mwahlgreen
Posts: 10
Joined: Mon Jun 29, 2020 12:43 pm
Location: Køge/CPH Denmark

12V power only on when AC charging is active?

Wed Feb 24, 2021 4:36 am

Hi

Does anyone know where I would find a signal like this in the car?
Inside the OBC would be prefered.

I am looking into adding a small fan inside the OBC for longer life time of the electronics. I am thinking about even adding a small Peltier element together with the fan, heatsinks (one inside (cold) and one on the outside of the OBC (hot)) and a thermostat.

kiev
Posts: 1421
Joined: Sun May 03, 2015 7:15 am
Location: The Heart o' Dixie
Contact: Website

Re: 12V power only on when AC charging is active?

Wed Feb 24, 2021 5:44 am

That is an interesting idea, i'm sure we will all be wanting to see how it works.

From what i have found there are several 12V lines running to the OBC/DCDC converter, some have fuses and are connected directly from the auxillary battery and are "hot" all the time. But the wiring is small gauge and not intended for a large current draw. Other 12V lines are discrete signals for status and command with low current capability and even smaller wire.

i wouldn't recommend to try using any of the status/command lines to draw current for a fan; use a fused power line to provide the current source, and use a small circuit to detect the command and drive a relay or transistor circuit to switch the fan on.
kiev = kenny's innovative electric vehicle

coulomb
Posts: 267
Joined: Sun Jun 10, 2018 8:32 pm
Location: Brisbane, Australia

Re: 12V power only on when AC charging is active?

Thu Feb 25, 2021 6:33 am

mwahlgreen wrote:Does anyone know where I would find a signal like this in the car?
Inside the OBC would be preferred.

Off the On Board Charrger relay would seem to be the obvious place:


Image

As Kiev says, depending on the thickness of the cable, you might need to connect further back towards the relay. Perhaps find A-107 to see if the yellow wire is thicker than the violet. If not, you might have to go back to the relay and run your own wire. Or use the violet wire as a digital signal to turn on power for the fan (etc) near the charrger itself.

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