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Discussion Starter #1
When my car finished it's (hill top) charge this morning, the Bolt started making a loud noise. Kind of like the engine revved up to 3 or 4 thousand RPM, which seemed strange for an electric car. It continued for a minute or so, till I unplugged it - I had to leave for work. No idea how long it might have continued otherwise.

Is this normal? What is causing the noise? I've never heard it before - I'm not always in the garage immediately after charge completion, but I expect I would have been there at the right time at least a few times in the past 4 months, but never heard anything like this.

I don't find anything relevant in the owner's manual, except maybe this, which does not seem quite on point anyway:

"The charging system may run fans
and pumps that result in sounds
from the vehicle while it is turned
off. Additional unexpected clicking
sounds may be caused by the
electrical devices used while
charging."
 

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Most likely it's the cooling system doing it's thing. Not sure where you're located, but with warmer weather it's more likely to need the cooling while/after charging.

LEAF drivers never hear these noises - no fans or pumps in their passive system :eek:
 

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That could very well be it. The ticking noise is something additional that you may hear but what you've experienced could very well be just fans and pumps like the owners manual states. Kind of hard to make it relevant when we really don't know what they're "supposed" to sound like.
 

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Discussion Starter #4
Most likely it's the cooling system doing it's thing.
Perhaps. But why would the cooling system stay silent/inactive through 8 hours of charging, and then turn on at high fan speeds immediately AFTER the charge was completed? If cooling is needed, isn't it needed during the time when charging is heating the battery or other components?? They're already cooling when the charge is over.

I'm thinking this makes no sense, and it must be something else. Hopefully not a malfunction...
 

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Perhaps. But why would the cooling system stay silent/inactive through 8 hours of charging, and then turn on at high fan speeds immediately AFTER the charge was completed? If cooling is needed, isn't it needed during the time when charging is heating the battery or other components?? They're already cooling when the charge is over.

I'm thinking this makes no sense, and it must be something else. Hopefully not a malfunction...
Hmmm.
Perhaps I misread your original post? The car made no fan noise at all thru the entire charge cycle itself? Or did you just happen to be near the car when charging completed and heard the noise?

The fan will cycle on/off as needed during (and even after) charging. I've been in the garage as the Fit EV stopped charging and heard the fans spin up. The Bolt has 3 separate cooling systems -cabin, battery, and inverter/electronics. Charging creates a fair amount of heat, and there is a fair amount of thermal mass to cool in the battery. We are so used to EV's being quiet that having it sound like a vacuum cleaner can be disconcerting - hence the statement in the manual.

As the weather gets warmer, your likely to hear it more often. Chevy recommends keeping it plugged in when stored in a hot environment so the cooling system can keep battery temps in line long after charging is complete
 

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Discussion Starter #6
Hmmm.
Perhaps I misread your original post? The car made no fan noise at all thru the entire charge cycle itself?
Yes that's right, more or less. The car does make a quiet hum while it charges, but after 4 months of ownership and charging almost every night I've never once heard the loud vacuum cleaner noise I heard yesterday. It began just when charging was completed, and the need for any active cooling had presumably just ended.

As I say, you could be right, and it could be cooling, but that really does not make sense. It would be as if your PC's CPU fan stayed inactive while you use the computer, and then spun up just as you turn off the computer. Computers do not in fact work that way, for obvious reasons. Does the Bolt?
 

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As I say, you could be right, and it could be cooling, but that really does not make sense. It would be as if your PC's CPU fan stayed inactive while you use the computer, and then spun up just as you turn off the computer. Computers do not in fact work that way, for obvious reasons. Does the Bolt?
Well, the size of the battery is much larger than the CPU in the computer. As the cells in the battery charge, they heat up, but it may just take time for the combined heat of all the individual battery cells to transmit heat to the temperature sensor to trigger the cooling cycle...

...or it could be that the system is programmed not to consume any electricity to cool the battery (which would slow charging down), but when fully charged and connected to an external system, kick off a cooling/maintenance cycle using the external power supply to "optimize" the battery temperature that it wouldn't otherwise do.
 

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Discussion Starter #8
Well, the size of the battery is much larger than the CPU in the computer. As the cells in the battery charge, they heat up, but it may just take time for the combined heat of all the individual battery cells to transmit heat to the temperature sensor to trigger the cooling cycle...

...or it could be that the system is programmed not to consume any electricity to cool the battery (which would slow charging down), but when fully charged and connected to an external system, kick off a cooling/maintenance cycle using the external power supply to "optimize" the battery temperature that it wouldn't otherwise do.
Thanks for the suggestions, but these don't make sense either. It is a trivial matter to locate a heat sensor inside the battery as needed to sense heat in a timely, accurate manner. We are living in the 21st century, after all.

The battery must begin to assume room temperature as soon as charging ends - even without fans, though it would take more time. And surely it is even more undesirable to consume electricity for cooling after charging ends rather than before, since this will leave me without a full charge.

Of course, just because something doesn't make sense does not guarantee that it's not happening. But I doubt GM is guilty of either of these two particular bad design possibilities.
 

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I have no backup for this, but there could be some sort of maintenance cycle that only runs when plugged in - not charging. You can still pull power from the EVSE when the batteries are topped off to run things, so you wouldn't necessarily be "without a full charge". Think preconditioning your car...
 

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Discussion Starter #10
I have no backup for this, but there could be some sort of maintenance cycle that only runs when plugged in - not charging. You can still pull power from the EVSE when the batteries are topped off to run things, so you wouldn't necessarily be "without a full charge". Think preconditioning your car...
Sounds plausible to me, though I don't know what preconditioning means nor why it requires so much noise from fans or other components. If it is a normal maintenance process, Chevy really ought to provide some warning/info in the manual, as it's a bit disconcerting the first time it happens to a new customer. I was able to unplug the power cable without difficulty, so I guess that means it was not locked on and removal should not cause any problems for the car, but again, some reassurance to that effect in the manual would be nice. Thanks.
 

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The fans will come on as needed and don't care if the car is charging or not.

The temp sensor likely is located in the pack somewhere, but not likely on each individual cell. There is a "heat sink" effect. The batteries will heat during charging, but it will take a certain amount of time for that heat to spread from the cells to the rest of the pack. The shape of the pack means that some areas are likely to heat/cool faster.

This article claims a total of 6 temp sensors attached to "certain cells".
http://sandyblogs.com/techlink/?p=7070

It is not unusual for EV fans to come on soon after charging.

ICE vehicles can have the fan start after the vehicle is shut off as well. This is a similar situation in that the generation of heat has stopped, but the existing heats takes time to reach a sensor that starts the fans.
 

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Sounds plausible to me, though I don't know what preconditioning means nor why it requires so much noise from fans or other components. If it is a normal maintenance process, Chevy really ought to provide some warning/info in the manual, as it's a bit disconcerting the first time it happens to a new customer. I was able to unplug the power cable without difficulty, so I guess that means it was not locked on and removal should not cause any problems for the car, but again, some reassurance to that effect in the manual would be nice. Thanks.
Ya, some info from Chevy would be nice on this one. My volt makes some whirling fan noises when charging, but nothing "loud". A side note- I may be wrong, but I don't believe that the car ever actually locks the lvl 2, 240V charging cable into the car. That is a feature reserved for lvl 3 DC charging because DC power is much more dangerous than AC.
 

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100% speculation here, but could you have accidentally activated the 'remote start'? I mention it because you said you needed to head off to work. I'm guessing you did not, but at least wanted to put it out there as one possible reason the car started to make noises. Hopefully not a malfunction.


The manual says "Remote Start
This feature starts the heating or air
conditioning systems and the rear
window defogger from outside the
vehicle.
Use remote start to heat or cool the
interior when the vehicle is plugged
in to maximize electric range by
utilizing electricity from the electrical
outlet. Normal operation of the
system will return after the vehicle
has been turned on."
 

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This makes me think of the portable LCD projectors we use at work. While the lamp is on, the fan runs at a fairly low speed unless the temperature gets really severe. But once you turn the lamp off, the fan runs at max speed for several minutes trying to exhaust all the heat from the projector. As long as the thing expects the power to stay plugged in, it doesn't panic about cooling because it knows more power to keep the fan running is coming... it's only once it realizes the power might go away shortly that it really blitzes the fan. Similar deal here maybe? Of course, the Bolt isn't worried that you might zip it into a carrying case where it will cook itself...but it might want to conserve battery power for moving the car rather than cooling the battery.
 

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This makes me think of the portable LCD projectors we use at work. While the lamp is on, the fan runs at a fairly low speed unless the temperature gets really severe. But once you turn the lamp off, the fan runs at max speed for several minutes trying to exhaust all the heat from the projector. As long as the thing expects the power to stay plugged in, it doesn't panic about cooling because it knows more power to keep the fan running is coming... it's only once it realizes the power might go away shortly that it really blitzes the fan. Similar deal here maybe? Of course, the Bolt isn't worried that you might zip it into a carrying case where it will cook itself...but it might want to conserve battery power for moving the car rather than cooling the battery.
In theory that seems to be the case since its all for supporting heat dissipation but of course in this situation we're working with something much bigger, still same concept. I think even some regular gasoline engine cars do this too.
 

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In theory that seems to be the case since its all for supporting heat dissipation but of course in this situation we're working with something much bigger, still same concept. I think even some regular gasoline engine cars do this too.
Yep: in many ICE cars, as soon as the engine stops, the water pump stops circulating coolant through the radiator, so on a hot day the electric fan will kick on full blast for a while to get the under-hood temperature under control.
 

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I heard the same noises you are talking about for the first time while my car was charging this evening (Right at the end of the charge cycle). It just so happens today was the warmest it has been in awhile, I drove a lot today (a lot of highway) and my wife pulled her minivan in the garage right after I started charging. Combining all of that, it was quite warm in the garage. I'm pretty it was just the cooling fans for the charger/battery/whatever else it cools running high to dissipate the heat away. I mean I could feel the heat coming out from around the front left tire area, I guess it blows that way or that is specifically the charger cooling fan.
 

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Yep: in many ICE cars, as soon as the engine stops, the water pump stops circulating coolant through the radiator, so on a hot day the electric fan will kick on full blast for a while to get the under-hood temperature under control.
My very first car, a 1976 Rabbit, had a thermostatically-controlled electric fan because the transversely-mounted engine meant it couldn't be mechanically run from a crankshaft belt. It was an unusual arrangement at the time. I remember the fan staying on after I stopped and got out of the car and having people tell me that I forgot to turn off the engine...
 

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The manual says that's exactly what might happen, and it did.

So what's to debate?
I assume it is just because when that fan is going full blast, it is actually kinda loud and we area all accustomed to our Bolts being quiet. I know when I heard it my first reaction was "what the **** is wrong with my car" before I took a step back to think about and read the manual. Then after that I realized it just happen to be the first time I was hearing the cooling fans going full tilt.
 
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