# Estimating remaining energy/distance

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cyclepete
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Last seen: 12 years 6 months ago
Joined: Tuesday, May 27, 2008 - 10:26
Points: 64
Estimating remaining energy/distance

I find the "energy remaining" bars on the console hard to use to estimate how much time/distance I have left. It's pretty quantized. Plus it seems unreliable. On some rides on windless days and flat ground (using assist level 2), it'll show a third gone 10 miles into a ride, and other days, under identical conditions, it'll show a half gone. But in both cases I usually end up with nearly the same distance by the time I'm down the the last 1/2 bar. Typically at 36 miles.

Some of this variation seems to be whether I've recently used up most of the energy in the battery. A full recharge, instead of the partial recharges I normally do, seems to get it back on track.

I have the "distance remaining" option turned on. But that just uses the last couple of seconds of use to estimate how much further I can go. That and the "time remaining" functions are useful to figure out the rate you are using power, but not how far you can really go.

What I'd really like is to be able to check, about 1/3rd into a long ride, how much energy I really have left so I can figure how much farther I can go, assuming the same conditions.

I've thought of looking at the voltage on the battery to do this. Assuming a linear relationship between voltage and remaining energy, and knowledge of the charged and discharged voltages, this would be easy. But I'm assuming that's what the bar display is already doing.

Any ideas?

chas_stevenson
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Last seen: 12 years 11 months ago
Joined: Wednesday, December 6, 2006 - 17:14
Points: 1309
Re: Estimating remaining energy/distance

I will let you know that using voltage as a state of charge is more inconsistent than the bars you are currently using. The voltage must be tested under load but because the load on an EV is always changing there is no way to get an accurate reading. The best thing I have found is a Cycle Analyst meter. One place in Australia is EV Power Australia LTD., in the US you might want to try ebikes.ca. This meter can tell you how many amp hours you have used as well as other good to know information. With this information and the knowledge of the total amp hours available you can make an educated guestimate of how much farther you can travel.

Grandpa Chas S.

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