Battery monitor inconsistency

[simsydav]

Hi this is my first post on the forum but I've been reading bits and pieces which have proved helpful.

Bought a second hand Carrera Crossroad E which had been barely used and was very cheap. Got a second (new) battery to give me more range.

The charge level is displayed on the battery itself (4 bars) and on the little screen on the handlebars (3 bars). They normally roughly match up, but today after cycling 30 miles the read out on the (new) battery is 3/4 bars, while the one on the handlebar screen is 1/3 bars.

Which is likely to be the most correct? I'm not sure how either work out the remaining charge, but it seems a bit odd that they would be reading so differently to each other.

Thanks for any help!

 

[vfr400]

You should use a meter to measure the actual battery voltage.

 

[Benjahmin]

They shouldn't be understood as meters in the sense of a fuel guage.
They indicate instantaneous voltage (with some damping effect) and will vary over the course of a ride. For instance, when going up a steep hill using high power the display will drop significantly, then recover as you coast down the other side.
So it reads voltage which can only give a loose interpretation of charge/capacity left in the battery. I'd say a 3 bar display is pretty useless and (as I see vfr has just said) a dvm will be more useful to you.
A fully charged healthy 36v battery wil show 41.5-42v.
An empty battery will be around 32v.
Charge to suit your usage, normally just before a ride if possible.
Don't leave it fully charged for long periods.
Don't leave it at low voltage (34v or below) for long periods.

 

[Nealh]

Wire in line directly between the battery and controller a cheap 2 wire voltgae display to give real world reading.