Danshell - I've had more than a few of these cheapies battery packs over the years. I'll make my reply in two sections - the battery pack, and the solar component:
Battery PackThe 50000mAh capacity is certainly over-rated. I posted on another forum about these over rated cheap Chinese battery packs. They are false economy for a few reasons including using cheap cells that don't last - so after about 12 months or less you find significantly lower battery capacity, or they may be using mismatched old recycled laptop battery cells which can be dangerous when recharging.
A clue to the fact that they are not the capacity they advertise is to look at the weight of the battery bank. Typically these higher capacity battery banks use a number of 18650 Lithium based cells in series. A good quality Panasonic manufactered 18650 cell weighs about 46-50grams. Looking to the weight and size of the battery bank, now the highest true capacity 18650 cell manufactured by Panasonic is 3400mAh. So to get around about 50,000mAh, you need around 14 x 3400mAh cells (or over 20 x 2200 mAh cells) which would bring the weight of the batteries alone to at least 700grams. With your whole unit being 205grams, it is definitely not near the advertised capacity.
For reference, a good quality (non-solar charging) battery bank like Anker's Astro E7 25600mAh
http://www.ianker.com/product/A1210011 weighs 450grams.
If you are interested, this guy does really good tests on batteries (and torches)
http://lygte-info.dk/review/batteries20 ... %20UK.html He has a summary on this page about the weights of various li-ion 18650 cells and their capacities.
Also note that sometimes it's been known that dodgy sellers fill the powerbank with packs of sand to make up the weight difference of using fewer cells for example
http://says.com/my/tech/cheap-china-pow ... -with-sand and
http://life.yinteing.com/wp-content/upl ... eated2.jpg.
Granted, some powerbanks use flat lithium-ion power packs (like those used in tablets and phones), but usually the shape and case will give you an indication of what cells are used inside.
Next, if you look to the price of quality 18650 cells, they can range from about $8-$10 ea for genuine Panasonic cells of about 2400mAh, to upwards of $13-15 for 3400mAh cells. Once you work out the price that would cost, even from a manufacturer's bulk purchasing, it would be difficult to imagine a seller being able to supply a legitimate 50000mAh powerpack at much of a discount.
There are more than a few teardowns of various battery packs on the web. For example, this one by Gough Lui of a supposedly 30000 mAh powerbank:
http://goughlui.com/?p=3930He also puts it back together with some better quality replacement cells and tests it again:
http://goughlui.com/?p=4321.
Note that with 8 x Genuine 3400mAh cells (27200mAh total), it still takes well over 24 hours to charge. That makes sense if the input charge takes 1A, it would be slower again if it was 0.5A. So if you had a genuine 50,000mAh capacity power bank charging at 5V 1A input, it would take a number of days to fully charge.
Also this is another forums post from the Malaysian forums lowyat.net:
https://forum.lowyat.net/topic/2793169 showing the testing of various powerbanks and teardowns of various powerbanks.
With the one you have, you can open it up yourself and have a look inside to see what they have used and work out the actual capacity of the cells.
Solar I am not a big fan of the combined solar panel/battery banks like the one you linked for a number of reasons:
- As you found, the panel is usually too small with too low an output to adequately and quickly charge the battery (so you tend to use the AC power input to charge more often, and going off grid this can be pointless).
- The battery attached to the solar panel will get really hot during charging especially for a few hours in direct sunlight, and can lead to the battery shutting down and not charging, defeating the purpose.
- The bigger ones with built in batteries tend to be quite heavy for backpacking.
I posted previously about some of my experiences with solar panels when hiking in this thread
viewtopic.php?f=21&t=18151#p246900For reference, my Goal Zero 7w panel charges a 5000mAh battery from empty to full in about 10 hours (over 2 days). Via USB the Goal Zero outputs 5V at about 0.5A (this is for my version bought in 2012/2013 – I think the latest version has upgraded the circuitry and now outputs 5V at up to 1A). My 10w (Instapark Mercury 10) panel cuts that time down to about 5-6 hours as it outputs a higher current, and a 13w panel (Goal Zero 13) brings it down to about 4-5hrs, which can output up to 1A. The 7w panel fully charged a Sony camera battery (1000mAh) directly via USB to the camera in about 2 hours in direct sunlight. Note that the charging times can vary depending on the USB battery packs' charging input current - ie. it would charge slower if it only charging input at 0.5A.
For your battery pack, assuming that it is 50000mAh and that the solar panel component was able to provide a 1A charge, it would still take some 50 hours to charge fully from flat. So you might find that you end up using up the stored power in the battery pack at a much faster rate than you can recharge.
