How do AC KwH consumed and DC KwH Stored compare ?

There are obviously losses involved in Charging . A bunch of them. Battery Heating, increased pack resistance over time, efficiency of the charger and cables, yada yada.

Skipping the theorizing ( please !). Does any body keep records of their AC KwH consumption vs. how much charge they are getting ?

I would like to know , using a new battery and one operating at 8 bars , how much electricity I am going to buy
to achieve a charge. Pick any number of KwH stored that is convenient.

I am thinking in terms of % efficiency. for 1 KwH stored.. how many KwH are required from my AC source ?

Assume either 3.3kw or 6.6 kw charger and 240v AC supply.

Ball park based on experience and qualified by pack condtion.. is what I am after.
:ugeek:

I will give you some information about charging energy from the wall but I will not try to relate it to actual DC bus energy because comparing the two quantities depends upon how you measure the DC quantities. If you use the A/C a lot and drive a bit aggressively like I do, you can expect about 3 miles per kWh measured at the wall using a 30-ampere or larger L2 EVSE. I saw no noticeable difference in efficiency between the 2011 when it's original battery was down to 8 bars and with its new battery. The 2015 is about the same.

The dash display typically shows 4 mi/kWh while the energy consumed from the wall is typically 3 mi/kWh with my driving style.

Gerry

blimpy said:

Skipping the theorizing ( please !). Does any body keep records of their AC KwH consumption vs. how much charge they are getting ?

Click to expand...

I charge at 3.8 kW (240 V x 16 A) and generally see a charging efficiency of about 88-91%. But, although the wall charge used is quite precise, the number for the amount of charge available to be used by the car is a bit crude since I base it on the dash miles/kWh reading, which is rather coarse. The calculation goes like this:

wall miles/kWh ÷ dash miles/kWh = charging efficiency.

It is has been reported that charging at 120 V, 12 A is about 75% efficient but it has been almost four years since I've charged at 120 V and I never did the measurements needed for the calculation. The reason that slower charging is less efficient than faster charging is because the system overhead — cooling pumps, inverter, and the like — has to run longer and that leads to more losses.

FWIW, although perhaps not what you are actually looking for.

Well, the real question was..... as the battery ages, less power is actually stored, and more is converted to heat.

Or to put it another way.. you charge for the same length of time at the same rate.. but less energy is actually available to use when the batter has aged... vs how much was available when new.

There fore.. there Is a reduction in efficiency... KWh in vs KWh out.

I do not believe that the battery efficiency is a constant.. as shown in the nice chart ( full of valuable info )
but rather the batter efficiency declines with age.

So I guess I can answer my own question.. maybe.