battery problems and fix?

[bobosalad]

our robotics team does not know how to treat batteries... we started with 4 good batteries and one flat line dead one this 2010 season. over the season we have killed one more leaving us with three. i assume it is because of uneducated people shorting the batteries out. does anyone have battery advice for me and the team including how to store, how to charge, and maybe how to fix a dead one?
thanks

[Wolfgang]

Well, it's good that you have multiple batteries for starters. Is there anything your robot does which consumes more of the battery? How low are you letting your volts go? My team typically switches to a new battery at 5 volts. You should probably store the battery in a room where it never gets too warm or cold, especially cold. In colder areas batteries can leak out energy because of the lower atmospheric energy surrounding it.

[bobosalad]

well we switch out a battery before it gets below 8 or 9 really because the robot operates better under those conditions. as well if we have the time i put them on a slow charge, but that one time that a battery is shorted kills it

[DonRotolo]

You should search for a LOT more info about how to treat batteries, but here is a condensed version:

Lead-Acid batteries (like the ones used by FRC) do not like deep discharge (10.5 Volts is deep discharge). This causes the chemistry in the battery to "wear out", leaving the battery weaker and eventually unable to take a charge. So, change your batteries often, don't stress them so much.

They also very much do not like staying even a little discharged for any length of time. A week at 50% discharge will cause measurable damage. So, recharge your batteries immediately after every use. (An unused battery can sit 2 to 3 months without any care, but at that point it MUST be charged up again, or it will be damaged).

Of course, handling them carefully (e.g., lift by the case, Never ever by the terminals or attached wires)(don't drop them)(make sure to treat the case like it was fragile - it is) (etc.) is just good safety practice.

Make sure the wires stay firmly attached - a loose connection will suck down all your power (turning it to useless heat) making the robot seem to eat batteries fast.

Good luck.

[Jon Stratis]

Some of our standard practices:

- ALWAYS lift by the case, NEVER by the battery leads
- ALWAYS check for shorts before plugging something in. This only takes a few seconds with a multimeter
- Fully charged batteries get one of the white Anderson tabs stuck in them to indicate they are charged.
- Drivers are trained to swap batteries often.
- For batteries used for "bench top tests" (in other words, to run motors directly as we debug mechanical issues), we replace them at minimum every 2 hours, more often ever hour. As these batteries don't discharge much, they recharge very quickly.
- at every meeting, the first thing we do is to plug in all uncharged batteries.
- At every meeting, the last thing we do is unplug all charging batteries.

Something important to note: If the batteries are left plugged into the chargers and the chargers are unplugged from the wall, the batteries WILL drain back into the charger, leaving you with a dead battery the next morning.

[Al Skierkiewicz]

A few of the things that kill batteries as pointed out above.
Holding by the leads is like lifting a person by their ears. The terminals will break apart inside the battery leaving you with a battery that reads 12 volts with a meter but can supply no power.
Over charging by using a car charger instead of the supplied charger. charging at greater than 6 amps raises the temperature of the battery causing the battery to vent to atmosphere. The electrolyte eventually dries out or causes an internal short.
Dropping the battery causes the individual plates to break off inside the battery. This causes one or more cells to have reduced capacity. The battery may run the robot for a minute or so and then suddenly drop by two volts. If you drop hard coming off the bump this could be the effect.
Extreme current demand can cause the internal plates to buckle and twist causing internal damage. If you have sticky wheels and tank style drive and push the limits of the drive system constantly, then you are stressing the battery.
I suspect you may have other problems. You might try giving details as to what conditions the battery died under.

[Kage]

another thing that our team learned is to never leave charged batteries on a concrete floor, because for some reason, that drains them.

and also, check the leads on the batteries and make sure they are not touching your battery compaqrtment on your robot.

our compartment this year is a tight horizontal slide-in fit, and I told someone to put the terminals on the battery a certain way so they would not short out...but they put them on the opposite way, and needless to say, we had alot of sparks, some black marks on the compartment, and a dead battery...

[Joe Ross]

Originally Posted by Kage

another thing that our team learned is to never leave charged batteries on a concrete floor, because for some reason, that drains them.

How did you measure that? http://www.thebatteryterminal.com/Te...n_Concrete.htm

[Jon Stratis]

Originally Posted by Kage

another thing that our team learned is to never leave charged batteries on a concrete floor, because for some reason, that drains them.

and also, check the leads on the batteries and make sure they are not touching your battery compaqrtment on your robot.

our compartment this year is a tight horizontal slide-in fit, and I told someone to put the terminals on the battery a certain way so they would not short out...but they put them on the opposite way, and needless to say, we had alot of sparks, some black marks on the compartment, and a dead battery...

I would HIGHLY recommend getting some heat shrink/electrical tape around those terminals. All of our batteries have heat shrink covering all of the previously exposed metal contacts (the tabs from the battery, the stripped end of the wire leads, and the bolts holding them in) that make shorts like you described impossible. But even with that precaution, we make sure the terminals can't possibly touch the frame, just in case a hole appears in the heat shrink and we don't see it.

[Al Skierkiewicz]

I would add to Eagle's advice, watch when you are attaching the wire terminals to the battery terminal. It makes a difference in which orientation you mount them and on what side of the battery terminal. If you are using the KPA or similar cable clamp style temrinal, simply turn the connector so that the screw faces the inside of the battery then mount on battery terminal on the side facing in. This allows the battery case to protect the terminal from damage.