Powerfilm USB +AA Solar Charger on Pack


With the batteries straight out of the storage drawer (so not quite charged) it happily charged my Samsung Galaxy S4 Mini (1900 mAh battery) in this configuration at 1% a minute in dappled sunlight (cloudy Spring 20C day) yesterday.

I have mounted it to my Zpacks Blast (Zero) pack with some Lineloks and Dyneema. The phone slips into the pack’s back pocket whilst it is being charged. This is a very light option but will prove too inconvenient in practice, so I will be switching them for plastic buckles and 1 cm webbing today. Then I will quickly be able to move it out of the way when I want something out of my pack.

I fixed the broken wire I had in this unit yesterday. You should never allow a solar charger to flap uncontrollably in a heavy wind! I can see that a lot of reviewers of such units have had them fail. I suspect excessive flexing is the cause.

As configured the unit weighs 176 grams including two Eneloop 2400mAh batteries (ie minus the ‘tail’). My Bushnell Mini Solarwrap weighs 116 grams including the AA/AAA battery charger, so an increase of 60 grams. For that 60 grams you get more storage (and you can always have a couple of extra charged AAs for additional storage – at 30 grams each). Bushnell do not quote their storage capacity but I suspect somewhere between 1500 and 2000 mAhs. The Powerfilm unit also has 50% more solar cells and they are clearly much more efficient. The Bushnell unit says it will take 10 hours of sunlight to charge its internal battery. The Powerfilm unit says it will take about 4 hours to charge the two 2000 MAh batteries it comes with, so it has2 ½ times more muscle. Well worth the 60 grams.

Many reviewers of such units clearly have no understanding whatsoever of how such a unit works. Many return them saying they will not charge their iphones & etc. Now electricity (like water) will not run ‘uphill’. If you have a larger battery to charge and it is already filled to over the capacity of the charging unit it will not charge at all.

Another delusion is that the unit should fully charge the appliance to be charged. If you view the two connected batteries as a full water tank connected (on the level) to an empty water tank you will understand that the water will only flow until they are both half full. It is the same with batteries. A full 2400 charge in the charging unit will  (in the absence of sunlight) charge the appliance’s 2400 mAh battery to 1200 mAhs ie 50%. When the phone etc has run down some more, it will charge it some more, eg to 40%…and so on.

Notwithstanding the above, in the Powerfilm unit, if the two AA batteries are fully charged and the unit is in full sun it has a capacity above the 2000 or 24000 mAhs the batteries supply so it will charge a battery which is larger (eg 3500 mAhs).

I swapped out the standard 2,000 mAh batteries http://www.theultralighthiker.com/eneloops-rechargeable-batteries/ for the Eneloops Pro 2400mAh versions http://www.theultralighthiker.com/eneloop-pro-aaa-battery/ to give the unit a little more muscle. I also cut off the unnecessary ‘tail’ the unit (photo below) comes with saving 10.5 grams. A new unit may weigh even less than this one.


You can charge AAA batteries if you carry a couple of AA to AA A converters.


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