My Tongxin kit bike

[Peej]

Thanks for the advice Flecc - now have to see what the falling pound has done to the battery prices!

 

[Peej]

Hi Frank - thanks for the info. I was a little surprised that you were only getting 20-25miles from the 10ah battery. Perhaps this is due to less pedal assistance or other factors? I will look to purchase in the range 10-15ah on the basis of the advice from Flecc and yourself.

 

[frank9755]

Yes, have a think about what range you need and what weight your're willing to carry - which will depend on how you're mounting the battery.

I put my range down to high speed, but your comments are interesting, John. This is a 20mph+ bike so the wind resistance is much higher than at say 15mph. I've got some high gears on it, with a small 11-tooth sprocket and a 48 tooth chainring giving a top gear of around 120" - so it can be pedalled quite effectively.

When I used my Wisper battery on it (13Ah) I would get about 25miles range at a speed of 20-24. The same battery gave approaching 40 miles on the Wisper at lower speeds (17-19mph) over the same terrain - both being pedalled hard in addition to motor.

The other data point which I'll share with you, Peej, is that the 10Ah LiFePO4 gives about 25 miles on the Wisper with my wife riding and significantly lower pedal input.

 

[Peej]

Speed must be one of the main considerations then? My average speeds over longer distances (40+ miles) were much lower at 12-14mph. When the bike was ridden by my wife the average speeds were lower still at around 9mph which combined with my wife's considerably lower weight(!) might account for the way she was able to get a range of over 30miles despite much less pedalling input. Had a go at bidding for a "Ping" 15ah battery last night but was outbid - prices seem to have risen due to exchange rate but will keep trying.

 

[frank9755]

You don't actually need to go through the auction - just send Ping an email saying what you want and he'll quote a price!

 

[john]

Speed must be one of the main considerations then?

Lowering the speed has several affects which improve range:

- air resistance is lower
- the percentage of rider input is higher
- the motor may be running at a more efficient rpm