darthpuppy
Posts: 73
Joined: Fri Feb 23, 2018 3:30 pm
Location: SoCal

12v battery and using accessories - how does it recharge?

Fri May 11, 2018 5:12 am

From the Nissan Leaf forum, I had learned that the big traction battery recharges the 12v battery that runs all the electronic interfaces. However, it doesn't charge the 12v battery if the car is plugged in. The result is that if someone leaves the car plugged in while they go on a 2 week long trip, when they get back, the 12v battery is dead and the car has to be towed because the electronics won't work to start the car.

I want to install a dash cam that I would like to have run continuously even when the ignition is off. I want to make sure it doesn't drain the battery and I get stuck because the 12v battery is dead even though the traction battery is full. For the Leaf, this would not be a problem IIUC per the above as the traction battery would simply charge the 12v battery as needed and there is no way a dashcam is going to drain that in any short period of time.

Does anyone know how/when the 12v battery in the PHEV Clarity is recharged? Is it from the 17 kwh traction battery? Or does it have an alternator that recharges when the car is running hybrid? Does it only recharge when the car is on? Or will it keep the 12v battery topped off as my dash cam drains it while it sits while I'm out of town for a week? Does it shut down the 12v recharge when plugged in like the Leaf does?

jzchen
Posts: 39
Joined: Mon Mar 26, 2018 5:22 pm
Location: Arcadia, CA USA

Re: 12v battery and using accessories - how does it recharge?

Fri May 11, 2018 10:36 am

Our prior car was a '13 Ford C-MAX Energi. Plugged in would help keep the 12 V battery charged, opposite of your concern. I have not read much about the LEAF, but that's not a wise design, in my humble opinion. Hopefully Honda didn't do the same as Nissan...

I'm not sure how exactly the 12 V battery is charged, but my suspicion is a DC-DC converter...

AnthonyW
Posts: 2
Joined: Thu Apr 12, 2018 12:20 am

Re: 12v battery and using accessories - how does it recharge?

Wed Jun 20, 2018 7:54 pm

The DC-DC converter which is built into the IPU converts voltage in the high voltage battery into 12 volts to supply power the 12 volt battery and 12 volt lines.

slatelsnarp
Posts: 10
Joined: Sun Mar 11, 2018 2:18 pm

Re: 12v battery and using accessories - how does it recharge?

Wed Jun 20, 2018 9:45 pm

If you want to run the dashcam while the car is off (parked), you need to get one of those little interface boxes (all the dash cam stores sell them) that monitors the battery voltage and shuts off the dash cam below some preset voltage.

It is not clear (probably not) that the Clarity would run the DC-DC converter to re-charge the 12V battery when the car is off.

There is also a more expensive solution, a few companies sell batteries that plug into the lighter outlet (or, direct wire to 12V), and then you plug the dashcam into the battery box. You can see examples at "Black box my car", such as one made by Black Vue, and another company there. They are very pricey, but make your dashcam systems somewhat independent from the car's 12 V battery. The battery box charges when you drive, and discharges in park mode. You can charge the battery in your home too (e.g. if you only do short drives, with long park times).

darthpuppy
Posts: 73
Joined: Fri Feb 23, 2018 3:30 pm
Location: SoCal

Re: 12v battery and using accessories - how does it recharge?

Thu Jun 21, 2018 3:06 am

So as I figured, the 12v battery gets charged from the big battery. But that still leaves open the question of when or if there are gaps in that charging like on the Leaf where it won't charge the 12v battery if the car is plugged in. So I don't yet have the info I need to know if it is safe to plug the dash cam into a line that is always live.

The additional modules mentioned above are a viable option. I'd hate to go that route if it is completely unneeded based on how the Clarity works. But as an early adopter of this model, I guess I may have to experiment. Though since I routinely drive the car well away from home, I'm not brave enough to risk the experiment proving that the dash cam will discharge the battery and leave me stranded when I'm a long ways away. So I will probably go the safety device route.

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