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I have a Ni-Cd battery (8AA) 700 mAh 9.6 V, taken from an RC car. However, is no longer capable of powering up sufficiently the RC car.

Specifically, servo works fine but motor can't spin. Instead, there is a sound came from the PCB (I guess from the conductive area of motor's power cables). In addition, after a while, servo can't turn the wheels.

Battery is fully charged (multimeter is showing 10.2 V). However, I can't imagine that there is something else wrong. Is there any way to ensure that battery isn't working properly? Could this mulfunction be due to the amperage?

Battery neither has been charged for a long time, nor was in operation. Anyway, how should I treat to a Ni-Cd battery?

Thank's in advance.

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closed as off-topic by Leon Heller, placeholder, Chetan Bhargava, Matt Young, Nick Alexeev May 18 at 16:40

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the repair of consumer electronics, appliances, or other devices must involve specific troubleshooting steps and demonstrate a good understanding of the underlying design of the device being repaired. See also: Is asking on how to fix a faulty circuit on topic?" – Leon Heller, placeholder, Chetan Bhargava, Matt Young, Nick Alexeev
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Shouldn't have been downvoated without comment. –  dempap May 17 at 14:17
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people are allowed to downvote without comment, although I consider that it is generally rude to do so. I added +1 to balance it. –  Russell McMahon May 17 at 14:22
    
It may be your battery. An 8 cell Ni-Cd fully charged would likely be closer to 11.5 volts, but could be less. Also, the motor could be stalled, drawing a lot of current draining the battery rather quickly and then the servo will stop too. The suggested tests below are the way to go. Good luck –  Filek May 18 at 6:46

2 Answers 2

up vote 2 down vote accepted

From what you say it sounds like the car MAY be damaged.

However, storing NiCds for a long time can damage them if they are stired discharged, and old NiCds sometimes "just get tired".

You could:

  • Try running the car from another source of 9 to 10V and see how it behaves. Supply needs to be able to supply the required current.

  • Try operating a light or other equipment from the battery and see how long it lasts.

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Try putting the car up on a block so that the wheels don't touch the ground and operating it from a bench supply. Note any problems and also note the peak current draw.

NiCad batteries in general are known for having very high peak current capacity (at one time, large NiCad batteries were used to start jet engines), but as they get older, this parameter is one of the first to fail, and maybe your battery is no longer capable of supplying the starting current required by your car's drive motor. Try measuring its terminal voltage with various resistive loads, up to the current noted in the previous paragraph.

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