Saturday, November 12, 2011

LiFePO4 AA Batteries - Part 2.75: Charge / Discharge & Recharge Test

I charged up my all four LiFePO4 batteries and put them into my Tayami QuickDrive R/C racing car with the four dummy batteries.

The fresh charged-up battery voltage for two LiFePO4s was 6.8V in total and both sets are measured to be about the same. The car was then driven in a full-sized football court in full speed for about 10 minutes. It seemed that the overall weight of the car with batteries was just too light but yet it had too much power such that I could feel that it slipped around more seriously especially for sharper/acuter turns where the control was lost momentarily. Unlike NiMHs, which heated up seriously for this high and continuous current drain application, the LiFePO4s only warmed up very slightly. The proves that this type of new rechargeable battery technology is really very suitable for high drain applications. It also explains why large-size electric cars also use it.

The batteries got exhausted after playing the car for more than ten minutes, which I think to be about half the time for what my 2450/2650 Energizer NiMH batteries could deliver (but the achieved maximum running speed is lower). And as I've mentioned above, the NiMHs always heated up very seriously whenever high current was drained continuously and for longer period.

The exhausted LiFePO4 voltage was then measured. It was found to be 5.2V for two (but only about 2.4 to 2.5V for each). At this low voltage, the batteries actually could not deliver any large enough current for the device to be workable.

After this full charge, I then recharged the LiFePO4 batteries with the charger, now it required for more then one and a half hour to fully charge them again. As before, the fresh charged voltage for two is 6.8V. And, this time the batteries are warmer then what I charged them for the first time for half-depleted/half-full batteries, but yet, the charging process is surely not as hot as that of the NiMH batteries with my expensive Maha charger.

So, the conclusion about the battery performance is once again that LiFePO4 is clearly superior to that NiMH old-tech and the total usable energy capacity is really not as low as it is specified, as all the battery juice has been almost used before the device cut off itself because of low voltage that is reached prematurely.

Okay, this is the end of my this purely text-based report. I blog, you decide!~ (If you still can~~)

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