Mystery of Wattage Ratings

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ttibsen

Member
Joined
Jul 13, 2021
Messages
5
I am thinking about getting the 2021 Leaf SL Plus. I see 2 specs on the vehicle - 62 KWH and - 160 kW AC synchronous electric motor. What is the significance of these 2 numbers? I am guessing that the 160 kW rating on the motor is analogous to the 100W rating on a lightbulb so in other words, the motor is rated at 160,000 W - is that correct? Then, what does the 62 KWH mean?
 
62 kWh is the size of the battery pack, which dictates how much energy the car can hold (how far the car can go on a single charge).

160 kW is how much (max) power the motor can use (roughly, more power = more acceleration).
 
Thanks for clearing that up for me - that's a good explanation. So I am not sure on how to do the math but in my neck of the woods, electricity costs 12.5¢ / kW hour. Could you use that rate to tell me how much it would cost to fully recharge the battery on the 62 kWh Nissan?
 
jlv said:
62 kWh is the size of the battery pack, which dictates how much energy the car can hold (how far the car can go on a single charge).

160 kW is how much power the motor can use (roughly, more power = more acceleration).
160 kW is also a peak power value, what you might draw for a short interval when you "floored it". Average motor power at highway speeds would be on the order to 15-20 kW.
 
If you have a continual load of 20 kW for 1 hour (20 kW * 1 hour), you'd have used 20 kWh. 20 kW * 3 hours --> 60 kWh. Multiply the units and values.

If you had a 100 watt device * runs for 1 hour --> used 100 watt-hours or 0.1 kWh. 100 watt device * 10 hours --> 1000 watt-hours --> 1 kWh. Also, you'll notice on your electric bill, you're billed per kWh.

If you're in the US, demand charges residential bills are rare but if you had them, those are in kW. You'd get billed billed both for energy (kWh) and demand charges (per kW).

I don't recall the power level you need to maintain 60 mph on level ground, but let's say it were 20 kW (it's probably a bit less). In 3 hours, at 60 mph, you'd have traveled 180 miles...

Notice that the EPA range ratings on Leaf Plus are a bit over 200 miles: https://fueleconomy.gov/feg/Find.do?action=sbs&id=43665&id=43666. Also, 1 hp is ~746 watts. 160 kW -> ~214.5 hp. In some places of the world, they will list engine specs (even for ICEVs) in watts or kW instead of hp. Also, sometimes, I've seen them in PS (https://en.wikipedia.org/wiki/Horsepower#Metric_horsepower_(PS,_cv,_hk,_pk,_ks,_ch), aka German Pferdestärke).
 
ttibsen said:
I am thinking about getting the 2021 Leaf SL Plus. I see 2 specs on the vehicle - 62 KWH and - 160 kW AC synchronous electric motor. What is the significance of these 2 numbers? I am guessing that the 160 kW rating on the motor is analogous to the 100W rating on a lightbulb so in other words, the motor is rated at 160,000 W - is that correct? Then, what does the 62 KWH mean?

1 Horsepower is about 746 Watts. So that motor will output peak power of about 214HP

1 US Gallon of gasoline contains about 34 KWH of energy, so fully charged the car has the energy equivalent of 1.8 Gallons of gasoline. Fortunately, an electric motor is much more efficient than a combustion engine, so that 1.8 gallons takes you a long way.
 
ttibsen said:
Thanks for clearing that up for me - that's a good explanation. So I am not sure on how to do the math but in my neck of the woods, electricity costs 12.5¢ / kW hour. Could you use that rate to tell me how much it would cost to fully recharge the battery on the 62 kWh Nissan?
62kWh * $.125/kWh = $7.75
 
(Whoops... replied too quickly but I'll leave my reply here.)
Depends on the marginal cost of electricity. In Pacific Gouge & Extort land, if I were still on the default E-1 plan w/our woeful tiers, I'd be pushed into tier 2. See page 1 of https://www.pge.com/tariffs/assets/pdf/tariffbook/ELEC_SCHEDS_E-1.pdf. Each marginal kWh to charge an EV would cost me 32.6 cents.

(I'm in area X, code B, so per page 3, baseline (tier 1) is 309 or 315 kWh in a 30 day billing month.)
 
WetEV said:
ttibsen said:
Thanks for clearing that up for me - that's a good explanation. So I am not sure on how to do the math but in my neck of the woods, electricity costs 12.5¢ / kW hour. Could you use that rate to tell me how much it would cost to fully recharge the battery on the 62 kWh Nissan?
62kWh * $.125/kWh = $7.75

Yep, but I find it more useful to think in terms of fuel cost per mile
Most people get around 4 miles per kWh, so at 12.5¢ per kWh that works out to ~ 3¢ a mile. In the cold winter figure 3 miles per kWh, so 4¢ a mile.
 
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