Leaking Batterys

so heres the lowdown… Our robot voltage not under load was 10.25v, our voltage under load was about 8v. We took the battery off of our robot and we noticed that there was a bit of brownish liquid, we put some sodium bicarbonate on it. It sarted to fizz and found out that it was battery acid. We have had a few batterys go this way. The model number is mkes17-12… Has anyone had any problems with these?

I don’t think people have had many problems with those. If you’re getting a lot of them, then I have a few questions (and I am willing to bet that Al will have more):

–How are the batteries stored?
–How are the batteries transported from charging to the robot?
–Is there anything sharpish on your robot in the general vicinity of the battery? (And, in general, what is your battery mount like?)
–How are you charging the batteries? --charger type, battery orientation, surrounding area
–What kind of temperatures are they seeing?

What I’m trying to do here is track down the root cause of the leaking. Track that down, and you can eliminate it.

From what I’ve heard, the new batteries from the KOP this year uses AGM (Absorbed Glass Mask), meaning they’re much less resistant to the jarring forces of competition, especially with the bump driving this year.

We had an issue with one of our batteries at San Diego. Originally, our battery box was set up to have the battery upside down, and we managed to make it start leaking around the vent after the top after going off of one of the bumps and landing hard. We redesigned the wiring setup for the battery and started mounting the battery upright and we haven’t had any leaks since.

#1 The are stored inside of a climate controlled room kept at 68 degrees farenheight
#2 the batteries are transported inside of a custom made acrylic case (each battery has it’s own case and is strapped in a vertical position.
#3 There are no sharp object within 6inches of the battery and is strapped down with a sinch strap and held in with angle aluminum(1x1x1/4)
#4 Charger type: * automatic speed charge model number sc-600a made by schumacher* ** Battery orintation:** upright surrounding area: * climate controlled room with plenty of airflow*
#5 not seeing anything other than 68-75 (room temperature)

He’s using the MK ES17-12, which is the older battery. (The new battery is the NP18-12 made by EnerSys.)

I’m thinking that the safety vents are triggering, which is why I asked that list of questions. I’d like to find out why they’re triggering.

I guess we can also add:

–Did you go over the bumps or have a hard landing of any form shortly before noticing the acid?
–Is the battery upright or sideways (or upside-down) in the robot? Noting the answers posted already, I’d guess upright, but it never hurts to make sure.
–What’s the charge rate that you use when charging?

We are mostly using the MK ES17-12 batteries, and I think that our incident was caused by an extremely hard landing off of the bump that caused the safety vents to trigger.

We did plenty of research when looking for batteries on Cheif Delphi and found out that the MK ES17-12 was the best battery to buy.

We have not gone over any bumps today. The battery was laying in a horizontal position the whole time. The charge rate on the battery is 6 amps but we are very sure that this is not causing any problems as this has only happened to 2 of our 8 batteries.


Was there anything unusual you noticed with the robot before the acid leaked?

As a temporary measure, I’d suggest putting the battery upright, if possible. This will lower the chances that the vent valves release with acid ready to exit.

Beyond that, I’m way out of my depth, and will confine myself to hoping that Al Skierkiewicz finds this thread.

there was nothing really weird with the robot before…

also there is a chance that it could be the orientation, but there is nothing we can do before davis regional

These are Absorbed Glass Mat (AGM) Valve Regulated Lead Acid (VLRA) batteries. The electrolyte is in a saturated glass mat sandwiched between the plates, there is supposed to no (or at least minimal) liquid electrolyte that is loose in the cell. Any hydrogen and oxygen produced in the cell during operation of the battery is supposed to recombine, returning the water to the mat so that it does not dry out. If the gas production rate gets out of the hand the valve releases it when the pressure in the cell gets to high. This can happen with high charge rates, charging a battery that is too warm, or excessive discharge rates that heats the battery. If you put a battery that is too hot (from high current loading) on a charger, it might go into thermal runaway and this can ruin the battery.

If your batteries measured 10.25 volts without load they were more than fully discharged, this limit being 10.5 volts. You should avoid fully discharging the batteries, it shortens their life.

The battery can be operated in any orientation, but upside down is not advised in case the valves release some gas and there is a little loose liquid at the valve. The battery should be vertical when charging.

If you run these batteries too hard, or charge them too fast, they can dry out and die prematurely. A sign of this is excessive heat during use or charging.

We had some minor leaking from the top of one of our batteries a couple of years ago, cleaned it up and load tested it, and it has remained one of our better performers for several years now without any further issues. Clean them up, give them a proper charge, and load test them. If they pass the load test and don’t show any further leaking, they will be fine.

We load test at 20 amps load, recording the time they take to reach 11 volts (under the 20 amp load, and note that we don’t go all the way to 10.5 volts). Any battery that gets too close to below 1000 seconds, or so, on this test gets pulled from competition service. A typical battery will last 1500 seconds, while a really good one will last close to 2000. We charge overnight using a three stage charger before testing a battery.

Lastly, you might have done everything right and the batteries might have just given out.
That little 18 amp-hour battery has a really hard life in a FIRST robot.

Have fun,

I’m the battery “expert” for our team, not because I want to be, but because I have had a lot of experience in my life as an electrician working with them. I want to quote this post again because it has a lot of really great information and add my emphasis to it as being correct.

This year, my team started tracking our batteries using a device called the CBA III http://www.westmountainradio.com/CBA.htm which does testing of a battery automatically. We are able to spot a weak battery ahead of time, as well as document each battery’s condition for comparison in the future.

I’m not endorsing the CBA III. It could be better for our purposes if it could do a test with a bit higher discharge rate. But you can do the same thing with any load (large resistor bank, space heater element, car headlamp, etc.) and set up some sort of recording voltmeter to chart the discharge.

The main idea is to test all your batteries on a single, known load, so that you can compare the discharge from a known level (fully charged) to a known level (11.0V is a good point) The time it takes for good batteries should all fall into a certain range and you will be able to identify any outlyers quickly.

I’m not sure what might have caused the leakage the original poster experienced. It could be simply a bad battery, but more likely it was some incident that he is unaware of and will never know, now, that stressed the battery beyond it’s limits. In any event, a battery that rests at less than 10.5V is clearly damaged in at least one cell and should not be used.

One of the easiest things a team can do to extend the life of their batteries, which costs nothing to do except for a little education, is to implement a usage-charge-rest cycle. Number all of your batteries. When you use them start at 1. Use 2 next and put 1 on the charger. When you use 3, put 2 on charge. If you have more discharged batteries than chargers, make sure they go on charge again in order. Work all the way through your bank of batteries before starting over again with 1. Always go in order because it leaves the maximum time between uses and maximizes the time after charging for the battery to cool down. (Very important.) When you are at a competition for more than one day, pick up where you left off int the cycle. If the next fresh battery at the end of the previous day was number 4, use it first even though batteries 1,2, and 3 are now charged. This equalizes usage so battery 1 doesn’t get overused and all batteries get equal time.

If you find you don’t have enough time in competition to keep up with this cycle, it means you don’t have enough batteries or chargers. We have 12 batteries and five chargers, which is probably overkill, but I’d recommend at least 6 batteries and 3 chargers as a minimum for a team serious about competing. If you get into the final rounds at a competition, you’ll want at least three fully-charged, fully cooled batteries ready and on the field.

A last point: be careful how much you discharge the battery in use. A two-minute match isn’t a problem, but practice often stresses a battery more. Watch the battery voltage as you drive and when it dips below 10V change the battery. It’s less stressful on the battery and it charges faster with less heating if it is not fully discharged.

We only got up to 12 batteries by getting a few each year. The fact that the older batteries still stand up means we are handling their care properly. We still have some of the dark gray Gelled Electrolyte batteries as well that are 7 years old and still in good shape.

Properly handled, properly stored and charged, and properly mounted, these batteries should never leak a significant amount of liquid.

We have actually labeled our batteries and have done what you suggested. We now have 6 batteries and 6 chargers.

With your information provided i have come to conclusion that it was because we discharged the batteries to a very low level.
I have a question for you though:
Is it safe to use a battery after it has leaked, but has been cleaned up?

If the leak was through the valves, not a crack in the
case, and it no longer leaks after being cleaned up it is
safe to use. If the battery shows a continuing problem
in this regard you should recycle it.


I wrote this this morning but the internet connection broke at the hotel. Posting now at home.

The MK battery and the Enersys/Yuasa/Genesis battery this year are both AGM batteries designs. If the battery came off the charger at 10.25 volts, you likely had a dead cell already. If the same battery coming off the charger was 8 volts under load, one of the cells was dead and the other was at greatly reduced capacity.
I have a theory that the AGM batteries when dropped or otherwise mishandled, tend to jamb the internals together causing an internal short. the excessive current in the short causes high internal heat which bulges out the side and causes some leakage. One thing I look for in one of these batteries is obvious damage to the case. About 99% of the time I find one corner flattened, or deep marks where the battery has fallen on something or a lot of floor debris jammed into the case. All of these indicate a drop at some point. As Doc has pointed out, these batteries normally can be used in any orientation. In high current conditions and during charging, I recommend that the battery be mounted in the upright position.

the battery came off of the charger at around 13v we tested it. it went to 10.25 after driving for about an hour, but the robot was not on for all of that time

Unless it sat for a few hours first, or you put a small load on it for a few minutes before you tested it, you were measuring the battery’s “surface charge”. That tells you almost nothing about the actual state of health of the battery. A badly sulfated plate, or even a broken one that only has a small fraction of its bulk actually connected, can still be charged to full voltage. It just won’t have anything like the capacity it should.

A stack of hearing aid batteries can also read 13v, but they won’t run a robot.

On our driver station after running the robot for awhile it read at about 12.6 so the battery is in good condition. They have only been to one regional.

And for the hearing aid batteries… it might be able if you stack them and then wire them in parallel.

Thank you for this wealth of knowledge. As a former FIRST student and 3 year mentor i did know that running the batteries below 10.5 volts can ruin them.

All of the batteries are stored in upright positions and mounted in the robot in a horizontal position. None of them have been dropped or damaged in any way. We think that it’s a combination of the battery voltage dropping and rookie luck of getting 2 bad batteries.

As a result of this, the team is looking into doing a load test this summer to further our knowledge of the batteries and understand for ourselves why the problems occurred. Thanks for the link to the load tester!

We are also looking into making is a rule to mount batteries in a vertical position in the following rules to help avoid any possibility of leaking because of the orientation of the battery.

  • Ryan Epperson
    Team 3256 Mentor

I know this is somewhat off topic, but I was under the impression that AGM batteries were more impact resistant than gel cells?