PiP Charging Efficiency

I agree with your math but since most people only know the kWh reported by the vehicle it might be appropriate to promote 14% as the conversion factor from kWh reported by the vehicle to kWh at the wall.

i.e. 85kWh x 1.14 = 96.9 kWh at the wall as used for calculating MPGe.

The PiP spreadsheet uses 1.15 as the conversion factor.

Any idea how seasonal ambient temperature affects the charger's efficiency?

 

Do you leave your KAW plugged in all the time and/or correct for that? If yes, that is probably a penalty of ~1% in your measurements. (21 hrs per day * 40 days * 1.4 watts = ~1.2 kwh). So your results are similar to mine a couple of months ago...I found 9-10% charging loss when most of it was on 240v...guestimated 10-11% for 120v (based on all 240v followed by 120v and a slight increase in losses).

Also, I measured a KAW, WattsUp Pro against my home smart meter and found a 30 watt variance at ~1350 watts...so that is a 2.2% meter error one way or the other.

Mike

 

Why the 21 hrs, 40 days? Doesn't the 1.4 watts occur for all hours the cable is connected to the power source. Of course its negligible compared to the current while charging but its still there. In any case that 1.4 watts is part of the cost of charging the battery hence should be used in determining the equivalent amount of gas per the current cost of gas and all kWh used.

 

Because you have to have it plugged in while charging and it is part of the charging overhead at that time. But when you are out driving around it isn't needed.

Mike

 

Interesting, that's much lower than the Leaf at 120 volts reported at My Nissan Leaf Forum • View topic - "typical" Miles/KWh figures for a couple scenarios?. I wonder if the Leaf really does have a lot more charging overhead (partly due to some pumps running while charging)? I wonder if there some built in fudge factor into what the PiP reports?

 

Have you been tracking how many kWh it takes to charge a depleted battery? It would be useful for inferring the kWh used to charge from L1 by using the battery percentage reported by GreenCharge, which is more precise battery measurement from Entune.

I would measure it myself, but my Kill-a-Watt died a few weeks after I bought it...

 

I totally agree

 

I define it as driving in EV only and shutting off the car the instant it automatically switches to HV. Primarily because, on my commute I can get it to do that relatively easily and it is exactly repeatable. Sure if you drive in HV for a while you can lower the SOC more. But you can't stop the car at nearly as precise SOC.

Mike

 

For the purposes of inferring from the GreenCharge reported battery percentage, it means anytime GreenCharge reports 0%. Based on my observations, this appears to be the same as the switchover to EV, which occurs at 6 bars. Since GreenCharge reports 0-6 bars as 0%, aka depleted, an average kWh over several charges should provide a reasonable value for inference.

To me, it's a little unusual to see a variation of 1 to 8 bars pulling into the garage. In HV mode, the HSD actively tries to maintain between 3-6 bars. I've only seen 0-1 bars when going uphill while the HSD is warming the engine and even 2 bars is pretty rare. I usually see 5-7 bars. The only conditions I can imagine where you'd see such variation are:

1. if the garage is at the top or bottom of a hill
2. EV miles have been held in reserve and switching back to using them before the end of destination a little late leaves some battery charge.

Are there other situations? Also, if there's a way to more easily get down to fewer bars at a destination, I'm curious as well.

 

I thought the Leaf uses air to keep the battery cool/warm. Of course with a bigger battery it may have more fans. I usually hear the fan in my PiP when charging even on cold days.


iPad ? HD

 

Have you considered evseupgrade.com for your PiP's L1 portable unit so you can get 240v?
Toyota : EVSE Upgrade, Your EV Charging Solution
Efficiency is a tad better @ 240V - besides being quicker.

 

The Leaf has no battery cooling system at all, not even a fan. The modules are inside a sealed casing. There's a bit more about the sealed casing at http://www.nhtsa.gov/pdf/ev/Nissan_Presentation-Bob_Yakushi.pptx.

As for "using air", well, I suppose there is some airflow when the car's moving and heat is emitted from the pack but that's about it.

Drivetrain - MyNissanLeaf mentions what's liquid cooled.

 

After reading several articles about it, I had to figure out the "adjustment of the battery’s internal resistance" to try and understand how they kept it cool. It is air cooling but its more passive than I was led to believe.


iPad ? HD

 

^^^
On the Leaf, there were some early articles claiming there is a fan inside the casing to circulate air, internally. But, supposedly that's not true, at least not on production models.

Nissan's made claims that they don't need active thermal management (In Race to Market, Nissan's Electric Car Takes Shortcuts | Autopia | Wired.com), but so far, that's proven to a be fatal mistake for those in hot climates (e.g. Phoenix).

 

The active "adjustment of the battery’s internal resistance" may be what's causing the loss of charging efficiency although it would interesting to see different Leaf owners KW measurements using 240 and 120V charging. Although in all seriousness how many Leaf owners actually use 120V.


iPad ? HD