This morning I used Silent E for a scenario outside its design plan: I dropped Tatiana off on my way to work. It's about 5 miles out of my way.

Knowing that my battery capacity was limited, I drove quite carefully. I drove a route that (I hoped) would reduce the overall distance; I braked carefully and utilized coasting as much as possible; I accelerated so that my voltage never dropped below 110V on my 120V pack. I even started with an overcharged pack.

When I got to work, I had driven 11.7 miles, and my resting voltage was 122V.

Is that good?

Heck if I know. This is just a WAG, but let's assume voltage declines linearly with battery capacity: if you've got 50% of your voltage, you've got 50% of the energy in your battery pack left.

I know that DEAD is 10.5V, and FULL is 13.2V (although on these damaged batteries, full appears to be 130V; we'll ignore that for our calculations). If all 10 batteries were the same, the pack would be dead at 105V and full at 132V. Since I'm at 122V, I must not be dead.

But we never want to get below 80% of the battery capacity (or 20% full). The voltage range is 132 - 105 = 27V. 20% of 27V is 5.4V. So I would never want to be below 105 + 5.4 = 110.4V.

But that's only if resting voltage is a good linear indicator of battery capacity. Somehow I doubt it is. On the EV list, they say the best way to measure battery capacity from voltage is to check the voltage under load. That's why I keep my E-meter on its voltage display: I don't want voltage to drop under 110V even while I accelerate, and I can watch the voltage under load.

10 miles into the trip, my E-meter thought I was down to 20% of the pack. Around that time, I was actually using 1st gear. And even mild acceleration was dipping below 105V, if only for fractions of a second.

I hope someone can tell me how to interpret this data. I intend to ask the EVDL later tonight.