Vex IQ battery testing

So I bought a tester… And I’m curious of the best way to use it. Any knowledge I have has a couple of decades of dust on it.

I tore apart a charger and I have this setup:


Yes, I almost started a fire. Let’s ignore that for now…

I have two 5ohm resistors, and I can set it so it drains the battery until it gets to a certain voltage.

When I put a battery on it, it tells me the initial voltage. I then tell it at what voltage it should stop draining.

I have three options with the resistors. Just use one, or use the two in series or in parallel. (So I could have 2.5, 5, or 10 ohms) With just the one resistor it drained the battery at about an amp to start. Which resistance best emulates a competition VEX IQ Robot?

Also, what is the best voltage cutoff? I’m currently thinking I should set the cutoff to 7.2v. I’ve been using 6v for the cutoff and that gives me a good test for total capacity, but I want competition capacity.

Or am I barking up the wrong tree?


From what I read NiMH batteries that VEXIQ uses could be discharged with 3C-5C rate, depending on packaging. I guess it is 6A-10A for 2000 mAh battery. So new battery should handle 2.5 ohm loads.

Also they say that if nominal NiMH cell is at 1.2v, fully charged is at 1.4-1.45v and discharge cutoff is about 1.0v before it gets into unsafe voltage that could damage the cells. So, yes 6.0v sounds about right for the discharge cutoff.

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