The Battery Tender 12V 35W Mountable Solar Battery Charger (MPN 021-1174) is a 35-watt solar panel with a built-in 3-step automatic microprocessor controller. The manufacturer positions it as the largest panel-and-controller combination in its lineup, for keeping 12V batteries charged where no outlet is available. Compared with the brand's 5W and 17W panels, the 35W model delivers roughly twice the charging current of the 17W, which matters for larger batteries or cloudy regions. Its IP67 weather rating and 5-year warranty support outdoor use on motorcycles, ATVs, lawn tractors, and stored cars. Owner reports on user forums are mixed, with some finding slow recovery during overcast periods, so set expectations for maintenance rather than deep discharge recovery.
Owners on user forums consistently point out that a solar panel wired straight to a battery can overcharge it, so the integrated controller is the feature to pay for. A plug-in maintainer needs an outlet and extension cord, while this unit runs from sunlight alone. Keywords buyers search for include "35 watt solar battery maintainer 12V," "solar trickle charger AGM and lithium," "IP67 solar battery charger for ATV or motorcycle," and "solar battery tender for stored car without outlet." The manufacturer lists compatibility with AGM, gel, lithium, and sealed or flooded lead-acid batteries, and the kit includes alligator clip and ring terminal cables plus a 6-foot quick-disconnect extension, which the manufacturer says brings total reach past 15 feet.
No. The manufacturer states the controller is built into the 35W kit, so no add-on regulator is required for a standard 12V battery.
The manufacturer lists AGM, gel, lithium, and standard sealed or flooded lead-acid batteries as compatible.
The included 6-foot quick-disconnect extension, combined with the other cables, gives the manufacturer-stated total reach of more than 15 feet.
The panel has four mounting holes, and the manufacturer offers a printable mounting template. The manufacturer's portable charger guide recommends mounting grommets for permanent installation on flat surfaces and suction cups for temporary windshield placement.
Mounting is a basic drill-and-fasten job. Use the printable template to mark the four holes, and choose a flat, unshaded spot with the panel facing the sun. The manufacturer's portable charger guide estimates about 10 to 15 minutes for most vehicles. For a permanent setup, the manufacturer recommends the ring terminal cable, while the alligator clips suit temporary connections. Per the manufacturer's solar charger manuals, keep the negative lead away from carburetors, fuel lines, and thin sheet metal, and always confirm battery polarity before connecting. Owners on user forums also advise against mounting the panel where shade from gutters or equipment will reduce output.
