Battery rejuvenation


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 On the  29 September 2005 I bought a Giant Twist Lite Gents electric bike. The original, 6.5Ah, battery is still going strong. In March 2007 I bought two 24V 8Ah Salisbury NIMh batteries to provide extra powered milage.

The first (Salisbury1) has performed well until the present time (July 08).  The second (Salisbury2) has never been as good as the other one but still provided reasonable extra mileage. However in late June it failed after about three miles. As it is out of guarantee, I decided to have a go at rejuvenating it by subjecting it to charge/discharge cycles and to do so I set up this test rig. 

The 12V cup heaters are connected in series to provide a load, then shown immersed in water and the temporary battery connections connected to a multimeter and the load. 

 

  

For comparison I first tested Salisbury1, see tests 1 & 2.  This showed a small improvement on the already good capacity,  see tests 1 & 2.

Note: The struckthrough readings are ignored on the graphs.

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I then tested the second (Salisbury2) battery. Test1  showes it's pitifully low capacity. Further charge/discharge showed improvements until I reached the sixth and final test. 

Note: The struckthrough readings are ignored on the graphs.

 Please note that although there may be errors in my calculations, as these errors are repeated for every test I feel that the trends shown in the results are valid. A test run will be done when the weather improves and I have the time to do it.

Before the test run, only two of  the three LED's lit when the battery was switched on.  During the run, although the battery life was greatly extended, the power assistance did not seem to be as great as with the other two batteries.