Let me begin by saying I know the Summit was not built to break any speed records, however because of it's mass I thought it would work well to compare vehicle speed between 9000mAh/28C/2S LiPo's and high quality, matched, 4600 (labeled capacity), 7-cell, Nimh packs. I must also add this test was not meant to be a comparison of runtime between the two battery types. Being significantly larger in capacity, the 9000mAh LiPo's will have noticeably longer runtimes. Keep in mind the Nimh packs give up a useable 4150mAh to 4200mAh of capacity so it would be completely unfair to compare them to the 9000mAh LiPo's after a long, extended runtime.
Before listing the results it must be stated I am not going to respond to undue criticism, blatant meanness, or rude comments, nor will I respond to comments about the Summit not stressing the packs enough to show up a true difference. I did not perform this test to provoke a LiPo versus Nimh debate; in fact I ran the test for the beginners who are frequently asking how the two packs compare in performance. My intent was nothing more and nothing less.
Top speed test; May 21, 2009, using a bone-stock Traxxas Summit and an EagleTree data logger and their GPS module. First I ran 9000mAh/28C/2S SMC LiPo packs for top speed on level pavement followed immediately by similar runs on a level, mowed lawn. Then I repeated the test using matched, 7-cell, Nimh packs. Here are the results:
Max speed on pavement; 21.9 mph
Max speed on mowed lawn; 18.9 mph
Max pack volts: 8.36 V
Min pack volts: 7.84 V
Avg pack volts: 8.25 V
Nimh4600 mAh, 7-cell, Matched
Max speed on pavement; 23.9 mph
Max speed on mowed lawn; 19.8 mph
Max pack volts: 9.81 V
Min pack volts: 8.19 V
Avg pack volts: 9.32 V
Because many people claim Nimh packs gradually slow down and lose noticeable power after only a few minutes, I ran the Summit at full throttle bursts, back and forth across a mowed lawn, repetitively for 5 minutes, then immediately repeated the Nimh speed runs again:
Nimh4600 mAh, 7-cell, Matched, after previous speed runs and an additional 5 minutes of wide open throttle
Max speed on pavement; 23.5 mph
Max speed on mowed lawn; 19.3 mph
Max pack volts: 9.14 V
Min pack volts: 8.79 V
Avg pack volts: 8.84 V
I did not repeat the 9000mAh LiPo speed test after a similar 5 minute run because I knew it would not change much due to the large capacity of the packs. Overall the results pretty much speak say it all. For the record I am NOT anti-LiPo, as the vast majority of my RC running and racing is done with LiPo.