Jumping the Jeep: An alternative cost-effective solar cell example app

A solar charging kit, inexpensive as-is and purchased after further promotional enticement, enables keeping a remotely located vehicle battery topped off.

One of the things I enjoy most about technology is watching a new approach (along with products based on it) hit its high-volume stride, typically driven by one or only a couple of early applications, and then just explode from there, both replacing precursor technologies and expanding into brand new applications and markets. This has certainly been the case, for example, with LEDs. See, for example, my recent teardown (where they replaced fluorescent tubes) for an example of the former, and an earlier teardown (where their low power consumption and DC voltage foundation enabled the development of a light bulb with integrated battery backup) for an example of the latter.

A solar revolution

Or take, as another technology case study, solar cells. Their combination of efficiency and cost-effectiveness, in combination with equally pervasive lithium battery technology, has enabled widespread replacement of predecessor SLA-based energy storage systems, both portable and whole-home permanent installations, while dramatically expanding the accessible market for such devices. At the same time, they’re helping create entirely new categories of products. Take, as a humble example, Renogy’s 10W solar trickle charger kit, two of which I purchased back in October 2024 and one of which I recently, belatedly, and finally pressed into service:

Right now, as I write this, they’re selling on Amazon for $25.17 each, brand new. A year-plus ago, during Amazon’s Prime Days sales, I got them off the Resale (formerly Warehouse) site in used, like-new condition for $17.74. I don’t think they’d even been opened by the prior purchaser(s) prior to getting returned. The intent at the time was to use them to keep the batteries in two of my vehicles, then outdoor-stored at a lot about a half hour drive away, trickle-charged up. But I could never figure out how to securely attach the solar cells to the vehicle covers, far from routing their outputs to the battery compartments. That said, I eventually figured that latter part out: SAE extension cables:

One of the vehicles, my 2001 Volkswagen Eurovan Camper, is now parked in my garage for critter-protection purposes. The other, a 2006 Jeep Wrangler Unlimited Rubicon, most recently mentioned last March when I discussed its then-drained battery state, is still down there (now with a permanently disconnected battery). A few months back, when I drove down and checked on it, my preparatory suspicion was confirmed; as happens every few years, the combination of persistent sun and still-frequent precipitation (rain, snow, hail…) exposure, along with also-frequent wind, had disintegrated the cover:

Successful experimentation

While waiting for the replacement cover to arrive, I had a bright idea; this’d be the perfect time to finally try out that solar cell kit! My original idea was to mount it to the now-exposed vehicle hood. But then I realized that I had an even better option available, inside the vehicle:

in combination with the 12V auxiliary power connector built into the console:

As you can see from the above image (which I snagged from an enthusiast forum thread post to save me an hour-long round-trip drive to the storage lot to take my own shot; that’s not actually my rig), there are two of them. One, the “cigarette lighter” located within the ashtray, is ignition-switched. It obviously won’t work for my purposes. The other, while (I think) still fused, otherwise routes directly to the battery; it’s always “hot”. That’s the one I needed and used:

And it works perfectly! My perhaps-obvious concern was two-fold:

It’d either not work sufficiently (or at all), leaving me with an eventually-drained battery once again, or
It’d work too well, not terminating the trickle charge when it sensed a “full” state, thereby also leading to the battery’s demise (along with who-knows-what other issues).

Two weeks later, when I went back and checked (in the process of installing the new vehicle cover), I happily discovered that all my worrying was for naught; it was working exactly as planned. Now I just need to figure out how to securely attach the solar cell to the outside of the new cover, and I’ll be set! Suggestions, along with more general thoughts, are as-always welcomed in the comments!

—Brian Dipert is the Principal at Sierra Media and a former technical editor at EDN Magazine, where he still regularly contributes as a freelancer.

Jumping the Jeep: An alternative cost-effective solar cell example app

A solar revolution

Successful experimentation

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