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I was driving on EV mode with the battery well charged. All of sudden I saw the EV sign went off and heard the loud noise of the engine running. On the screen for vehicle energy, I saw a straight green line, indicating that engine was running to charge the battery. The whole episode would go away in a minute or so and the the EV sign would come up again. First it happened only once a week or so, but today it happened three times in my commute home. Does anybody know what this is?
 

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Two batteries to charge

In one of the three manuals available on the car, I read the 12v batterie is charged by the engine. I just did an on-line scan and couldn't find it but when I have the time I'll try again with my paper manuals. That could be one of the reasons the gas engine runs on occasion when it appears the traction batteries are well charged. The A/C and heater systems are powered by the traction (high powered batteries) batteries.

All of the cars run the engine in this manner, it's not abnormal. Remember to smile when you pass gas stations :smile_big:.
I was driving on EV mode with the battery well charged. All of sudden I saw the EV sign went off and heard the loud noise of the engine running. On the screen for vehicle energy, I saw a straight green line, indicating that engine was running to charge the battery. The whole episode would go away in a minute or so and the EV sign would come up again. First it happened only once a week or so, but today it happened three times in my commute home. Does anybody know what this is?
 

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In one of the three manuals available on the car, I read the 12v batterie is charged by the engine. I just did an on-line scan and couldn't find it but when I have the time I'll try again with my paper manuals. That could be one of the reasons the gas engine runs on occasion when it appears the traction batteries are well charged. The A/C and heater systems are powered by the traction (high powered batteries) batteries.

All of the cars run the engine in this manner, it's not abnormal. Remember to smile when you pass gas stations :smile_big:.
It would be impossible for the engine to charge the 12v battery since there is no alternator or even a fan belt. I believe the 12v is charged by the traction motor battery via the dc-dc inverter.
 

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Page 4 in online manual, main battery charges 12 volt

From Honda PHEV 2018 manual page 4, under Battery Type:

Battery Types
There are two types of batteries in this vehicle. A standard 12-volt battery, which powers the airbags, interior and exterior lights, and other standard 12-volt systems; and a high voltage lithium-ion battery, which powers the propulsion motor and recharges the 12-volt battery.
http://techinfo.honda.com/rjanisis/pubs/QS/AH/ATRW1818OG/enu/ATRW1818OG.PDF

I thought the Generator would have supplied a charge for the 12 Volt battery, but apparently the lithium-ion battery does.
 

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I see someone found another passage in the manual indicating the traction battery charges the car. I don't dispute that but I did read somewhere the 12v battery is charged by the engine running. I need to find it, I know it wasn't on page 4 but deeper in the book. It may have meant the 12v is charged from the generator (there is a 2nd generator/motor) when the engine is running. I still believe that, as the 12v needs a way to be charged when you're traveling cross country and only keeping the traction batteries charged via HV/charge. Maybe it gets it's charge both ways?

Either way, Honda figured it out. The 12v even runs the electric power steering.
It would be impossible for the engine to charge the 12v battery since there is no alternator or even a fan belt. I believe the 12v is charged by the traction motor battery via the dc-dc inverter.
 

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It would be impossible for the engine to charge the 12v battery since there is no alternator or even a fan belt. I believe the 12v is charged by the traction motor battery via the dc-dc inverter.
I meant to say dc-dc converter not inverter since it's already dc voltage and inverters basically inverts ac to dc. My understanding is that the dc-dc converter powers ALL 12v devices in the car passing current thru the battery and out to the 12v devices. The 12 v battery does not have the capacity to power the headlight, heater, ac, power steering, wipers,defroster,radio, and power seat if they all came on load at the same time.Any 12v load is taken from the 348dc traction battery by the dc-dc converter and sent to the battery where it's taken out by the 12v devices. It is also my understanding that the ONLY job of the 12v battery is to close electrical contacts to "wake up" the electrical system to get the car ready for duty.
 
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