How much heat is normal with level 2 charging

[EVHOO]

We bought our 2017 Bolt at the end of last year, and only used the level 1 charging until about a month ago. I then had an electrician installl a 240 volt circuit and a Clipper Creek charger in our garage. I have charging set for hilltop mode, but have done a full charge on one occasion. When I do a charge starting from about 80 estimated miles remaining, I notice that by the time the charging is finished, the car is pretty warm around both fenders. I haven't measured the surface temperature of the fenders, but would estimate it to be between 105 and 115 degrees F. When the green charging indicator goes from 4 sequential blinks to solid on, to solid on, I then usually hear a loud pumping noise for a few minutes. I assume that it's the pump for regulating heat distribution in the battery pack. Another thing I notice is that the charging cable is a bit warm, a bit warmer than my hand, during the early part of the charging period. By the latter part of charging, when the window indicator is blinking 4 times, the cord is less warm indicating that a lower current is flowing.

Does what I've described agree with other Bolt owner's experience for the amount of heat generated while using level 2 charging? I would add that the garage ambient temperature was probably 80 degrees or so the last time I charged the car.

 

[Lectrikchilipepper]

I have a long work commute so went to L2 charging within a eek of owning the Bolt. What you describe matches my experience also. 32A charging does warm the cord a bit. Why end charging in warm weather there is some heat kicked out from front underside of car. I wouldn’t be concerned but see what others have to say.

 

[iwatson]

I originally purchased a 2011 Chevrolet Volt in 2012. I equipped my garage with a 32amp Blink EVSE at that time, however the Volt's Charger is only a 3.3 kw Charger. The math is Volts x amps = watts. Kilowatts or kw means thousands of watts so 3.3 kw is 3300 watts. So take 3300 watts and divide by 230 volts = 14 amps. The charging cable never got warm when I would charge the Volt.

Now I have a 2017 Bolt which can charge at the full 32 amps. Now when charging on the same 32amp Blink EVSE 230 volts x 32 amps = 7360 watts or 7.4 kw The charging cable is warm and I feel the heat you are describing that I never encountered before. Actually I think the Bolt charger is rated at 7.2 kw but voltage can fluctuate from day to day or from location to location. In the U.S. two-phase power is called 220 or 240 volts with 240 being pretty much the upper end, and I think it can go as low as 208 on the lower end. So I just picked the number 230 as an average.

Anyway, I believe what you are experiencing is normal and I just threw in the math lesson for free. When I first got started with electric cars I didn't understand this but I really think it helps to understand the math.

As designers work to increase charging speed they are faced with the problem of how to disperse the heat that is generated from higher current flow.

A recent news story describes that GM will be experimenting with a protocol for much faster charging for future EV models. A solution that is in development now and part of their testing is liquid cooled charging cables to disperse the heat.

 

[GetOffYourGas]

Just to add / finish iwatson's math, the charging cable has some internal resistance, 'R'. The power loss through the cable (which turns to heat) is I^2 * R where 'I' is the current. So in his case, if he went from 14A to 32A, the amount of heating increased by a factor of 5.2! (32^2 / 14^2). So it's not surprising that he would have a noticeable increase in heat generated.

As to the title question, when L2 charging a Bolt at 32A, it's normal for the cable to feel warm. However, you should be able to grip the cable and hold it indefinitely. If it's too hot to hold onto, something may be wrong (such as a poor connection in the cable or improperly sized wires).

 

[iwatson]

Thank you to "getoffyourgas" for the resistance math. I really appreciate it. I love soaking up knowledge about as much as the Bolt loves soaking up electrons. BTW - I looked through your cool road trip to Virginia Beach post and really enjoyed reading about your adventure. Loved all the great pictures you posted. Everytime I try to post pictures I have a hard time with it. I've done it in the past but must have forgot how. The last time I did it, the pictures showed for the first day and then they disappeared. Not sure why?

I sure would like it if you could teach me how. A lesson via "PM" would be nice if you have the time?

I think I may have mentioned that I have a motorhome for travel and that's one reason I preferred the Bolt over a Tesla. I have no plans to travel much in the Bolt (although you and others have proved that with a little patience it can be done), but rather when I travel by motorhome I like that the front wheel drive Bolt can be towed on a dolly. I looked quite hard at the Ford C-max energi, and although I didn't buy one I have a soft spot for that car. Mainly because It can be dinghy towed (4 wheels down), and because it has a tall-ish upright cabin like the Bolt for easy entry/exit. I decided against the C-max though due to it's short EV range and it's intrusive battery back, and because I couldn't persuade my wife to give up her Mitsubishi i-miev for it. But otherwise I really like that vehicle.

I see from your signature that you have the Bolt and a C-max energi. I think that's a great pair that compliment each other, if you have one driver with a short commute.

 

[GetOffYourGas]

Thanks for the kind words, iwatson. I sent you a PM with more details, but basically I use IMGUR to host the picture and then use a link to embed it in the post.

Travelling with the Bolt is more doable every year, as the CCS networks grow. But yes, it does require more patience, and a lot more planning. Basically, I have to plan a meal stop around a location with a QC. If I can do that, the trip is a piece of cake!

The C-Max Energi is my wife's daily driver. It used to be our family trip car, back when I had a Leaf. Her commute is about 2 miles each way. She rarely drives more than 15 miles in a day because evening family errands/activities are done in the Bolt. Both it and the Bolt are certainly easy to get in/out of. Yet they both have a compact footprint which is handy when parking in downtown Syracuse (or any city, really).

I would imagine an EV would be a great car to tow behind an RV. If you are camping, you often will have electricity available to charge the EV.

 

[SeanNelson]

...when I travel by motorhome I like that the front wheel drive Bolt can be towed on a dolly.

Buy yourself a 10mm wrench and be sure to disconnect the negative battery terminal before you start towing. Even if it's turned off, the Bolt will sense the rear wheels turning and the fact that the vehicle isn't level, and it will apply the parking brakes. Another motorhome owner on one of the Bolt forums learned this the hard way.

 

[iwatson]

I would imagine an EV would be a great car to tow behind an RV. If you are camping, you often will have electricity available to charge the EV.

Yep! That's the whole deal there buddy! I used to tow the imiev, now tow the much longer range Bolt. I had to tow the Mitsubishi backwards on the dolly, since it is rear wheel drive.

be sure to disconnect the negative battery terminal before you start towing. Even if it's turned off, the Bolt will sense the rear wheels turning and the fact that the vehicle isn't level, and it will apply the parking brakes.

Thanks for the advice, but I'm already aware. The Vehicle was towed from Texas to Tennessee immediately after I purchased it.

I have been a daily EV forum reader since 2008 (first Volt, then i-miev, now Bolt), and had already read (and saw his video) about the other owner's experience. So fortunately I was prepared. I have actually installed a negative cut-off switch. So the procedure no longer requires a wrench.

Any motorhome owner that undertakes towing a vehicle should read up on the vehicle to be towed (the "toad") and make sure that they understand the precautions that are necessary for a safe tow on their particular vehicle. Many toad vehicles require special procedures. The Bolt is no different in this regard. But for anyone reading this that may be considering the same type of usage "seannelson" is correct. Once loaded and secured on the tow dolly, make sure that the parking brake is off. Power down the vehicle and disconnect the negative cable on the 12 Volt battery so that the logic will not engage the parking brake while in transit. Failure to follow this procedure would likely result in serious damage and/or fire.

And shame on GM for not including this information in the owner's manual. There is a section in the manual devoted to RV towing, and this procedure is not in the manual. I have stated in another post on this forum that GM should include, in a future software upgrade, a menu setting for "RV mode" that disables the auto parking brake.

I am planning an RV trip in October and will try to remember to document and photograph all the procedures so that I can make an original post on this topic. As for now, methinks I have taken this thread way off topic!