Solar Panel Trickle Charger - Can I Reuse my existing 21W panel w/ USB output?

chrisisinclair

Im looking to add a solar trickle charger for my subaru for when I go on extended trips. I already own a pretty decent portable panel (Anker 21W with 2 USB outputs). I use this camping and it works fairly well even without full sun. The car is a 2017 Subaru Outback with an Interstate size 24 battery with 130min reserver / 700CCA. Forget the exact capacity but I upgraded it from the tiny stock SLA.

Can I use a stepup converter to go from the 5V USB output up to 12V and then run that into a charge controller hooked to the battery?

Id like to make  this as clean and modular as possible - basically Id love to be able to easily disconnect the panel and continue to use it port ably as needed. If I do need to purchase another panel that is a possibility as well.

Is the best way to wire this direct to the battery or can I jump through the OBDII port or maybe even wire it somewhere in the fusebox? I would prefer to avoid using up the cigarette lighter.

BB.

The general method is to get a ~5-10+ Watt solar panel that has a OBDII port on the end of its cable:

https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l2632.R-1.TR11.TRC2.A0.H1.Xsolar+car+bat.TRS0&_nkw=solar+car+battery+charger

~5 Watt is the "standard" for many cars that are shipped from overseas and sit in a lot before selling in the US.

If you want a bit more power, then a 10 Watt would be pretty nice for a larger battery and/or if you have other loads (like a Lojack or similar).

If you go with a >10 Watt panel, you probably should get a true 12 volt panel (Vmp~18 volts) and use a PWM solar charge controller... Or, you run the risk of "boiling your battery dry" from extended over charging (charge controller will stop charging when the battery is "full").

-Bill