Which Battery to Buy?
 

At the offseason events 1885 attended in the last two weeks, we struggled to maintain proper charge on some of our batteries. I'm not sure who/what/why or even how we got the batteries we have, but they're a mixed bag of some of the FRC legal batteries from 2014.

Problem is, not all of the brand new batteries hold proper charge for an entire match. The Sigma battery had the worst "life" - as in, it would start at 13.5V and always come back at < 10V according to the Battery Beak.

I found a comparison of specs for batteries related to the FRC-legal batteries, which led me to the fact that I don't know which specs actually matter for our use case:
http://www.atbatt.com/sealed-lead-ac...s-12180-nb.asp

Which FRC-legal models (other than the Enersys) worked well for teams this past year?

Re: Which Battery to Buy?
 

There is some information here on the topic

It stays on topic about as well as most CD threads do, but has a few tidbits of useful information.

One addition about he Werkers, they get hot when charging and never seem to reach a full charge. Not scary hot, but noticeably warm to the touch. I would not reccomend them for use by any team. We have had nothing but good luck with the Enersys and will continue to use them.

Re: Which Battery to Buy?
 

Sigma, National Battery (all black), Enersys, MK all worked well.

We had a couple of Sigmas and National Battery that had questionable cells, so we reserved them for non-competition. This is likely what you're experiencing too. For the most part, the Sigmas have been good. I did notice that the Sigma batteries we bought in 2012 are different than the Sigmas today in terms of color scheme and price (almost $10-13 more each!).

How long have the batteries been sitting? SLA needs to be charged to 100% every 6-9 weeks or so when in storage if I recall correctly (pinging adciv).

Re: Which Battery to Buy?
 

6 or 9 what

Re: Which Battery to Buy?
 

I would assume months?

Re: Which Battery to Buy?
 

Our Werkers lasted through a match just fine, but had odd charging right from the store. We use a ten battery battery tender unit and they never reached full charge on that unit. Tried a higher end Optima charger/maintainer and had the same result. The KOP charger never passed 75%. But the batteries got noticeably warm to the touch. Voltage read fine (13.4-13.6V) at full charge, but using a automotive load tester, we only got readings of 140-165 CCA. The Enersys and MK batteries all came in around 220-230 CCA.

We use the battery tender unit on the batteries for a week or so every month or two.

No matter what the care was, I still wouldn't recommend the Werkers as they both were lower performing straight off the shelf. We even picked the newest ones they had.

Re: Which Battery to Buy?
 

There's an old saying about "assume". Case in point: see his edited post.

Re: Which Battery to Buy?
 

I don't want to assume which saying you are referring to. Can you please clarify?

Re: Which Battery to Buy?
 

Are you sure you don't want an illustration for this? :p

Re: Which Battery to Buy?
 

I love it when people get my subtle dry humor.

Re: Which Battery to Buy?
 

Ether has humor? :ahh:

Sorry for the late edit. I got sidetracked while I was trying to verify the statement I made. It is still in a "I think that's the time recommended to me" category.

Have you performed a controlled test on your batteries? Different matches yield different power usage. Time to data log!

Re: Which Battery to Buy?
 

Jesse,
The indication of a drop of two volts indicates a damaged cell. Check the case and I bet you find a flat spot on one of the corners indicating a drop. Any SLA battery will get hot once it achieves full charge. All current that is not used for reversing the chemical reaction goes into heat. In general, the heat confuses smart chargers. For that reason, all charging should be performed on room temperature batteries.
Our batteries should be able to make it through a summer (3 months) without being charged. Many old timers might recommend they be left on trickle charge but only certain smart chargers will switch on a trickle/maintenance charge periodically. We do not charge over the summer except when participating in post season events. However, once we are back in the shop on a regular basis, we top all of our batteries off. We use a multi-station smart charger that produces a 5 amp charge rate at full charge per station.

Not all chargers are created equal and yours may be intended for 50 amp hour batteries or above. If so, your charger may be producing significantly higher charge currents than the 6 amps stated for these batteries. High charge currents could result in heating and less than optimal charging. CCA testing with a car type test set will result in extremely high and possibly damaging current draws. I recommend the Battery Beak for quick checks and the West Mountain Radio CBA IV for controlled testing.

Re: Which Battery to Buy?
 

Al, not sure if the hot battery comment was directed at my post or not, but our charger/maintainer is a 10 bank 2 amp charger. I'm not denying the fact that a battery will get warm when charging, but the Werker batteries we tried last year got warm immediately and never made it to full charge. This charger isn't going to damage the batteries, nor will the Optima 400 with a setting specifically for mulitple size AGM batteries.

Also, there are many forms of automotive CCA testing meters out there, don't jump to conclusions about what they do. You can't say every automotive tester will damage them (automotive includes motorcycle/moped), however I would accept that certain methods could damage a battery. All of our equipment is recommended and operated with the assistance of an electronics engineer and a lead acid battery specialist that work with us to make sure we can save money on batteries. We still use batteries in competition from four years ago because they still perform just fine and only slightly lower in performance than the brand new ones we get each year.

Re: Which Battery to Buy?
 

Andrew,
If the charger is truly making only 2 amps per output, then batteries should not get immediately warm. Either the batteries are defective or the charger is making way more than 2 amps (as in the charge circuit is shorted). Even with defective batteries, the KOP charger takes a while to heat a battery. The documentation talks about the four charge cycles but it doesn't really explain if the charge current is average or maximum. In general, CCA testers put a very low resistance load across the battery. I would be interested to know the model of the tester you use.

Re: Which Battery to Buy?
 

Thanks for the tips! I will forward this on to a student who can hopefully report back soon.