Quote:
Originally Posted by Karibou
That's impressive. If we put in a battery that isn't at full charge at the beginning of the match, it dies during the endgame or slightly before. I don't know how long they last beyond a match length, because we've never tried it. We know it doesn't work for us.
We have a cycle of 6 batteries. After experiencing several inconsistancy issues with older batteries last year, we purchased 6 new ones for this season. Even then, we discovered at our second competition that one of the batteries was a dud and we could not last half a match before we saw some failure in robot performance.
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Kara,
Even a new battery with a fresh charge will give you low voltage if the load is high enough.
I have uploaded a battery test I performed for team 177 back in 2006. You will find it
here.
This was the last time I did an "exhaustive" test. I usually only test suspect batteries...
We did the tests because the team thought that we had "bad" batteries. Several batteries had been marked as "bad" by the pit crew during a regional competition. That year, the game was "Aim High" and the requirements of the shooter mechanism, drive system, pneumatics pump, et cetera, was so great that the battery voltage would crash during a match.
The drive team needed to learn that, if they were pushing against another robot and shooting at the same time, their shooting distance would be compromised.
You will also note that the batteries did not significantly degrade over time. In fact, ignoring batteries dropped on a concrete floor or having the terminals ripped off because they were handled by the wires, I don't think we have had a single battery failure in less than 7 or 8 years of use and abuse...
We have always used the KOP chargers. We always store the batteries in a charged condition for the summer. Storage temperature is always between 55F and 95F (we have unheated/unconditioned storage). We always charge a battery as soon as possible after use. We try not to leave batteries on a charger more than 48 or 72 hours.
I would suggest that your team invest in a
clamp-on DC amp-meter and a good
battery analyzer and do some engineering in the off season to understand what is going on.
And before I hear from the peanut gallery: Yes, the current KOP batteries are a different part number but, IMHO, their performance should be very similar...
Regards,
Mike
Edit: At our next competition, I tested two batteries as they came off the field after a match to measure the charge left. This was my criteria for recommending "A battery will definitely last two matches and you can get three matches from a battery if you really need to.".