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Ever see a charge like this? This was at a public Chargepoint station that I have used many times and never seen the charge throttle back like this. Usually charges right around 6kW from start until approaching near full. In this case, the charge rate dropped from 6kW to about 4.25kW very early in the charge cycle, while SOC was still maybe only 30 percent. The car had been parked outside for about 4 hours at temps in the mid-teens before I started the charge. I would expect the charge to cut back if the battery was very hot or in severe cold (sub-zero), but not at fairly moderate winter temps like this. I tried stopping and restarting the charge, but it restarted back up at 4.25kW until complete. In total took about 10kWh, which is a typical charge for me, but of course took slightly longer - about 2.5 hours instead of the usual 2 hours. Drive home in EV mode was completely normal and charging at home also seemed normal, although at home I only have a 16A L2 and no way to measure the charge power.
 

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It would seem logical to me that charging current would be limited at temperatures below freezing. I have noticed that even regenerative braking seems to be limited a little more when it’s cold like that. I don’t think the batteries like to charge or discharge as heavily when temperatures are low.
 

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Discussion Starter #3
Back at the Chargepoint today with an OAT around 30F, with an another interesting charge profile. I'm pretty sure I have charged under similar conditions before without the charge rate being limited. If this continues, I may try doing a "master reset" (i.e., disconnect the 12V battery for a couple of hours).

568
 

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There are some sites that explain the necessary throttling during charging of lithium batteries in very cold temps.

From what I gather there is a chemical reaction needed at the cathode to accept the charge and this process is being compromised in cold temps. It indicates that damage will occur unless the charge is limited.

I suppose your chart show an increase towards the end due to warming of the battery during the charge.

lithium ion - Why charging Li-Ion batteries in cold temperatures would harm them? - Electrical Engineering Stack Exchange
 

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I think this is also coupled to the quick ICE start up in subzero temps.

The article explains the same processes are at hand during the discharging of lithium batteries.

Honda is using the ICE to limit the discharge of the battery during those conditions.

The ICE runs the generator thereby saving the amount of discharge of the battery for protection.
 

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There are some sites that explain the necessary throttling during charging of lithium batteries in very cold temps.

From what I gather there is a chemical reaction needed at the cathode to accept the charge and this process is being compromised in cold temps. It indicates that damage will occur unless the charge is limited.
Things have to get very very cold and a Clarity parked outside in the cold for a long time for the HV battery temperature to reach a point that the Clarity won't start, or can't be charged. There are many Clarity owners in very cold climates and reports of this are extremely rare, and could in fact be caused coincidentally by other problems such as a failing 12V battery.

The owners manual shows some messages that can appear, although I have never heard of anyone actually seeing these messages. One message says "Low temperature - power reduced" which the manual says "Appears when the power system temperature is low. Your vehicle has less ability to accelerate and may be harder to start on an incline". To avoid getting this message it recommends "U.S. Models - In extremely cold climates, keep the vehicle stored in a garage. Canadian Models - In extremely cold climates, keep the vehicle stored in a garage and connect the charging connector." (presumably so that the battery warmer can operate). This indicates to me that this message would normally not occur once you are driving as the EV system will generate its own heat, the problem is mainly when the car has been sitting in a very cold environment.

If things get even colder there is a message "Temperature is too cold for vehicle to operate". The manual says this message "Appears when the high voltage battery and other system control temperatures are too low to operate (approx. –22°F [–30°C] or below)." It then says "You must wait for an increase in the ambient temperature or move the vehicle to a warmer location". And then the manual bizarrely adds "Consult an authorized Honda Clarity Plug-In Hybrid dealer." Huh? Call the dealer and do what, complain about the cold weather?

Then there is a really bizarre message which the manual says only appears in Canada, "Temperature is too cold for vehicle to operate. Please wait while vehicle is warmed". Like the previous message the manual says this message "Appears when the high voltage battery temperature is too low to operate (approx. −22°F [−30°C])." However the advice is different than the other message, instead it says "You can start the engine and use the climate control system to warm up the interior. You must wait for an increase in the high voltage battery temperature to drive." I'm not sure what they are saying here, do they just mean you can warm the cabin using the engine while waiting for the sun to come out and warm things up outside? But you can do that in the U.S. also. So it implies that in Canadian models only, while sitting in the car waiting with ICE is running and heating the cabin the battery will warm up on its own. But how? I know of no way that ICE can provide heat to the battery. And it says in another part of the manual that the battery warmer only works while plugged in. But then why does this message about sitting in your car with ICE running waiting for the HV battery temperature to increase appear only in Canada? Maybe in fact electricity generated by ICE can power the battery warmer in those situations. That would make sense but they don't say it does that I am just guessing.

For some more background, Clarity has a separate water cooling system that is shared by and used exclusively by three components - the battery, the charger, and the DC-DC converter (which powers the 12V system). In warm weather the battery is cooled by this system as the heat from all three components is dissipated through a separate radiator. You can actually see this radiator if you look through the small opening in the far left side of the front bumper (the driver side). The similar opening on the other side of the bumper has nothing there and is in fact covered.

In cold weather this cooling loop can be used to warm the battery by sending waste heat from the DC-DC converter and charger to the battery. The DC-DC converter however apparently doesn't generate all that much heat. The charger generates more heat, however it of course only works while plugged in and charging. Meanwhile in Canada they have a battery warmer, which we don't know much about but my guess is that it is a resistive heater placed somewhere in the battery/DC-DC converter/charger cooling loop which heats the coolant which can then be circulated into the battery to keep the battery at a minimum temperature when you aren't charging.
 

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I think this is also coupled to the quick ICE start up in subzero temps.

The article explains the same processes are at hand during the discharging of lithium batteries.

Honda is using the ICE to limit the discharge of the battery during those conditions.

The ICE runs the generator thereby saving the amount of discharge of the battery for protection.
That's interesting I had not thought of that. I have assumed that ICE starts in these situations just to provide cabin heat. To test that theory, for those brave enough to try it you can turn off cabin heat and only use seat heat and see if ICE still comes on. If ICE still comes on then maybe it is to take some of the load off of the battery like you said.
 

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That's interesting I had not thought of that. I have assumed that ICE starts in these situations just to provide cabin heat. To test that theory, for those brave enough to try it you can turn off cabin heat and only use seat heat and see if ICE still comes on. If ICE still comes on then maybe it is to take some of the load off of the battery like you said.
@2002, the cabin heat thought is sounds right but at 5 below it really takes a long time for any heat to arrive from the ICE cooling water so it is not very beneficial for fast cabin heat.

I just could not understand why the ICE started with the full charge in EV mode.

I do think it is to limit the discharge rate rate for the battery to avoid the damage mentioned in that article.

Also it was mentioned it happens at 10-12 degrees and below, I found that to be consistent
 

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the cabin heat thought is sounds right but at 5 below it really takes a long time for any heat to arrive from the ICE cooling water so it is not very beneficial for fast cabin heat.
True with all cars, but you have to get the gas engine started in order to start generating heat even if it takes a few minutes to take effect. Remembering that this is in situations where the system determines that electric heat won't be enough to warm the cabin and it needs to be supplemented by the gas engine. Also the electric heat has a several minute warming period as well.

I do think it is to limit the discharge rate rate for the battery to avoid the damage mentioned in that article.
Not saying that's not possible however as I mentioned the theory can be proved or disproved through simple testing. Drive without cabin heat turned on and see if ICE still comes on. Fortunately you can still use the seat heater while doing this test.
 

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Discussion Starter #11
Now that we are into spring time temps above 40F, charging is back to a level 6kW until tapering off at the end, so certainly it was the cold holding it back.
 
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