Battery required by rule

A local battery supplier does not offer the right batteries for us.

The only legal source of electrical energy for the Robot during the competition is one MK ES17-12 12VDC non-spillable lead acid battery, or one EnerSys NP 18-12 battery, as provided in the 2012 KOP. This is the only battery allowed on the Robot.

It leads me to wonder several things:

  1. what if any are the differences between these two batteries?
  2. Is one or the other preferable for competition use?
  3. Do you have a preferred source of supply for either one?
  4. What speculation will you offer about why only these specific batteries are allowed for FRC competition use?

To answer question 3, AndyMark is an obvious source.
I haven’t shopped around to see if there’s a better deal, but $89 for two doesn’t seem too bad.

My opinion on question 4: The GDC wants to allow enough energy that we can do interesting and educational things with our robot, but not so much that it becomes unsafe. Allowing only one battery (or one of two nearly identical batteries) makes it much easier to accomplish that goal.

But watch the shipping cost – sometimes more than the batteries.

Good point. Regular shipping is $19.10 (for me, in New York, I just checked). But overnight is $167 - ouch!

They are heavy (13.8 pounds each), so be sure to check shipping before you buy from anyone online.

Both types of batteries are exactly the same in terms of specs and output. And I have seen teams use both interchangeably during competition.
Just remember to take care of your batteries!

I like the look of the Enersys batteries better than the MK ones, but that’s purely a personal aesthetically-based decision.

Multiple teams have found the Enersys battery to be inferior to the MK battery in terms of performance.

The specs are similar in many ways, but they are not identical.

The spec’d max discharge current of the MK ES17-12 is far higher than that spec’d for the Yuasa NP18-12. Whether or not that corresponds to reality is a separate question.

I wonder when FRC will decide to switch to 3-cell LiPo batteries instead?
They are much lighter, smaller, and have a more favorable voltage curve compared to lead-acid.

Well I take that back then…
In running though our batteries about half and half of each we have not been able to notice a difference so far.
But thanks for the info, sorry for the mis informed response.

LiPo would be nice…

I prefer the MK battery since they are manufactured in nearby Anaheim and I can pick them up at will call for $40 each, no shipping.

Call MK and see if they have a distributor that is local to you and save the shipping.

MK ships everywhere in CA via UPS ground for free as well. I don’t know if that extends to neighboring states also.

The MK may perform better when they’re good, but I’ve had many MK batteries fail. Probably due to abuse, but still, I have many dead MKs.

The old old dark gray Exides are still going strong.

Good to know about the differences, thanks. The exides may be going strong, but doesn’t the rule preclude their use this year?

As soon as someone suggests a specific part number for a LiPo or LiFePO4 pack that meets the energy/power requirements AND is cost-comparable and readily available.

Not until all teams learn what robust bumper mounting means.

I use liPo and LiFe batteries all the time in my personal projects and toys and love them.

I hope FRC doesn’t switch anytime soon; they simple aren’t safe and robost enough for the average FRC team.

The “average” “big” battery is a 2s 5 AH and that’s enough energy to cause serious fire and injury, a 3s 18 AH would be a bomb.

There is a type of lithium battery something with iron phosphate maybe. Anyways you can drive a nail through it and it will not produce any fire or smoke. The lithium batteries have a more favorable voltage cure, they are lighter, plus they last considerably longer cycle wise, enough to make up for the cost. I am in favor of them except that special chargers and battery management systems are required to use them. I think it would be nice to have them as an option but leave the current lead ones for anyone who wants to use them. Rookie team might have a problem with lithium.

The LiFePO4 type batteries are pretty expensive.

Here’s a cost comparison from my senior design project, LiFePO4 compared to sealed lead-acid (SLA). Note that in this particular application, weight is a HUGE disadvantage, to the tune of -10 points per kilogram (and any GDC members reading this: don’t get any ideas, please!). I want to say that it’s a total of 24V available, but for competition we’re running 12V.

Cost (for 2 12V cells)
SLA: $72
LiFePO4: $358 (plus $50 for charger)

Weight (for 2 12V cells)
SLA: 12.7kg
LiFePO4: 6.5kg

The main problem with Li batteries is like you say, cost. The other is that only some are safe considering the beating our bots take. I think the good one is a LiFeP. Probably more expensive too.

Mostly I’d just as soon stick with what we have because of the investment we have in both batteries and chargers. I could see stocking up on batteries and chargers the first year being a kilobuck expense.

Also, even though we are only 4 years old, we’ve yet to build a bot that even comes close to running out of juice in one match…

Here’s to a great year!