Wildly different battery readings

Joined
Nov 23, 2021
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I just got my Bafang BBSHD working the other night and decided to do a range test after charging to full. I managed to get to 21 miles before the C18 display read 0% and cut off power (I read online people with a similar setup got around 30-40 miles but my bike is quite heavy and it was subzero temps so I expected much less). But my battery itself has a little power meter and it shows it still has 2/4 (50%) lights on . This is quite a huge difference and Im wondering how can I calibrate either the display or the battery? My battery is 48v and I've gone into the controller settings and set it accordingly. I'm not super knowledgeable about batteries and electricity so keep that in mind. I've warmed up the battery since and the controller reads 12%, but the battery itself still reads half.
 
Clinterpottrmus said:
has a little power meter and it shows it still has 2/4 (50%) lights on

That little power meter measures no load voltage.

Under load your voltage drops below the preset. The higher the load the higher the drop. Cheap or bad batteries can't tolerate high loads so they sag. Ease off the throttle and it will go further without tripping voltage cutout.
 
The calculation/display of SoC% is at best wildly inaccurate, at worst meaningless blinky lights to be largely ignored.

Best is a coulomb-counting watt meter using a shunt, set to work in both directions

shows Ah drawn since last fully charged, reset to 100% SoC. Also how many Ah flow past in recharging, always a higher number.

Note the higher the current draw, the lower the Ah capacity actually available. And that capacity will be reduced a bit with every cycle.

With greater familiarity, and especially when doing the same trip regularly, your intuition kicks in as to how close you are to your LVC cutoff, or power de-rating point.

Many say the CAv3 is useful for this purpose.
 
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