Wandry,

I built a test load to discharge the battery in the shop. I used a couple old 375W movie floods which draw 3.7 to 3.1 amps as the battery goes from 42v to 30v. Average ~3.4amps. I got 8.5ah to LVCO.

I increased the load with by adding a 250W heat lamp to get a 4.5A average and got 7.5ah to LVCO. Both test were more than I expected from 5+ year old NiMH D cells.

Unfortunately neither test fixed the SOC problem, but did show that the SOC went to zero with 75% of the power still in the battery.

I tried 2 other SOC resets after searching how other bikes do a SOC re-calibration.
1. Ride bike until SOC=0. Wait 1 hour. Charge to full. Wait 1 hour. Charge to full again.
2. Turn on the display then hold the on button for 30 seconds.
Neither reset worked. i think I'll just have to give up on the SOC display.

BTW, my charger is the original, but doesn't behave as the label says. Turn on- red LED solid(stays red). Connect to bike, Yellow LED is solid. After few minutes, yellow flashes 1/sec, fan comes on. The yellow flash speed doesn't change so I don't know whether it is the slow or fast. I have yet to see the yellow turn green. If I leave it a long time, both the yellow and red turn off. I can't image that could be my problem, but ...?

I just got 2 new Li Ion batteries from Amazon for my add on battery https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I chose these 4.5ah batteries because they have 3 cells in parallel instead of the usual 2 for the same AH. A little bigger, but they should produce more amps and apparently they do. 1.5 hour charge time on my old Makita 18V charger.

Now, does this bike haul . I live in hills. One devil hill slows my wife and I to 3.5 mph on our tandem and me to 4.5mph solo. The E plus with the Makita's in parallel climbed it at 18mph with only a moderate assist from me. 29/30mph on the flat, not pedals.

I do some range and other test next week on my E plus Makita hybred.