I didn’t really get a chance to look at this years battery charger, but it seems to me that it is too small to keep our batteries at top charge during the competition. Does anyone else feel the same? Last years chargers were a lot more powerful, but according to the rules we will not be able to use them.
Considering that our robot can draw in excess of 100 amps in a match, I’m a bit worried that one little trickle charger isn’t going to keep us running at full power between matches. We had a terrible experience with a weak battery during the last match of the finals in the competition two years ago. We ended up changing the battery prior to the final two matches in front of an anxious crowd and while it added to the excitement of the match, this is something I’d rather not repeat.
Unfortunately for me, we packed this years charger before I could get the specs. Could someone please post what model the charger is and where to get an extra one?
one of the parents on our team is an electrical engineer (or he at least does lots of things with electricity), and he was explaining to us how the charger worked, and why it was taking so long to charge. then, when i asked if we could get a faster charger, he said that the battery would be able to physically handle a charger of 2 or maybe even 3 times the power, but it’s a question of whether of not FIRST will allow us to buy better chargers. you are right though, the current charger is very, very, very slow, and i’m rather worried about not having enough juice at the end of the day. not smoething i look forawrd to, especially in my first competition.
Alan we have the same problem. Glen from team 60 told us this weekend that too fully charge the battery it would take something like 23 hours. We are using last years charger and will not be using this years. I hope first realizes there mistake and retracts that rule.
from what i heard, to fully charge a completely dead battery would take more than 18 hours, although how much longer i’m not sure. but if you think about that, it’s still way too long. if your average robot can use one battery for approx. 15 minutes max, before the battery dies completely, we’re going to have lots and lots of dead robots. that is not a good thing.
is it possible to get a statement from FIRST saying that it is ok to have a more powerful charger? i would try to do this, but i’m not sure where to go. either that, or if someone could point this out if it’s in the rules, that would help too. thanks.
well anyway i think that FIRST only lest a certain amount of amph to be used by the robot so therefore by the schedule given to each team there should be only a certain number of matches to play in a day so as to be able to finish and still have some life left over!
This is a response to someones question on the First tech list. Apparantly the rule is C.20
> Frcengineers:
>
> Rule C20 states that only the battery charger supplied or one with
equivalent
> specifications may be used.
>
> The charger manual indicates an output of 1 Amp hour, less than the
battery’s
> capacity. We have some level of concern that this may be inadequate
for
> recharging during a match.
>
> Is it legitimate to use a charger of our own as long as its’ output
does not
> exceed
> battery specifications? [For example, we have a charger that can
output 2 Ah
> in trickle charge mode or 10 Ah in quick charge mode.]
A) You may not use that charger. See rule C20. You may use another
charger that does not exceed the specifications of this years charger.
Please note that teams will be allowed to recharge their batteries in
the Pits overnight.
FIRST MRT
Personally, I have a problem with this. Even if you leave a battery on a charger overnight, with the rate of charge these chargers give, you will only be able to charge ONE battery, and since you cannot get in to the pits at night, you will not be able to change over to the other battery.
Does anyone have this years battery charger specs? Again, I forgot to check this before we packed it in to the crate.
If this is the case, then i have a feeling that the final matches of the day will be seeing more than a few “dead” robots, because from what i’ve heard, the robots suck up a lot of juice. I understand that due to the battery design, too much power in a recharger will “blow it up”, but many people have told me that we should be using at least a 2AH recharger. Hopefully FIRST will change this.
During our robot construction we routinely charged our batteries with a constant 14.4 v, 20 amp power supply. We could charge the batteries in an hour from completely dead. They got only slightly warm and showed no sign of damage. Alas, we can’t do this in competition.
We have bought 8 batteries and are planning on buying 8 chargers identical to the one in the kit. We calculated with our power draw, we’ll change the battery every half hour (about 5 matches) and charge all 8 batteries overnight in the pits. What a waste of team money this is because of the “1 amp” charger rule!
However, does anyone know of a source for the chargers? We’re having trouble finding them.
wait, i thought you could only have a max of two batteries!! i know that for your own use, you cna have a bajillion batteries, but i thought for competetion, you could only have a max of two batteries for your robot. grr, why must this be so %%%% confusing?
> Can we use different brand batteries other than exide?
A) The only batteries you can use on the robot are the exide
battery from this year’s kit of parts or the Yuasa battery from last
year’s kit.
FIRST MRT
It looks like you may not purchase NEW batteries, but can use the ones from last years kit for a total of 4 batteries. The problem again is, how do you charge 4 batteries overnight with that little charger?
ok ,well that solves that problem, although i don’t believe my team has that muc hmoney to spend. oh well, looks like i need to go and get some money, fast. less than 3 weeks till the regional!
This year’s battery is 12V at 18Ah, the charger is somwhere about 14V at 1A.
Last year’s battery is 12V at 17.5Ah, the charger is some voltage I don’t know off the top of my head, at 4A.
So… assuming the charging is 100% efficent (HAH!):
18A at 1A/hour = 18 hours
17.5A at 4A/hour = 4.375 hours
Remember though, these values are for a totally dead battery (and they are a little small, I can gaurentee that it won’t charge at 100% efficency)!
I’d reccomend charging your batteries up all of the way, and putting some kind of ammeter on your robot and charger. This way you can have a pretty good idea of the charge state of the battery.
Why did FIRST give us this WIMPY charger this year? Why do they care what we use to put energy back into the battery? This, I think, is most uncool.
Were bringing last years chargers anyway, I can’t see why if they were legal last year they wouldn’t be this year, besides we now have four of them from over the years. I like the fact that the new one is small but our robot eats monster current this year and normally puts the low battery LED on after about 5 minutes tops.
I’m on a rookie team. We don’t have anything from last year to use. or extra money (were going to nationals) 1 battery lasted for about 3 4 hours of testing and a full batery lasted more than 2 hours of continous compition we did with other WI teams so i dont see why 2 fully charged batteries won’t last for a day.
It all depents on the load you are pulling. A bot with a 6 moter drivetrain will pull more than a 2 moter drivetrain. And if you spend all match in a tug-of-war, driving the moters near stall vs a ball getter where you are not running the moters so hard.
And if you are running the bot around alot, take breaks to protect to moters.
Hmm…
As I think about this, what if this was intended as an equalizer this year but no one noticed?
*Originally posted by Matt Reiland *
**our robot eats monster current this year and normally puts the low battery LED on after about 5 minutes tops. **
I can tell you that the LED light that tells you if your battery is low is not really to be trusted. It turns on when the battery drops to a certain voltage and it doesn’t matter if it stays there or not. Our robot you can drive for 30 sec. and the light will come on if you gas it full forward quickly. The thing to keep your eye on is the actual voltage on the control system display.