Feb 26, 2014 at 6:15 pm #1313808
I recently bought a Powerfilm USB+AA solar charger to keep powered small devices in extended outings. This is a fairly lightweight alternative that has been well discussed in these forums. Unfortunately the output of this solar charger is not strong enough to charge larger devices (like the Ipad Mini).
Anyway, I run into an accessory by Goal Zero called USB Smart Adapter. It only cost $4.79 and weights 0.3 oz and with that accessory plugged into my powerfilm USB+AA I have been able to get a "charging" signal on my Ipad Mini.
Just wanted to share this as I haven't seen the "USB Smart Adapter" being discussed here.
MarioFeb 26, 2014 at 7:08 pm #2077533
Nick GatelBPL Member
@ngatelLocale: Southern California
The iPad mini is looking for 5 watt (min) charge rate. Your unit only is putting out 1.5 watts (from a quick spec check). Get a bigger (higher watts/amps) solar panel.Feb 26, 2014 at 8:10 pm #2077552
I have the Goal Zero Nomad panel (7 watts) which is much heavier than the Powerfilm USB+AA so I'm looking for lighter alternatives.
I just got the Goal Zero USB Adapter which seems to work well as far as transferring the juice from the AA batteries on the Powerfilm USB+AA into the Ipad Mini. (Without the adapter that is not possible).
Right now, I have a couple of AA Rechargeable batteries transferring their juice to the Ipad Mini. In an hour and half I have bumped my ipad mini battery from 45% to 62% (and still going). I will report back once the transfer is complete and I do more testing.
MarioFeb 26, 2014 at 8:21 pm #2077557
Nick GatelBPL Member
@ngatelLocale: Southern California
AA batteries run about 1.5 volts. So you really need a system with 4 AA batteries (6 volts) to push voltage into your 5 volt device.
You need more watts. More watts = more weight. There is no free lunch.Feb 27, 2014 at 6:17 am #2077642
Joshua AbelBPL Member
I've played with solar panels and overall I think they're not very good. They just dont seem to really work that well, take forever and weather plays into how well they work. I would highly recommend just getting a battery pack. I carry a 12,000 mAh battery pack now and it keeps all the electronics i could ever want to bring with charged for well over a week. The weight penalty is offset by how ridiculous easy and zero fuss it is in comparison to a solar panel. Also, they're dramatically cheaper in price. ymmvFeb 27, 2014 at 7:57 am #2077670
The other concern with batteries and charging are the power requirements of "i" devices.
The iPad requires 2A at 5.1V to charge = 12 Watts
The iPhone requires 1A at 5V to charge – 5 Watts
This is why neither the iPhone or iPad can charge from a PC's USB port; it can only provide 2.5 Watts. Other devices can accept slower charge rates and even lower voltages; an android phone charges slowly from a PC; .5A at 5V = 2.5 Watts.
Portable power packs have to utilize step up circuits to increase the voltage and amperage provided by internal 3.7 volt lithium battery. While you could use multiple 1.2V rechargeable NiMH cells and a step up circuit to charge your "i" device, it would be inefficient and heavy compared to Lithium solutions.
I use an android, so I can get away with a slower charge rate in the field. I use a 3.7 volt battery in a small cradle to charge at a 1.2A rate = 4.4 Watts.
– Matt –Feb 27, 2014 at 9:43 am #2077701
That is the role of the “USB Smart Adapter”, somehow it tweaks the USB ports by changing their mAh ratings to deliver the requirements of the appliances being charged (probably within certain limits).
My Ipad Mini requires 5W only. And as I mentioned before I HAVE BEEN ABLE to Increase the battery reading on my Ipad Mini by 17% (i.e from 60% to 77%) using two fully charged AA Batteries.
Powerpacks or just bringing extra set of batteries is definitely a good / lightweight strategy. In my case I do enjoy outings in very cold environments so I need to be particularly careful about keeping batteries warm so they don’t lose their charge, because if they do, that’s it.
Still the idea of harvesting solar power is very appealing to me, for environmental reasons and as a potential UNLIMITED source of power. The tricky part is to have a lightweight system that actually works.
The Powerfilm USB+AA has been reported to be effective charging its two AA batteries even in not ideal conditions. Manfred Kopish has several mentions on these forums of successfully using this product on the field. I bought this product under the assumption that I would be able to power only small devices (i.e Steripen, GPS, Headlamp, camera, etc). Then I run into the “USB Smart adapter” which somehow tweaks the limited output on the Powerfilm USB+AA to deliver more juice than its manufacture’s specification.
Without the USB smart adapter I don’t even get a “charging signal” on my Iphone 4s or my Ipad Mini. If I plug the “USB smart adapter” into the USB port of the Powerfilm USB+AA I DO get a charging signal on my Ipad Mini and have successfully transferred juice to bump its battery at least by 17% points every time so 4 AA batteries (two at a time) should allow me to increase the battery in my Ipad Mini by 34% points, which is more than what I need (and all this without using the sun at all, which of course I intent to use).
So I have to test this in the field, but my plan is to bring a couple of sets of AA Batteries (1 set = 2 batteries) and have them permanently charging while I hike (2 AA at a time). I should be able to get 4 AA batteries fully charged by the end of the day. This gives me 10,800 mAh (4 x 2700) of renewable (on the field) power everyday. (Even if is every OTHER day, that should work fine for my needs). What is the weight penalty: 4.8 oz (4.5 oz for the Powerfilm USB+AA and 0.3oz for the USB Smart adapter). I’m not counting the weight of the 4 AA batteries since I was bringing them anyway.Feb 27, 2014 at 12:01 pm #2077755
Sounds like the USB+ smart adapter is the Ah step up circuit or it somehow fools the device into thinking it is getting more than 500 mAh. The Powerfilm mat already has the voltage transformer to get to 5V @500 mAh out, but won't kick out enough Amps without that USB+ thingamajig. At $5 for the device it is certainly worth experimenting with.
One other suggestion; I'd use standard NiMh and not the low self discharge ones (I.E. "hybrid", "pre-charged", or the included Eneloops). Self discharge of standard NiMh cells is 1%-4%/day at room temp; slower in lower temps. Eneloop (2000 mAh) and other LSD cells have at least 20% less capacity, though currently it is worse. Some standard NiMh cells boast up to 3000 mAH right now (which is phooey). Sanyo cells are among the best rechargeable batteries and they have 2700 mAh rated cells on the market. In your daily charging scenario I think standard cells will work better.Feb 27, 2014 at 12:11 pm #2077757
@b-g-2-2Locale: Silicon Valley
Can somebody intelligently explain how this Smart Adapter works?
–B.G.–Feb 27, 2014 at 1:19 pm #2077786
Dave MarcusBPL Member
@djrez4Locale: Rocky Mountains
I have the SolarMonkey Adventurer. OutdoorGearLab's review is here: http://www.outdoorgearlab.com/Solar-Charger-Reviews/SolarMonkey-Adventurer
Internal 2500mAh battery, 9.6 oz (Nomad7 weighs 13.4 w/o an internal battery), actually charges at or above rated output, as opposed to the Nomad which needs the smart adaptor to charge an iPhone.
Even lighter, if you believe the specs, but perhaps less durable, is the Bushnell Solarwrap Mini. Weighs 4 oz, 4 watt/1 Amp output, rumored 2200mAh battery. Dean F.'s review is here: http://www.backpackinglight.com/cgi-bin/backpackinglight/reviews/display_reviews.html?forum_thread_id=87398&skip_to_post=744719
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