Defective Batteries?
 

Hello Fellow Robotogeeks! Todd Lovelace, Chief Geek/Lead Adult Mentor here!

As a new member, congrats to Delphi for such a cool site! I've been so busy as the Chief Geek for Team 86 (Team Resistance....JEA/VISTAKON/Stanton) for the last 6 years that I've never hooked up with you folks!

A problem I saw at KSC this weekend was at least three team that had issues with batteries......

1.) Us'ns have a brand new (2002) battery that is unfit for sompetition use.....(and we accidentally let get into the "good" pile and it cost us a round!) (lesson to all!)

2.) Our neighbor in the pits (a veteran competitor) had a 2002 battery that wouldn't hold a charge.

3.) A rookie team that we took under our wing had battery problems that I think were battery issues, not battery maintnenace/management issues.

Suggestion: everyone ask around to see if they have or have heard about bad batteries (hope not)

Suggestion: load test your batteries to ensure they are ok before getting in the arena!

Thanks for the cool forum! Best of luck to all!

Me too!
 

Team 588 also had problems with one of last year's batteries dying on us. We would get about 1 minute in to a round before it would fail. The robot would slow, the light stopped when we tried to move, and eventually the radio shut down. It cost us a round (plus two of our practices) at KSC before we figured out it wouldnt hold a charge.

We too got a bad battery in our kit. It can't hold a charge for more than 30 seconds or so, and has always acted like this out of the box.

On the upside, the second battery works fine, but even that won't last us more than three or four matches.

We thought we had a bad battery but it turned out to be a bad charger!!

Remember...these are lead/acid batteries. NEVER let them die. If you keep them from year to year, charge them up now and then.

When the battery is given a full charge and then "dies" very quickly, this sometimes indicates that the battery was allowed to drain all of its charge and then was "recharged". Do not treat these like Nicads.

Yes these batteries are not NiCads but I can't beleive any team can draw these batteries down full discharge when used with the robot controller. It is possible to damage this battery by drawing well in excess of 100 amps for a long period of time. A high current (either in charge or discharge) will permanently distort the plates and cause an internal short. You do not need to routinely recharge these batteries to keep them for long term. Using common sense, do not store them where they will freeze or overheat, (temps of 50 to 90 degrees should be ok) do not allow them to rest against conductive matierials or each other(remember that some gray duct tape is conductive) and do not put them where they can fall and you should be OK. Charging does cause some electrolyte to evaporate so constant trickle charging or regular recharging will shorten their life to some extent. The good news is when these batteries start to reach the end of their useful life, they actually become noticably lighter due to the evaporation of the gelled electrolyte.

Also, this years competition appears to be a more physical one for robots than in the past. Although these batteries are built pretty well, they are not immune to "g forces" and can be damaged by a hard hit.
Please recycle old batteries as they contain lead and acids that should not be exposed to the environment.

We had a pretty bad problem with batteries on our robot this year. The low battery light would always turn on after only about 2 minutes of using a fully charged battery, and we could never turn in high gear because the battery couldn't handle it. Our problem went unsolved until midday on friday when we realized (after I got shocked several times by touching the robot) that our frame was part of the robot's circuit. It took up about an hour of checking connections before we finally realized that a screw in the drill motor was too long and it was touching the drill motor electrical connection. The screw tranfered the charge to the outer casing of the drill motor which tranferred the charge over the frame. After we solved that problem we didn't have any more battery problems. We used the same battery every qualifying match after that and it never got low.

Nice find, Jay.
That is one of the reasons we would like the inspectors to do an ohm check from battery terminals to robot frame during inspection. Teams should always suspect a circuit to robot frame when things go awry. Happened to us on a couple of occassions over the years. One due to contact with a robot and a couple when running wires through robot frame members.(Self inflicted when a few holes were drilled)
Good Luck All

One of our batteries doesn't hold much of a charge either...then again I believe it's got a dent in it from being dropped one too many times.

I did this when I was inspecting at the SCRRF scrimmage. It's not hard to do, even an ME like me can read an ohm-meter, and it only takes a few seconds. But I found at least one robot grounded to the frame. The team was very surprised, but they realized the trouble it could cause and got right to work on finding it. I hope they did eventually. I never heard one way or the other.

Maybe we should ask that an electrical check station be added next year at the Team Forum? After all this can be the result of repairs or inadvertent happenings and so would not necesarily be picked up by the standard visual check. Since it's a pretty clear cut type of thing I wouldn't have a problem manning it with volunteers from teams at the regional.

I HATE it when the magic smoke gets away, especially in the form of sparks!

Matt,
You know that repeated dropping of the battery causes all of the electrons to fall to one side, don't you.
LOL
I'm just giddy waiting for Great Lakes in a few days. See you all there.

Dropped Plate
 

In match 59 at the J&J on Friday, our partner in the blue alliance, team 555, had a dead battery halfway through the match. This wasn't an evil 9.0v computer cutout, this was a dead battery. I believe that I was told that two battery cell plates touched, which causes discharge and permanent damage to the battery. Now, I'd say it was defective, because there needs to be a realy hard hit to have plate brackets break. Well, they rot away, but these batteries were supposedly new...

We definitely have a defective battery but I'm not sure what we can do about it.

At the Great Lakes Regional, we had 2 batteries charging all the time when we weren't competing or testing the robot. Before every match we checked the batteries' voltages under load and 1 battery had a higher voltage everytime. The defective one never came close.

Battery Damage?!?
Yes it can happen. In practice, we had a terrible hit that launched our battery out of the practice robot. Now it's a boat anchor. No output and no continuity, so here is what I think happpened...
These batteries are really six individual batteries inside a big plastic case. The individual cells are connected (in series) internally with large metal bus bar. The buss bar is rigid and in a repeated impact situation can be expected to fail due to cracking. Since there are seven of these bars in every battery, a stress failure in any one will put you out of commission. A crack can show up as loss of capacity, intermittant output, or no output. Temperature will also play a role here, having a cold battery check good only to fail after the heating of running a few seconds of match time.
Thankfully, our death was in an old battery that was unfit for competition and soon to be recycled.
Good Luck All

How long would you say the batteries are good for? We have some 2000 batteries that I'm not sure about. Should they stil be good after 2 years of use in FIRST, or should they be on their way to the recycling bin?