Tag Archives: Chargepoint

How efficient is charging?

These days everyone is concerned with how much resources do they use. Tracking things down to the penny/gallon/kWh/etc. When you have an ICE vehicle there are no losses from fueling the tank: The amount of gas that went into your tank is exactly equal to the amount of gas that was extracted from the tank in the ground and is equal to the amount of gas that was in the tanker truck, etc. (within reason). When you plug in your EV its not the same: When you charge what happens? The battery and the electronics heat up. That heat is wasted energy. Not all of the electrons going through the charge cable end up in the battery. But how many? Is there a way to measure this?

Many modern charge stations will report out the kWh value they put into the car (Chargepoint, for one), in addition some home stations (like the Juicebox) also report out the kWh value. This gives us one figure, but to figure out the charge efficiency we also need another number: The kWh the car used from the battery. This value is the amount of kWh the car consumed that the charger replaced. Divide these two values into each other and you’ll get a measure of how efficient the charge process is in the FFE.

For example: This morning my commute in to work consumed 3.5 kWh according to Ford’s online application (one of the few values in the trip history that have been accurately reported here). Once at work I used a local Chargepoint station to top it off. Chargepoint reported that the car consumed 4.14 kWh during charging. This would work out to a 85% efficiency while charging (at least for the top 20% of the battery or so which is what these values amount to).

I’ll have to do the math again with a deeper charge and using the Juiceboxes values for a different comparison (I’m not expecting it to be much different but more datapoints is always better).

Update: The commute home consumed 3.3 kWh according to the trip meter and the Juicebox put in 4.2 kWh to charge it back up (about 79% efficient).

Also note that the amount of energy going in also is used to run the TMS (temperature management system) and thus when its running will lower the efficiency.

Update 2: After a deeper discharge (9.6) charging took 11.7 for an efficiency of 82%

Update 3: A normal commute usage (11.1) and overnight charge (13.0) yields: 85%.

Update 4: Another normal (10.3/12.4): 83%

Update 5: 10.5/12.8: 82%


How to charge?

Chargepoint just recently redid their website. Included with the refresh is this fancy video on how to charge:

I see a few posts now and then in the plugshare app where people aren’t familiar with how to turn on/off a chargepoint station. It really isn’t that difficult, although I learned something watching it: Typically I just unplug the car when I’m done–instead of turning off the station first (it would probably complain less if I did turn it off first! LOL).


New ChargePoint milestone

ChargePoint has announced that it is up to 50,000 members.

According to them the 50,000th member is a Tesla Model S owner from the bay area. This is good news: The more people sign up for ChargePoint the more likely the network will be around for a while. In Southeastern Michigan the largest network of public stations is with the ChargePoint network so you can see why I’m happy for their success.


Public Charging

A Chargepoint Public Charge Station

A Chargepoint Public Charge Station

Once you’ve driving your BEV around for a little bit you will, on occasion, have a need to grab a charge to make it home. In reality this is much like grabbing a tank of gas while you are out–although it does take a bit more time.

In the US there are two main public charging systems: Chargepoint and Blink. Unfortunately, at this time, the Blink network may disappear. Fortunately for me, however, my neck of the woods (SE Michigan) features quite a few Chargepoint stations:
SE Michigan StationsUsing a public station isn’t much more difficult than plugging in at home. The main difference is you have to first turn on the station. In the Chargepoint case this involves either using a Chargepoint card, using the app, or calling them (the phone # is on the station). Once the station is on just plug in and listen to the electrons flow (yeah ok its pretty silent).

When you setup your Chargepoint account you get a bunch of different options for notification. You can get a text if someone unplugs your car, when the charge is complete, etc. It is very fast too: Once I unplugged my car from a station to see what it would do even though the car wasn’t full yet. My phone got the text message as soon as the plug was disconnected from the car–I still had the plug in my hand when my phone got the text!

Of course using a public station does bring up an interesting discussion point: etiquette. What do you do if someone is already using the station you’re interested in, or are at?