Power Indicator confusion

waldey

Finding my (electric) wheels
Dec 1, 2012
9
0
I'm a little confused regarding the remaining power available to me on my 806 Alpino.
The LCD power display does not appear to work as I would expect. The remaining power changes up or down by up to two bars depending on how much effort I put into pedalling. Surely, this should be a constant indicator of the power remaining in the battery and diminish over time, not go up & down when cycling or freewheeling downhill - there's the power consumption display to tell me that.

After I finish my 6.5 mile commute, the power indicator is on 1 bar which, according to the manual (which shows a different model), leaves 55%. However, when I remove the battery and check the remaining capacity, it indicates 80% charge remaining. Which do I believe as I wouldn't want to find myself running out as the last 1.5 miles is a steep hill.

I would just like to know how to get a reliable reading without having to keep stopping to check the battery.

Cheers in advance
 

flecc

Member
Oct 25, 2006
53,559
30,848
This is normal. These content indicators work on the battery voltage which drops sightly as the content empties. Unfortunately when the motor is driving that also drops the voltage due to the current being drained, making the indication fall.

To get a more accurate idea of the content, just pause pedalling and shut off any throttle fitted for a moment. That will tell you the content with reasonable accuracy.

After stopping for a while such as after a ride, the battery can chemically recover slightly leading to a some rise in the content shown. Though the jump you see then is rather large, it's probably not far off the truth after doing only 6.5 miles. For certainty though always allow a safety factor, calling that reading 60% for example to be sure of not running out.
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Last edited:
D

Deleted member 4366

Guest
What you're seeing is voltage sag. It takes time for the battery chemistry to make electric power, so when you take power from it, the voltage drops a bit. The more power you take, the more the drop. The meter is showing the voltage from about 42 volts when charged to about 30v when discharged - divided into as many bars or LEDs as you have. When you get down to no bars, your voltage is too low and the controller or battery BMS cuts the power regardless as to whether it's sag or emptiness. It''s important that you understand this because when you're going up the final hill, the voltage sag can cause motor cut-outs. Even though you have enough charge in your battery to get home, the sag won't allow it, so you need to keep a bit in reserve. If you get these cut-outs on the final hill, you can improve it by turning down the power level, which reduces the sag, but of course, you get less help from the motor.
 

waldey

Finding my (electric) wheels
Dec 1, 2012
9
0
Excellent responses and thank you very much. Useful suggestion flecc, and one I shall put into practise as I have a short slightly downhill stretch before I climb that hill where I can freewheel and check the battery state.

Thank you too, d8veh for your guidance on voltage sag. I’m charging every day and find that on max assistance on the final hill I’m down to one bar. A combination of my weight, together with the severity of the hill is when the battery indicator drops rapidly down to a single bar having been indication full. This would appear to be the voltage sag as described.

It’s great to understand what’s going on; cheers guys, I really appreciate your advice.
 

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