Less charge with 110 and extension cord?

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Cooper901

New member
Joined
Jul 13, 2018
Messages
2
Hi all. We're new BMW i3 owners (2014 model). We've just charged using an extension cord from our living room lights 110v socket as we're installing a Level 2 home charger in 2 weeks.
We're not happy with the range we're getting. Could this be because the charge is not that strong or maybe it's not really "filling up"? I'll take it to a DC charger later and see how that goes.
Thank you, Cooper's Mom
 
Cooper901 said:
We've just charged using an extension cord from our living room lights 110v socket as we're installing a Level 2 home charger in 2 weeks.
We're not happy with the range we're getting. Could this be because the charge is not that strong or maybe it's not really "filling up"?
After charging, is the charge level displayed as being full? Full is full regardless of how charging occurred, so using a slow AC Level 1 (120 V) EVSE (the charger is part of the car, not the cable used for charging) would not reduce the actual range.

Be aware that the displayed range estimate is just that: an estimate. This estimate depends on several factors such as how the car was driven during the past 15 miles, temperature, etc., but it cannot predict how a car will be driven in the future, so the predicted and actual range could be quite different.

I'm guessing that your i3 is not set in iDrive to "Maximum" for AC Level 1charging so that it is not able to fully charge overnight. If your i3 were set to "Maximum" Level 1 charging, the circuit breaker would likely trip on the living room lights circuit because charging on this circuit is shared with other loads such as your living room lights.

Also, be very careful when using an extension cord to charge. If the extension cord isn't heavy duty enough to handle the charging current, it could overheat, melt, or even catch fire. Its electrical resistance would decrease the charging power as well which would increase the charging time necessary to charge to full.

Your AC Level 2 EVSE will make your i3 much more usable.
 
FWIW, it can take nearly a full day to recharge the newest i3 with the supplied EVSE in the USA if the battery is nearly flat. Plus, unless you bought a high quality, heavy gauge extension cord, you're wasting some energy in heating up the cable, not charging the car. BMW specifically recommends against using an extension cord mostly because most people will not choose one that is not going to create problems. Last (that I can think of), the conversion of 120vac to nearly 400VDC to charge the battery is less efficient with lower input voltages verses 240vac. And, keep in mind that power = volts * amps. The EVSE is limited on the maximum amps, and the car will follow that signal so it doesn't try to overload it. But, an inadequate extension cord, a worn receptacle, or the potential brownout of supply voltage some experience on a hot day (or night) could have the voltage lower than ideal...lower voltage, less power going into the car, longer time to recharge.

The supplied EVSE is going to max out at about 1440W. A CCS charger can provide 50,000W. The car, on acv is limited to about 7400W (with a few exceptions in other markets that can get higher).

There are a few cars on the drawing board that can utilize up to 350,000W inputs. As we start to see longer range EVs, being able to recharge them in a timely fashion becomes more critical for their usefulness. But, it's also going to be awhile before we see many of those around, partly because of our government's love affair with oil and lack of infrastructure spending. The private sector doesn't see a big need, yet, but it is coming. Porsche is introducing a vehicle that can utilize one that big in a year or so, and will be building some. There's hope, but it will still be spotty for years in the USA except maybe in California.
 
Thank you Jim. Yes, we used the proper extension cord (we do construction and these are used for compressors and large equipment). But I still think it wasn't a good, full charge. We're counting the miles today after charging up at a CCS fast charger. More to come...
 
Cooper901 said:
Yes, we used the proper extension cord (we do construction and these are used for compressors and large equipment). But I still think it wasn't a good, full charge.
If the car reported a 100% charge level, the battery pack was as fully charged as the battery management system would allow. It doesn't matter how the charge occurred, AC 120/208/240 V or DC 400 V. This is actually 90-95% of the actual full charge to prevent overcharging which would reduce battery pack life.
 
If you haven't figured it out yet, the estimated range is an inexact measurement. It is based on your last 18-miles or so of driving and assumes your next driving will be exactly the same including temperature. That rarely happens. A graphic example...I'd had my car in my garage at about 50-degrees F...moved it outside where it was about 10-degrees. After 3-4 hours sitting there, the indicated range had dropped about 20-miles, all just from the temperature. Drive along a high speed road for awhile just before turning the car off, then take it mostly on local, low-speed roads...I've had mine go 12+ miles before the estimated range number dropped. The obvious thing here is that the conditions were not the same.

different drivers will get different range, too, even over the same route. FWIW, this is true on an ICE as well, but on an EV, it takes a lot longer to refill the 'tank' and there aren't as many places you can do it!
 
I know BMW says not to use an extension cord but I think it's because they know most people will not use the right kind?

So would a 12/3 15 amp contractor grade extension (25 feet) be ok for the BMW 110v charger for use in a garage. Or should I aim for a 10/3 cord?

Thanks.
 
Before I got my OpenEVSE, I used a couple of different extension cords. 10AWG will work admirably, but it will be fairly bulky-basically imagine a dryer cord... For me I found the biggest source of heat was the connectors, while higher quality extension cords should have better receptacles on them, I found that a cheap little curly extension cord actually generated the least amount of heat out of all the ones I tried, as the connectors made good contact with the OUC's plug.
 
The gauge of the conductors will make a difference, but it will also depend on how long it is. A 25', 12g extension cord won't add much resistance and create heat along with a voltage drop. On a 25' cord at 12g, and 12A, the voltage drop would be about 1.2v, a 10g one, about .75v. IOW, not all that much. Power = volts*amps, so 1.2*12=14W loss on a 12g in the wire, on a 10g extension cord .75*12=9W. This does not include the resistance of the connections at each end...that is important as a sloppy, loose one, could create a lot of heat and power loss, with the attendant voltage drop, slowing the recharging in the car. Also, to minimize heat and voltage loss, do not have any excess cord coiled up. At the power levels involved, it's not much, but to get every watt you pay for, don't coil the cord while in use! IT can make a huge difference with high powered loads. If you have excess, and it's important to you, lay it out in a figure-8. A coiled wire acts like an inductor, which, on acv, will act like a resistor.

NOte, the conversion to DCV needed to charge the batteries isn't as efficient using 120vac verses 240vac, and neither is perfect.
 
The forum annoyingly plugs (pardon the pun) a wrong extension cord. This is a correct one https://amzn.to/2POxgcl A similar 50' cord is also OK, but if you a 25" will reach stay with it. Make sure that the outlet you are using is not old and lose. It must be a 3 prong type. While charging for the first time check the both ends of the cord from time to time. Both connection shouldn't be more than slightly warm to the touch.
 
Hey guys. Excellent. Exactly what I was hoping for. Here’s the link to what I’m thinking of getting at Canadian Tire; 25 ft 12/3 15 amp contractor grade extension cord.

https://www.canadiantire.ca/en/pdp/mastercraft-contractor-grade-extension-cord-12-3-gauge-0522319p.html#srp
 
tman66 said:
https://www.canadiantire.ca/en/pdp/mastercraft-contractor-grade-extension-cord-12-3-gauge-0522319p.html#srp

Ok, so this cable worked great last night. No warmth at all on the plugs at either end or along the cable. Thanks!
 
While a quality cord is essential, the current state of the receptacle is equally important. If the plug isn't hard to insert, the resistance may end up too high. That simple test won't tell you if the actual line voltage cable is connected to the receptacle properly.

More than one person has had issues with a bad receptacle in one way or another.
 
jadnashuanh said:
While a quality cord is essential, the current state of the receptacle is equally important. If the plug isn't hard to insert, the resistance may end up too high. That simple test won't tell you if the actual line voltage cable is connected to the receptacle properly.

More than one person has had issues with a bad receptacle in one way or another.

Noted, I had planned on replacing the outlet in the garage as I have throughout the house.
 
FWIW, I had an 'industrial' grade 20-amp 120V outlet that I plugged the car into, no heat buildup whatsoever. With the standard household 15amp sockets, it's luck of the draw- one in my garage got fairly warm, the other did not, the one that didn't get warm seemed slightly higher quality (different brand maybe?), but was installed at the same time as the other garage receptacle. Too bad the OUC doesn't have a rotatable prong, so it can be plugged into a 20-amp 120V circuit to provide 16 amps of power.
 
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