Hey all, trying to avoid having to tunnel through the firewall to the battery since the charging cord isn't long enough. Pin #16 is constant +12v. Pin #4 is chassis ground and #5 is signal ground. Which ground pin would I connect to a small solar battery maintainer panel to keep the battery alive during my 6+ month storage time? Cigarette lighter plug is not an option since it's cutoff when the car is off. Thanks.
OBD II port solar float charge fabrication
- Thread starter Jarpin
- Start date
Pin 4, chassis ground should be connected to the battery negative.
So the panel will be inside the car? hmmmm. I had a marine panel and usually just ran a cord under the hood directly to the battery.
Yes, inside the car, because it will be parked outside, and I need to keep the battery connected and charged in order to keep my car alarm operational in the event of a break-in.
On some cars, this setup would prevent some modules from going to sleep and using more current than the charger can produce, resulting is a dead battery. VW makes a charger specifically for this when cars may sit months in storage, https://www.ebay.com/itm/1309542631...f_C_oF3DYI54t_IFLUr_OPWrcJSnrB2AaAkJyEALw_wcB but the BCM has circuitry that recognizes it so everything stays asleep.
They make something like this that's relatively cheap...
Make sure you get at least a 6 watt panel, a 10 w would be even better. You loose half its rated capacity going through the window, even more if its tinted. Those little 2 watt sunvisor panels are worthless. I have a 6 watt that I put zip ties on and trap the ends in the window so it hangs facing south right up against the window but mine plugs into an always on aux port. You dont need a charge controller as these do not put out enough current to charge the battery but just keep up with parasitic drain.
Thanks... yeah mine is a 20 watt panel, so hopefully it won't be an issue during the summer months at all.
I have a 20 year old Subaru. I don't see it being as electronically complicated like a recently built VW or ANY modern car, so I'll give this a shot. If it turns out that there are things that keep draining it, I'll go straight to the battery with the alligator clips. I just wanted to try a neater connection first.On some cars, this setup would prevent some modules from going to sleep and using more current than the charger can produce, resulting is a dead battery. VW makes a charger specifically for this when cars may sit months in storage, https://www.ebay.com/itm/130954263126?_trkparms=ispr=1&amdata=enc:AQAFAAACUBaobrjLl8XobRIiIML1V4Imu%2Fn%2BzU5L90Z278x5ickkoCxs9oZ87s6SCciZiVuYR2Q92GEcGAeqCXNtr7xqs5b%2FVNsdbl9XZ7lD8%2B8TUkDs%2BChVNeJDqOa75A8dnD2gbaZVPVsTdj0YxXUPFIZ%2BvZh2OAUbg%2Byt3A8Dp%2FwO8Gy47AglrjqQvqmjZG9B1ZxI5gz9w2c7vqZ0PIeofyYv9FswTWeos4b4YVV04wE8O6WHTt0Xxd18WwqQDXwRBI0e9FuwKRzbyI6XdfpzarYStGhWZvp3qx%2BGCqOZBf%2FiiM9wlZcLZVDpszhb90U%2BgkEyj152Ga24ftUjdVR52saaKLp5mZVu1MSxz7ACxLX6GO2LiMMmtw5K3jYAb5ONBe%2FQKiwk4baAD%2FfUdanKX4QRylRnrU3ysqgyoZpg0FtXyqo6vwwg2nw2bPAVQsAK0hU19%2FCi8S%2B%2F8QQyRxImNq2QzGrcWf5Zi1BDLWKmC8%2BobqMWXthmJh82K72ZkDo2SralfuY9ReUznMbGcOUlwNWNI9jkQXWp3OzlhsqzbFsZFW4T3FMLC%2FcULTeL6DAS5oBsLtIv9eRKpDFvCBK5p4R2oekXWmp0DICQdi1RKsZiKQgC%2F6yHTLZaahOw5KJPF4xh3CMnUukHXUrLX44d4CTLcEf3r9u4MtpFI4JBPC9KmrHJ7QLF85jtUKZbDtpxxxc8U%2FloJy8DMeeuZDLUdIbG2YwKMUqDHqmp0ssDzx%2B2bAdMtMCk1m2c6s0redxoe2m%2BlmPPEaRo014I2CXpdPxKi80%3D|cksum:1309542631264478fd4a870440928251b4336c0df5c6|ampidL_CLK|clp:3268220&chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&itemid=130954263126&targetid=1192081307264&device=c&mktype=pla&googleloc=9007783&poi=&campaignid=11774733487&mkgroupid=113829509425&rlsatarget=pla-1192081307264&abcId=9300474&merchantid=8159294&gclid=Cj0KCQjwvYSEBhDjARIsAJMn0lg0j6dtXKcfkuESDkAXxuNf_C_oF3DYI54t_IFLUr_OPWrcJSnrB2AaAkJyEALw_wcB but the BCM has circuitry that recognizes it so everything stays asleep.
Before I would back-feed a thin wire with a couple of 100 mA I would get a schematic of the vehicle and back-feed some circuit with a decent size wire and decent size fuse, like a wire from the ignition fuse or something else with a decent size wire and fuse. If you do it to the OBD2 port there is a small chance that the wires to it are very thin and can not handle the current. And also there is a chance that positive is fed from a circuit board with a thin trace not big enough to handle the current.
It is safer to tap onto a circuit rated to handle the much more current than you will be pushing through it. And while you are at it, add a fuse to the wire to the panel that is rated for about 1.5 to 2 times the maximum current your panel can put out. Just incase the panel someday shorts out.
It is safer to tap onto a circuit rated to handle the much more current than you will be pushing through it. And while you are at it, add a fuse to the wire to the panel that is rated for about 1.5 to 2 times the maximum current your panel can put out. Just incase the panel someday shorts out.
It might be easier to "convert" the cig lighter outlet to always on.
chassis ground, but you can ground anywhere you like, all you need is the 12v wire
There is no need to suffer any forward drop with an additional diode, except the one that should already be there to protect the panel (should come with it or be built in already). If you really want to protect against the tiny chance that an interior solar panel will short out, that's what fuses are for.
On one plugged into an OBDII port you don't want a too big panel either. The OBDII wiring is thin.
Or wire it to another circuit that is always on.
I am not a fan of going through the OBD port for anything other than a scanner. You just never know what the wires are routed through, but a 6 Watt panel inside the car would be hard pressed to generate more than 3 watts at 14 v its about 215 mA. Anything 22 ga or over will have less than 3% drop over 15 ft. Of course the op said something about a 20 watt panel that might get to 10 or 12 watts inside and that triples the current. For that I would think a separate connection and a charge controller.
PV panel ratings are a little weird. The typical 12v panel probably shows 22v no load, and 1amp at a dead short. At 12v you get something in between, but not the 0.8 amps that a “10 watt” panel would be expected to provide. now, the tech has improved a lot and my numbers may be dated... but I get about 1 amp into 12V with a 50w panel on my camper shell. So: I don’t think the 10w panel, further derated if run inside, is going to push much current.
if youre committed, a flexible panel, glued to the trunk lid, would provide more reasonable trickle power, enough to use a real charge controller.
with my camper shell, this was fine... I was drilling holes in fiberglass. In a sedan... it would depend on how long I’m keeping the car. A wagon, however, could have a panel laid down on the long roof with the leads run under the rear lid weatherstripping, or perhaps down the windshield under plastic trim, into the hood. check for flexible panels on Amazon.
if youre committed, a flexible panel, glued to the trunk lid, would provide more reasonable trickle power, enough to use a real charge controller.
with my camper shell, this was fine... I was drilling holes in fiberglass. In a sedan... it would depend on how long I’m keeping the car. A wagon, however, could have a panel laid down on the long roof with the leads run under the rear lid weatherstripping, or perhaps down the windshield under plastic trim, into the hood. check for flexible panels on Amazon.
One of the reasons I love my 1.5W panel is because it's too small to need a controller.
