Solar battery maintainer

Picked up a 1.5 Watt Solar Battery Charger from harbor freight. As our truck is no longer daily driver it can set up to a week or two without being driven. I could hear it when starting the batteries just drained from self-discharge & the electronics. Have a nice maintainer but plugging in, attaching to batts, disconnecting to use truck just not convenient. I use small maintainer on the jeep-which can set for 2 months and works well keeping batteries alive. I was thinking of hardwiring one of the maintainers in truck but would still mean plugging in. Figured the lil solar unit would be less hassle in something driven more frequently. If it works...

The solar unit is rated at 1.5 watts, voltage 12-24v. If it can keep up with truck electronics would be ok-even partial ok. Just need to check on occasion. Could be this thing only generates enough to power its own led. Weíll see. Iím installing-if it works or need say a 5 watt or larger wiring will be done. $12 worth playing with. As laying on the dash, plugging into lighter will get old Iím hardwiring with a switch. which is really all this documents. That & my observations on how this thing is wired. Seen quite a few reviews stateing 'it just quit'. As I collect any info that appears to support either it works or doesnít I'll add.


Just FYI Harbor Freight special.

Eyeballing what to do....

Ok this is pretty simple. Though Iím installing the lil solar charger, I also want to allow components, switch/wiring etc. useable if I end up replacing with an actual battery maintainer. The maintainer/charger would be hard mounted in engine bay. Its 110v cord would run to front of truck terminating with male plug fixture allowing plugin in truck with short extension cord (much like the diesel block heater). Output from charger will go thru fuse to dash mounted switch then to batteries. Simple. I guess I could reuse is dash switch some of the wireing..on to solar install.

I want the solar panel to set on dash, I want it semi-hardwired verses plugging in & out-so will use a switch to turn unit off (your supposed to disconnect when starting). The dash mounted switch will turn off output from charger, Cord from panel long enough so panel can be slipped under dash mat when not being used. The unit comes with battery clips or power outlet plug (cigarette plug). Decided to use the power plug because it has a fuse in it. Running wire down behind dash to cigarette plug. Thought about hardwiring to back of cigarette lighter plug, but next to mine is a holder/hanger for gadgets, it has a hole in it. I can simply run cord thru the holder, plug into cigarette lighter. If I need to use plug for something else (never have) just unplug the solar & hang from holder. Simplifies wiring-use its built in fuse. Once wiring is run behind dash I donít want to have to resnake if panel needs replacing, (or just want to remove temporarily so Iím adding another male/female plug. Other than just plugging in new panel it also gives me a switched power lead on top of dash that I could use for something else..SO now we have a plan.

FYI. This panel is wired I guess to protect itself, I assume most of these are similar. Exposed male end from panel is ground when unplugged from connection ends, however live end at plug or battery clips , the exposed male pin is HOT, the red bat clip is hot when plugged into panel! The plug is fused, clips are not so you have an exposed unfused HOT lead-. Really needs a switch on panel-if you simply unplug the cigarette plug or disconnect the battery clips, positive is exposed and still hot could short panel. If you unplug the male/female plugs from panel but leave connected to source, the male exposed male pin from either battery or cigarette lighter is HOT. If exposed cigarette plug end touches something itíll blow fuse either in plug itself or worse in your fuse panel, if using the battery clips-dead short to battery-either way potential for short. Absolutely no mention in literature when you unplug panel or disconnect battery clips that you need to unplug cord male/ female plug from panel. My assumption a lot of folks who have their panel just quit have popped the fuse inside plug-there is no mention of replaceable fuse inside plug. If your using the battery clips you should add an inline fuse! I doctored the parts picture above to clarify.

Wiring plan A

First added another male/female plug to panel. Cut the outlet wire from panel with about 14" lead. Solder another plug on it. (Need to VERIFY the polarity of wiring if splicing. Mine the wire with white stripe is positive. Color doesnít matter as long as positive output ends up at center of plug or red battery clip.) soldered other half of plug to cut wire.


Add another plug to outlet wire. Should have sleeved wires...
Allows removal of panel without pulling wire.

Second which I didnít get pic of, cut positive lead wire before lower plug, added 2 lengths to go to & return from new switch.


My highly technical drawing...

Nowhere in the documentation did it say panel had diodes or otherwise wouldnít draw from battery at night. I assumed it did but I took apart to verify. Yup, There are diodes on both negative and positive leads so it wonít use battery at night. Odd they didnít state on box or documentation. However I want to insure this cannot draw power from truck so added another diode inside the plug on positive lead. Plus switch Iím using has pilot light, it would pull power from truck at night or when panel output less than switch led without extra diode.This deletes the possibilty of using wire on dash to power somthing else.


New added diode (and the undocumented internal fuse). Simply unscrew end to change.


Just pic of wiring exiting hook panel & switch location.

Well new switch trim ring isnít much bigger than required hole. When cutting I chunked a piece and switch didn't cover, errr. Spent more time trying to make a trim piece to cover oops than installing panel. Took several tries to get washer shaped bezel to fit snuggly under switch and large enough to cover hole.


Used bottom of TV dinner plate, thin & black.

New 'trim bezel"....to cover botched hole...just in case you didnít notice. Good grief.


But itís done! Simple project-actually kinda nice-hopefully it works. Get in just flick switch-panel out of loop.

If this little panel doesnít work Iím already seeing that adding an on board maintainer will be easy (and probably better for batteries). Running its output to harness instead of solar panel. However instead of plugging other end into cig lighter id run another plug directly to batteries. Or I might redo altogether, insure that maintainer actually is reading batteries. Well see-maybe this s lil guy will surprise me. Possibly due to size and ease of adding another on dash if not enough current to keep up is adding another solar panle in series. From what Iíve read up to 5 watts is okay, most say 15watts before you need a regulator, or as long as charge is less than usage. Which to me sounds like eventual draw down. Be nice to know actually standby usage number of truck. Not sure how youíd measure that.

Oh I looked around there are some guidelines on differnt formus for checking electrical drains. Apparently hovers around 50mA typically ok. which this lil panel could handle. Sticking electronics, alternator with bad diodes etc can significantly increase drains to the point repairs needed, so if your battery drains down on couple of days verses weeks may be other problem than normal drains.

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