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#1
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Batteries
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*?:
Enersys (P/N: NP18-12) MK Battery (P/N: ES17-12) Battery Mart (P/N: SLA-12V18) Sigma (P/N: SP12-18) Universal Battery (P/N: UB12180) Power Patrol (P/N: SLA1116) Werker Battery (P/N: WKA12-18NB) Power Sonic (P/N: PS-12180 NB) Yuasa (P/N: NP18-12B) Panasonic (P/N: LC-RD-1217) Interstate Batteries (P/N: BSL1116) Enersys (P/N: NP18-12BFR) Enersys (P/N: NP18-12B) *Yes, we know what was legal last season may not be legal next season. |
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#2
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Re: Batteries
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. |
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#3
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Re: Batteries
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-Nick |
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#4
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Re: Batteries
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!
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#5
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Re: Batteries
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.
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#6
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Re: Batteries
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.
We have always gotten our Enersys batteries from Portable Power Systems: http://www.portablepower.com/12_volt...nesis_NP18-12B 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. ![]() So, I have one vote for MK from Allen so far... |
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#7
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Re: Batteries
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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. https://docs.google.com/spreadsheets...g0_mqTdVg/edit These are tested at a 7 AMP drain and a cut off voltage of 10.5 Volts. Here is a sample graph from one of the the battery test. https://docs.google.com/file/d/0B0dr...VYNF94THc/edit |
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#8
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Re: Batteries
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. |
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#9
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Re: Batteries
Why so many every year? As long as you take care of them during the off-season, they should be fine for many seasons of use. My team still keeps around a couple of 2011 batteries because they actually perform just as well as the batteries we got this year.
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#10
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Re: Batteries
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#11
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Re: Batteries
[tangent alert] You could say that about much of the robot though.
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#12
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Re: Batteries
I'll admit I could have worded that better. What I meant is that it's the beginning of the power path so it affects the performance of all other systems.
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#13
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Re: Batteries
Allen,
The mechanics of this bad cell failure (in my best guess) is that through damage, either drop or robot hit, some of the plates in a cell become dislodged from the connecting terminals. As such the remaining plates still function normally but the cell has a lower amp hour rating as it will become depleted before the other cells. If we were to test at full current, it might show as a change in available current at 400-500 amps. When testing at the manufacturer's spec, you will see the battery run a normal discharge curve, in some cases more than hour, before the bad cells actually become evident. To visualize, say a cell has 10 positive plates and 10 negative plates. The battery gets dropped and one of those plates either cracks or comes completely off the output terminal plate. Since the plate area is directly proportional to the available current and the amp hour rating, any reduction will reduce both of these measurements. The CBA testing will establish a fixed current load that will calculate the amp hour rating without the need to measure max available current. Since both are affected by damaged plates, just knowing that a reduced cell amp hour rating is enough to declare the battery "practice only". Close examination of the battery case will almost always point to case damage from the drop or hit. If you search "AGM internal structure", you will find a variety of pictures and other links to get an idea of what could go wrong internal to these batteries when dropped. |
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#14
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Re: Batteries
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Part of the reason we don't test that low is to save time and part of it is because, though observation only, batteries that are drawn that low (always on the robot or powering an inverter) don't seem as healthy afterwords but that could just be observation bias. |
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#15
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Re: Batteries
Yes,
The cell may be just shy of running out of energy at 10.5 volts. For that matter even the lower cutoff voltage may not show a partially damaged cell. The lower voltage will catch more defective cells than at 10.5 volts in my opinion. In some cases, internal temperature may exacerbate the intermittent connection. I had one battery that confused me for a while because when the cell got close to dropping off the graph, it suddenly produced a lot of "noise" over a period of 20-30 minutes before dying. These voltage peaks and dips were several volts. I came to the conclusion that the cell had partial damage and the noise was caused by the plate intermittently making and then breaking contact with the terminal plate. |
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