phidauex
Well-Known Member
- First Name
- Sam
- Joined
- Dec 8, 2020
- Threads
- 16
- Messages
- 846
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- 1,562
- Location
- Colorado
- Vehicles
- 2021 MachE 4EX, 2006 Prius, 1997 Tacoma
- Occupation
- Renewable Energy Engineer
A few thoughts - as far as the battery, 80% is better for the battery than 90%, which is better than 100%. It won't matter right away, but it could matter over many years. Either way the holdback on the MachE battery is generous so even a reported 100% is probably more like 92% or 93% of the chemical SOC.
As far as energy required to go from 70-80% and 80-90%, no, both cases will use about the same amount of energy. Internal efficiency of batteries is pretty flat through most of their curve. Where this becomes less true is at the very margin, more like 97% to 100% of real charge (which you can't access on this car anyway).
Faster charging, however, is less efficient than slower charging, since energy losses in the battery are mostly due to ohmic heat generation, and those losses increase with the square of current, so doubling your charge rate is 4 times the lost energy. But again, you don't need to worry that much about it, because the home 240V L2 chargers are still only charging at around 0.15C, which is a very gentle charge rate. You might become concerned about it if your primary every-day charging was on a DCFC, but that won't be true for most people.
As far as energy required to go from 70-80% and 80-90%, no, both cases will use about the same amount of energy. Internal efficiency of batteries is pretty flat through most of their curve. Where this becomes less true is at the very margin, more like 97% to 100% of real charge (which you can't access on this car anyway).
Faster charging, however, is less efficient than slower charging, since energy losses in the battery are mostly due to ohmic heat generation, and those losses increase with the square of current, so doubling your charge rate is 4 times the lost energy. But again, you don't need to worry that much about it, because the home 240V L2 chargers are still only charging at around 0.15C, which is a very gentle charge rate. You might become concerned about it if your primary every-day charging was on a DCFC, but that won't be true for most people.
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