Battery Model Number Questions.
 

My team ordered 3 batteries from batterysharks.com. We got two Sigmas Tek SP12-18's and one Sigmas Tek SP12-18HR.

The Sigma SP12-18 is legal but I am wondering about the SP12-18HR. I cant really find a difference in the two. Will the SP12-18HR be legal?

Re: Battery Model Number Questions.
 

I would email FIRST per the blue box below that rule.

Re: Battery Model Number Questions.
 

f you look just under R31:

Re: Battery Model Number Questions.
 

http://sigmastekusa.com/files/specsh...18%28NB%29.pdf

http://sigmastekusa.com/files/specsh...HR%28NB%29.pdf

Based on the spec sheets there is some difference in performance between the two. As others have said, contact FIRST to get a reading on the legality of the battery... Without FIRST saying it's OK, if presented with one of them at an event I was LRI at, I would personally look at the spec sheet and say the two are not equivalent.

Re: Battery Model Number Questions.
 

I agree with Jon. There seems to be a fairly large difference in the 2 batteries. Without FIRST's consent I would deem illegal.

Re: Battery Model Number Questions.
 

What's the big difference in the specs?

The max amps? Take a look at the 360 max amps for the ES17-12.

The Ah? Take a look at the discharge curves for the SP12-18HR vs SP12-18. They are identical.

Re: Battery Model Number Questions.
 

Any ideas about how long approval or disapproval from frcparts will take? I sent a request on the 3rd and have yet to hear back from it. I know they're busy up there in N.H. but I had to replace a couple of bummers fast. Right now they're being used on test runs and not in competition.

Re: Battery Model Number Questions.
 

The max discharge current of the HR is 270 Amps and the non HR version shows max dicharge current at 180 amps. Wow.... I like the HR version better....should be able to trip the main robot breaker much faster.

It will be interesting to see if FIRST considers the HR legal.

-Hugh

Re: Battery Model Number Questions.
 

The spec max discharge rate of the ES17-12 is 360 amps for 30 seconds, or 720 amps for 5 seconds.

Neither datasheet says what the voltage is at their spec'd max discharge.

It will be even more interesting to see what their rationale is if they do not consider it legal.

Re: Battery Model Number Questions.
 

I agree that the graphs on the second page are identical, which doesn't seem to make much sense to me, as the data on the first page (specifically the tables) is different. The differences I see are:

- weight
- Rated Capacity
- Max Discharge Current
- "Constant Current Discharge" table values
- "Constant Power Discharge" table values

I'm a software engineer, not chemical or electrical, and frankly, the details of how all of those numbers impact robot performance is a bit beyond me - That's probably why FIRST asks teams to e-mail for approval for an equivalent battery. They can't rely on all of the LRI's having the ability to judge battery data sheets to determine if a battery is equivalent for our purposes.

That said, from the two tables, it appears that you can pull more current/power from the HR battery over an equivalent discharge time period. To me, that seems to indicate a difference that might be noticeable on a robot.

Re: Battery Model Number Questions.
 

Yes, if you believe the tables instead of the discharge curves.

If the specs of the EK17-12 and NP18-12 are to be believed, they might also indicate a difference that might be noticeable on a robot.

Just sayin'

Re: Battery Model Number Questions.
 

Just another marketing department ploy it would seem. When a manufacturer sheet doesn't give you all the details it is impossible to know. Both batteries do not meet the max current specifications of other batteries but they also do not specify the max current vs. time that the other sheets specify. The only clear differences are the weight which is slightly higher for the HR version and the internal resistance which is 15 mohms compared with only 11 for MK batteries. It is unlikley that the HR version is significantly different in performance than the standard version for our use. I suspect the graphs are the same as this is an industry standard 18AH battery which must conform to those criteria. It is the same as the published sheets for other manufacturers. I suspect that the tie up at HQ is that many people are on the road at events these days. Competition season is tough on these guys.