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Could I connect to the ODB socket to trickle charge my car battery with a solar panel on my Toyota Prius 07, and how to?

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  • Welcome to Motor Vehicle Maintenance & Repair! Are you talking about the 12v battery or the high voltage battery? Jun 23, 2021 at 9:37
  • The 12 V battery Jun 23, 2021 at 12:55

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that's actually a good idea - some cars' cigarette lighter is switched with ignition (meaning it's off / not connected to the battery when the key is out of the car)

it think this is what you're looking for: http://www.kerrywong.com/2020/03/06/making-an-obd-ii-solar-trickle-charger/

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  • Thank you so much, that link is perfect. Thanks for taking the time to answer. Jun 23, 2021 at 10:16
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    That article is so wrong, It's bad to leave a modern car for a week? A properly running vehicle can sit for much longer than a week and still start perfectly fine. If it doesn't, either the battery needs replaced or there is a fault in the electrical system somewhere. I have a hybrid that's sat for over a week without running and had 0 issues. My truck sometimes sits for a month without being used and again the battery starts it just fine.
    – Phaelax z
    Jun 24, 2021 at 14:14
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    @PeterM It took several weeks for my hybrid to go flat in the pendemic we are in. I just want to mitigate this issue in the future. Jun 24, 2021 at 14:52
  • @Phaelaxz the question was about applying charge from a solar cell to car battery via the obd2 port - the mentioned article explains that quite well. It's another question why the battery may be empty (it's old; driving and seasonal habits don't allow for proper top up - think driving short distances when it's cold outside with all lights on etc) All modern cars still have a 12 volt battery, that is required for the car to work (even electric cars - eg. tesla - and hybrid cars; I stand to be corrected on this). Also truck battery cca is much higher than car battery cca.
    – PeterM
    Jun 25, 2021 at 17:06
  • I never said cars don't have a 12v battery, most stopped using 6-volt systems by the end of the 50s. And I'm not sure when trucks came into the conversation. If that's the driving pattern, sounds like he'd need a trickle charger to maintain the battery, in which case I don't see why the solar idea wouldn't work.
    – Phaelax z
    Jun 25, 2021 at 17:22
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I'd just go directly to the battery in the back, it's under a plastic cover on the right side, I'm sure you're familiar with it having jump started it before. Use a 2A fuse and you'll be all set. My '10 Prius runs dead if it sits for two weeks or so, it's common on cars with the touch less key systems.

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NO. The OBD II socket is a terrible place to do that.

While it does have always-hot power available, it is intended for a tiny amount of power for test equipment such as OBD II scanners. It was never imagined to be a general-use power port. Getting connections wrong here can fry your PCM and other expensive onboard electronics.

If you look closely at the fuse block, it probably has auxiliary terminals exactly for this purpose. You can wire that to a socket (e.g. a cigarette lighter style socket, or other kind) and plug in your solar there. And then, you can use that port for all sorts of stuff. And mechanics won't see anything alarming in that - it's commonly done. They won't like seeing things on OBD II ports that aren't diagnostic related.

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    Most likely it will be fine for trickle charging, though. Even a 0.1mm2 wire can withstand continuous ampere of current. If using a PWM charge controller, that would equal to about 18 watts of panels.
    – juhist
    Aug 18, 2022 at 9:59
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The first thing I would do is to check if there is a 12 V outlet (aka a cigarette lighter) in the car that is "hot" when the car is off. If there is, that would be a very convenient place to plug in a solar panel. Solar panels trickle chargers that plug in to the 12 V outlet seem to be a fairly common item.

You could connect to the ODB2 port, but that's not what it's for and you would have to both find the connector and make sure you understand the pin out lest you add to your problems...

I also think it's worth asking why you want to do this. If you're driving the car with any kind of regularity -- say more than 30 minutes a week -- that should be sufficient to maintain the battery charge. So, if your battery is running down, it may be that the battery is due for replacement or that there is a "phantom load" that is draining it.

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