Battery Chargers

Hello all, we are planning on getting more batteries and chargers.
originally we were going to get the charger from the KOP:

However i came across this one,

Which does 2/8/12 AMP, instead the KOP which is 2/4/6.
Would charging at 12/8 amp do any harm to the battery?
I know the faster the charger the short the life but for competition we want to be able to run it at the fastest speed possible.
In short what is the largest possible AMPage we can charge the battery?

idk what it would do to the battery, but it wouldnt be good we have about 6 batteries running off the KOP chargers, and at competition not 1 is below 90%, meaning one is 90% and all the rest are full of charge

Read the battery specs, max charge rate is 5.4 amps. so even the kit charger running at 6 amps is slightly pushing it.

Absolutely DO NOT charge FRC batteries at a rate of greater than 6 amps. The batteries will be permanently damaged and may go into a severe failure mode while charging.

The max charge rate is 6 amps. The IDEAL charge rate for these batteries is 2 amps.

We use this charger. It charges 10 batteries at a time, at a sweet 2 amp rate. Keeps them in good shape.

You are much better off buying more batteries and charging them at the ideal rate rather than destroying batteries and creating safety hazards from ruptured batteries.

BTW - on a related subject everyone should replace the alligator clips on their chargers and use Anderson SB connectors to plug into the battery.

Yesterday I saw a team connect a charger with alligator clips into the SB50 connector, the clips touched each other, welded themselves together and turned WHITE HOT. It was an amazing site to see but this exercise is better left to Adam and Jamie on Mythbusters, not a FIRST pit.

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6 amp MAX it is.

This is last year’s rule below (which seems to be missing this year)

<R41> An automatic battery charger rated for a maximum of 6 amperes must be used to charge the supplied batteries. When recharging the KOP batteries, either the charger provided by FIRST or an automatic charger with an equivalent charging current rating may be used.

I don’t know if the rule changed this year or just an over site in the rules to date; however, since this is a safety thing, might just stay with last years rule until this is clarified.

Good luck to you

Our team has several chargers, but the one I prefer is a CTEK 3300.

From it’s manual (pdf) …
“The MULTI 3300 operates in a four step full
y automatic cycle. It starts the charging with an almost constant current (0.8A or 3.3A) until maximum voltage (14.4V or 14.7V) is reached. At this point the charger switches to constant voltage, and the current supply to the battery is gradually reduced. If the current drops to 0.4A, the charger switches to pulse maintenance. If the battery is charged and the terminal voltage of the battery falls to 12.9V, the charger automatically starts again at the first step of the charge characteristic.”

Prior to buying the CTEK, our batteries were charged using the Schumacher SC-600A. Using the CTEK, we’ve discovered several “bad” batteries, with sulphated plates, that were not fully charging.

I know this is an older thread but it suits my question perfectly so I figured I would use it…

I am currently in the process of designing a battery cart for my team. One of my mentors suggested I look into a battery charger that could charge multiple batteries at once. Unfortunately I know nothing about electrical, so if someone could post some links to good chargers that could charge 9 to 12 batteries at once, it would be greatly appreciated.

After squeaking through Peachtree on one battery charger, we bought two of these at Walmart. Never had a problem with them through Palmetto and Championship–we annotated the icons with some labels to make it easy to glance at. We ran them at 6A during the competition day to ensure we always had one to run, then plugged up a battery to each to charge overnight at 2A.

The insurmountable problem with charging multiple batteries at once is that each battery has slightly different needs at the moment, and using a single power source for charging fails to meet optimally the needs of any of those batteries.

In other words, each battery does best when connected to its own charger.

There ARE chargers that have several independent charging circuits (which I think is what you are seeking), I have seen them, just note that these tend to be quite costly. This one has 3 banks for $170, a 6-bank is $650+ (but at more than 6A, can’t use it at competition), and for that money you can buy a lot of individual chargers like the one Billfred suggests above.

The other thing to consider: survivability. If one individual charger bites it during competition, odds are you’ll be alright.

If your umpteen-bank charger goes down Saturday morning…

Thanks for the advice! I think we decided on one 3 bank just to try it out and the rest will be the individual chargers billfred suggested along with the couple we already had at the shop. Thanks again!


After reading about it in another thread, we gave the Auto Meter BusPro-600s a try. After running it for 2.5 years we love it.

It’s a little on the expensive side, but it’s been worth every penny. Some of the features we like the most are:

  • Removes sulfating automatically
  • Each battery is on its own charging circuit
  • Built-in float control so you can leave your batteries plugged in while in storage and not damage them
  • Built-in reverse polarity, short circuit and overload protection

That is the one we use. Don, this charger is six independent chargers, one for each output. We had one output die on us last year, an open MOSFET. It was easily replaced and we are back in business. We replaced all of the gator clips with Anderson connectors. We also made a stand out of some 80/20 so we can set it up with the cables suspended.

1675 also uses that charger, or one that looks very much like it. A few years back we took a dolly/handcart, bolted the charger to one (back) side, and welded pieces of aluminum for the on the other (front) for the batteries to slide into, angled a little less than 45 degrees from vertical. 3 rows, 2 batteries each. Anderson connectors on the ends color-coded to the diagnostic lights, and elastic straps to make sure the batteries stay in place while rolling. Can lay down or stand up (99% of the time ours is standing up), no balance problems because of the flat bottom of the cart being pushed steady by the batteries on that side.

This is what our battery cart uses. We have not had a problem with the tender. We also put the Anderson connectors on each of the ten chargers. The chargers each have their own fuse and break away point(just a bit past where the Anderson connectors/alligator clips are) which makes them really easy to take out of the cart. Since there is ten(admittedly not the fastest charger) you can go through a whole regional qualifiers with charged batteries and the ones from your first matches have had a day to charge. or quantity over speed.

Even with extra tournament tiebreakers our robot has had a fresh battery and never ran out of juice. Pit crew remembering to zip tie the connectors together is an entirely different issue


Another vote for the battery tenders, I have the 12v jr model I use on both of my stored cars during the winter.

I haven’t done any of 237’s batteries with it but it would work fine and also great during storage of the batteries. I know the site lists it at $39 but they go on sale at times through other sites, I paid $26 for mine.

Just to make sure my facts are straight…
6 amp chargers are bad for battery life but good for quick charging
2 amp chargers are good for battery life but bad for quick charging
4 amp chargers would be ideal for both (according to my electrical guy)

My team orders new batteries almost every year and the old ones become practice batteries. Right now we have a total of 10 batteries that we use (4 for practice 6 for competition) do you think that the 2 amp charger could charge 6 competition batteries quick enough for an entire day of competition? (assume including the fast rotation of elims)

If not does anyone know of any good 4 amp multi-bank chargers?
P.S. Thanks for all the advice and help everyone its helping me a lot.