Hello everybody,
I am sorry for my ignorance on what happened. One of our lead acid batteries is scaring us, no one on our team has any idea what happened. All we know is that in the morning there was something definitely wrong. The sides of the battery are bulged, as though there was a reaction that created pressure. Yet oddly it seems to only be affecting one side. It seems that the top (the black part) is separated from the battery. Also when we entered it smelled as though there was a gas leak in our shop. Though this may be a separate event. If anyone has any ideas on what happened I would love to know, and possibly save our remaining two batteries.
I can’t comment on what caused it but I am surprised the vents didn’t pop up. We had a bad battery and the vents popped up and stunk up the whole hallway.
We had two of ours do that recently too. I’ve read that it can be caused by being over charged but the charger we use is supposed to prevent that.
I’m wondering if it might have something to do with the batteries having been used laying on their side while in the robot. None of our 2015 batteries did it, but a 2014 one did and i think a 2012 battery might have been the other one.
That battery needs to be sent to be recycled. It is bad. Either a cell shorted out or it was charged with the wrong high rate charger.
Make sure the max charge rate is 6 amps, 2 is better. Microprocessor controlled 3 or 4 stage charging is best and make sure it is compatible with AGM / GEL batteries. Liquid cells like in auto batteries have a different charge profile.
We have had maybe 3 or 4 failures in 12 years ? We keep 14 batteries in service, so altogether we have not had a real problem.
If you want help figuring out what went wrong, you might need to provide some clues. Like, what was done to the battery? was it just sitting in a nice dark cool room all by itself? was it connected to a charger? was it exposed to temperature extremes? was it shorted out? How old is it?
As mentioned, it doesn’t really matter for this battery, but if you have others that might be mistreated some how, it would be helpful for you to tell us all that you know about what was done to the suspect battery.
The charger we use is also designed to prevent overcharging as well. As for the batteries being laid on there sides, I do not not think so, the rest of our batteries have laid on there sides and have not done anything like this.
Ok one of our mentors is taking the battery to a hazardous waste recycling center. Also when I get back into our shop I’ll try to find out weather the charger is 6 or 2 amp, also if it is Microprocessor controlled. However I am fairly certain it is 3 amp.
I know we were charging the battery in preparation for a demo tomorrow. Though our charger is designed (as stated before) to prevent overcharging. As for possible temperature shifts there is a high possibility as our shop is not air conditioned. Shorted out I do not think so, the connectors were fine. If there was a short it would be in our charger. Also as stated before the battery was given to us in 2010 for frc. I guess it may have run its life.
Well thanks everyone for your replies.
The_42nd_Paradox
Grabbing a battery by it’s wires instead of the built-in grips (the battery terminals are not mechanical supports and pressure on them will crack the internal plates)
Dropping a battery onto a hard surface, also rupturing or cracking internals (can inspect for dented corners)
Very deep discharging maybe >80%
Sensitive to over-charging (a bad battery can give confusing feedback to a good charger)
Overheating (hot storage, hot surface)
*]Not maintained in a charged state (leaving them to slowly discharge all summer will damage them)
But just age will eventually lead to deterioration and then overcharging even with a smart charger can occur.
I often see people using chargers that make lots of claims about overcharging this and that but I have lots of experience with batteries (built electric vehicles and computer room battery backups). I rarely trust a battery charger I either haven’t got extensive historical data or at least a complete schematic and source code for.
I have lots of wet maintenance free batteries around. I check them for temperature and any signs of leakage and if possible collect any data I can for their behavior often. The real important thing is to not have these things spraying acid everywhere because that might just be the start of your troubles.
All in all after doing FIRST on and off for 20 years I think the battery selection for FIRST is adequately safe. Though it wouldn’t surprise me to see an occasional issue here and there.
As others have pointed out, once you recognize you have a battery in a bad state it is important you dispose of it not leave it laying about. You don’t want someone happening upon it later and compounding the safety issue.
Daniel,
This is common failure for these batteries. In almost all cases, an inspection of the bottom of the battery will show some damage. It is likely that the battery was dropped at some point. The construction of these batteries reduce the gap between plates (compared to previous gel cell types) and that gap is filled with a wet glass mat. When dropped, the plates may move to close the gap. Eventually when charged, the charge voltage exceeds the breakdown provided by the gap and causes a short internal to that cell. When that occurs, temperature skyrockets in that cell, demonstrated by the swelling of a small section of the side of the battery. Temps rise so fast that the small gas valve cannot release all of the pressure. A combination of high temperature and excessive gas pressure causes the case to warp outward. When the battery cools, place it in two plastic bags to prevent the leakage from damaging other parts and hands and recycle as advised above.
Remember that each cell is rated at 18 AH and each cell is capable of providing 500+ amps when fully charged. That is easily 1000 watts per cell until the the energy is given up as heat and the cell discharges. The damage due to dropping will not always show up immediately but I have seen a few brand new batteries that have exhibited these issues.
These batteries can be used in any orientation and can be charged in any orientation. I personally only charge when battery is standing up to give the pressure valves a better chance of doing their job.
If you could supply a picture of the bottom of the battery, we might be able to see the cause.
I just got a look at the battery, sorry for the lack of photos my phones camera is from ~7 years a go, flip phone. Regardless I could see no major damage to the bottom, no cracks or obvious dents. However the bottom did seem scraped up, but that may just be due to normal wear and tear.
Well regardless from this point forward we will only charge batteries under supervision. Hopefully this will reduce our problem.
Eidt:
Just found the battery charger specs after posting this. Here is the charger we are using:
Also if you get a Deltran, search online. The street price is about 500 bucks, much less than list price.
Using this Deltran charger has given us stunningly good results in maintaining batteries in a very good fashion and maintaining a long life. The 2 AMP charge rate is ideal for the types of 18AH batteries we use. Frankly I think it is the best and works great for competition if you have enough batteries to manage the longer charge time.
Our other battery support system is essentially identical to the one [here](file:///Users/cbarker6/Downloads/Battery_Cart_Instructions%20(1).pdf) except we use a different battery charger. This is the charger that we use
It has a 5 AMP peak charge rate. I don’t have scientific evidence but my feeling is that the 2 AMP Deltran is much better at helping the batteries live a long life. The reason we have this system ( 14 chargers @ 5 AMPS ) is to support 8+ hour long multi-robot public demos. It is hard on robots and batteries.
A picture of the system is here.
It has been updated to have a mid-rail plug mounting system like Team 900’s.
As for the Schumacher chargers - I just don’t like them, at all.
One more time - we REALLY like how the 2 AMP Deltran takes care of batteries.
If they work for you and you like them, ignore my comments, but in my experience they seem to ‘get lost’ when changing batteries and we would just unplug the charger from the wall and re-plug it in. But it may be we are just too impatient.
First off a flooded lead acid battery is not designed to be used or charged in any other position other than upright. They should never be charged on the side as the acid may leak out and the plates may fall out of their brackets and short out.
There are two other types of batteries AGM (absorbed glass mat) may be used horizontal or at an angle but still it is recommended to be charged upright. Gel batteries are better than flooded since the plates are suspended in a jello like liquid helping hold the plates apart and perform better since the gel acts as a dampening agent.
We have transitioned over to AGM batteries for the safety of being sealed and being designed to be used at other orientations. They are also a bit more environmentally friendly since they have nominal lead in them.
