8.4 v charger?

[Maximus123]

any other teams get an 8.4 v dc 500mA charger in their kits? we did... weird...

[Joe Ross]

It's to charge the 7.2v backup battery which you should have also gotten in your kit.

[Maximus123]

we also got the 7.2 charger as well, isnt that the charger for it?

[tdlrali]

Our backup battery charger has no LED so it's hard to tell when the charging is done.. Did everyone get that one?

[Maximus123]

wont the 8.4 v cook it?

[Joe Ross]

Originally Posted by Maximus123

wont the 8.4 v cook it?

A battery charger must charge at a higher voltage then the terminal voltage of the battery. The 8.4v is correct.

[Alan Anderson]

The charger we received in the kit has no way of letting you know that the battery has been charged. I'm not sure it even checks -- we left a prior year's backup battery plugged into it over the weekend, and it was very hot when we got back to it. That battery seems not to hold a charge very well any more...

I am invoking justified paranoia and directing that our team not use this year's backup battery charger unless we find reliable documentation that it indeed will not overcharge the batteries.

Our team doesn't use the kit one. We have a couple of preformance RC car chargers that can fully charge the battery in about 15 minutes, and then let us know with a deafening beeeeeeep when it's done. One of them also has a graphical LED display on the charging progress.

[tdlrali]

yeah, i'm using the older, bigger one (black) since i wasn't sure about this year's. that one at least has a LED (green and red)

[eugenebrooks]

Originally Posted by Alan Anderson

The charger we received in the kit has no way of letting you know that the battery has been charged. I'm not sure it even checks -- we left a prior year's backup battery plugged into it over the weekend, and it was very hot when we got back to it. That battery seems not to hold a charge very well any more...

I am invoking justified paranoia and directing that our team not use this year's backup battery charger unless we find reliable documentation that it indeed will not overcharge the batteries.

Most of the chargers for the NiCd battery supplied in the kit over the past several years will overheat the battery if you leave it on the charger overnight. If you want to do that, you need to use a charger that terminates the charge properly. Unfortunately, use of the KOP charger is required by the rules in the pits. We simply do not leave the backup battery on the charger overnight. As soon as the battery starts to get warm it is fully charged and you need to take it off the charger.

Eugene

[billbo911]

Originally Posted by 114ManualLabor

Our team doesn't use the kit one. We have a couple of performance RC car chargers that can fully charge the battery in about 15 minutes, and then let us know with a deafening beeeeeeep when it's done. One of them also has a graphical LED display on the charging progress.

Although this is really the best way to do this, considering the time crunches we face during competition, I hate to tell you, it is expressly against the rules.

<R56> The 7.2v backup battery may be charged on or off the ROBOT. When off the ROBOT, the
battery is to be charged with the provided 7.2V backup battery charger. When mounted on
the ROBOT, the backup battery may only be charged from the 12VDC primary battery using
the Battery Charging Circuit available from Innovation First Inc.

I wanted to take the approach you are using last season, but when I asked this specific question to the Q&A system, the response came back that the provided backup battery charger must be used.

Sorry, I don't mean to burst your bubble, but at least now you will know how the rules committee sees this rule.

[Al Skierkiewicz]

Originally Posted by Maximus123

any other teams get an 8.4 v dc 500mA charger in their kits? we did... weird...

Maximus,
You received two chargers? The 8.4 volt charger will overcharge and likely destroy the 7.2 volt battery. Use the 7.2 volt charger. To slow charge NiCad batteries they are charged with a constant current power supply as the supplied charger does.

The rules are very specific this year, only the supplied 7.2 volt charger for off board charging or the IFI charger for on board charging. There is no provision for any other chargers, sorry but you are best to leave them home.

[tdlrali]

8.4v charger is the one for the 7.2v backup batteries. Take a look at other chargers, their output voltage is always slightly higher than the battery voltage. This is required to charge batteries correctly.

However, I don't understand why they force us to use the charger we got in the KOP. Yes, I know that they don't want any team to have an advantage, but this years charger is potentially dangerous for the batteries, as it does not (seem to) shut off when the battery is charged, and it also has no way of letting the user know that the battery is charged.