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I am a new 2018 Clarity plug in owner and am confused as to how to charge the battery while driving. I know the ICE is supposed to charge it, but I can't quite figure out how to make that happen.
 

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I bought my Honda Clarity 2019 used. It wasn't clear to me right away either how to activate the ICE charging mode (when it charges the battery even when you are not coasting downhill or breaking). I hold the HV mode button in for 3 seconds to engage the HV Charge mode. This helps when I hit a low of 2 bars to recharge up to about 5 or 6 bars during long drives for better performance prior to a steep incline or accelerating for on-ramps and at green lights.
 

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I am a new 2018 Clarity plug in owner and am confused as to how to charge the battery while driving. I know the ICE is supposed to charge it, but I can't quite figure out how to make that happen.
When you first start out the car will be in EV mode, and the gas engine will not come on unless you press the accelerator pedal too far. It will stay in EV mode until the EV range reaches 0, at which point the gas engine will come on. It will now be in HV mode even though the HV indicator does not appear. In HV mode it operates like a regular hybrid, meaning that it uses both gas and electric. In HV mode the gas engine will automatically charge the battery as needed to keep it from getting too low, however EV miles will remain at 0. But that's no problem because the car works fine in HV mode. If you have never owned a hybrid before it may take some getting used to how the engine sounds in HV mode because the RPM's will sometimes seem disconnected to what you are doing with the accelerator pedal.

If you don't want the EV miles to drop to 0 then you can press the HV button, the gas engine will come on and it will try and keep the battery charged to the general proximity
of what the EV miles were when you pressed the HV button. For example if you have 20 EV miles remaining and press the HV button, ICE will come on however initially it will just be warming up, so your EV miles will continue to decrease to maybe around 18 miles, then after the engine is warmed up it will automatically charge the battery to keep it within around 18-20 miles EV range. If you want to switch back to driving in EV mode then just press the HV button again, and the HV indicator will go away, and the EV miles will start decreasing again.

Some people like to use HV mode when driving on the highway, and save EV miles for city driving.

If for some reason you want to use the gas engine to increase EV miles you press and hold the HV button and that puts it into HV Charge mode. HV Charge mode is similar to HV mode except it will charge the battery up to just over halfway. Most people seem to only use HV Charge Mode when driving in the mountains so that they have enough battery available to assist with climbing steep grades.
 

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I am a new 2018 Clarity plug in owner and am confused as to how to charge the battery while driving. I know the ICE is supposed to charge it, but I can't quite figure out how to make that happen.
From HV mode press and hold the Hv button until battery charging is indicated. It should remain in charge mode until batteries reach about 70% charge.
 

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I'm curious. Why does HV Charge mode only charge the battery to 57%? Couldn't it theoretically charge the battery to 100%? I presume there's a mechanical or electronic rationale behind this percentage?
 

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I'm curious. Why does HV Charge mode only charge the battery to 57%?
IIRC, the 57% “rule’ has to do with some obscure CARB regulation. I think the BMW i3rex fell under this too being only allowed to use 1.x gallons from the 2.5 gal onboard tank. Tesla, for a very short period of time, used swappable battery packs to get around another CARB rule. Games.....

The ultimate answer to the question is: MONEY. ;)
 

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I think the BMW i3rex fell under this too being only allowed to use 1.x gallons from the 2.5 gal onboard tank.
From what I understand BMW wanted the U.S. version of the i3 REx to be classified as a BEVx in California, i.e. a range extender, which would give it an extra $1,000 in Clean Vehicle Rebate compared to a regular PHEV, and which presumably gave BMW more CARB credits also. California considers a BEVx to be a car that drives primarily electric but which has a small electric motor and gas tank in case of not being able to make it to a charging station. Generally speaking, according to California a BEVx should not be able to go farther on gas than it can on electric, thus the software limitation only allowing using 1.9 gal of the 2.4 gal gas tank, a "virtual" loss of half a gallon. California also required a software modification that the car could not be manually switched from electric to gas, instead it automatically switched on the gas engine when EV range was nearly depleted. Although apparently many U.S. owners installed a hack that someone wrote to get around the limitations.

I have never heard of a CARB regulation that limits Clarity HV Charge to 12 bars (60%), but then again I have never heard of any other explanation for it. Until now my guess has been that the Honda engineers expected HV Charge to be used mainly for the mountain type of scenario, and they designed it so that you could set HV Charge and basically "set and forget" and it will automatically take it up to what they considered a reasonable level of backup EV range for an uphill climb. That's my guess anyway.
 
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