approx multimeter reading of battery when only 25% left

footpump

Esteemed Pedelecer
Mar 19, 2014
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my older 10.4 bottle battery seems to give about 15 miles of range I am then down to 1 led out of 4 on handlebar display 3 lit when stationary.

the last mile from home is hilly, and having had to push ebike a couple of times in the past would rather avoid this.
so I would like to get some idea of what the multimeter should read if battery down to say 25%

fully charging yesterday meter reads 41.5v did not go up to 42v despite leaving charger on longer
 

Woosh

Trade Member
May 19, 2012
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there are 10V difference between fully charged and when the BMS switches the battery off. So 25% corresponds to 41.5V - 7.5V = 34V.
However, you need to go easy on the motor, keep to assist level 1 or 2, if you pull a lot from the battery, its internal resistance will cause the voltage to sag, dropping the voltage further than battery depletion alone.
 

anotherkiwi

Esteemed Pedelecer
Jan 26, 2015
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I think you might find now that at 25% the battery sags so badly on your last hill you may need to have 33% in "reserve". I only use my 10.4 Ah bottle in parallel with another battery now or when I want to go to the supermarket on the flat.
 

footpump

Esteemed Pedelecer
Mar 19, 2014
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thanks all I normally use level 2 medium out of three, from a full charge on a slight incline battery sags to one light on display yesterday.
used level three for 3 miles as it was raining.
7.8 miles in total but it takes 3 hours of charging until green light on charger.
 

footpump

Esteemed Pedelecer
Mar 19, 2014
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have just recharged to 41.5v 13.2 miles ridden ,med assist today
battery did read 36.5v but in the warm has now risen to 37v
led status between 1 and 2 out of 4 when riding.
so if I am correct 34v would be approx. 25% left

thank you