Battery Chargers

[Alan Ing]

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?

[Ian W.]

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.

[mnkysp6353]

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.

[Ian W.]

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.

[DaBruteForceGuy]

IAN ru still up?


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!

[Katie Reynolds]

Originally posted by Alan Ing
Last years chargers were a lot more powerful, but according to the rules we will not be able to use them.

... where in the rules does it say you will not be able to use last years chargers?

- Katie

[Alan Ing]

Hi Katie,

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.

[Ian W.]

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.

[jeffreym]

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.

[mnkysp6353]

I think its .87 amps

[Ian W.]

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?

[Alan Ing]

Ian,

This is straight from the First Tech list

[Alan Ing]

Ian,

This is straight from the First Tech list.

> 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?

[jeffreym]

If you look at message 376 in the FIRST Yahoo forum you will see the following:

> Also could we buy more batteries as long as we only use one in the
> bot at a time?

A) You may buy more for use as spares.

The solution - lots of spare batteries and a charger for each one of them!

[Ian W.]

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!