onboard charger efficiency ?

  • Thread starter Thread starter drdrei
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This topic got me thinking. I have been tracking my charge from empty (two bars 0 EV range) and over 15 readings consistently pull only 13.65kw from the wall to fill up to 99-100% charge. I take the readings from my JuiceBox Pro 40 so it could be possible it does not read correctly but if it does and we are at 90% efficient on a level 2 then I'm only adding 12.25 kw to my battery. If anyone has an idea to confirm what is getting pulled from the wall for this type of setup I'm all ears.
 
Here is the paper on the Honda on-board charger in the Fit EV. https://www.hondarandd.jp/point.php?pid=872&lang=en

Below is a plot of the efficiency at various power levels for 240V charging from that reference. Note that the final number they quote is 87.9% efficiency for the charger.

FitEV_ChargerEff.webp


The OP's question was about 110V charging, but I'd guess that this plot may be a good first estimate at ~87% efficiency at ~1.2 kW.
 
I live in a place where it gets to be 90-105 degrees F. for 3 months in the summer, at night. When I charged the Clarity, the fan would go on to cool the battery while it was charging. The longer the charge time, the more energy was used to cool the battery. I charged the Clarity with the 120V charger for a while, before my L2 charger was installed. From the usage notes on utility bill, I noticed that it took 10% more power to charge using the 120V charger, and I believe that was due to the car having to continuously run a fan, and pump to move the coolant, for a longer period of time, to cool the battery while the car was charging.
 
dGarry48 said:
Good stuff. It looks like got a good accuracy.
Click to expand...

I can't speak for accuracy, but it is good enough. The only quibble I have is that it is quite hard to pull the charger plug out of the meter. This was the case with both my cars (but then it doesn't fall out). I only really notice because I have arthritis in my hands and no strength in my grip, but my 82 year old cousin was able to do it with no trouble.
 
Also, keep in mind that the 'empty' 0 EV range could have varying amounts of charge still in the battery. On mine I have seen state of charge (SOC%) percentages from as low as 4% up to 14% with 0 EV range. Typical is 10%, but it will vary.
 
A note is that charger efficiency may or may not include the overall system efficiency (battery efficiency) depending on study.

Clarity has 12.5 kWh usable. The capacity is indicated in some tech paper somewhere, I think the cells are 27 Ah and they use 20 Ah or so.

On my L2 charger it usually takes 13.5 or 14.5 kWh from empty to 100% SoC (2 bars to full).
 
The charging efficiency, including all losses between wall and the EV battery cells, is usually cited at 85% for electric cars. It's possible to get a higher figure if you're doing only a partial charge, because efficiency drops as the battery cells approach a full charge. So I've seen citations for up to 90-92% for individual charging sessions, altho almost certainly for a partial charge with the battery pack almost empty.

izudin said:
I think you use a way low efficiency. I monitored energy usage for some time with KillAWatt, while charging at home and (assuming that battery pack capacity is 17kWh) came with the efficiency around 96%
Click to expand...

I've seen a lot of arguments over what the actual figure should be for the usable battery pack capacity for the Clarity PHEV. If your math indicates a 96% charging efficiency, then your figure of 17 kWh is probably off. Perhaps that's the full capacity, but you should be using the figure for the usable capacity, because that's how much of the capacity is actually being used.
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