E-Revo with Twin Force Tranny

[Lonewolf039]

OK, I figured out how to reset the safety timer on the Triton charger to 720 minutes, and I did a 1/10 C slow charge last night. I repeaked the batterys at 4.2 amps just before heading out. Performance was the same, run time slightly longer, so the slow charge might have equalized the cells a bit, but didn't restore any voltage. At 1 minute into the run, I got 55.5 amps peak and 11.1 volts minimum, for 616 watts peak. I also got the same numbers at 5 minutes. At 8 minutes, voltage was down to 10.2 volts under load. At 9 minutes the batterys started to dump, 3600 mah used. At 10 minutes, end of run, the lowest voltage recorded was 7.6 volts, 3900 mah used. Performance was rather weak throughout the run.

I ran the numbers through the top speed calculator:

Differential Ratio: 2.8461538461538463
Transmission Ratio: 2.36
Other Ratio: 1
Spur Tooth Count: 54
Pinion Tooth Count: 15
Total Voltage: 11.1
Motor KV: 4400
Tire Diameter (inches): 5.8
Tire Ballooning (inches): 0
Motor Current Draw: 55
Motor coil Ω: 0.0073
Spur/Pinion Ratio: 3.6 : 1
Total Ratio: 24.18092 : 1
Tire Circumference (inches): 18.22 inches (462.82mm)
Total Motor Speed: 47073.4 RPM
Vehicle Speed: 33.59 MPH (53.96km/h)
Effective Speed Rate: 3.03mph/V (4.86kmh/V)
Effective KV Value: 4240.85
Motor Torque: 0.09 ft-lbs
Final Torque: 2.13 ft-lbs

Top speed of 33 mph looked about right. When the batterys were new, the voltage stayed up around 12.5-12.6 under a load of 70+ amps. The higher voltage in the speed calculator puts top speed at 37 mph, which was probably pretty close. Now they can barely put out 50 amps. If I had know how crappy the nimh batts were, I would never have even bothered with them. I really did not think I was abusing them. Oh well, live and learn. I am now charging them at 5 amps, so I'll see if a bit of torture will wake them up. I really don't care if they blow up now.

[Lonewolf039]

Well, run 2 was a little better. At 1 minute the voltage was 12.82 volts at 54.38 amps. At 5 minutes, voltage was down to 11.84 volts at 55.48 amps. Pack dumped at 3700 mah. So the higher charge current did raise the voltage up for a bit, but these batterys are on their last legs.

Anyways, there haven't been any pics for a while, and I know we all like pictures, so here we go.








And my highly scientific measuring method A whatts up meter in a baggie zip tied on.

[Lonewolf039]

I got the battery holders done tonight. Turned out not too bad. I wish the Revo didn't have that hump on one side of the chassis. It makes the one battery stick out 1/4 inch more than the other one. I've been thinking about cutting up a chassis and tigging in some holders that are nice and centered.