Our team has been using the standard Enersys NP18-12 batteries for the last several seasons. We typically buy a new set of competition batteries every year or 2 and relegate the old batteries for testing and practice. With the expansion of the list of legal batteries this past year we are looking for feedback from teams that have experience with batteries other than the Enersys NP18-12. We had a battery start leaking this weekend around the top seal and are looking to replace batteries this coming season and would like to know which batteries are “top quality” and which have a reputation for not holding up. Our experience with the Enersys batteries has been hit or miss. Some seem much better than others. For reference we have a nice battery testing setup including a West Mountain Radio CBA with dual 500W amplifiers. We are building new battery charging station(s) this fall around Autometer BusPro-660 chargers and are looking to replace our competition batteries with “top quality” batteries. Now that we have a competition season behind us does anyone have any advice on the “best” batteries to go with based on the 2014 legal battery list*?:
Hey Chuck, I have been very happy with the MK batteries. If you call them and tell them you are a FIRST team they give you a pretty good deal. We have paid about $40 each including shipping. We normally order 6 during each build season.
They’re customer service has been great. We had an event we needed the batteries for and they were able to work it out with the UPS driver to deliver the batteries to me in a parking lot after they got picked up from their distribution center in Houston. It was pretty crazy.
I know it doesn’t exactly answer your question, but check out your local Batteries Plus. They usually don’t have a lot of variety, but they’ll likely have something that’s on the approved list. Also, if you register with them as a corporate account (all it requires is a phone number, and they’ve never called me) you get a rather large discount… I want to say it was almost 3 for the price of two last time I went! At any rate, that should save a little bit on shipping!
I used YUASA or Power Source at work for emergency lights, emergency notification systems and fire systems. They would perform better than some other brands we used. I never seemed to have any issues. Even under extreme loads, they did not have to be replaced as often as I thought.
Thanks for the info so far guys. For clarification by “best” batteries I’m not necessarily looking for cheapest. As with anything, I know some batteries are better quality than others but I don’t really have enough experience with different battery brands to know which are “high quality” and which to avoid. My philosophy is EVERYTHING on the robot starts with the battery so why risk using anything less than the best quality. We all pay a lot of money per match to play in FRC and I have seen may teams loose many matches because of battery issues over the years. Why risk it with el cheapo batteries? I just don’t know which on the list have the best reputation for quality.
I’m not saying at all that we are unhappy with the Enersys batteries and in the absence of info as to a better option I would likely buy more Enersys from PPS tomorrow if I had to. I’m just wanting more info from the collective FIRST community to make a more informed purchasing decision between now and whenever the time comes. I figure everyone would like the benefit of knowing what batteries seem good and what seem not so great. With a few thousand teams using probably tens of thousands of different batteries now there has to be some good and bad recommendations especially given how opinionated folks on CD can get.
We used them right away and I don’t remember having any problems.
We have been testing batteries using a CBA III this summer and plan to continue during the year.
If anyone is interested here are the first test results, these aren’t that useful until we start seeing what happens to them over time. We also didn’t run baseline tests on them when they were new either.
For those of you that are using the CBA, I recommend that you test at 7-10 amps and 8 volt cutoff. This will give you curves that match the manufacturer curves for most batteries. The CBA has a top current draw of about 7.5 amps, the CBAIV will do a little more. It helps to test batteries once or twice a year and use the overlay feature to see the difference in tests.
BTW, let West Mountain know you are a FIRST team, I have been trying to get them to be sponsors for a couple of years. They are located in a Milwaukee suburb.
The CBAIII we have can only sink ~7.5A @ 12VDC. We have/do run tests at 7.5A like Allen and Al suggest above but also run tests at higher current draw (50A/75A) using the dual amplifiers. FRC bots pull a lot more current for a short 2 minute match than the 7.5A tests simulate. We like to stress test our batteries under conditions that more simulate FRC bots. We have identified under-performing batteries this way.
What I understand you to be saying (please correct if this is not the intending meaning) is that you have identified under-performing batteries which would not have been identified with the 7.5A test alone. Is that right?
I suppose it would be unfair to say that they wouldn’t eventually be found to be under-performing with a 7.5A test. We have had a few batteries that seemed OK testing at a lower current draw (~7.5A) that dropped off rapidly at a higher current draw (~50A). I will try to pull up some CBA data/plots this evening and compare.
I’ll have to look again at the battery test files but I don’t think I usually test them to as low a cutoff voltage as Allen (10.5V) and AL (8V) suggest. IIRC I usually set a cutoff voltage of 11.5V.
I’m interested to know why Al tests all the way down to 8V. We went with 10.5V as that’s about as bad as we have ever had a battery come off the field. We don’t compete with voltages lower than that (no load voltage) so we didn’t feel it necessary to drop them that low. Maybe we should be lowering the cut off voltage.
In 2009, our battery voltage would drop down to 7V after a heavy match, and under load, during the match, would display around 6V. We came very close to a brownout.
Of course, we were using 9 or 10 motors that year, and they were always on 85% of the time.
But its definitely possible to have the robot operate at dangerously low voltages, so it might be relevant to test the battery down to low voltages.
Basically the same philosophy with us. I think the 50A test cutoff at 11.5V usually take 6 or 8 minutes or something like that. Again, I’m pulling from memory right now so let me look at the data and verify but the tests go much faster and, well, you know how many batteries we usually bring to competition so it really speeds the testing process up as well. I know there will be comments about this process being harsh on the batteries and that manufacturers test at a lot lower current draw for a lot longer period of time but we aren’t using these batteries like that so my philosophy is why test them like that? We stress a battery for 2+ minutes through a 120A breaker. 50A or even 75A draw for a few minutes seems reasonable to me. I actually wish I could figure out how to program the CBA & amplifiers to cycle the current draw to like 100A or 150A for a short time (seconds) then draw less and sort of simulate a 2-3 minute match. That would seem to be a better indicator of how well the batteries will hold up the way we use them.
For what it’s worth we used to always charge our batteries using the 2A setting on our chargers. A couple of years ago (through our battery testing) we found the batteries seem to do better charging them using the 6A setting. We just got some of the Autometer BusPro-660 chargers which are 6 bank 5A chargers designed for SLA. I hope they work out well. I guess we will see this coming season.
All this battery testing discussion is great and useful but I really hope the collective community can provide some good insight into what their experiences were this year (good or bad) using battery brands other than the Enersys.
Do you typically run a fresh fully charged battery at the beginning of each match or is it possible the batteries had been used in one or more matches previously?
Our team rule is one match per battery per day. We put a freshly topped off battery in the bot at the start of every match and don’t use it again that day if we can avoid it.
We DID use a fresh battery every match, and still do.
One aspect that drained our battery, we had 2 large fans on the back of our robot. If we got into a pushing match (which, in lunacy, happened a LOT. And pushing matches draw a lot of current from the CIM motors), we would activate both of our rear fans, at 100% throttle, which caused a HUGE drain on the battery. However, it almost always would win the pushing match…
From the inspections I did, I didn’t see many teams using many batteries other than MK and Enersys. Most teams don’t do any testing or even keep track if a battery is good or not. It would be nice to know if any of the other brands are better than what we have been using.
We have a stock of batteries from the last few years and have only just retired our batteries from our first season this past year. We had the option to get a few batteries from our local Batteries Plus store with an excellent discount and gave them a shot.
They were the Werker brand battery and we had some good experience with the brand through electric car racing. We used them all season and never had an issue, but they did test low in the available current department and no load voltage. They tested comparable to Enersys batteries that were two seasons old when load tested. Of our ten batteries that we brought to competition, the Werkers were placed at number 9 and 10 in our rotation behind every other battery we used. I would have to get into our shop to see the numbers, but I do remember them being comparable to a three year old competition used Enersys battery that had also been used for practice for two years.
They also seemed to not last as long by the ever so scientific kids driving until the lights go out method.
Again, we still used them and never had any performance issues with either of them in competition.
I took a look at the most recent suite of CBA tests we ran on the 13 new Enersys batteries we got this build season (12 purchased new + 1 KoP). The test were run the week before our first event. We ran 4 separate 50A tests with cutoff voltages of 10.5V (same cutoff Allen uses). The 13 batteries ranged from ~3AHr to ~5.5Ahr. Each of the tests take about 5-7 minutes to complete.
We have an off season next weekend so maybe we should run them through again and see how they are holding up. I’ll add it to the list of stuff to do this week!
