Solar Charger for AA Batteries

Steven Lake
Steven Lake Solar Expert Posts: 402 ✭✭
Hi again all. Need some opinions this time. I'm looking for a good solar battery charger for AA batteries. I've got all the big stuff covered already, so I may as well go after the little guys now. As such I've been looking at a variety of small solar chargers for everything from AAA to D cells, but I'm really not coming up with anything I like. Or I should say, nothing I feel comfortable with. At least not until I talked with you guys about it.

I'm looking for something I could use out camping, or carry around that's more or less just plug and play easy to use. (I have no issues with the more complicated stuff, but I have others who will be with me that fully fit the definition of PEBKAC) Light weight would be nice, but not a big issue. But what we can charge with it is. Now, in order of sizes, and priorities, here's what I'm looking to charge.

1. AAA and AA. (biggest priority, used for most devices and/or secondary charging)
2. C and D. (lower priority. Would give us a few more options, but we have workarounds if not possible)
3. 18kmah Battery pack. (Unit Requires 19v to charge it. Energizer 18000mah battery pack PS, it's an awesome little battery pack for single pass charging of video cameras and other devices in the field)

So, what would you guys recommend for a solar charger to meet these needs? Well, per your personal opinions anyways.

Comments

  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Solar Charger for AA Batteries

    There are several threads here, if you search.

    I like to use the fact that many NiMH (if that's what your charging) can take a C/8 charge with out being regulated, they will disapate the extra charge as heat. Check the batteries your intending to recharge. When I was bicycle touring I used some SLA batteries like this and now I guess I'm surprised they made it 8 months.

    Many items are moving to Lithium batteries, which require charge regulation, which is why usually they don't have removable batteries. A small 6V panel with a simple voltage regulator for 5V and a USB outlet can charge many of these devices using their usb charging cord.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar Charger for AA Batteries
    There are several threads here, if you search.
    *sigh* And once again the search engines fail me, because I sure didn't find any when I googled, or else I wouldn't have asked. Got any you can link me to? :(
    A small 6V panel with a simple voltage regulator for 5V and a USB outlet can charge many of these devices using their usb charging cord.
    Yeah, I looked at a few and wasn't all that impressed with the offerings. The only ones I was moderately impressed with was the stand alone box units, and I was a bit questioning on those.
  • Photowhit
    Photowhit Solar Expert Posts: 6,002 ✭✭✭✭✭
    Re: Solar Charger for AA Batteries

    yes a tricky search, since everything around here has solar and batteries and 'aa' is too short a string. Solar hiking brough up a few, I'll see if I can't figure out a go search string, I'm running to town now...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Solar Charger for AA Batteries

    Google has been a bit weired here the last week for me... Sometimes it works fine, other times it returns nothing or almost nothing.

    -Bill:confused:
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Solar Charger for AA Batteries
    Photowhit wrote: »
    yes a tricky search, since everything around here has solar and batteries and 'aa' is too short a string.
    "The" is a common word and has been omitted from the search. "Who" is a common word and has been omitted from the search.
    No search criteria specified.
    Not a real search, btw...
    SMA SB 3000, old BP panels.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Solar Charger for AA Batteries

    For the AA's - PowerFilm foldable AA charger. Charges either 2 or 4 cells, in pairs. 2 cells charge quicker. The tip is not to totally exhaust your cells, but take advantage of opportunity charging if you can. If you have the luxury of daylight, allow for an extra 1 hour beyond the solid charge termination. I'm not fond of the combo usb/aa folding charger as only 2 cells can never do a good job with usb for my uses. I stick to the plain old 4-cell AA foldable.

    The reason for this is that PowerFilm does it right by taking it up to 80% SOC quickly, and then slowly charging the rest - the extra hour. Many chargers put into solar use will reset or continuously apply a delta-v detection trigger when shade crosses a panel temporarily. Folded, fits into a large cargo-pants pocket.

    While it isn't the most efficient, a 2-step process may be much more convenient. Instead of dragging all my toys out into the sun individually, I just charge up a large AGM, and then at night use that to recharge the smaller cells. This allows for much higher quality charging such as Powerex/Maha chargers that run from DC. In a pinch, the Tenergy T-9688 is a lesser quality but ok charger (4 cells at a time, but individually charged - good!), perhaps the rebadged CCrane Quick-charger 2.

    Note that if you are into 9v recharging, the only one that does it right (with delta-v detection) is again a Maha / Powerex 9v charger which conveniently runs from dc as well. I also use an Energizer 9000 myself for various sundry things and like it alot - except for the fact that the battery is not user-replaceable.
  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar Charger for AA Batteries

    lol. So I guess I'm not the only one having issues with Google then. ^_^;; As for the powerfilm charger, would this one work: http://www.amazon.com/PowerFilm-USB-AA-Solar-Charger/dp/B001RMBHMK/

    It seems to come pretty highly rated. Plus it would do what I'm after. Now, on a side note, I ran across this while searching: http://www.amazon.com/HJS-Universal-20000mAh-Portable-Multi-Purpose/dp/B005UV1ACQ/

    Aside from one disgruntled customer who got a dud, the reviews are all 5 stars, and while it doesn't do AA charging, it does allow for you to run your laptop off it, or charge other battery packs, cell phones, PDA's, tablets, MIDs, etc. It's not a need at this time, but it is an interesting discovery and could allow me to run my laptop in a grid down situation. (especially since I'm not fully solar yet.) It's not a must have, but it is interesting, so I figured to point it out. :)
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Solar Charger for AA Batteries

    Yep - the PowerFilm is nice, but also take into account heat issues. In the summer, that entire unit along with batteries recharging directly in the sun may get very hot. The PowerFilm can take it, but lesser-quality batteries may not. :)

    Heat is the second reason I use a two-step process so I'm not melting my toys in the sun. It is also the reason you see marketing photos of devices being used in frigid snowy mountains in the background, not hot desert scenes. A few of the boutique solar toys commonly show use in ski-resort areas only. :) And most of the plastic is black, not white!

    That other pack referenced looks interesting but note that the AH rating is typically at 5v, not 12. It may use a switching upconverter to get to other voltages. Thing is, are you willing to risk frying an expensive gadget on the quality of that little interior switcher if it fails? Another reason I run from pure dc for the small stuff - even if it takes two steps.

    I'd rather spend that kind of money on a quality panel, CC, and battery, and Maha charger, and do things in two steps. Just be cautious of the toy stuff.
  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar Charger for AA Batteries

    Huh, was looking for more information on the unit by google surfing and found a direct competitor that actually got a higher recommendation than the PowerFilm.

    http://www.amazon.com/Goal-Zero-19010-Guide-Adventure/dp/B005XVBIL6/

    Never heard of Goal Zero, but so far I'm only seeing one minor issue (that's since been fixed) and the rest all seems to be roses. Anyone ever heard of these guys? From all the reviews I've seen they seem to have a better following than Power Film.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Solar Charger for AA Batteries

    I'll just say that I was not happy exchanging three of those chargers, (each an upgrade) along with a larger folding panel that had two bad modules. I just wanted stuff that worked and guess I was unlucky with bad QC. Apparently experiences from others are different. Note that you can ONLY charge 4 at a time - no less. That will contribute to burning it up and harming cells. This was noted in the docs and errata slip that comes with the chargers.

    The AA's are probably relabeled Rayovac low-self-discharge. I put them on the Maha CH-9000 analyzer and they seem to be good quality after analysis, although not up to the standards of Sanyo Eneloops. Still useful though.

    When I saw that PowerFilm uses a Morningstar Sunguard as their charge controller for their larger folding systems, I looked into them a bit deeper and have been happy ever since. Neither GZ nor PF are inexpensive. For backyard fun, the GZ might do. If it has to save your life, I'm taking the PowerFilm stuff.

    Take the reviews with a grain of salt - most don't know how to find their hours of solar-insolation and purchase the proper amount of panels to support their systems, nor how to calculate their power usage in order not to run in a defecit-charge scenario.

    If you want REAL reviews on nimh batteries, chargers, etc, please visit CandlePower Forums, where battery / flashlight geeks like me get the real scoop.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Charger for AA Batteries

    steven,
    the charger i have was in one of the links coot linked to, but you may have overlooked it.
    http://www.gnbatteries.us/servlet/the-265/IC-dsh-U6S1234-dsh-LED%2C-hitech-charger%2C-aa/Detail
    it does aaa, aa, c, and d size up to 6 batteries and each charges singly. that means each battery you put in there is charged by itself and not in series with another battery like many other types. that allows odd battery numbers to be charged such as 1, 3, or 5. it also switches to float mode after charging.8) only complaint is you have to be careful with the small connector into the charger as the wire is heavier than the connector can take if carefree with it.

    i love this charger and use it allot and i've had it for years. i may buy another if i think of it as you never know.

    ps-this site may give you more info on it than the one i previously listed.
    http://www.batterymart.com/p-ic-u6s1234-led-universal-consumer-battery-charger.html

    pss-sorry as you can't do a 19vdc battery pack readilly from this charger so if you want to use that you will need to do something fancy like dc to dc conversion into a special charger, maybe?
  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar Charger for AA Batteries

    Neil, thanks for the links. As for the 19v charing, it's not a big deal. The big pressing need is AAA and AA charging. Secondary is C and D, and the 19v is sorta on the fridges. IE, it'd be nice, but not necessary kinda thing. As for the chargers you listed, that's a very good unit. However, I need a solar charger sorta like the PowerFilm. Now if that has an accessory panel that can hook into it, that'd be a win. If not, I'm probably gonna go with the power film.

    PNjunction, I was kinda wondering about that. The couple of "engineering issues" really threw up a red flag for me. But then again I've had units with those being reported and had no issues myself. Having been a tech reviewer myself I'm pretty keen on picking up the good reviewers from the fake/sloppy/amaturish/bought ones. That's why I put what stock I did into the pro review of the Goal Zero. But as you can see I wasn't completely sold on their "glowing review", hence since I take the opinions of you guys a bit more highly than some unknown (you guys have a lot more solar millage than most) I came here to double check the findings, and it looks like I'm glad I did.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Solar Charger for AA Batteries

    I think you'll be happy with the PowerFilm for AA's at least. Just remember to allow for an additional hour or so after the full charge signal is lit, since that is really only about 80-85% charged. Usable for most people at that point, however it may be a reason for some poor reviews for those that take time to measure voltages / analyze it.

    Note that instead of outright rejecting cells with high-impedance (old stock, deeply dishcharged, abused etc), it will at least attempt to bring up the voltage by trickling at first before heading into a fast charge. So it has some smarts.

    Do yourself a favor and use quality cells from the start. Some reviews reveal that they are trying to revive drugstore-quality cells from the 1990's, mismatched cells from kids toys etc and want to keep them alive well beyond their normal lifespan - even if they have ridiculously low capacity even after being revived. While there are a variety of good cells out there, the standard seems to be Sanyo Eneloops as the enthusiasts reference.
  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar Charger for AA Batteries

    Yeah, I've been highly impressed with the Eneloops, so I'm gonna go that route. Now, I do have a question about this that has me curious. The unit says you have to have a special adapter to charge AAA's in there. I'm guessing that it's either a special insert with special circuitry, or more likely it's just a spacer designed to allow the AAA's to fit in the cradle. If it's the latter, would simply AAA to AA spacers work? I've got a set of these I use for upsizing smaller batteries into larger devices (PS, if you don't have some of these you really should get some. They're awesome. :D) and I'm guessing that, baring special add on circuitry, they'd do just fine for what's required. Would I be correct in that assumption?
  • Sparkletron
    Sparkletron Solar Expert Posts: 71 ✭✭✭✭
    Re: Solar Charger for AA Batteries

    My advice is to avoid anything marketed as a "solar battery charger". Instead, get a good charger that can be powered directly from 12 VDC. This one is excellent because it tells you how much energy went into charging each battery, allowing for all kinds of metrics and analysis. This one is not good because it requires more than 12v to run.

    Once you get a battery charger that can be powered by 12v, it's a simple matter to add solar to the mix, because so many PV systems are designed around 12v. With a 10 watt panel, you wouldn't even need a charge controller. Just get a small 12v battery (7AH should be fine). Battery stays indoors and out of the sun/heat/cold/rain. Panel goes outside. Panel charges 12v battery. 12v battery charges all your other batteries.

    This is a robust and flexible system that will outlast all the "solar battery charger" junk. Batteries can be charged at night because they're being charged from the 12v battery and not directly from the sun. That same charger can be powered via VAC with a power brick. Or from your car battery. The 12v battery can be used to power other things--not just the battery charger. All the parts can be replaced/upgraded as needed. The only disadvantage is cost (but you get what you pay for), and while it's portable, it's certainly not for backpacking.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Charger for AA Batteries

    i agree with sparkleton and the one i pointed out does operate from 12v also and it does have 2 cables. 1=ac adapter 2=12vdc cig lighter adapter.

    as far as adapters go it could be like this in keeping the cords with cig lighter connections.
    http://www.semsons.com/unusbcarchar.html

    if you try that powerfilm then let us know if it met your needs and is regulated and powered well enough to operate for your stuff.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Solar Charger for AA Batteries
    My advice is to avoid anything marketed as a "solar battery charger". Instead, get a good charger that can be powered directly from 12 VDC. This one is excellent because it tells you how much energy went into charging each battery, allowing for all kinds of metrics and analysis. This one is not good because it requires more than 12v to run.

    The PowerFilm is certainly not junk, and is the only solar charger that takes into account the fact that you might have shadows or passing clouds. Ordinary chargers, albeit excellent ones like the Maha 9000 linked to, will reset or get confused under deep shadow or passing cloud. This leads to a reset back to default charging currents, resets timers, etc - and worst of all subjects already charged batteries to multiple instances of delta-v detection at 1000mah initial current when it is not necessary.

    I use one of these myself, but only off-the-solar-grid so to speak, by merely charging a larger agm and bringing that back in at night for a two-step process where there is no chance of cloud/shadow reset. Still, one must account for the fact that cells are exothermic during charge, and both charger and battery are in direct sunlight - although you can shade the batteries with the extra flap - but when it is 100 degrees ambient in the Nevada desert, it is not the best idea. Most junk solar chargers are either useless slow-roasters, or will quickly expire at 85 degrees. :)

    Quick note about the 9000 not commonly known - the VERY first voltage you get when you insert the cells is actually an impedance check. The 9000 will kick out cells with an impedance higher than about 2.2. You can gauge the health of the batteries when the data is presented once, and only once during insertion. (after this one-time reading, the true cell voltage will be displayed thereafter.

    1.6 = very health new cell, full capacity available
    1.8 = middle aged - electrolyte drying, capacity decreasing
    2.0 = old aged - cell has met it's EOL, dry electrolyte, or you just picked up a pack of shelf-queens from the supermarket 5 years old or worse. More resistor than battery.

    This is not something mentioned in the 9000 manual, but if you are buying new batteries and keeping track, write these values down when you get new cells for reference.

    The Powerfilm does it right by taking the SOC up to 85% or so quickly, and then trickling in the rest after an hour beyond the normal indication for a finished charge. Many don't know about this. That way, passing clouds don't confuse the charger, or subject the charged cells to repetetive delta-v EOC detection. On a similar note, the Maha 9000 will also dump in 120mah total in two extra hours of charging before going to a true 10ma trickle. This is part of a conservative / safety measure on Maha's part after delta-v detection to ensure the cells are truly charged fully. Others might have delta-v's that are delayed, and risk missing the trigger.

    I would keep a careful eye on using AA-AAA adapters in the powerfilm. While eneloops can be safely charged at 1C, the AAA's will charge up very quickly, and being exothermic, it would be a good idea to keep an eye on them, or not charge them on top of dry grass etc. Common sense stuff. I don't do AAA, so you are on your own there.
  • Sparkletron
    Sparkletron Solar Expert Posts: 71 ✭✭✭✭
    Re: Solar Charger for AA Batteries
    PNjunction wrote: »
    Ordinary chargers, albeit excellent ones like the Maha 9000 linked to, will reset or get confused under deep shadow or passing cloud.

    Not if you use it the way I suggested, because the charger would never be powered directly from the sun.
    PNjunction wrote: »
    The PowerFilm is certainly not junk

    The PowerFilm is certainly not a robust and flexible solution. But it is more in line with the op's request that the solution be simple and suitable for hiking/backpacking. It's only a 2.2W panel so I wouldn't expect miracles.
  • Shadowcatcher
    Shadowcatcher Solar Expert Posts: 228 ✭✭✭
    Re: Solar Charger for AA Batteries

    My philosophy is to realize that 'where you are now is not where you will be in the future' and when you design for what you think you need now you are setting up a problem down the line. I use our Maha at home and it goes with us in the teardrop, it is powered there by the Morningstar inverter fed by the 185W solar panel into a Sunsaver.
    The anticipated needs morphed and additional loads have been added. XM radio, 3G hotspot, chargers for camera battery, chargers for cell and iPad and laptop... My advice think bigger than what you think you need!
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Solar Charger for AA Batteries
    The PowerFilm is certainly not a robust and flexible solution.
    Seriously, how robust and flexible does one need to be to charge 4 AA's? I can say that it is made of the same good material as their much larger flexible panels. Their charge algorithm shows me that even at this small scale, solar charging was part of the design, and not an afterthought.
    It's only a 2.2W panel so I wouldn't expect miracles.
    Only if you are thinking in terms of 12v. The powerfilm only needs to run at .600ma at 3.6v so 2.2w is plenty for quick charging. This also happens to coincide with Maha's recommendation to run 0.3C minimum current for AA charging of 2000mah cells, although that is needed for accurate delta-v detection, whereas the powerfilm just runs quickly up to 80% and then slow charges the rest of the way - on purpose.

    Note that this isn't speculation - I tend to comment on things I actually own and test.
  • Sparkletron
    Sparkletron Solar Expert Posts: 71 ✭✭✭✭
    Re: Solar Charger for AA Batteries
    PNjunction wrote: »
    Seriously, how robust and flexible does one need to be to charge 4 AA's?

    Hard to say without knowing all the facts. Does your life depend on it? Then I would hope you'd choose the most flexible and robust system you can afford. Also, the OP expressed a desire to charge more than just AAs. My suggestion is FLEXIBLE enough to accommodate other chargers and charging at night while the OP is asleep. I can't imagine a more efficient way of charging. Charging during the day... deprives the OP of the use of those batteries when they may be needed most.

    Before this tussle turns into hundreds of posts, let me just say that you offered a good solution and I offered one as well. Your suggestion has merits as does mine. I think the OP has enough information to make an informed choice, or to post if more info is needed.
  • PNjunction
    PNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Solar Charger for AA Batteries

    I think we agree to agree. :) Post #8 in this thread discussed how I prefer a "two step" process exactly as you describe (although I never run without a CC).
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Charger for AA Batteries

    let's revisit this as more inline with steve's original plan. with that energizer xp18000 the big problem he would have is charging that from solar. small controllers would only bring it to about 24v and we don't know how critical the input voltage of 19v is. if it is like many ac adapters then this may be at 24vdc, but if critical then some further efforts would be needed to bring the voltage inline and a possibilty could even be a high current linear regulator ic arrangement to accommodate it. of course one could also place up to 10 diodes in series rated for at least 3.5a to drop the voltage on a pwm or linear type regulator or cc. (not a common current value, but 6a is)

    the other problem would be the pvs to charge the xp as it would need a higher vmp to operate a proper charge. maybe 2 of the 12v pvs or one of the 60 cell pvs. it would require at least 3.5a and does mean not very portable to charge this main xp hub for recharging the other devices. if cost is not as important then you could use an mppt cc to down convert the voltage from the higher voltage pvs, but getting to the target voltage of 19v may not be so easy to do as i'm not sure off hand what mppt ccs may accommodate this odd voltage. the diode arrangement is not advisable to use with the mppt cc, but i believe it would be fine with pwm ccs.

    i think steve would like options to charge this xp18000 rather than the other obvious routes we would choose, but this is proving to be just as difficult. unless you get somebody to come up with a special regulation circuit aimed at this odd voltage straight from the pvs then the other methods we invoked start to seem more viable.

    imo, 2.2w isn't really viable when talking of many batteries that need charged, many of which can be large in capacity. also the charge time window will be small even for a sunny day.
  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar Charger for AA Batteries

    Yeah, that's my whole point with the power film. I mean, if I wanted to go with the solar setup that's been suggested for proper solar charging, I may as well just slap one of those Maha chargers on my battery bank or portable array and call it good. And it would be good if this were being done at home. But it won't be. I'll be out on the trail when I'm using this. (well, when it gets warm anyways) And when you're hiking it's all about the weight. So for me, when humping my normal 40lbs of gear, the extra 20-30lbs of solar gear you're suggesting would completely kick my *** to Texas and back. The power film + batteries on the other hand shouldn't add more than a few pounds total to my pack, which isn't that big a deal. +2lbs I can deal with. +30, not so much.
  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar Charger for AA Batteries
    Also, the OP expressed a desire to charge more than just AAs.
    Well, AA and AAA are required for what I need. The others were simply optional choices that I wanted to explore if they were either possible or available. If not, then no biggy. I kinda figured that they wouldn't be, but I've been surprised before, so I figured it wouldn't hurt to ask. :)

    (ps, I really need to check for other pages of replies before shooting off my mouth. lol.)
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Charger for AA Batteries

    if you opt for only the aa and aaa batteries to be charged then go with a larger fold out pv with simple linear regulator and plug this into the battery charger of your choice. if the powerfilm has a regulator (not sure) and it can accommodate more power then maybe feed another portable pv to it either by itself or in parallel. remember that today's batteries hold quite a bit of capacity so even 4 aa batteries could require over 10ah by themselves and you may have need to charge more batteries than this.
  • Steven Lake
    Steven Lake Solar Expert Posts: 402 ✭✭
    Re: Solar Charger for AA Batteries

    Not to sound like I'm a complete blockhead (which I probably am), but could you show me an example of what you're thinking? Maybe a diagram or something?
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Solar Charger for AA Batteries

    sorry for the delay as i've got many issues to address at this time, but i will attempt more detail of what i have on my mind. know that i am not good with drawings and diagrams so i need to address my thoughts more in detail.

    now i don't know if the powerfilm is properly regulated or not as some solar battery chargers just feed the power directly from the pvs with no regulation. i can't tell if this product is among those that do this or not and it's not very good for your batteries if so.

    anyway, assuming it has a regulator in it, we don't know if it could handle more power through it as the 2.2w pv may not be sufficient to properly charge your batteries in the allotted time the sun stays out. so if it is possible to parallel more pv, portable thin film or not, then it should be done. another 2.2w pv paralleled may possibly suffice here.

    say you have 8 aa batteries to charge in a 5hr solar window of time. assuming 100% efficiency the 2.2w divided roughly by 1.5v would give 1.46a. distributed to 8 batteries is 1.46a/8=.183a. if that is a nimh at 2500ma then you would roughly need 2500ma/183ma=13.66hrs. you just won't get that much time of full sunshine to complete the charge to those batteries. remember that was some very rough math and in reality it will be worse than i indicated.

    being i am not familiar with the powerfilm, can you say if it has a regulator circuit in it and how much power it can process safely? problems do exist for the other chargers out there like the maha and one i pointed out as they do have voltage input limitations as they cannot take the full voc of a pv necessitating a regulation circuit. controllers need another battery in most cases to work (small lead acid battery at 12v), but all that is really needed is a straight regulator to keep the voltage from blowing out the battery charger input.

    maybe your solution could be to buy multiple powerfilm chargers to meet your needs? i would not bother with something like the powerfilm if there is not a regulation circuit in it to control the charge to the batteries.