They said that we could ONLY use the MK 12 volt battery as our maing power battery, aren’t they the same as last years batteries? the previous years batteries are 12 volt, can we still use them?
anyone know?
-Thanks
The batteries are slightly different from those last year. I’m not sure of exact specs. You are not aloud to use batteries from last year as this would create an unfair advantage to those teams who dont have those batteries from last year
It is not the voltage of the battery that is different. It is the model number. If you would go look at your batteries from previous years you would notice the are exide ES-xxx* model number. EX-xxx* != MK 12
-John
*I do not know the exact model number off hand.
Specs for the 2007 battery are here.
Specs for the 2006 battery are here.
The new one appears to have about 10% less stated capacity at 1C discharge rate. So if you could use the older battery you might get an advantage over a team using the new one – which is almost certainly the reason why the older ones are not allowed this year. For more, see this post.
You are not aloud to use batteries from last year as this would create an unfair advantage
And it is definetly fair to all of a sudden make the batteries from previous years extinct in order to make the teams who collected their batteries from previous years and who can’t afford to buy 10 extra batteries like other teams go through all the trouble of possibly losing qaulifiers due to the fact that the batteries don’t charge fast enough.
Sadly there’s nothing we can do about that. Might as well learn to deal with it. Big disappointment but oh well.
Not every team is going to be in a match at the same time. We do know how to share.
Everyone’s in the same boat. Everyone has only 2 batteries and no collected batteries from previous years. That is, in fact, MORE fair than everyone but rookies having a collection of batteries from prior years. You can still use old batteries for testing and practice day. You have more chargers than the rookies. With even a little bit of effort on your part to solving the problem you could make 2 batteries work just fine for a regional. If you buy just one extra battery you should be more than covered. They can be had for around $50.
I speak from experience by the way. 57 takes just 3 batteries anywhere we travel and we don’t have any problems.
One of the bullets in <R46> says:
I interperet that to say that we can only use the 2 batteries provided in the kit. Opinions?
If that is FIRST’s intention, I don’t think it could be enforced. (How would FIRST know if a team brought more than two batteries to the regional?)
That said, I wonder if that is a mistake in the manual.
That rule was the same last year as well. You will be able to buy more of the same battery and use them, as long as they are the same as the ones in the KOP.
Expect a clarification in the Q&A or a Team Update.
No. I would interpret that to mean we can’t use a battery in the kit, and another battery not in the kit at the same time on the robot.
I would interpret this:
<R53> The only legal main source of electrical energy on the ROBOT during the competition is the
12VDC non-spillable lead acid battery provided in the 2007 Kit Of Parts. That 12V battery is
the MK Battery, ES17-12.** Additional batteries may be purchased through a local MK
Battery supplier. **
To mean that we can purchase additional batteries, and therefore, use them in competition, as long as they are MK ES17-12s.
-Nate
Agreed. R46 covers what you can use ON the robot at any time. No using 2 batteries at once, no using a different battery on the robot. Doesn’t cover what you can have at the comp. So I would expect some Q&As but no updates on that.
Don’t know if anyone has noticed this, but the new batteries seem a bit heavier as well. We pulled out the scale today and clocked them at about 13.5lbs, which is about 1.5 lbs more than the old batteries (someone correct me if I’m wrong that the old ones weighed 12lbs)
Richard,
There are some major differences between the two sections of spec sheets you posted.
That’s a huge difference. The Exide battery from 2006 had a 230A max discharge. Can anyone confirm which of these is right? Am I missing something here? If the max discharge has dropped all the way to 90A, we’ll definitely be reconsidering our motor usage.
Based on the spec sheets linked by Richard, the new batteries are only about .4 lbs heavier
The old exides list approx 13.44 lbs while the new MKs list 13.82 lbs
I’m more concerned about the max current draw - like Karthik said, if the draw is that much different than it will definitely have an impact on robot performance and capabilities
I’d guess that the 90A figure in the top section is an error. The lower section shows 360A maximum discharge current for 30 seconds. Also, the discharge time vs. discharge current curves shown near the bottom indicate several minutes capability at 3C (54A) discharge current; this is similar to the 3C capability of the older battery. It appears the new and old batteries are similarly constructed, and that the new one is designed for slightly (~10%) lower capacity. This may be a design trade-off to allow higher short-duration discharge currents. (A little more lead, a little less acid.):]
Karthik,
The specifications on the MK site are very close to the specifications for the old battery. The differences are slight enough to merely be differences in testing methods or the influence of the marketing departments. A close inspection of the discharge curves show that they are at slightly different currents from the batteries we have used in the past. A quick interpolation of the data would show them to be almost identical. Let’s face it, a battery of the same physical size and chemistry with the same amp hour rating is going to be pretty close in performance. You can only pack so much lead and acid into that package. I hate to have to buy new batteries this year but if those are the rules then so be it.
As I am reading this chart it seems the new battery has a HIGHER discharge rate. 5 seconds @ 720A this years battery and last years battery is 5 seconds @ 230A. Therefore it would better seem the new battery is BETTER for burst and a quick pushing match…
-Mike
Mike,
Although that specification looks different, last year’s battery was capable of the same high current for short periods and when new and fully charged. “Your mileage will vary.” In fact most teams will not be able to draw this kind of current simply because there are other limiting factors like the combined resistance of the wiring, breakers, speed controllers and connectors.
Remember that the real test will be how much you can draw over a two+ minute match and remain above 8 volts, the critical cutout for the RC.