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Measuring current draw with a wattmeter

Measuring current draw with a wattmeter


Old 07-24-2011, 02:31 PM
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Default Measuring current draw with a wattmeter

Well, I ended up with a wattmeter - got it from hobbypartz for 18 bux. Figured I'd run a couple of my RC's on it to see what these things pull. ]

This was done in my street with bald tires (cityblocks on 1/8th and calibers on 1/10th), Ran them both for a few min. Tried to get as much load on the motor as possible without holding it down, or causing artificial load. Lots of max power from standstills. Of course this is not going to be common max power draw for anyone that races/bashes on dirt - this is pretty much as hard as I can run them without getting onroad tires. Had loads of traction.

Used Gens Ace 5000mah 40c's on both.

First run, my HB VE8/D8/HHH rig. Tekin 1900kvw/RX8, geared 23/50 4S


2nd run - my Hyper10SC, Novak 4.5 w/ 14mm rotor, MMP, geared 17/42 2S



-Wattmeter stated 100A max - I'm assuming accuracy suffered beyond that.

Had some fun with this and kinda learned a few things. I almost thought the current draws would be closer than they were.

Things to note:

Not sure why the voltage was goofy in the 2nd run, I'm showing min voltage (UM) of 7.44, and max only 7.46. thats approx 3.72v/cell. Measured the batteries afterward and they were right in the 4.1xv/cell range.

1/8th scale voltage drop was greater, but still the max voltage was low. I suspect this is an error/calibration issue with this meter.

I'm going to try some of this at the track next time - and see how the numbers differ after a number of laps at race pace.

Looks like my 5000mah 40c's held up fine, and didn't get close to their 200A limit.

Kinda cool to see power consumption - Hell, if my 1/8th scale is 80% efficient, thats nearly 1.7 horsepower

I'm sure there are a number of holes in this - but I couldnt get to a track today and had a few charged batteries
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