UKH

I noticed today the indicator lights on my battery show one extra bar than what is shown on the display (battery shows 4 bars, display shows 3 bars). It's a shimano setup. Is this norm? Do I need to do something to regulate the battery with the screen? Which is generally more accurate?

I get the something similar, but reverse, with my Dillenger setup. There are three power level LEDs on the battery pack that seem to behave as expected but the handlebar display appears to use a different scale (log?). I can do a 20 mile ride and the battery has lost one bar but the handlebar display will still be full. I start the next 20 mile ride (without charging) and it takes about 5-8 miles to drop one of the 5 bars on the display and then the others start going out relatively quickly. By the time I am almost home from the second ride, both the battery and display are normally down to 1 bar (which is where I stop using the assistance so as not to stress the battery too much).

Lithium-ion batteries have a non-linear discharge curve (voltage over charge) which varies with age and across individual batteries, so for an accurate charge indicator you really need to calibrate the system (and recalibrate for time to time). If your battery management doesn't have a battery calibration function (I'm not familiar with bike battery systems) then any indicator will be a somewhat wild guess and I wouldn't be surprised to see two independent indicators give different charge levels. Lithium-ion battery management - particularly for extending lifetime - is quite tricky and I suspect many bike battery management systems are quite crude compared to that in something like a Tesla car.

Most 3 level indicators show >50% (1 bar), 50-79% (2 bars) and 80-100% (3 bars). But it's only a rough indicator "just for fun".

It's as good as you'll get without some really fancy management chip/circuit board in the batteries.

I've been riding a Dillinger 1000W 48V battery for 3 years now and my battery capacity has changed somewhat over 2000 commuting miles. Indicator on the battery pack just makes suff up, the 'bar' indicator on the controller give a rough guess if it can be bothered but over all these miles, by far the best indication is the battery actual voltage in real time if you have that function available on your controller.