3 ms·

No, capacity of the battery isn't what determines the wattage at which you can recharge. It's the physical power supply constraints. If I have a 250v, 25 kWh b

No, capacity of the battery isn't what determines the wattage at which you can recharge. It's the physical power supply constraints. If I have a 250v, 25 kWh battery, I can charge it at 250 V, 100 Amps for 1 hour or at 250V, 1000 Amps for 6 minutes. What charging rate I select depends on the voltage and chemistry in the battery. Can the battery support charging at such a rate. The charging current rate is limited to the max operating current of the battery. If the above battery can supply a max current of say 50 amps, then you will have a max charge rate of 250V, 50 Amps for 2 hours.

petre 9y ago
What makes it confusing is that the charging rates are given as 10C, meaning 10% of nameplate capacity.
- kumarvvr 9y ago
  Might be fererring to nameplate power capacity.
- zAy0LfpBZLC8mAC 9y ago
  nC means n*capacity/time, so 10C for 10kWh is 100kW
- jsjohnst 9y ago
  That’s wrong. 10C means 10x the nameplate capacity. If I have a battery that outputs 40Ah, 10C means I can give it a charging current of 400A.
jsjohnst 9y ago
Here’s some napkin math based on a few assumptions. Assumptions: The article is correct and it’s an 800KW battery pack for the semi. I’m also going to go with a conservative assumption and assume 2C charging rate for the battery pack. I’m also going to assume that the semi will have the ability to take in a 480V charging current because it simplifies wiring and is easier to get in an industrial capacity. With those assumptions, you’ll need 1.6MW of power, something that can be easily delivered with less than eight 500MCM cables (roughly 1” copper cables including insulation that weigh about 2lb a foot and are still rather flexible). This seems in line with the charging port photos I’ve seen for the semi. Neither the cables or the power needs are that dramatic, there’s wind turbines that put out that much power individually along I-70 in Kansas for example where there is thousands of them.

petre 9y ago

What makes it confusing is that the charging rates are given as 10C, meaning 10% of nameplate capacity.

kumarvvr 9y ago
Might be fererring to nameplate power capacity.
zAy0LfpBZLC8mAC 9y ago
nC means n*capacity/time, so 10C for 10kWh is 100kW
jsjohnst 9y ago
That’s wrong. 10C means 10x the nameplate capacity. If I have a battery that outputs 40Ah, 10C means I can give it a charging current of 400A.

jsjohnst 9y ago

Here’s some napkin math based on a few assumptions. Assumptions: The article is correct and it’s an 800KW battery pack for the semi. I’m also going to go with a conservative assumption and assume 2C charging rate for the battery pack. I’m also going to assume that the semi will have the ability to take in a 480V charging current because it simplifies wiring and is easier to get in an industrial capacity. With those assumptions, you’ll need 1.6MW of power, something that can be easily delivered with less than eight 500MCM cables (roughly 1” copper cables including insulation that weigh about 2lb a foot and are still rather flexible). This seems in line with the charging port photos I’ve seen for the semi. Neither the cables or the power needs are that dramatic, there’s wind turbines that put out that much power individually along I-70 in Kansas for example where there is thousands of them.