[William75]

Hi everyone, just wondering if there are any recommendations for a solar battery tender for an agm battery?

I park my car for 3 weeks at a time outside in Canada and would like to set a solar tender in the window to ensure smooth starting when I get back to the beach. Any recommendations?

Thanks in advance.

[bimmer456]

Don't know of any quality solar tenders as I don't have any experience with them. If you can use a plug in battery tender just plug it in once a week with an extension chord you should be good. The unit will tell you when it is fully charged and you can unplug it. Not quite as easy as set it and forget it, however.

[chowser51]

There’s a few on amazon with mixed reviews

[bimmer456]

It may depend on the amount of sunlight you're receiving during the winter months which is when your recreational gear will most likely be on standby the most unless it's a snowblower. The solar panels will need to provide enough power on overcast days to charge the battery so that is another consideration vs the consistent power from an outlet.

[William75]

Thanks everyone Ya I park it while I fly offshore so no ability to plug and unplug it. The car sits at a heliport for the three weeks. I will check out amazon and see what I can come up with.

[Smartpat]

When I bought my car a few years ago the dealership threw in a new NOCO solar charger for free, saying they use the same one for cars sitting in the lot. Can’t remember if it was BLSOLAR2 or BLSOLAR5. Didn’t ended up using it because my car is a daily driver.

[bimmer456]

3 weeks should be fine the battery should still be good but doesn't hurt to use a solar charger. Not sure if you can charge from the cigarette lighter may have to use the under hood posts and route the cable into the car with the panel on the dash. It may depend on how cold it gets where you are parked. Also you can keep a battery pack in your trunk like a powerall that you can charge off the trunk cigarette lighter while you drive. It packs enough punch to jump start your car in emergencies and can hold its charge for a few months.

[Gen13 F36]

Damn your in Canada... I was going to say leave your keys at my house and I'll drive it for ya😁😏

[Wires]

You being in Canada, it is a waste of money. Right now sun hits 45-60 degrees on the horizon at peak day which gives you almost no solar output. You need to mount the panel so that the sun's rays hit at a perfect perpendicular angle for maximum efficiency. But being so low in the sky, you lose a lot of energy just getting through the atmosphere (hence the reason we get that crappy white snow stuff. )

Years ago I had one on my car, but even during peak summer, you'd only get 1A of charge, for the couple peak hours of sun per day which wasn't enough to trickle charge the battery.

If you lived more near the equator (or southern states), it might be of benefit. Where are you parking it?

[William75]

Cool thanks, I will hold off on the purchase and see how the car is when I get off the rig in two days you guys rock.

[bimmer456]

I honestly would like to see how well it actually works. Maybe there are reviews of these things on YouTube just not sure I could trust it myself. I like my "old school" plug in unit that's kept my battery alive through at least a couple winters on a car I don't drive much.

[Billfitz]

I plug in my battery tender every night when the temperature goes below 20F, or below 32F if I'm not going to be driving for a few days. It's not so much about having adequate charge to start the car, it's about battery life. These cars draw a substantial amount of current when they're technically 'off', a lot more than the old days when it was a clock and that's all. That constant current drain in cold temperatures significantly lessens battery life. With BMW batteries going for $150 and up a tender is well worth using, and it's nice knowing that you'll never go out on a cold morning to a dead battery.
If you get one you want it rated for at least 20 watts. Less than that might be OK in the summer, but between low light and short days I wouldn't use one less than 20 watts in winter.

[Wires]

Won't disagree with an actual battery tender, but the solar ones are a bit of a joke since they are low wattage and so dependant on solar load as well as angle to the sun.

Lead acid batteries need to be topped up every month or you risk damage to the cells over time.

[Billfitz]

Good thing we don't have traditional lead acid batteries.

[bimmer456]

AGM batteries last longer than flooded cell, but it's also because the battery is in the trunk and not exposed to the elements or next to a hot engine.