Will running the AC on a schedule every week keep the 12 volt battery charged?

JustAnotherPoorDriver

JustAnotherPoorDriver

Active Member
Going to be out of town for about 5 weeks and for various reasons need to leave the car outside. Last time I did this, came back to a dead 12 volt battery.

I recall that the 12 volt battery gets topped off from the traction battery when the car is on. Does anyone know whether it also gets charged when the climate control is being used on schedule?

Wondering whether setting up one or two times a week where the climate control comes on for half an hour would provide sufficient top off to keep the 12 volt battery from dying. Also wondering how many times I could do that before exhausting the traction battery...
 
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This seems like it would work. I'd bet that you will use about 1 kWh per hour of operating the A/C (much more in cold weather with the resistance heat). I would try it with battery fully charged for an hour and see what it does to the battery (measure how much you have to put back in to get back to full charge). I'd lean toward once per week for the 5 weeks if you pushed me to guess, and that you will have about 1/2 to 2/3 of the traction battery charge left when you get back. But take this with a grain of salt, as I am doing a lot of guessing here....
 
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Robert_Alabama said:
This seems like it would work. I'd bet that you will use about 1 kWh per hour of operating the A/C (much more in cold weather with the resistance heat). I would try it with battery fully charged for an hour and see what it does to the battery (measure how much you have to put back in to get back to full charge). I'd lean toward once per week for the 5 weeks if you pushed me to guess, and that you will have about 1/2 to 2/3 of the traction battery charge left when you get back. But take this with a grain of salt, as I am doing a lot of guessing here....
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Actually thinking of scheduling middle of night so that the AC uses less electricity (if it's cool, the compressor will cycle off). I'll try it.

One complication with all this: unlike charging I think climate is server-based, so nothing gets stored on the car. If the place I park has unreliable 4g it's possible it will never trigger the climate during the 5 weeks.
 
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JustAnotherPoorDriver said:
Going to be out of town for about 5 weeks and for various reasons need to leave the car outside. Last time I did this, came back to a dead 12 volt battery.
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Will there be access to a 120V AC power source while the car is parked outside? If so, use a battery maintainer such as a Battery Tender.

If not, and assuming the car is not parked under cover, you could try a 5-10 watt solar maintainer. The panel can sit on the front dash and be plugged in to an unswitched (always hot) cigarette lighter receptacle. I can’t recall if, or where, the Clarity has an unswitched 12V power outlet. Alternatively, the wire may need to be routed to the battery terminals in the engine compartment. I prefer the solar option, it works when power is not available or becomes interrupted and if everything is inside the car it is highly tamper resistant.
 
Landshark said:
Will there be access to a 120V AC power source while the car is parked outside? If so, use a battery maintainer such as a Battery Tender.

If not, and assuming the car is not parked under cover, you could try a 5-10 watt solar maintainer. The panel can sit on the front dash and be plugged in to an unswitched (always hot) cigarette lighter receptacle. I can’t recall if, or where, the Clarity has an unswitched 12V power outlet. Alternatively, the wire may need to be routed to the battery terminals in the engine compartment. I prefer the solar option, it works when power is not available or becomes interrupted and if everything is inside the car it is highly tamper resistant.
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No electricity--parked in the campus police lot (I'm faculty). I thought about a solar maintainer (posted a post about them a few weeks ago in the 12V battery thread), but I'm scared by some of the posts/amazon reviews of people where the charge controller blows.
 
JustAnotherPoorDriver said:
I'm scared by some of the posts/amazon reviews of people where the charge controller blows.
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10W or less don’t use charge controllers. I’d recommend a 10W panel. Don’t bother with anything less than 5W. Been using a 10W Battery Tender for the past 8-10 years. There’s certainly some cheap crap out there and the BT isn’t the lowest cost option. It has, however, worked flawlessly.
 
I am not sure but I would think that running climate control would not be the same as the car being on so the 12v battery may not charge...
 
Joe17 said:
I am not sure but I would think that running climate control would not be the same as the car being on so the 12v battery may not charge...
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A simple way to eliminate the guesswork would be to measure the battery voltage when the A/C is not running and again when it is running. 12.6-12.8V is not charging, 13.5-14.0V is charging.
 
Joe17 said:
I am not sure but I would think that running climate control would not be the same as the car being on so the 12v battery may not charge...
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That's the implication from what Honda says about how the 12V battery gets charged.
 
Ok, so the manual states “The DC-DC converter may operate while the high voltage batteries are being charged, the vehicle is in READY TO DRIVE mode, or the remote climate control is operating. In this state, the DC-DC converter supplies the 12 volt power to the system even if the 12 volt battery terminal is disconnected, and almost every part including the battery cable is electrically active. Therefore, be careful not to get an electrical shock.”
 
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