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Thread: What is generally considered the best BMS for 72v Lifepo4 builds currently?

              
   
   
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    What is generally considered the best BMS for 72v Lifepo4 builds currently?

    Searching through the forums I see lots of different threads on battery builds. And instead of asking on each of them I thought I could ask the question here.

    What is generally considered a go to supplier of BMS units for electric motorcycles?
    I am familiar for E-bikes, but the high AH draw stuff seems harder to find a straight answer. Stuff on Ali-Express doesn't reveal much from a review stand point. So I am just curious if there is a go to brand that people are using for current builds.

    I plan to build a 72v pack that needs to be capable of 300ah peak, and roughly 150ah continuous.

    It will be a 24s. -ish pack. Still deciding on cells configs. Thanks for any insights

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    Senior Member Stevo's Avatar
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    This has been a trouble free product for me: https://www.thunderstruck-ev.com/bms/
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: eVOR.v3.4
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    Quote Originally Posted by Stevo View Post
    This has been a trouble free product for me: https://www.thunderstruck-ev.com/bms/
    Looking at the website, is their system primarily for cell balancing? or does it also manage current/ah usage? I say that because it's not looking obvious to me where the large leads to the battery would connect, I'm only seeing balance leads. Is this the case? I didn't know that was an option as I'm only coming from an Bike wide of things.

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    Senior Member Stevo's Avatar
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    Do you mean for monitoring aHr and max A draw? I use a Cycle Analyst to keep track of charge cycles, odometer and amperage readings. The Dilithium is monitoring and balancing at the cell level as well as pack voltage and battery temperature monitoring.

    Sent from my Pixel 3 using Tapatalk
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: eVOR.v3.4
    WORX.VOR.v3.2

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    Senior Member Stevo's Avatar
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    There is a Hall sensor on the + lead from the pack that monitors amperage. The LCD display is not necessary ... It's an extra. It has a few menus accessable by touch screen. It can show cell voltages, pack voltage and amperage

    Sent from my Pixel 3 using Tapatalk
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
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    This is helpful info. I may follow up with a question or two as I decide on the final model.

    I hadnít thought of running a cycle analyst for battery monitoring and and what not. I purchased a kit that came with a ct22 display that just shows info from my Kelly controller and overall V of the battery. Not as advanced as what it appears the CA can achieve.


    I was under the impression most large electric motorcycle batteries would run their negative lead through the bms itself to manage over current issues and shut off once low voltage. (This is how most of the ebike BMSís Iíve weird operate. They eventually shut off on their own to prevent over draw or temp issues) Hence why a lot of the bms searching I was doing was looking for 72v 300a capable boards. But it makes more sense to go the route your describing and just monitor current and overall voltage using a shunt instead and using something like a cycle analyst to do so. That way Iím not running massive DC voltages through a potentially sketchy BMS I have no experience with from AliExpressÖ

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    Senior Member Stevo's Avatar
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    My Sevcon controller has the low voltage cut off programmed, not the BMS.
    The Cycle Analyst HC uses a shunt on the negative side of the pack.


    Sent from my Pixel 3 using Tapatalk
    Last edited by Stevo; 21 May 2021 at 2339.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: eVOR.v3.4
    WORX.VOR.v3.2

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    Old EV Racer EVcycle's Avatar
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    I also run a Cycle Analyst HC on ....everything.
    No bms. I was using 4.2V (or 3.6V) 2 amp battery chargers with Headways so I got a even charge every time. Worked really well.

    I have plenty of leftover chargers if you decide go that route.
    EV Ed
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    You could probably bypass discharge mode with one of the cheaper Bluetooth bms units and just run the charger through it. Your design shouldn't use so much of the battery capacity that running low is an issue anyway. Monitor pack voltage to keep an eye on this.

    Sent from my SM-T380 using Tapatalk

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    Quote Originally Posted by Frank View Post
    You could probably bypass discharge mode with one of the cheaper Bluetooth bms units and just run the charger through it.
    Thatís a great point. With the size battery bank Iím building either 24s 6-10p depending, I need to make a decision on what size capacitors on on the BMS in the first place. Either capable of 1ah 5ah or 10ah balance is what Iím thinking. Obviously smaller capacitor units are cheaper

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