[MikeyBolt]

At 1600 miles, I decided to do my first rough calculation of battery capacity. I left this morning with 83% battery (my set limit) and returned home with 71% remaining with 7.3 kWh used. So 7.3 kWh used 12% of the battery. That's 7.3 * 100 / 12 = 60.8 kWh capacity.

Obviously that's a rough estimate with so little energy used and only round numbers used for percentage. I guess worst case scenario would be that the actual numbers were 83.49% to start, 70.49% at the finish, and 7.349 kWh used... which would give 7.349 * 100 / 13 = 56.5 kWh capacity.

I'll have to redo the calculations after running a longer distance but I rarely go very far. At least it seems to prove my capacity is in the expected kWh range.

Mike

 

[Vertiformed]

@MikeyBolt, many of us do these kinds of calculations, but they're pretty hard to do right. As you noted, rounding errors can make a big difference. Using an ODB-II reader can give a slightly more accurate read of the displayed percentage (and a very accurate read of the “raw” percentage). Which one is better is a little tough to extrapolate.

Fundamentally, this stuff is complex. Even with gasoline, technically how much gasoline there is in a gallon depends significantly on temperature, so a gallon of gas in summer may be much less than a gallon of gas in winter (see this blog post that dives into it). Also, in many places there is a summer formula and a winter formula, with different energy properties. Thus, “how much energy in a half-full 20-gallon gas tank” is surprisingly hard to answer.

For batteries, there are the questions of how accurate the state-of-charge percentage really is, how accurate the current/voltage metering for the battery is, what the temperature of the battery is, and the discharge rate/pattern.

I generally feel that if you charge to 100% and then drive down to 50%, you have a somewhat useful read on what half the battery capacity might be, and if you do it on similar days on the same kind of driving, say a year apart, it may provide some clue as to any degradation. Or it may not.

In any case, over time everything decays. Rather than worry about that and perhaps start thinking about how you yourself are slowly wearing out, better to go for a drive and enjoy the limited time you and your Bolt have together.

 

[MikeyBolt]

In any case, over time everything decays. Rather than worry about that and perhaps start thinking about how you yourself are slowly wearing out, better to go for a drive and enjoy the limited time you and your Bolt have together.

At my age, most of my "cells" are bad. I don't worry about those either. Sometimes we do things out of curiosity, not worry.

Mike

 

[Slaa]

I charge to 83% too but figure if you get to 50% the kWh is roughly half your capacity?

 

[Fivedoor]

I charge to 83% too but figure if you get to 50% the kWh is roughly half your capacity?

It would be roughly 1/3 of your capacity (83-50=33)... ow did you get 1/2?

Keith