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Li-ion - LiFePO4 - car battery

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  • Li-ion - LiFePO4 - car battery

    Any experience with these small and light 12V Li-Ion LiFePO4 batteries in car use? Seems that even an really small 5Ah battery is enough for starting an car engine, but probably so small wouldn't last for long..? Starting amps goes well over the specs... I have been looking for a battery in 20Ah size, it should have enough grunt to start the car for several times in a row. But what about the charging rate(C), can a LiFePO4 battery in this size handle the car alternator charging?

    Audi UrS4 Avant 2.5 20vt - twincharged - Project
    Audi 80q B4 Sedan 2.2 20vt - Daily user
    BMW 320d Touring e91 M-Sport - Daily user
    BMW 740iA e38 - Project

  • #2
    Forget li-ion and lipo if you dont want burn down your car and/or garage.

    Typical 20Ah LiFePO4 has max discharge 3C and max peak 10C for 5 seconds. 200A is joke for a car battery in the north.
    Optimal charge is 0.5C and maximum charge is 1C with temperature monitoring.
    1989 Audi 80 Quattro
    1994 Audi 80 Quattro Competition

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    • #3
      LiFePO4 should be quite safe. Nothing near as dangerous as "RC" LiPo batteries. Was thinking more of using as a trackday battery and summer use.

      For example this battery has been proven to work well: https://www.rennsportshop.com/de-top...A-LiFePo4.html

      Audi UrS4 Avant 2.5 20vt - twincharged - Project
      Audi 80q B4 Sedan 2.2 20vt - Daily user
      BMW 320d Touring e91 M-Sport - Daily user
      BMW 740iA e38 - Project

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      • #4
        Your link says that this battery should be charged only with a special charger.

        If you want to charge it on a car you need somekind of special charger between the alternator and battery.
        1989 Audi 80 Quattro
        1994 Audi 80 Quattro Competition

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        • #5
          Special charger is just so it stops the charging when the battery is full. Other wise no difference from a normal charger. Car alternator voltage isn't a problem. And I guess the charging amps depends on how empty the battery is..? If the battery is empty then aalternator will charge with high amps and when battery is close to full(close to max voltage) it will drop amps down..? Have I understand right?

          Some batteries has charge rate 3C or more. 3C 20ah would be 60A. Also ssome batteries has smart electronic and protection.

          Audi UrS4 Avant 2.5 20vt - twincharged - Project
          Audi 80q B4 Sedan 2.2 20vt - Daily user
          BMW 320d Touring e91 M-Sport - Daily user
          BMW 740iA e38 - Project

          Comment


          • #6
            The 8ah battery in the link is 10C so it makes 80A charge rate.

            Audi UrS4 Avant 2.5 20vt - twincharged - Project
            Audi 80q B4 Sedan 2.2 20vt - Daily user
            BMW 320d Touring e91 M-Sport - Daily user
            BMW 740iA e38 - Project

            Comment


            • #7
              Originally posted by Thuppu View Post

              Some batteries has charge rate 3C or more. 3C 20ah would be 60A. Also ssome batteries has smart electronic and protection.
              These batteries have no electronics and no protection. You have to somehow switch claimed 550A if you want protection.

              If your charge voltage will be around 14V and the battery can take 10C charge as claimed, it should work.
              1989 Audi 80 Quattro
              1994 Audi 80 Quattro Competition

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              • #8
                Quite strange there is no more interest in these? 20-30kg vs 1-3kg and much smaller size. Seems there is quite good experience in car use even with the small 5Ah sizes...

                Audi UrS4 Avant 2.5 20vt - twincharged - Project
                Audi 80q B4 Sedan 2.2 20vt - Daily user
                BMW 320d Touring e91 M-Sport - Daily user
                BMW 740iA e38 - Project

                Comment

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