Tuesday, November 5, 2013

How Long Will it Take To Charge an i3?

The i3 will charge in about 3 hours on a standard level 2 supply.
Since installing public charging stations at my restaurant in Montclair NJ, I have conversations with EV-interested folks nearly every day. One of the most popular questions they seem to always ask is how long does an electric car take to charge?

I wish I could just give a quick answer, but it's just not that easy. Nearly every EV takes a different amount of time to charge since they have different size batteries and the also have different charging rates. Then you throw in three different levels of charging (120V, 240V & 480V DC quick charge) and there isn't even a single answer for every car. For instance if I said the i3 takes about 3 hours to charge I'd be correct. However I could also say it will charge to 80% in under a half hour (DC QC) as I could say it takes about 15 hours (simple 120V household outlet) to charge and I'd still be correct. So I try to quickly explain the different methods of charging and the fact that every car is different without totally confusing the person or making it sound so complicated that they are are turned off by it all. After all, getting gas may be expensive but let's face it, it's very easy to understand!

The size of the battery, the onboard charger and the supply provided will all work together to determine how long your EV will take to charge. The vast majority of the time most EV owners will charge their car they will do so on a 240V electric supply, so I'll focus on that here. One advantage "little battery" EV's like the i3 have is since they have a small battery, they will charge relatively quickly, provided they have robust onboard charging capabilities. The i3's standard 7.7kW charger will fully charge the battery in under three hours which is pretty good compared to the other EV's on the market. Only Tesla (9.6kW charging standard) and Renault (43kW Chameleon charger) offer an EV with a faster level 2 charging rate than the i3.

Miles Per Hour:

One way to condense the conversation about charging time is to simply say how many miles of range per hour of charging you get. The i3's small battery (18.8kWh usable) combined with its relatively fast onboard charger will allow you to gain about 30 miles of range for every hour you are plugged into a 240v 32 amp supply. This will be something I really welcome. My MINI-E could accept up to 12kW's and I would get about 30 miles per hour of charging. However after a recent BMW software tweak my ActiveE only gets about 15 miles of range per hour and it feels painfully slow, especially when I need to charge to get somewhere. I am
so looking forward to getting back to charging at 30 miles per hour when I get my i3. Being able to charge quickly on a standard level 2 supply is really helpful and once you've been able to do so you don't want to go to a slower charging rate. The car becomes imminently more usable when you can charge it quickly so I'm glad BMW is offering a pretty robust onboard charger. Now of course I wish it was a 9.6kW charger like Tesla uses, but that's just the part of me that is never satisfied speaking. In reality 7.7kW's is fine for a car with a 22kWh battery. It will charge twice as fast as my ActiveE and deliver about the same range, and that will really make the car much more versatile.


  1. Quick charge is really what will make electric cars mainstream. Tesla understands this and is doing it themselves. Without quick charge cars like the i3 are in shackles and limited to short trips. Even with "quick" level two charging they just can't be your only car. If you don't have a long electric range you need quick charge stations. I am holding out hope BMW will invest in them like Tesla and Nissan

  2. Very good blog, and gain a lot infulence from you to make me decided buying an I3 Rex, waiting for my delivery now, and not sure if I want to buy and install the Level 2 charger at home or not, since I daily commute is about 40Miles round trip, for regular home 120V outlet, do you think that I need LEVEL 2 for now?

    I am thinking get a Clipper Creek HCS-40 early next year, is it compatible?

    Tks in advance.

  3. The these cars are COMMUTER cars. That's what they are designed for. Less than a 100 ml/day, which in fact is what over 96% of Americans drive daily.

  4. My 2015 bmw i3 range extender is charging at rate of 5.7kwh with L2 charger. I am using charge point chargers that support at least 6.6kwh. I confirm that because Nissan leafs using same charger and get charge at 6.6kwh when I took my car to Irvine bmw they said nothing wrong with charging
    From Irvine Bmw “A maxium charging power of 7.4kw is possible however the system is still dependent on the size of the line cross section which was used in the electrical installation.”