Hopefully you will give it a go. I am probably not able to fully charge a nearly depleted 18650B with my 15 watt Goal Zero panel. I charge well before near-depletion whenever possible. We all appreciate your earnest inquiry and studied responses. By-the-way, I am primarily using an Xtar MC1 single bay, simple charger off of a USB connection, as my NiteCore i2 would not function with the panel. The larger Xtar chargers that I have are equipped with digital displays, and I do not wish to use electrons towards monitoring.
Thanks for sharing your experience.
I'm very tempted to give it a try despite the discouraging responses thus far.
If a "15W" panel that costs >$100+ can't even charge a single NCR18650B in a day, then something seems out of whack. Highway robbery much? Something seems amiss there. Li-Ion charging is a pretty efficient process. A 12WH cell should only need ~15-16WH (all charging losses included) to charge (on a poor efficiency charger design). You're saying, you don't think the goalzero 15W panel could average 2W output over 8 hours in the sun?
In your experience, would you say the MC1 is "tolerant" of low input power? IE: will charge anyway, just at a reduced rate?
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Not sure what happened to my previous post, so I'll try again -
I use a few solar panels when hiking, but haven't used them for charging 18650 or 14500 cells yet. I use them for charging camera, NiMH AAs for my GPS, UV water filter and flashlights.
I looked a some of these 5W panels a while back (I can't remember the brand, but it looked similar to the Sunkingdom one) and found that it was lacking in output current. The 5W panel I tested was outputting less than 0.5A, and the AA charger I was using didn't like the lower current. It did manage to trickle charge a USB li-ion battery pack though.
Thank you very much for sharing your experience, and taking the time to re-post a lost-post. This helps me "frame up" what I am up against here. Less than 0.5A may not be a deal breaker, depends on the behavior of the charger.
I now have 2 Goal Zero Nomad 7W panels, an Instapark Mercury 10W panel, and a Goal Zero Nomad 13W panel. The 13W panel is a bit too big and heavy to take backpacking. I use the Instapark Mercury 10W as a middle ground, as it can output a higher current than the 7W panels. The Instapark is meant to output a max of 2A, but I haven't been able to achieve that in direct Australian sun, with the devices I've plugged in. My USB AA chargers only accept an input of 0.5A, but using a tablet that can take 2A, I have tested the Instapark panel at up to 1.5A. The Goal Zero Nomad 7W panels output less - between 0.8A - 1A.
Sounds like that instapark panel isn't too bad of a deal (good power output for ~$50). Unfortunately, at a weight of about 1 lb, that doesn't really "pay" for itself very well. I could carry 8XNCR18650B's for the weight of that panel, which is more than I would ever anticipate needing in any single trip. By my figuring, the weight of the solar charging system would have to be less than 8oz to meet a comfortable "break-even" point for me, where I opt to leave behind 4 spare cells (only carry 2 spares instead of 6), and bring up to an 8 oz solar charging system along. The beauty of that 4oz panel I found on there, is that it would actually make my pack lighter. I'd leave behind 8 oz of spare cells, and bring along a total of about 5oz of charging gear instead (panel+mc1). 3oz is 3oz, and in backpacking, those ounces add up, everything has to be scrutinized, limits have to be imposed, especially since we also pack fishing gear (have that down to ~1lb per person).
One of the issues you might face is what happens when you get cloud cover or are in shade while it is strapped to your pack. I've noticed some panels stop charging devices after cloud cover, not sure whether the controller is shutting it off, or the device isn't accepting the reduced current.
Yea, need to figure out more details about this.. My understanding though, is that the MC1 is a good device for a solar setup because it won't allow any reverse "bleed-down," as could be the case with some solar panels when in the shade/dark when connected to some devices.
I haven't heard of the Sunkingdom brand but be aware of the cheaper solar panels out there. A mate bought a 13W panel that looked extremely similar to the Goal Zero Nomad 13 panel from a seller on eBay. It came from China, and size wise it measured up and looked like the Goal Zero. When we tested it out in the same conditions charging the same model of phone, it was clear that the Chinese copy wasn't up to scratch. It would only output around 0.5A, while the GZ 13W would output around 1.3-1.5A.
Makes me wonder if KITROBASKIN's GZ is a counterfeit, based on his reported experience with it... hmmm...
I'm using a device like this
http://www.adafruit.com/products/1852 to check the current outputs from the solar panel. I previously used a spliced USB cable and my multimeter, but this is a bit neater and easier (although the red display can be hard to read in direct sunlight).
I was planning to pick up Xtars version of the same type of device to test with if I do decide to buy something, but based on the feedback so far, nobody seems to think that 4oz panel will do anything useful, so I may not even be bothering.
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My favorite solar charging solution is Cottonpicker's folding solar chargers. He's on the forum, and makes them by hand to order. They far outperform the commercial stuff that's out there, and are extremely well built. He sets them up with built in ports for your ipod, computers, phones, batteries, battery packs, etc....whatever you need.
Thanks for the heads up, I'm trying to locate a recent sales thread but not having any luck. Sounds like he isn't doing this anymore. Though, a DIY isn't necessarily out of the question for me, but I'd prefer to buy a ready-made product. The market appears to have enough options and competition to more or less ensure that any DIY attempt would be more for the novelty of DIY than for any value-add.
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First off, if you look closely you will see that I said the solar panel was waiting on money, so I don't have it yet. Now, since this discussion, I was doing some research and found out that the price dropped $20, so I went ahead and ordered it - it is scheduled for mid-week next week. If you can wait that long I will give a quick report as soon as it arrives.
Second, I think you should plan to put a power bank between the solar panel and whatever else. As you may have seen on the other threads, one of the problems with direct charging is the variable output of the solar panel(s). By using a power bank, it will accept whatever output is available and store it away. Then, in the evening or over night, the power bank can be used to charge whatever, even if it takes all night. I personally really like the Maxboost Electron banks. Mine is the 15,000mAh, but they also make one at 10,000mAh. One really nice feature is that they have a digital % of remaining charge display.
And last, but definitely not least, I think you would be much happier with this panel: Anker® 14W Dual-Port Solar Charger with PowerIQ™ Technology. It is about twice the cost, but produces almost three times the output, and is made by a recognized name in portable solar power. It is the one I have ordered so we will see how it does next week.
Sorry I did read your previous reply incorrectly. I think I got it mixed up with someone else's response.
I appreciate your thoughts on the matter. Unfortunately, I don't see any way for a 28oz solar panel and a 10oz redundant power bank to break even on weight vs just carrying more charged cells. For that much weight I could just carry an additional ~20 X NCR18650B's (on top of the 2 or so spares that would come along regardless plus those that would already be in the headlamps and handhelds). From a back-packing perspective within the context of the type of trips we will be able to take, the break-even point is going to be if a functional panel + 1 cell charger weighs as much or less than bringing 4 more spare 18650's (about 8oz). 20 spare cells (26 total including a "baseline" of 2 spares and 1 cell already loaded in each headlamp and hand-held) would be ~3 months worth of use, maybe more. A 3 month expedition isn't happening, our schedules don't allow for that, so it doesn't make sense for our power system (solar or not) to weigh as much as a 3 month supply of batteries.
PS: I am not a camper or hiker, so that does influence my choices somewhat. I am more preparing for the power failures I expect to see in the next couple of years caused by failures in the regional power grids.
Back-packing requires careful attention to weight. I'm not as "serious" about the weight reductions as many back-packers, (we bring a good camera, fishing gear, comfortable sleeping pads, roomy tent, etc), but it is important to me to be careful how I am "spending" the ounces in my pack. I'll carry more weight if it provides me with a creature comfort or benefit or activity that I consider to be with the "cost" in weight. In this case, I'm actually looking for something small, low power, and light weight. I expect the performance to be low, but don't need much to create a sustainable and be beneficial system. One way or another, I will likely have enough cells on any trip to make it through rain or shine anyway. With so many modes on these headlamps, there's really no reason not to be able to stretch out a single 18650 for a week or more if necessary (Which is about as long as any of our trips would ever be anyway). I mean, the runtime in firefly 3 mode (~9 lumens, which is plenty for most camp/kitchen stuff) is basically an entire week on an 18650 anyway. Yes, one could theoretically leave on 1 week trip and leave the headlamp on the entire week at ~9 lumens the entire time, without swapping the battery the entire trip). Point being, I'm not trying to power a search and rescue operation or or a portable guitar hero session or something.
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I've played with cheap panels, and that's just what they are, CHEAP. I'll never buy a cheap one again. My two favorite are the Goal Zero and Suntactics. I once went for six months charging my IPhone from only the GZ panels and AA batteries that comes with them. Not once did I plug into the wall outlet.
Never have charged a 18650 from one though. Maybe I should try and report back.
Big difference between just the 5 watt and the 8 watt, yet not much difference in size.
Love my solar panels, play with them all the time.
Thank you for sharing your experience.
I see that suntactics has a 6" X 11" folding panel that weighs 8 oz, that is a "true" 5W panel, for $130. (made in USA). That looks like a very high quality panel. When paired with a charger it would be borderline in terms of weigh to benefit ratio, and potentially overkill, as I really don't need a "true" 5 W panel to achieve sustainability, but I'm going to bookmark that one.
Based on your experience with cheap panels, do you think they might deliver even half of their rated output in full sun? Reason I ask is that, I'd actually rather have a 2-3W panel (even if it claims 5W on the box) that weighs 4oz, than a true 5W panel that weighs 8oz for this application.
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Thanks everyone for your participation, feedback, ideas, and interest in the topic. This is great stuff.
If I may be so bold to try to steer the conversation away from any panel that weighs over ~8 ounces or is larger than ~100 sq inches. It doesn't matter if it could power a whole zoo, it doesn't do me any good to be larger or heavier than this as I could just carry more cells at that point. I'd love to hear more experiences and/or thoughts about small (weak) light weight panels, specifically if anyone has used them with an MC1 charger.
Regards,
I'd be very interested. 
