Allpowers 140W Portable Solar Panel Charger Expired

Where do you live? I'm in Texas and I think state law here prevents any entity from restricting property owners from using devices to harness solar energy. This even extends to clotheslines, which are classified as solar energy devices. Of course even if the law is on your side, you may not want to start a row with your neighbors.

just bought a travel trailer with AGM batteries - can I use this to charge them? I have a zamp connector, but I've seen SAE to MC4 connectors on amazon for $13 that come with the polarity switch. The alternative setup I've been looking at is the renogy briefcase, but this is half the price. The renogy comes with some kind of controller that stops charging the batteries when they're full. Not sure how that technology works yet. Still learning.

Besides this solar panel you need a MPPT solar charge controller.
You always needs a solar charge controller.

Probably shouldn't engage, but I'll supply a different viewpoint and people can decide for themselves whether it makes sense to buy for them.

Most solar panels these days have a warranty to produce 90% of the rated output at 25 years. If you oversized your panel:inverter ratio by the recommended 15-20% to allow your inverter to operate in the efficiency sweet spot, your annual production will likely fall by less and the panels should keep producing even after that. Enphase microinverters have a high MTBF and have a high chance of lasting 25 years, like the panels. String inverters are more efficient and cheaper on average but also have higher failure rates, often within 10 years. I clean my panels with a quick spray down 2-3x per year and have been producing the expected output for the past 3 years. And so far my roof has not been damaged or leaked (this shouldn't be a problem if installed correctly and solar installers that know this provide a 25 year warranty on their roof penetrations if done on a relatively new roof).

Shall we do some math on break-even time and savings?

In Southern California, the electricity prices have gone up about 30% in the last 3 years, and we now pay about $0.36/kwh during off peak. They will likely continue to rise.

For a 5kw system at a price of $2.82/w (about the average southern California price a few months ago per energy sage) installed (pre 30% tax-credit), that becomes 1.97/w after the tax credit. So you pay $9870 for the solar after tax credit. If you put in your address and system info on pvwatts.nrel.gov, it will tell you the first year output. For the 5kw system in this post on my roof/orientation, that's 7800kwh in the first year. By the 25th year that could fall to 90% or 7000kwh (maybe not though if inverter max output which is less than panel max output).

Assuming stable rate of degradation, let's say that's about 7400kwh/year x 25 years = 185,000 kWh. $9870/185000= $0.05/kWh produced over the 25 year lifetime. At the current electric rates, your avoided lifetime electricity cost over 25 years would be (0.36-0.05)*185000=$57,350 and your savings just increase every time the electric company raises rates. $57350/25 years = $2294/year savings. $9870 solar cost/ $2294/year savings= 4.3 year break-even if rates stayed the same for that 4 year period.

(This math gets worse if you don't submit an interconnect for solar before April 14th, 2023 in California and you get stuck on NEM 3.0, so don't try to use this simplistic math in that case because they drastically devalue the buyback rates for solar.) And is you live in a state that has really cheap power, like $0.10-15/kWh, then the payback would be longer, or if your state doesn't have close to 1:1 net energy metering buyback.

So perhaps in bargain_Hunter's area the math isn't as good but I don't think a blanket statement holds true.

just bought a travel trailer with AGM batteries - can I use this to charge them? I have a zamp connector, but I've seen SAE to MC4 connectors on amazon for $13 that come with the polarity switch. The alternative setup I've been looking at is the renogy briefcase, but this is half the price. The renogy comes with some kind of controller that stops charging the batteries when they're full. Not sure how that technology works yet. Still learning.

The Renogy solar suitcase system that I have, has the solar charge controller built into the unit. I used this to charge my lead acid batteries in my RV for a couple of years, it works well to keep the batteries topped off. Yes, the Renogy suitcase is more money, and heavier, but it is a welcome addition when boondocking.

If you are at all handy, do some research into adding rigid solar panels to the roof of your rv. You should be able to add a 200w solar array with a MPPT charge controller for $400 or so.

Thanks for the info. I appreciate it. I'm thinking of getting that renogy setup especially if it goes on sale in the next few months. I don't need it until May. I don't know if I have it in me to cut into my roof and I want to be able to park under the shade while having the solar panels out in the sun.

In mounting the panels to the roof, there is no cutting into the roof. The panels screw into the roof using brackets. Many people run the wires through the roof vent for the refrigerator, I ran my wires through the channel where the awning attaches to the outside wall. I can understand the concern in doing this.

For the Renogy suitcase or other portable solar panels, you can buy extension cables to move the panels further away from the rv in order to keep them in the sun. I made my own cables for doing this. One advantage to rooftop mounted panels, they won't walk away with some lowlife person who thinks they need them more than you.