Originally Posted by Jason Carmichael
Because the charger is only using 3.3 KWh, the load on a circuit of a 30 amp/240v is less than the 15 amp/120v.
You have to understand how a 240V circuit is wired for this to make sense. A 240V circuit is literally 2 120V circuits. A 120V circuit has Live and Neutral wires, a 240V circuit has 2-120V live wires. A 240 V circuit at the circuit breaker is literally 2-15 amp circuits next to each other.
A level 1 charger maxes out the live wire on 1-15 amp circuit. (15 amps)
A level 2 charger uses at most 90% of the capacity of the circuits. (13.5 amps each wire)
These are maximum possible current draws, with ideal wiring and minimal resistance (Ohms about 8 ohms for these numbers).
Watts = Volts x Amps
Volts = Watts ų Amps
Amps = Volts ų Watts
Ohms = Volts ų Amps
Cold weather makes Ohms rise, this is more resistance. More Ohms causes a much higher current flow to keep the same watts. Amps squares as ohms increases. Watts also equals the sqaure of Amps x Ohms. W=A≤ x O
I think you might have a typo in one of those equations.
I think when the resistance increases and the voltage stays constant, the current decreases.
Where did you get 3.3 KWh? Is that your estimate for energy to fully charge the PHEV battery? I thought it was a bit more than 8 KWh.
I agree that there's likely to be less current flowing in a level 2 charging circuit, and so a somewhat higher safety factor if you have concerns about the electrical wiring in your garage. But if you are using a dedicated 120V circuit that is in decent condition for Level 1 charging, I don't see that as a significant consideration.
I read an article about 120 vs 240 charging in regard to which is best for battery life. It stated that while 120 volt charging does not heat the traction battery as much as 240 charging does, it charges and heats the battery for a longer period of time making 240 volt charging slightly better for battery life in the long run. I am currently charging with 120 volts and it is working well for me but I will most likely install a 240 circuit in the near future to maximize battery life. I tried to find the articale to post a link but couldnít find it second time around.
Interesting idea and one that I hadn't considered. I wish you could find that article. I've read that the cooling fan can come on when charging, but I've yet to hear any sound to indicate that it was running. On the other hand, I'm usually asleep by the time it reaches the end of the charging cycle. Perhaps I'll make a point of charging during the day some time and check on it near the end of the cycle to see.
Level 2 is slightly more efficient than Level 1. But only slightly. I estimated that if I fully charged the PHEV battery every day, level 2 would save me about five cents/day in electric bills. Considering only the savings on the electric bill, I estimated the payback period for installing Level 2 hardware at about 78 years. Of course, if there's a benefit in terms of battery longevity, that might be a different matter.