Re: Which Battery to Buy?
 

Which company do you work for and what are the applications for these systems?

Side note, I consider the SLABs we use to be 10Ah, as that is spec capacity at the 1 hour rate. We've tested them at a 10A discharge and they produce 14Ah new. Also, If you're going through 10 batteries a year, I'd like to see what you're doing during practice. I do believe you are doing something which is shortening the life of the batteries.

Back on thread... I work with Aircraft Batteries as part of my job, including Lithium Batteries (not Boeing 787). I still see lithium batteries as too dangerous for use in FIRST. This includes LiFePO4 batteries. The failure modes of lithium batteries are still too dangerous and can produce toxic gases fairly easily. When combined with the abuse from personnel who will not know how to handle them properly and the robotic impact environment, we're going to burn down a building if we use them.

Re: Which Battery to Buy?
 

Trust Automation, can't comment on what the applications are.

We practice a LOT, and do it year round. That easily goes through 10 per year. We're not the only team that does this.

Re: Which Battery to Buy?
 

We purchase at least 10 new batteries every year.

Re: Which Battery to Buy?
 

That is $450 spent right there! Instead, it would be better to invest in a more expensive battery ($100 per battery instead $43.50 (AM)) that lasts several years!

I highly doubt that there are going to be batteries like that. However, what is a deal is struck between USFIRST and a battery manufacturer such as A123 Systems?! I think that the price per battery would drop significantly for FRC teams all of a sudden!

Re: Which Battery to Buy?
 

That sounds like a real problem....for maybe 2% to 5% of teams?

The rest of us get by using the same batteries for several years.

Re: Which Battery to Buy?
 

Everyone who uses the same batteries for several years would likely have better performing robots if they weren't forced to do that.

Re: Which Battery to Buy?
 

I'm sorry, I didn't really get you so my reply might be off topic. Typically, batteries will have a decline in performance as they age. This is due to chemical processes such as sulfation. I guess that the team would slowly accommodate to the aging of these batteries by making their robots more efficient, but there's a dead limit before it becomes impractical. It would be nice to have a robot that isn't a dead piece of equipment due to 10 year old batteries :D (I wonder if that would even be legal :D).

Also, as batteries grow older, their "C", or Charge rating declines. This means that these batteries can pump less juice safely and effectively.

Re: Which Battery to Buy?
 

Yash, what he's saying is that because of the reasons you mention, teams that are "forced" (due to finances or other reasons) to compete with the same batteries for several years aren't going to perform quite as well as teams that buy new batteries every year (and mark the older ones as "practice" if they even bother to keep them).

Re: Which Battery to Buy?
 

There is one variable that has not been touched on in this thread. The original post talked about problem post season. How much did the impacts the robots endured this year affect our battery life?:confused:

Re: Which Battery to Buy?
 

Most of us have other things hampering our robots' performance more than battery degradation...

Re: Which Battery to Buy?
 

Following this logic, nothing should be improved ever because many teams have trouble with ________.

Re: Which Battery to Buy?
 

Or, we have other priorities. Mostly, getting a robot built.

I'm surprised y'all haven't come up with some lithium batteries for use during practice. I'm sure we'd all like to hear about some experiments in this area.

Re: Which Battery to Buy?
 

I've used RC grade LiFePO4 packs to run a practice bot w/ no issue. 13.2V nominal, 16.8 Ah. It passed the subjective test of a few minutes of practice.

Others have done experiments as well.

Re: Which Battery to Buy?
 

At some point the FRC market will be large enough for a custom designed battery. Are we there yet, maybe not. It is interesting to think about though.

3500 frc teams x 4 new batteries a year per team average x 43.50 per battery = $609k spent on batteries per year for frc?

If we assume for every battery a team buys, it has to take one out of service, thats about 14,000 lead acid batteries to properly dispose of a year?

(I admit my numbers are likely off, just food for thought)

Re: Which Battery to Buy?
 

Unfortunately, that's not a lot of money at the end of the day.

I don't see what benefit (from a business case) a custom battery would provide. It's definitely an interesting thought though.

In my experience, we (836) took only a few batteries out of service since we started paying attention to how we use the batteries 4 years ago. I doubt we [ab]used them as much as 254 does, but they will last more than a season or three if properly maintained.