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DIY: Battery for long shots
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  • I may be able to contribute here on how to lengthen battery life .. I have raced RC cars competitively for 6 years and have quite a good knowledge of looking after batteries and getting maximum life from them.

    It's quite hitech .. we use tyre warmers .. peltiers on the motors before the race .. and traction compound where the venue allows it. We'll take the batterries off charge with 60 seconds to starting grid. My car hits a 128km/hr in 23 metres from a standing start .. it's 1/10 scale

    I was around when NiMH were the battery choice and lipos were illegal and I raced through the transition to lipo. During a race, depending on which motor is used an RC car can flatten a 5300mAH lipo in under 5minutes.

    The high power levels accelerate the decline in battery life. What follows applies to the relatively low consumption that our rigs require.

    As no two cells are identical, with a 6 cell NiMh pack as it supplies current, each battery discharges a different rate. (FYI the cells are 1.2volts). If you use the type of charger where you connect +ve to one end of the pack and -ve to the other. The charger decides what to do based upon the total voltage measure across the 6 cells. remember they have discharged at a different rate. After multiple discharge and charge cycles you end up with the situation where some cells are overcharged and others are undercharged, at some point a cell in the pack will either be cooked through overcharging or excessive discharge.

    To prevent this we used dischargers, which takes every cell down to .9 volts generally pulling about 20 Amps, and then we use a chargers which charge each cell individually .. as I progressed upwards in motor power and speed .. I was chewing through 4 battery packs every 10 weeks (we have 4 races per week each) at about $120 a pack. I was buying matched cells which cost a fair bit more but last a lot longer, even if you don't handle them correctly.

    Discharging each cell independently is more important than charging each cell individually.

    This is why many batteries and chargers have multiple pins for example the old NP1s. A quality charger will discharge to .9v before charging.

    It's similar but different with lipos .. while they don't require discharging .. they do require that all cells are charged to the same level .. or you end up with one undercharged cell and one overcharged cell. And once a lipo cell drops below .. 2.6 volts I think (the principle is hopefully clear) .. it's dead .. the next time you charge it .. it will swell up and eventually cause the good cell to burst inot a fireball.

    You will find two types of lipos .. those with only a +ve and a -ve and those with a tap for each cell.

    To maximise life of lipos .. buy batterys with the tap and you need a charger that charges each cell individually.

    I hope this is of assistance to some .. remember no two cells are identical. Buy a quality battery and chances are the cells will be more closely matched.

    That said sometimes I abuse the batteries deliberately .. If I was chasing trophy, I'd overcharge a pack to get that extra speed off the start and lead into the first turn.

  • Here is a link that explains it better than me

    That's a standalone balancer, you can get chargers with the balancer built in

  • As a follow up to my previous post where I wondered if the step-up/step-down module could be coupled with the 6400 mA li-ion bike battery, I'd like to report that I received them both, assembled them up and ... as a preliminary test I must say the whole thing seems to work.

    In fact while connecting the battery straight to the camera it would give me the ugly "this battery cannot be used" warning, when I plugged in between the step-up/step-down module and adjusted the output voltage to 8.5 v, the camera did not complain anymore.

    Now I only need to find out how long the power will last and how to properly recharge the battery.

    Does anybody know if I can use the ordinary charger we use for the original batteries? The 6400 mA Li-Ion battery seems to be made by 4 18650 4.2v 3200 mA batteries connected in series and in parallel.


  • @Sangye it from ENG camera body. Rig is myself construction. This battery from ebay, just bought my Lilliput in ebay. It is old model.