Battery Charger

VEX V5 General Discussion Technical Discussion
1

Hey I got a question! Since our team is crazy about performance we want to charge our batteries to the maximum, meaning discharging then charging to 100%. After some research online I found the following charger / discharger.

http://store.savagess.com/product_info.php?cPath=21_30&products_id=1104

Would this work with the VEX battery packs? Also I am guessing this is legal to do in FTC. Also if anyone knows of any other better chargers that would be great.

Also HAPPY NEW YEAR!!!

2

Based on what I read on the page at the URL you supplied, the Super Brain 977 Twin charger that I use has important features the Accu-Cycle lacks.

Differences that I think are important are that the Super Brain let’s you choose how much current you push/pull during charge and discharge operations (to control how fast you charge the battery); and that it keeps track of (and displays) how much current* is supplied or absorbed by a battery during discharging/charging.

I am unaware of any prohibition against using a non-Vex Charger. I/we (FTC 368) use the one I named above.

Blake

  • = The charger really tracks milliAmpHours (mAHrs) delivered or extracted. A mAHr is an amount of charge. mAHrs can be converted directly into Coulombs. Coulombs are the SI units used to measure amounts of charge. Amperes are Coulombs/sec. A good analogy is saying that Amperes are like Gallons per Second of water flow, and AmpHours are like Gallons of water.
3

Well now that I looked at the Super Brain 977 Twin that looks like a far better charger than the other one. Thanks!

4

Hey what settings do you use with the SUPER Brain, I charged a few VEX batteries but I want to make sure I am not frying them. Really fun to see how much more charge you get out of the thing compared to the junk vex chargers. :smiley:

I am using a charge rate of 1 amp, discharge rate of 4 amps, a ?Delta V? of 30 mV (think thats what manual called it).

That sound right?

5

The cahrger defaults to using Delta V of 5 mV per cell in the battery. That would be 30 for the six cells in 7.2 V battery and 40 for eight cells in the 9.6 V battery.

I usualy use 50 mV for both Vex Battery types. I hope that using 50 mV helps me aviod premature shutdowns of the 977 when I am discharging and charging the batteries; and I hope that I am not damaging the batteris by doing that.

I usually charge and discharge at 2 Amps when I’m not in a hurry and when the battery is working well.

When I am in a hurry I move the charge and discharge rate up to 3 Amps.

For the batteries (from eBay, Radio Shack demo model, etc.) that don’t seem to want to store much charge, I switch to discharging and charging at 1 Amp. I do that so that the battery chemical have plenty of time to go through their changes and hopefully that lets them eventually find their way back to peak performance.

Blake
PS: I’m not a NiCad Battery expert. I don’t even play one on TV.

6

Well at lest if we both kill our batteries we can blame each other. I just like the idea of calling our batteries OVERCLOCKED!!! :wink:

7

I believe First is asking us to use the official vex chargers this year. It is possible that other chargers would overcharge the battery and give the robot more speed.

How long does it take to charge batteries on your new charger? We can charge one that was completly dead in about one hour.

8

I have only done three batteries so I can’t say yet but it near 45-60 mins depending on starting charge and charge rate. As for overcharging yes it possible but unhealthy for the batteries in the long run, so in the end it would hurt us. So I will stick with stock charge rates but I will say that the discharging and recharging gets the extra power that the vex chargers don’t always get (yet to be fully tested).