Home Charging Poll: How much power?

[VaderMachE]

You know what that hole under the cable reel is for - right?

Yep...this was right after electrician finished. But thanks for noticing.

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[phidauex]

To the question of what charge power is most efficient at home, the trick is that you have three types of energy loss during charging - fixed losses (running the controls and communication systems), linear variable losses (losses that increase gradually) and exponential losses (losses that increase rapidly). The sum of all these losses means that in most power conversion equipment you have a maximum efficiency that is somewhere near the upper levels of the power range, but not at the top or bottom.

Here is a quick Google Sheet showing an example for an ER battery:

I'm guessing on nearly all the values. I think they are reasonable guesses based on my knowledge of similar systems, but they are WAGs all the same. If anyone knows more, or has an example from a similar vehicle, I'll update the sheet.

The short answer is that for the internal charger, depending on the constant losses and the charger efficiency, the peak efficiency is probably around 40-50A, which is convenient given the size of most EVSEs.

Lower charge powers mean less thermal losses, but your constant losses become a larger component of your consumption, reducing total efficiency. Higher charge powers spread out your constant losses, but the thermal losses really start piling up.

Given that battery degradation below 0.20C is very low, I think that the difference between 0.08C and 0.11C is negligible from a degradation perspective. Technically 0.08 would be less degradation, but you are really in the noise at those low charge rates.

There are a few subtle dynamics I'm missing here such as the sensitivity of charger efficiency to power, the constant cooling losses varying with power and duration, etc., but the overall shape of the curve should be illustrative.

For me, this means that I'll probably charge at my EVSE's maximum, though I might lower it a bit if my utility starts a demand charge program that increases my costs if I charge at a higher rate. This also suggests that going to a very low power (10-20A) to "trickle charge" is probably not a good proposition for total consumption, the charge efficiency down there is not very good at all.

 

[ChasingCoral]

So far it looks like most folks are using 40A chargers.
https://www.macheforum.com/site/threads/home-charging-poll-how-much-power.6031/

 

[ChasingCoral]

Here's the other charger poll.

 

[JCHLi]

Here's the other charger poll.

This one I did find, and was less helpful in my scenario...

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