PiP: Measuring Charging Loss

With gasoline, you get nearly the full value of it, regardless of how many times it was pumped or sits in a tank. With electricity, there are losses at every stage; generation, transmission, conversion, storage, utilization, all of which can happen several times along the way.

 

Under my point of view, charging loss is from the supplied OEM EVSE into the vehicle, that amount is probably negligible.
The other and most important is the internal charger conversion loss, and think there is not published data available.

 

Does not the top20 MPGe list take the 15% loss in its formula? I thought it did.

 

There is good data for 240v charging from this INL report on page 3:

http://avt.inel.gov/pdf/phev/fact2013toyotapriusphev.pdf

It shows DC out of the battery is 86% of the AC used for charging. Or, put another way, 16% more AC was used to charge the battery than was discharged later. These tests were done at around 45 mph or, in other words, at a particular level of power being drawn from the battery. Higher power draws generally imply slightly reduced battery efficiency.

The same tests done on a Volt showed 89% of AC out of the battery or, putting it the other way, 12% more AC than the DC discharged from the battery when the car was driven at 45 mph.

http://avt.inel.gov/pdf/EREV/fact2013chevroletvolt.pdf

INL unfortunately does not show results for 120v charging which is usually significantly less efficient.

The INL vehicle testing overview page is:

Advanced Vehicle Testing Activity - Plug-in Hybrid Electric Vehicles/Extended Range Electric Vehicles

 

By itself, storage through-put efficiency is only part of the picture. Conversion and utilization efficiencies are just as important.

 

You do realize that a lot of energy in gas, and involved with creating it also doesn't reach the wheels?
There's finding the raw stuff, there's extracting it, there's refining it, there's still transporting it, there's still converting the chemical energy into mechanical energy (lots of which gets wasted as heat), and there's still losses due to friction throughout the drivetrain. Gas also goes stale if it's sitting unused for a long time, with the octane rating going down; to avoid knocking, that'd also mean less MPG.

There's no free lunch.

 

Of course, but electricity is a slippery fish compared to other energy mediums. Everything you do with it involves losses, whereas chemical energy (gasoline) is much more stable. They both involve significant overhead; from production to transmission to storage to conversion to utilization. Just trying to complete the picture.

 

Everything you do with gasoline involves losses also.

But yes, people do tend to ignore anything before stuff reaches their hands, be it anything prior to the pump, or anything prior to the outlet.

 

Well sure, but that's not how you will be measuring L1 since you won't be hooking equipment up to the battery input wiring like they did. Instead, you will be measuring 120v AC input vs the kwh used from the battery as shown on the display inside the car.

When people casually talk about charging efficiency they are usually referring to AC into the car vs DC out of the battery so they are implicitly including battery efficiency in addition to AC-toDC charger conversion efficiency.

 

does anyone know what the car is reporting, and how accurate it is?

 

I think it would shock most of us to know how much work is involved to give us the consumer items we take for granted.

 

Back in 2012 I posted my methodology and results.
Basically, I charged from a ChargePoint L2 charger for a couple of weeks (with 3 or 4 L1 charges at home mixed in). I summed the ChargePoint stats for kwh for each charge and added in the few readings from home (kill-a-watt). I drove about 150 miles all on EV, with the minor exception of one mandatory ICE triggering (124 mile event) and subtracted out those miles. I then compared to the kwh reported by the PIP. I got a 9 point something difference...and concluded 9% losses with L2 (since the few L1 charges were at a higher loss percentage).

Mike

 

i'm running with that, thanks mike!

 

Here are my results for plugging in the Kill-a-watt for 2 weeks.

I would of tested longer but wanted to be able to take my EVSE with me this weekend.

Method of measurement - P3 P4400 Kill A Watt.
L1 charging
Kill a watt reading 64.77 kWh
Usage from EV Driving ratio screen 56 kWh
15.66% charging loss if my math is correct.
Temps 40s to 60s F. Left the EVSE plugged in most of the time.

 

Since the EV ratio display truncates the kwh ...you could have been at 56, 56.5 or 56.99, right?
56: 15.7% loss
56.5: 14.6%
56.99: 13.6%

Mike