Electric Bikes – Winter Riding


The odometer is creeping upwards on the bike, I am now taking the longer routes to and from the shop just for the fun of it, but the battery state was worrying me a little. Even after a full charge, the battery state was dropping to one bar while riding up steep hills, just a few minutes after charging the battery.

I found this really cool site that sells LiFePO4 (LFP) batteries, and everything I read makes me glad that I went the way I did with battery size and type. They have a power point presentation on LFP battery knowledge, from which I extracted this graph, which shows how the ambient temperature changes the voltage output from LFP cells. The purple line is 0 degrees, and the brown 25 degrees. The average temperature for the last few weeks at the time I ride has been about 4 to 5 degrees, obviously a lot closer to the purple line than the brown. The bike still performs, but under load you can take another couple of tenths of a volt off that graph, so the actual voltage measured may drop down to less than 3v per cell, which would explain the low power gauge readings. The battery recovers quickly when the power drain is reduced, and still shows 3.2 to 3.3 at rest, so its not a big deal really.The range is still good, 30km on the second power settings and still plenty of oomph!

I am really looking forward to summer now – those 27 degree days will be excellent days to go for a bike ride.

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