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EV batteries are measured in kWH (Kilowatt hours) or 1000 watt-hours - a watt hour is a unit of measure of 1000 watts of a electricity for 1 continuous hour. The Bolt comes with a 60,000 watt-hour battery - or 60 kWh battery. Charging a Bolt battery from empty requires 60,000 watt-hours.

How do I calculate watts?

Turns out the math is simple:

you need to know 2 factors about your electrical supply (or charger).

Volts

AMPs

watts = Volts * AMPS

watt-hours = (Volts * AMPS) + time

In the US electrical circuits are typically either 120v - 120 volts or 240 volts. 120 Volts are a typical wall plug in your home or kitchen or room, most home appliances are 120 volt devices, and 240 volts are typically: ovens, electrical water heaters, electric dryers, air conditioners, hot tubs

(* in the US volts vary for 120 volt from 100-130 volts, and 240 volts vary from 200 to 250 volts - it all depends on your electrical provider, your houses main panel, time of day, overall load on the grid and so on and so forth). For purposes of this posting we're going to use 120 volts and 240 volts which is the "ideal" goal of the US electrical system - your actual watts will vary based on your actual home supply characteristics. If you can measure your home's voltage you can adjust the math below to actual volts and the watt calculations will change slightly.

Electrical Circuits are installed in panels with am AMP rating for different voltages (120 or 240). Typically breakers are rated at peak/temporary load, and continuous load. For continuous load you have to de-rate the breaker by 20% - so a 10 AMP breaker is only rated to deliver 8 AMPs of continuous load. Loading a breaker at more than 80% of it's rating continuously is not recommended and can cause problems.

Charging an EV is considered continuous load (any load for more than 3 hours) so the 80% rule is in effect.

so let's figure out how do we calculate charging time for a given charger for a Bolt.

Typical home Plug - 120 volts on a 15 AMP circuit - derate by 20% - 12 amp continuous load

120 volts * 12 AMPs = 1440 watts or 1.44 kw - do this for one hour at you get 1.44 kilowatt hours

charge the Chevy Bolt from empty with this charging rate and you divide 60 killowatt-hours / 1.44 kilowatt hours = 41.667 hours - that's best case and there is about a 10% loss with the chargers so 41.667 * 1.1 = 45.8 hours - we add a 10% fudge factor to deal with various in-efficiencies in the whole charging infrastructure.

so it will take 46-48 hours to fully charge an empty Bolt from a normal house hold plug @ 12 amps on a typical home 15 AMP circuit.

The Chevy Bolt Default 120 volt setting - 8 AMPS - since many homes were never built with continuous loads in mind - Chevy has taken a conservative approach and defaults the Bolt's 120 volt charging rate to 8 AMPS (or about 50% of a 15 AMP break's load - this is to account for poor plug quality and potentially poor wiring in some homes) - so the math for this default setting to fully charge a Bolt from empty is

120 volts * 8 AMPs = 960 watts or 0.96 kw

60 kwh (volt battery) / .96 kw = 62.5 * 10 % fudge factor = 68.75 hours or there about

some homes/garages have 120 volt / 20 AMP circuits - these are typically used for engine block heaters and use a different plug from the normal household plug - 20 amps * 80% - 16 amp continuous load

120 volts * 16 amps = 1920 watts or 1.92 kilowatts

60 kwh / 1.92 kw = 31.25 hours * 10% fudge factor = *1.1=34.375 hours or about 35-36 hours to charge from a home 120/20 amp circuit - you'd need to find a EV charger for this however because Chevy's charger that comes with the car doesn't support this type of plug/circuit

as you can see 120 volt house hold circuits really don't do the job - to properly charge an EV you typically want to use a 240 volt circuit. To do this there are lots and lots of choices for various EV charges are all sorts of different AMP Ratings. Typically you want to buy an EV charger who's maximum AMP rating matches or exceeds your EV car's charging capability.

The Chevy Bolt can handle up to a 40 AMP circuit, with a 32 AMP continuous draw. So any EV charger up to 40 AMPS will charge your Bolt much faster than your typical 120 volt house hold circuit. Typical 240 volt breakers are: 16 AMP, 24 AMP, 30 AMP, 32 AMP, 40 AMP, 50 AMP, and in increments of 10 AMPS upto 200 AMP circuits (typically a 200 AMP breaker is on most homes for the entire house, most US homes have 80, 100, 125, 150, 200, 400 AMP main whole-house breakers)

Math for charging at 240 volts for various AMPS are:

16 AMP 240 volt breaker - 240 volts * 12.8 AMPS = 3072 watts or 3.072 kw = about 22 hours to fully charge an empty Bolt

20 AMP 240 volt breaker - 240 volts * 16 AMPS = 3840 watts = about 17-18 hours to fully charge an empty Bolt

24 AMP 240 volt breaker - 240 volts * 19.2 AMPS = 4608 watts = about 15-16 hours to fully charge an empty Bolt

30 AMP 240 volt breaker - 240 volts * 24 AMPS = 5760 watts = about 12-13 hours to fully charge an empty Bolt

32 AMP 240 volt breaker - 240 volts * 25.6 AMPS = 6144 watts = about 11-12 hours to fully charge an empty Bolt

40 AMP 240 volt breaker - 240 volts * 32 AMPS = 7680 watts = about 9-10 hours to fully charge an empty Bolt

------------------------------- Bolt can only handle 32 AMPS - math below is for a 50 AMP circuit which may charge other EV's faster, but not the Bolt - since it will only use 32 AMPs regardless of "bigger" AMP ev chargers -------------------------------

50 AMP 240 volt breaker - 240 volts * 40 AMPS = 9600 watts = about 7-8 hours to fully charge an empty Bolt if it could handle a 40 AMP charge rate which it can't.

Typical public chargers on the West coast from Chargepoint network are 208 volts at 30 amps charge rate (I don't know what the breaker is but the car reports 30 amp charge rate) or 6,240 watts.

208 Volts * 30 amps = 9620 watts or 11-12 hours to fully charge an empty volt from your typical J-1772 public charger.

Charging times will be less for actual usage since most people only drive 40-60 miles a day - you can do the math for kWh usage - at 4 miles per kWh for the Bolt - typical 60 mile/day usage = 15 kWh to recharge at the end of the day

running the table for this approximate charge times are as follows at various voltages and charge rates

120v @ 8 amps for 60 miles of driving = approximately 12 hours charge time

120v @ 12 amps for 60 miles of driving = approximately 9 hours charge time

240v @ 16 AMP circuit for 60 miles of driving = approximately 6 hours charge time

240v @ 20 AMP circuit for 60 miles of driving = approximately 5 hours charge time

240v @ 24 AMP circuit for 60 miles of driving = approximately 4 hours charge time

240v @ 30 AMP circuit for 60 miles of driving = approximately 3 hours charge time

240v @ 32 AMP circuit for 60 miles of driving = approximately 3 hours charge time

208v @ 30 AMP charge rate for 60 miles = approximately 2.64 hours charge time - typical J-1772 Public Charger (Charge point)

240v @ 40 AMP circuit for 60 miles of driving = approximately 2 hours charge time

-------------------- Bolt Cut off -------------------- 32 AMPS is maximum charge rate for a Bolt --------------------

240v @ 50 AMP circuit for 60 miles of driving = approximately 1.5 hours charge time

DC Fast Charging is another whole ball of wax - and the typical math there is 400 volts * some number of AMPS - the wattage ranges from 24,000 watts (charge point) to 50,000 watts (evGO) and some DCFast chargers in Europe are going as high as 100,000 watts. The math is a little complicated because you can not charge the battery at the same rate during the entire charge cycle, the closer to full the battery is the slower the charge, you can only pump maximum wattage into the battery when it's close to empty. But basically…

24,000 watts would charge the Bolt from empty to full approximately 2.5 hours

50,000 watts would charge the Bolt from empty to full approximately 1.2 hours

100,000 watts would charge the Bolt from empty to full approximately 0.6 hours or about 40 minutes

keep in mind the numbers above are theoretical and times will likely be longer because you have to taper the charge rate once the battery gets above 80% charge rate you can no longer pump full wattage into the battery - so it will take longer to charge the last 20% than to charge the 1st 80% of a battery

Tesla superchargers are 400 volts * 400 amps and therefore 160,000 watts - so if we had an adapter you could charge a Bolt in 22 minutes - LOL - but again that's theory- and I think the DCFast charging hardware on the Bolt is limited to 60,000 watts so any DCFast charger offering more than that would be ignored by the Bolt and it would only charge at a 60,000 watt level regardless of how much power the charger offered above that.

I hope you've found this posting useful and I _KNOW_ the internet will correct any mistakes (people on forums are ruthless that way - ) - I'll be happy to answer any questions and if necessary post any corrections.

Enjoy your Bolt! I'm having super fun with mine!!!