Climate control using battery while plugged in
- Thread starter ztev
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knightmb
Well-known member
ztev said:
Yes, Nissan has a little fudge factor on what 100% SOC is, so often if you unplug a Leaf while charging and the dash reads 98% SOC, it rounds it up to 100% SOC. That 2% margin is where some cell balancing fits in when fully charged. Also, keep in mind that if the Leaf is plugged in and the heater/AC is using more power than what the EVSE puts out, the missing power is made up by the battery. So if it is really cold outside and you have it plugged into a 3 kW EVSE for example, but it takes 6 kW to warm up the cabin, the battery makes up that missing power. Once the cabin is warm inside and the power requirements go way down, then power can return to the battery to top it off.
But the OP has a 40a EVSE and the 27.5a Leaf charger so should be more than enough to even charge the battery, not deplete it, IF the power was actually coming from the wall. Note I know it doesn't actually come from the wall but the battery that gets charged from the wall but nonetheless 27.5a should be more than enough to replenish any heater use. I've found one only needs about 17a @ 240v to break even with a fair amount of heater use, anything above that should actually charge the battery and not deplete it.
OP, did you notice if the last of the 3 blue dash LEDs were flashing? If not it may not have been pulling anything from the wall. I can never remember the correct order but it's either the car needs to be OFF before it's hooked to the charger or ON but again if the dash LED is not flashing, it's not pulling anything from the EVSE. Note AFAIK you CANNOT have the heater ON and be charging with a pre-13' Leaf, when the car is ON anyway, you can do it with the timer for preheating though.
OP, did you notice if the last of the 3 blue dash LEDs were flashing? If not it may not have been pulling anything from the wall. I can never remember the correct order but it's either the car needs to be OFF before it's hooked to the charger or ON but again if the dash LED is not flashing, it's not pulling anything from the EVSE. Note AFAIK you CANNOT have the heater ON and be charging with a pre-13' Leaf, when the car is ON anyway, you can do it with the timer for preheating though.
knightmb
Well-known member
I agree, but when the battery is at 100% SOC (that Nissan allows for anyway), you can't place a 6 kW load on the charger when the batteries are in parallel with the same circuit that is running the heat sitting at 100% SOC. At that voltage level, the charger has ramped down the power to a few hundred watts to balance the cells. You can't be both 100 watts and 6,000 watts on the same circuit. The onboard charger is feeding in 100 watts because the battery is basically full, but the heater needs 6,000 watts to heat the cabin, so by the Ohm's law, the battery is going to have to make up that difference until it reaches a SOC low enough that the onboard charger can feed 6,000 watts into the circuit safely without damaging the battery. It's a physics limitation more than a design limitation. Otherwise, Nissan would have to install two OBC so one could work exclusivity with the battery on a separate circuit and the other would power the cabin AC/heater with another circuit.jjeff said:
Knightmb is right. The HVAC pulls high voltage from the battery only (never the EVSE) so if the car has tapered the charge because the battery is close to full, then the climate control will pull much more power than the EVSE is providing.
Thanks for the info everyone! I assumed that may be the case, but just wanted to make sure. From what I could tell, the car was charging at the same time (i.e. both my EVSE and the third blue light on the car were blinking). Good to know that it pulls from the battery, and not directly from the charger in this scenario, thus requiring a "buffer".
knightmb
Well-known member
Yeah, nothing is wrong, just the way things work when near 100% SOC. If the Leaf was sitting at 80% SOC and then you started the climate control, all the power would easily come from the EVSE (your home power) and still have plenty left over to feed into the battery at the same time.ztev said:
That makes sense and now that you mention it I think I might have also seen this scenario with my 32a EVSE and my Leaf with a 6.6kw charger. I was kind of bummed out as I really needed the range and wasn't too happy to leave with anything less than 100%, but in the end, ended up making my trip with a little to spare.knightmb said:
It does not actually discharge the battery enough to make a difference to range because the power draw from the wall ramps up as soon as the cell voltages drop enough to allow for more charging current. The difference between 98% and 100% on the dash display is actually very little stored energy.
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