Author Topic: Battery Question  (Read 72 times)

Offline Adamsavage79

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Battery Question
« on: November 08, 2019, 03:23:58 AM »
I had the ebike out today @ around 0 Celsius, and I almost drained the battery. I thought I had enough juice and some extra when I left, as I was reading in the low 52 volts when I left. When I brought it in after riding it, in a strong head wind plus it being cool outside. I got a reading of 47.2 volts and as it warmed up. It's gone up. However, this was @ like 2:30. The battery should of warmed back up in only 1-2 hours. I've taken readings throughout the day and it's now up 48.6. Normal ?

I'm going to assume it is, as the battery has been acting normal. I just forgot I've been using it in cooler temps and in strong headwinds, plus hills.

Offline Bikemad

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Re: Battery Question
« Reply #1 on: November 08, 2019, 06:35:55 PM »
The increased aerodynamic drag of a strong headwind will have a dramatic effect upon battery consumption, and the following graph shows how a small increase in speed will greatly increase the required power to maintain that speed:



According to the above graph, a typical motor would draw ~110W @ 15 mph (on the level with no headwind). If you were travelling at 15 mph with a constant 10 mph headwind, the wind resistance (and the required power to overcome it) would be very similar to travelling at a constant 25 mph with no headwind.
This would produce a much higher current draw of ~500W and would also reduce your battery's range to ~22% of what it could manage at 15 mph without any headwind.

If you typically had a 20 mile battery range at a constant 15mph, this range would be reduced to just 4.4 miles when riding into a constant 10 mph headwind.  :o

If you then add extreme cold temperatures and steep hills into the equation, the poor battery will be subjected to a really hard workout.
Low ambient temperatures may be good for magnets, wires and motors, but lithium batteries tend to be more like me, and I really don't appreciate low temperatures.  ;)

Alan

 

Offline Adamsavage79

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Re: Battery Question
« Reply #2 on: November 08, 2019, 10:23:37 PM »
Ah yes, headwinds really drain a battery. You gotta think about how hard it is to pedal in a strong headwind, then imagine going up a big hill. Cold air isn't too much of a factor for human powered, unless you consider the cooler the air, the denser it is and harder to push through. I've noticed in the summer, with no wind. It take little effort to pedal, vs winter. In short, winter sucks!

I'm guessing it was normal for the battery to "Bounce back". I just get paranoid at time.