is getting close to the cost of a 100Ah Lead Acid, of which you anyway can only use up to 50% if you want the Lead Acid battery to last long. I do not plan to run an inverter from the Li-Ion battery, only 12V fridge and other 12V appliances. More concern with the capacity than current delivery. The max current drawn from the Li based battery would be between 15-20A. Would this still fall within your definition of a “small” battery pack? 😉

    • 4S, 15-20A? Yeah, still in the ballpark of small. Just keep everything related to high current path on the PCB as close together as possible. Again, take the evaluation board as a reference.

  4. Busy organising the Eval kit for for the BQ40Z80, will then be able to go through the process of configuring, calibration etc before committing the design to a PCB. Will use the VRUZEND (https://vruzend.com/) end caps to create a small pack for testing. Last question, see a lot of info on cell balancing, which I understand is important and understand why it is needed and the BQ40Z80 actually flags when it is in the process of cell balancing. But most of the designs cannot do cell-balancing when you have a varying load and charging connected simultaneously, which according to the documentation of the BQ40Z80, it can do. Had you any long term experience with this aspect of a design/battery lifecycles? I presume a “maintenance cell balancing” cycle every 6 months or flagged by the BQ40Z80, would be needed even if cell balacing can be done on the fly with a pack that is in continues use.

    • No experience with cell balancing so far. I run only new cells and do not monitor all parameters every time. So cannot tell whether balancing kicked in or not. I think its more an issue on aged cells or when cycling packs often.

  5. Hi,
    Is 15-20A itself just “still in the ballpark of small” zone? I am looking to design a BMS board for multirotor drones requiring 4S or 6S supply with BLDCs whose consumption ranges from 30A to 40A depending on the payload. So, what do you think? Is the BQ40z80 feasible for these ranges?

    Also, I came across this BQ25155 IC which is for 1 Cell batteries. So, can multiple ICs be used in series for 4 or 6-Cell batteries? Can we do that with the usual 4S/6S batteries or should we specifically fabricate our own batteries to suit this application?

    • The BQ40Z80 is able to handle up to 100A. Feasibility is linked to current drawn. Higher the current the more attention you need to pay on PCB design.

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