I've driven it around for about an hour now, and the 48V LED is still green.
Dennis, if you have the LiFePo
4 pack, the battery voltage is likely to be too high for the gauge to function correctly.
These simple gauges were originally designed for use with lead acid batteries, which have quite a pronounced voltage drop as the battery is discharged or loaded. The lithium batteries however have a very gradual voltage drop throughout the discharge period until they reach a point where the voltage suddenly drops very quickly very near to the end of their discharge cycle.
The following diagram is not meant to be 100% accurate, it is purely intended to give a rough comparison of the typical discharge curves for the three types of batteries that are commonly used:
A 13 cell Lithium Polymer pack would be almost the same as the LiMnO
2 curve.
I don't know the actual figures, so let's simply assume that the battery gauge Green and Amber LEDs are meant to go off at 51V
(~50%) and 45V
(~85%) respectively with a lead acid battery pack.
If you look again at the above diagram, you should be able to see that the LiFePO
4 pack would need to be ~90% discharged before the Green light would go off, and almost completely exhausted before the Amber light would go off.
I think this might explain why you've been able to drive around for so long without the green light going out. However, there is also another possible explanation, if you have a 36V throttle and a 48V battery, the green light will stay on continually until the battery's
BMS eventually triggers the Low Voltage Cut-out!
I tend to use my battery gauge solely to indicate that power is turned on, and I rely on my Turnigy Watt Meter to measure the capacity in Ah
s that has actually been used, this gives me a reasonably good indication of how much battery capacity I still have available to use.
If the battery runs too low on my bike, I can simply pedal my way back home again, but with your Morgen, I imagine it would be much more of a problem.
If your Mercedes had a over optimistic fuel gauge, you'd probably carry a spare gallon of fuel with you just in case. So you might want to consider installing a small reserve battery pack so that you can simply switch over when the main pack runs out unexpectedly.
Alan 
