Posts: 619
Joined: Tue Feb 24, 2015 1:23 pm
Delivery Date: 09 Mar 2015
Leaf Number: 402162
Location: North Las Vegas, NV

Using OBD port to charge 12v Battery

Wed Apr 05, 2017 3:33 am

This seems like the better place to ask this. Since the cigarette lighter is not active when the car is off, is it safe to use the OBD port to charge the 12v battery? i was looking at one of these on Amazon. ... UTF8&psc=1
2013 Leaf SV - Cayenne Red - QC Port - LED Headlights

Posts: 1662
Joined: Wed Jan 13, 2016 9:10 am
Delivery Date: 13 Jul 2014
Leaf Number: 422121
Location: MSP MN

Re: Using OBD port to charge 12v Battery

Wed Apr 05, 2017 5:48 am

Sounds like thats what it's meant for but note it's VERY low current, it will not recharge a discharged battery but will hopefully maintain a charged one. I say hopefully because one guy in AZ measured it in full sunlight and on the dash got 66ma and on the roof got 132ma, very minuscule when you consider the smallest battery maintainer is probably 500 or 1000ma(.5a-1a).
IMO this little guy will be lucky to maintain losses by the computer and any other vampire loads on your 12v battery, kind of like the stock SL solar panel on the rear spoiler, more show than go :) Here is a copy/paste of a good review.

"ByW. Severinon March 3, 2016
Got this to maintain the battery in my minivan that gets driven only short distances maybe weekly.

I tested the output. Placed on the dash in full Arizona sun, it delivered about 66mA to the battery. Placed on the roof of the car, so not behind any glass, it produced double that, about 132 mA.

So here's the problem. If you have a vehicle that is electrically alive 24/7 with stuff running like the security system, key fob transponders, etc., 66mA is not enough to maintain the battery long term let alone charge it (assuming 7 hours of sun per day). 132mA might be enough, but that means I have to keep the solar panel sitting on the roof and not securely inside the vehicle.

Above all, do *not* think that this is a battery charger. It is a battery maintainer, at best. A little simple math will make the point. An average car battery has a capacity of about 40 amp*hours. To fully charge a battery is then 40 amp*hours divided by 0.132 amps = 303 hours. At 7 hours per day, that's 43 days to charge a battery – presuming the battery is not supplying power to security systems, etc. while it's charging."

Lastly while this maintainer doesn't have any forum of BMS, it sounds like with the minuscule output of this maintainer it wouldn't really need one unless the battery was the size of a security system battery backup, with something the size of the Leaf 12v battery, no problem without BMS.
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