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Old 04-16-2011 | 06:20 PM
  #22  
MTK
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From: Whippany, NJ
Default RE: Rx battery


ORIGINAL: cmoulder

I got in 6 more flights this morning.

I arrived at the field early enough that, while windy, it was still fun to fly. The last couple of flights were done with gusts kicking up 25-30 mph (estimated, but it was damn windy!) By then, it was not fun any more.

First flights with the dual FP 350mAh Rx batteries were interesting, in a good way. I topped off the Rx batteries with a Polycharge 4 (non-balancing charger) and voltages read 8.32 and 8.29. I checked voltages after each flight and one battery was drawing more than the other, but only by a small amount. At the end of the 6 flights the voltage of Batt 1 was 7.96V and Batt 2 was 8.14V. So I could have - as Arch assured me earlier - easily gotten 12 flights from these 2 tiny batteries.

Upon recharging (with the balance taps on the Cellpro 10S), Batt 1 took 105 mAh and Batt 2 took 47 mAh, for a total of 152 mAh, which when divided by 6 flights is about 25 mah per flight.

Granted, I am flying the humble Intermediate sequence and am learning to be judicious with my control inputs, but this was quite a surprise.

Regarding the difference in battery draw, the regs were factory set identically for 6.2 volts, so I am guessing the small discrepancy is caused by slightly different resistance in the connecting wires, wire length or connector contact/conductivity. Just to be sure, I re-checked the Tech-Aero regs with Ed's EZ Set Programmer and they were indeed reading 6.19v and 6.20v. With such minimal amp draw, the slight discrepancy is not an issue.

EDIT: While putting the batteries back in the model I remembered that the receiver is a 7-channel and that I had to use a Y connector for Elevator 2 and the second battery, which probably affects the resistance and accounts for the difference in current draw.
Bob,

How long are your electric flights? Compare to the SAP gasoline powered set-up which draws about 250+ mah per 20 minute flight (includes radio plus ignition). After 75 minutes of flying on the 1780 mah lipo, it measures about 7.5V