Recommendations for reliable, budget friendly batteries and how to best treat them?

Our team was experiencing some brown-out issues that probably stem from bad batteries. We bought them during the 2020 season and have been using them ever since. Upon experiencing our issues, we did some more research and learned that there is much more we should be doing to preserve our batteries. So please leave any recommendations of reliable, up-to-date batteries to buy as well as any preservation actions that your team may take.

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MK batteries r pretty nice and they usually have a relatively reasonable price and reliable customer service. We bought a few this year and some dropped from 130% to, say, 110% within minutes but per customer services’ instruction, it would stop having this issue once we depleted and used them for at least 20 cycles. You can check out this thread for sources to purchase batteries: Best Purchasing Source for FRC Legal Batteries

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Keep them charged.
Nothing hurts a lead-acid battery than being in a discharged state.

There are many older threads on this topic, search.

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I’m working on a cheaper way to do an energy storage test…

A painfully won lesson: you need to do an energy storage test before each competition if you can afford the tool. We had TWO 2022 batteries that went from 18,000 to 1,600 mAhrs between our first comp and TRI! We don’t know -when- that happened :frowning:

If you don’t have the tool, run a 3 minute practice match on each battery. That would have caught our bad ones. Good for drivers too!

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Question for teams working out of a school where you don’t have access over the summer, how are you ensuring your batteries aren’t left sitting for 2 months with no charger/use?

For 10 months out of the year, I’d imagine some kind of trickle charge setup would be good to ensure the batteries aren’t left depleted too long (input/suggestions for this kind of setup would be great too). Do you then send your battery setup home with a mentor/teacher to monitor over the summer?

To sum it up I guess, how do you put your batteries into “long term” storage during the summer/offseason?

*I’d say this question relates really well to OP’s post, but if mod’s feel it necessary, we can split this into it’s own thread too *

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We just top them off before the school year ends. Which may not be the most perfectly correct strategy, but it heads off the worst outcomes.

Batteries do discharge slowly over time even more so if you aren’t putting them in a temperature controlled place during the summer so leaving them uncharged for 2 ish months might hurt the batteries in the long term.

If you want to keep them charged there are options to buy battery tenders (essentially trickle chargers but smarter because they know when to start/stop) but these can be expensive to use on an entire fleet of batteries.

Sending the batteries and chargers with a mentor and teacher is a really safe and cheap option, although more effort for said person, but regardless of whichever option you do I would invest in a battery analyzer tool and check the batteries after the summer in the case something unnoticeable happens.

Also charge at lower amps like 2 instead of 5 or 6. There are maintainers that will allow you to leave a battery plugged in for long periods of time and it will allow some discharge then it will fill. We have multiple Noco Genius 2 with Anderson AB50 plugs on them to keep our batteries

In the age of older chargers that just dumped current blindly into the battery, I could see this aiding longevity. I’d like to see the receipts for this still being valid in an age where most every charger has smarts to it and they’re trying to top off the battery just right.

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Our team was experiencing some brown-out issues that probably stem from bad batteries.

Good advice here – but brownout can have multiple (or other causes). If things were good with some batteries, you are probably good on other causes. But there are quite a few very common causes for this sort of thing, including the connections to the batteries and going from there.

Also, COVID was really tough on batteries for many teams that couldn’t look after them.

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Low amp charging is best we use this

Really doing a load test is the best way to see if the battery is good or not.
I know this is a bit of an expense but our HUB got one last year and shared it with the teams. It is kinda amazing.
Got rid of 3 batteries that seemed good on the battery beak! And 1 more that is practice only

If you drive your batteries down to the point at which your robot’s motion is stuttering and struggling to move, you are already damaging your batteries. Most teams probably discharge them further than they ought to when practicing.

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  1. I would still like the receipts on lower-current charging with a modern charger being better for the battery’s short-term or long-term capacity.
  2. …you know 'ya went and linked to a charger rated for the highest FRC-legal charge rate with zero adjustment options to turn it down, right?

And it’s easy to get sucked into that trap. We were at SCRAP last year trying to dial in out our (fully open-loop) shooter at the practice field, and the kids kept running it and running it and running it wondering why their shots were missing low. I touched the NEO briefly (quite toasty, quelle surprise) and finally had to stop them like a parent trying to keep their preschooler from going through the McDonalds playground one more time so we could get ready for the next match.

Yeah, two amp charger would probably be better for the overall health of the battery. Granted I am not an electrical engineer in, Or do I play one on TV.
It’s a good overall charger solid and robust and one that you can bring to competition.

I was unaware that FIRST regulated the type of charger I could use. Never had an RI check that as they were going through their list.

There also comes a time when you should stop using some batteries and get them replaced, depends on how much tolerance you are willing to accept in batteries.

@sanddrag the bots start the stuttering at 10.5 Volts. The RoboRio has a “brownout” bit that turns all the motors off when it hits that threshold. I’m not sure how long they stay off.
The key bit there is that it’s 10.5 Volts under load. A 200 Amp motor load will pull it right down! I had to do some teaching with the drivers on this… Don’t just hold the stick and let it stutter; just ease the stick forward and find a happy speed!

The brownout kicks in at 6.3 volts (Rio 1) or 6.75 volts (Rio 2). See the below link for more detail.

If only one motor is stuttering, that’s more commonly due to a breaker trip. They’re auto reset breakers so will come back on in a short time.

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