I’ve installed a volt meter before but whilst that gives you a real time time pack voltage, it doesn’t tell the whole story of remaining range unless the lipo pack has rested and you do some maths.
The Chinese are now selling high current coulometers:
I bought the 350 Amp version as my board pulls a peak 100A current, which is way over the next one dwon (50Amps, 100 burst)… Cost me £30 delivered.
This records Mah used (or AH in my case). You set the battery capacity and it decreases as you use the board, and increases as you charge it. Actual Ah used, not guessed - as it’s measuring it. I’ve tested it today and it’s bang on accurate. It also calculates charging time, and discharging (riding time).
Firstly, it shows 2Amps going in when on charge. My charger is rates at 2Amps. So that’s a good start.
Went for a ride today. I know my board does 12-13 miles on one charge (24Ah) - use 20Ah for safety.
I went 8.66 Miles The screen showed I had 8.17Ah remaining. 34%, 22.9volts (3.83 per cell) with 22 mins esitmated ride time remaining (it works this out as you ride (or when you are charging it to give you a full charge esitmated time). I would aim to ride it down to 15-20% remaining to leave a nice amount still in the packs for safetly/longevity. So if the coulometer is accurate enough, I’d expect to use another 4.Ah to leave it at 4 Ah remaining, which is 17% of my 24Ah pack. I’d probably quit at 4.5Ah/5Ah to add a little safety margin.
If you do the maths that’s 0.94Ah per mile. I know I can go 13 miles so If you add the remaining 4.4 miles, multiply by 0.94Ah = 4.14Ah to get me to 13 miles . Take that off the 8.17Ah that shows as remianing capacity. That leaves you…4.03Ah = 17% = spot on!.
So I can reliably ride knowing that I have from 100% to 20% rideable power. Anything under 20 and I’ll get close to hitting my low voltage cut off.
Below: Fully charged
And after 8.6 Miles: (and a bit dusty)