Batteries

[eugenebrooks]

Originally Posted by Al Skierkiewicz

This is pretty unusual for batteries to be bad out of the box. Although I can't open the file (I will try from work tomorrow) it would appear that the battery might not have fully charged. This can occur when there is a high resistance connection to the charger. I would double check all electrical connections, charge it up and try it again.
It is interesting to note here that an 18 AH battery cannot supply 18 amps for one hour. The spec sheet lists the test parameters and the final test voltage vs. time but it should be noted that the battery changes output with temperature as well.

We finally got our current regulated capacity tester running, and have tested two ES-18 batteries from 2004, and the two EX-18 batteries that arrived in the KOP for 2005. Given a constant load current of 20 amps, and a cutoff voltage of 11 volts, the two 2004 batteries lasted 32 minutes, while the two 2005 batteries lasted 22 minutes.

The capacity of the EX-18 batteries does appear to be 50% lower.
If your robot will have high current draw you need to pay careful
attention to this issue...

[Al Skierkiewicz]

Gene,
Interesting results...It appears that the 2005 batteries do match the power curves in the documentation so it is surprising that the 2004 batteries produce better performance than the new batteries. It is pretty odd. One of our parents is working with SnapOn Tools on battery check instruments and brought in an impedance checker that they make. We ran impedance checks on all of our batteries (some more than 4 years old) and the recent batteries even back to 2001, maintained their specified impedance. The oldest battery we have still only measured about 20 mOhms after all this time.

[lynca]

We are also having unusual battery drops but it might be due to our motor setup. We will test out the batteries to verify the 2004 2005 differences.

[supersy77]

i was just wondering becuase are old batteries 2003, 2002, are not up to pow. I was wondering would a deep cycle help the battery keep its power again.

[Al Skierkiewicz]

It is unlikely that battery conditioning will help with these batteries. They have a very defined charge/discharge lifetime (about 400 cycles as I remember) Older batteries will certainly be close to that number if you practice and use your old batteries often. Lead acid batteries do exhibit other problems but I don't think you are having any of those issues.