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Author Topic: Thunderbolt Magnum 100-Watt Solar Panel Kit from Harbor Freight - any good?  (Read 1404 times)

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Offline SimpleMan

Re: Thunderbolt Magnum 100-Watt Solar Panel Kit from Harbor Freight - any good?
« Reply #5 on: March 21, 2021, 06:58:40 AM »
Quote from: Matthew on March 21, 2021, 02:36:39 AM
A couple points --

1. When it comes to batteries, you need a good deep-cycle golf cart or marine battery. You can get 12V batteries or (2) 6V golf cart batteries and connect them in series to get 12V. The more AH (amp hours) the better. Batteries are the shortest-lived and most expensive part of any solar power off-grid system. Look at "Batteries Plus Bulbs" website, under Duracell deep cycle batteries. That is what I have on my "wish list" for my solar panel system. I have collected a handful of 100-watt panels I've bought over the years, but can't really use them for anything without batteries. Right now I have a single 12V deep cycle battery and a portable 120 watt solar panel with built-in charge controller. This is good to power many items, but I should eventually expand my collection of batteries.

2. Inverters. Yes, you can get a cheap cigarette lighter inverter at the gas station for $20. BUT that is going to be complete crap. A) it will be low wattage, less than 90W and B) the 120V AC output will be crap -- specifically, it will be a MODIFIED SINE WAVE instead of the usual PURE SINE WAVE that comes out of your wall outlets.

Pure Sine Wave inverters are widely available, and have come way down in price since 2006 (I was pleasantly shocked myself!) so this is the route you should go. Why do you need a pure sine wave inverter, even though it costs more? Because some items, especially anything with a motor, will REALLY CARE if they are denied a pure sine wave. They will hum, buzz, or even be damaged. I wouldn't mess with the cheap inverters; you don't want to ruin or damage the equipment you plug into them.

You will get the most out of your battery if you can buy a few native 12V appliances: lights, fans, chargers, etc. You can even get a double USB plug outlet that plugs into any 12V cigarette lighter plug. Then you can run anything 5V USB. The advantage of 12V appliances is that you lose the inefficiency of an inverter. If you run a 20W light bulb directly from battery, it costs 20W. But if you go through an inverter, that 20W bulb probably costs you 25W or 28W. That inefficiency is wasted energy. No inverter is 100% efficient in converting 12V DC into 120V AC power. So go directly from battery as often as you can, even if that means buying another power cord for your laptop, radio, etc.

P.S. When trying to off-grid, or even for backup purposes, the first line of defense is DOING WITHOUT. The most efficient way to cook with solar is to put away your solar panel & battery, and get out some firewood or a solar oven. :) In other words, reduce/eliminate as much as possible, and THEN (and only then) try to get solar panels & batteries to meet your needs. Just for starters, ANYTHING INVOLVING HEAT doesn't work well with solar. You don't want to dump electricity into a high-resistance element to generate heat: electric stoves, hot plates, hair dryers, clothes dryer, hot water heater, etc. Those things are better accomplished with the sun directly (a.k.a. "passive solar"), a campfire, or the wind.

Once you've optimized and reduced your electricity needs, THEN you worry about going solar.
Not just on account of this, but I've had the night to sleep on it, and I am more inclined than not, to take the thing back to Harbor Freight.  It almost qualifies as an impulse purchase (though I'd been thinking about it for a few weeks), and $275 with tax is a pretty big chunk of change for a toy that I have to question how much we'd actually use it.  I'm going to keep it for a couple more days, unboxed, then will probably take it back.  The $15 off was all  needed to push me over the edge, but it only works out to about 5% off.  Save a little, spend a lot.

Good concept, but the rigamarole involved probably isn't worth it.  My son and I can study other things for science.  There is nothing mandatory about this particular topic --- our state just prescribes broad subject areas, and how you get there is up to you.
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Offline Ladislaus

  • Supporter
Re: Thunderbolt Magnum 100-Watt Solar Panel Kit from Harbor Freight - any good?
« Reply #6 on: March 21, 2021, 07:11:52 AM »
Quote from: Matthew on March 21, 2021, 02:36:39 AM
A couple points --

1. When it comes to batteries, you need a good deep-cycle golf cart or marine battery. You can get 12V batteries or (2) 6V golf cart batteries and connect them in series to get 12V. The more AH (amp hours) the better. Batteries are the shortest-lived and most expensive part of any solar power off-grid system. Look at "Batteries Plus Bulbs" website, under Duracell deep cycle batteries. That is what I have on my "wish list" for my solar panel system. I have collected a handful of 100-watt panels I've bought over the years, but can't really use them for anything without batteries. Right now I have a single 12V deep cycle battery and a portable 120 watt solar panel with built-in charge controller. This is good to power many items, but I should eventually expand my collection of batteries.

2. Inverters. Yes, you can get a cheap cigarette lighter inverter at the gas station for $20. BUT that is going to be complete crap. A) it will be low wattage, less than 90W and B) the 120V AC output will be crap -- specifically, it will be a MODIFIED SINE WAVE instead of the usual PURE SINE WAVE that comes out of your wall outlets.

Pure Sine Wave inverters are widely available, and have come way down in price since 2006 (I was pleasantly shocked myself!) so this is the route you should go. Why do you need a pure sine wave inverter, even though it costs more? Because some items, especially anything with a motor, will REALLY CARE if they are denied a pure sine wave. They will hum, buzz, or even be damaged. I wouldn't mess with the cheap inverters; you don't want to ruin or damage the equipment you plug into them.

You will get the most out of your battery if you can buy a few native 12V appliances: lights, fans, chargers, etc. You can even get a double USB plug outlet that plugs into any 12V cigarette lighter plug. Then you can run anything 5V USB. The advantage of 12V appliances is that you lose the inefficiency of an inverter. If you run a 20W light bulb directly from battery, it costs 20W. But if you go through an inverter, that 20W bulb probably costs you 25W or 28W. That inefficiency is wasted energy. No inverter is 100% efficient in converting 12V DC into 120V AC power. So go directly from battery as often as you can, even if that means buying another power cord for your laptop, radio, etc.

P.S. When trying to off-grid, or even for backup purposes, the first line of defense is DOING WITHOUT. The most efficient way to cook with solar is to put away your solar panel & battery, and get out some firewood or a solar oven. :) In other words, reduce/eliminate as much as possible, and THEN (and only then) try to get solar panels & batteries to meet your needs. Just for starters, ANYTHING INVOLVING HEAT doesn't work well with solar. You don't want to dump electricity into a high-resistance element to generate heat: electric stoves, hot plates, hair dryers, clothes dryer, hot water heater, etc. Those things are better accomplished with the sun directly (a.k.a. "passive solar"), a campfire, or the wind.

Once you've optimized and reduced your electricity needs, THEN you worry about going solar.

All good points.  In terms of batteries, some companies (including Tesla) now make Lithium Ion batteries (like found in electric cars) for backup power use.  Unfortunately, they cost thousands of dollars.  I bet they come down in price as there's more competition.

For shorter term use, it's probably not a bad idea to charge a few of the deep cycle batteries off of the grid, rather than waiting for the solar panels to fully charge them.  Then you have them ready and charged when the time comes instead of waiting for solar panels.   Some parts of the country (such as where I live) don't get a ton of sunshine, so you may be waiting a long time.  You can also supplement a system with wind generators.

There's also a product out there where you can ride a stationary bike to generate current ... get some exercise while also generating electricity.

As for myself, I have a dual-fuel backup generator (runs on gasoline and propane).  I have a little propane cooker and a vent-free propane heater.  All I need is ... the propane.  I intend to get a few of the 100-lb. propane tanks.  Even though my house uses natural gas, if I ever have the funds, I might get one of those really large back-yard propane tanks.

Oh, and some companies are now making solar roof shingles, so next time you have to get your roof redone, it might be worth a look.
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Offline SimpleMan

Re: Thunderbolt Magnum 100-Watt Solar Panel Kit from Harbor Freight - any good?
« Reply #7 on: March 21, 2021, 11:24:38 AM »
Well, now I'm more inclined to keep it, seeing as 25-watt panels at HFT are $69.99, and the whole 100-watt array is only $105 more on sale.  I had thought of just getting 25 watts for our solar power experiment, but I'd still need a battery (the one I got from HFT is indeed deep cycle).  Will probably let it sit here unboxed for a few days, I have the receipt, and their return policy is fairly generous.  I've looked on Amazon and the HFT price is very competitive for what you get.

Can't decide if my diffidence about this matter is more worthy of Hamlet or of Piglet :facepalm:

I could never work at HFT (I've thought about it to supplement retirement income) because I couldn't be around all that hardware without buying too much of it with the employee discount... "Hello, my name is SimpleMan and I'm a tool-a-holic... 'Hello, SimpleMan'..." :jester: 

(lame joke there at the expense of AA, an organization that, thankfully, I've never had need of)
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Offline SimpleMan

Re: Thunderbolt Magnum 100-Watt Solar Panel Kit from Harbor Freight - any good?
« Reply #8 on: March 22, 2021, 08:44:09 PM »
Really running this "do I return it, or do I not return it" thing into the ground...

I checked the HFT receipt and they give you 90 days to return unopened, unused items.  I have never heard of such a thing in retail.  Don't get me wrong, it's good, but that is three months.  Unbelievable.  So unless my son and I are seized by a horrible urge to open it up and set it up on the patio, we can wait till summer.  Our family finances through the rest of the year will be clearer by then.  We are running over budget right now, but we had some unexpected expenses, and I am hoping that frugality in the next couple of months will enable us to make it up, and possibly even leave money for the solar setup.

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Offline SimpleMan

Re: Thunderbolt Magnum 100-Watt Solar Panel Kit from Harbor Freight - any good?
« Reply #9 on: April 01, 2021, 06:48:52 PM »
After analyzing our family's month-end budget, I finally overcame my buyer's remorse and opened the package.  The panels were actually much easier to assemble than I expected.  It was late afternoon creeping into very early evening before I got everything set up, but according to the meter on the charge controller, the 12V battery was charging despite the setting sun.  I have the battery and the charge controller up on a single layer of bricks on the patio, then covered by a plastic storage bin placed upside down, in case the weather would get bad (not forecast, but forecasts can be wrong).  I have a battery-clips-to-cigarette lighter sleeve adapter on order from Amazon, should arrive Saturday, and my 12/120V power inverter (150 watts) ready for when I get done charging.  If all of this works, my next task is going to be securing the panels in some way, possibly with cinder blocks on top of the mounting stands.  Our ever-vigilant HOA (they're actually not all that bad, I've heard of worse ones) would not much cotton to panels on the roof, so for the moment they will have to be out of street view on the patio.  Better than nothing.
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