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  • Need help on 12v lithium battery

    Just got a 12v 160ah lifepo4 lithium battery using on a 55lbs thrust trolling motor. I've only used it twice and both times the voltage reading would dropped rapidly and the battery shut down completely with 70-85% life left. Please help if anybody has any ideas on this issue. Thanks

  • #2
    Bummer, sounds like someone sold you the right battery to make them money. Either the battery is a dud, was never fully charged, or your motor has too high of draw for the battery rating and the protection (BMS) circuit shut down, Also, be aware that Li battery power quickly drops below 60F, and you could have a full, cold battery that cannot give any power till it's warmed up. Oh, the sales droid never told you about that ???

    here's a read http://nordkyndesign.com/protection-...battery-banks/

    use at high and low temps https://batteryuniversity.com/learn/...w_temperatures
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    • #3
      Do you have any way of measuring the Amp draw? All batteries sag in voltage under load. If you don't have an Ammeter, try running the motor at half or quarter throttle as a crude diagnostic.
      Some Lithium chemistries have better abilty to deliver short power surges than others. Do you have any specs on the battery.
      Last edited by Ampster; 02-04-2020, 12:40 PM.
      9 kW solar. Driving EVs since 2012

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      • #4
        Trolling motor draw 52 amps at max speed, with the 160ah capacity of the battery it should last for 3 hours at max speed.

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        • #5
          Originally posted by Tonyp12347 View Post
          Trolling motor draw 52 amps at max speed, with the 160ah capacity of the battery it should last for 3 hours at max speed.
          Okay, that is less than 1C but the voltage sag you are seeing is probably because that battery is probably not designed with a lot of Power Density. In Lead Acid terminology Power Density is analogous to Cranking Amps. Batteries with Energy Density are often called Deep Cycle. After it shuts down, can you reset it by turning it off, then after a minute or so then on? Then if it resets you should have enough power to limp home.

          The solution is a different battery, add another battery in parallel or lighten up on the throttle.
          9 kW solar. Driving EVs since 2012

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          • #6
            Originally posted by Tonyp12347 View Post
            Just got a 12v 160ah lifepo4 lithium battery using on a 55lbs thrust trolling motor. I've only used it twice and both times the voltage reading would dropped rapidly and the battery shut down completely with 70-85% life left. Please help if anybody has any ideas on this issue. Thanks
            I am curious how you are charging, what are the charge parameters (charge set points, times, etc) and how you determined it was at 70-85% SOC when it cut out?

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