I am thinking it would be a good idea to have a solar panel/ charger of some sort to keep rechargeable batteries working if /when TEOTWAKI happens, and all the devices’ and stored batteries have been run dry.
Does such a device exist that could charge batteries available on the general market… 4 AA, C or D cells? Could a solar charger do that number of cells at once? I’m not a tech savvy guy, so does anyone make a solar panel that you just set up, plug into a charger, and done? How long would a charge generally take?
Thanx!
Your best bet would be a solar panel (The bigger, the better, of course, specially for less-than-optimal situations, but smaller also means easier to carry) paired with a dc/dc converter. If you wanted to also do multiple different cells at once, you would need a proper charger.
Solar panel—>dc/dc—>charger—>cells
I have Blitzwolf BW-L3. It has 2 USB ports and in good sun I measured ~ 2,5A from both ports, or ~1,8- 2A from 1 port. I did not charge Ni-Mh batteries, but have paired it with a Tomo S4 charger with 4 18650 batteries, then I can further charge safely 1-2 devices from the Tomo - it can be connected in between and first charges the device, then it charges the batteries inside. I find this setup good, as your device is always charged and safe, and if there is enough sun, you also have full powerbank. Instead of Tomo you will be able to plug in some 4 slots universal USB charger like Lii-402 and charge Ni-Mh batteries.
You can get away with the smaller BW-L2, but I was able to measure 1.4A max from one port. Hope this helps.
I agree with kaybi but I gave him the idea 
If you aren’t particularly skilled with electronics then the simplest option is a wide-voltage USB regulator like this:
https://www.amazon.com/GERI-USB-Module-8-50V/dp/B00W52N8XW/
And then use whatever USB chargers you have. This approach is both less expensive and more modular than combo panel/charger units.
You would want both a 12vdc system with a couple/few 12v AGM/SLA mother batteries, to handle your 12vdc chargers and you’d want a smaller <21w 5v USB solar charger for USB type stuff and USB power banks.
And then here’s my dinky 14w Sunkingdom jobbie during 84 hours without power last year after IRMA.
So, get both, depending on your needs. Mother batteries and USB power banks are the key, since you can charge them up during the day with solar and operate your stuff at night.
Chris
Question regarding the Tomo S4 powerbank/charger since you’ve already tested it with solar charger.
Will it continue charging when the USB voltage drops (eg. cloud cover) or it just stops charging until it is plugged/unplugged again?
(ie. is that DIY powerbank “solar-charger” compatible?)
Are you sure there will be sun if it happens?
If it does not, you may choose from a solar powerbank to a comprehensive tesla-powerwall-based solar system.
If you’re using a solar panel with built-in 5V USB output, it’s often a good idea to charge a powerbank and then use that to charge your devices or power a USB-compatible battery charger.
That way, the only device that has to cope with solar power fluctuations is the powerbank. Apple products are particularly picky about their power sources…
Of course, if the powerbank breaks or is discharged, you can still plug a device directly into the solar panel. It’s just that you may need more constant sun, or be ready to unplug / replug the device if it starts ignoring the panel.
Some panels do have an auto-reset built in, though, which simulates unplugging and replugging the device in the event of power fluctuations and saves you having to hang around to do it manually. My 28W EasyAcc panel does that, but my 14W Anker one doesn’t, so check the spec if you want that option.
Actually yes, both the panel and Tomo reset, as the meter in-between shows current flowing after I fold the panel and unfold it (simulating cloud).
I am also using the Tomo exactly to be in between the panel and the device, also tried one Xiaomi battery, but Tomo gives to the device 1.8A vs. 1.2A Xiaomi. I have tested both BW-L3 and BW-L2 models and they autoreset almost immediately.
I have a few portable solar panels. from few watts to 60w. of my 2 smallest usb panels, i find this one best:
https://www.aliexpress.com/item/BOGUANG-5V-5W-ETFE-green-portable-solar-panel-charger-Efficient-Portable-flexible-quality-cell-phone-camera/32831460752.html
features very efficient solar cells which makes it half the size of other red folding ones of the same (sort of) wattage.
Made from ETFE laminate = something like 20year life, water proof, doesn’t scratch easily unlike cheap pet panels better for use in sandy places, good well functioning usb output. still works in low light!. something like 600ma max output.
note that usb socket is not waterproof so dont soak it but if underneath it is dry then the face of the panel can get rained on.
oh and its very cheap! i think i paid £10~ for mine in total. looks like price has gone up or maybe i got it during a discount time. watch the price. china sellers tend to have it at silly price for a few days the discount to more realistic one. £15 is still quite good. maybe they send it in a box now instead of just a jiffy bag unprotected from being accidentally stepped on.?
I recommand it.
You’ll die of old age before that thing charges anything up.
Sorry to say.
With solar, the bigger the better and you can pretty much cut in half anything ANY solar charger claims, unless you’ve personally measured things with a good volt/amp meter.
Chris
if you want to power 20w devices then yes you would die of old age
if you want to charge 1 phone, tiny touch (like lumintop geek), 1x 18650 3AH cell usb power bank, then its great. used it on a little walk for a test in july. worked very well, attached it to rucksack, near the end of day. for a short while walking test with a usb power meter.
other wise you want 100w setup (50w in reality). or my 100wh lifepo4 + 60w (30-35w in reality) solar setup
http://social.aross.me may have some pics of the little brown wooden box.
https://joindiaspora.com/tags/mytechproject
I was just impressed by that little panel. for the price and what you get. it was lot lot better then most small cheap and expensive usb panels. I assume the person asking didn’t need .*Watts of power as they where talking about aa batteries.
with a usb AA charger you can use a usb panel to power a AA usb powered charger.
https://www.aliexpress.com/wholesale?SearchText=usb%20aa%20charger&catId=0&=&=&=&initiative_id=
Yeah, I have an Xtar VC4, two Liitokala 100s and two Liitokala 202s for USB charging, but they all require at least 1A of current for 1A charging rates and in the case of the Xtar, it wants a solid 2A of input.
The OP mentions 4xAAs, so the bigger, the better.
Mother batteries, like you have, are the way to go unless you’re out hiking the A.T. and are minding your ounces.
Remember, it’s hot sitting out in the sun for a few hours.
Chris
Thanks for the info!
As Chris mentioned, there are pitfalls. Unfortunately you will need to do some research or experimentation to work out which chargers will work with a solar power source.
In my experience, there are precious few AA chargers that will work correctly with a low-power or fluctuating source, even if the panel itself resets the port after clouds. The GoalZero Guide10+ is very good when paired with the Nomad 7 panel in any kind of lighting, but it is very expensive and needs to charge 4AA or 4AAA at a time. I also use mine as a buffer pack to run my Sanyo Eneloop USB charger for doing 1 or 2 AA or AAA.
Some USB power banks can act as a buffer pack, but many will not. I can’t recall if the correct term is “passthrough” or “bypass” but many USB packs will either not output at all whilst charging, or will not hold a regulated 5V. My otherwise excellent Xiaomi banks are examples of ones that won’t work properly as a buffer.
One of the best and cheapest buffer packs I’ve used has been a simple Miller ML-102 loaded with an 18650 or 266650 Li-Ion cell. It is easier to find small, portable, solar compatible USB chargers for Li-Ion than for NiMH. The Xtar MC1 (and the Miller above) both keep trickling current into your cell even with very low output from the panel.
If you want to reliably charge large numbers of devices or cells, then a 12V setup like Chris has posted is the sensible way to go. It may not suit backpackers or canoeists, but as a static installation or for vehicle use you get much more capacity and reliability. Splash out on an MPPT charge controller if you want the best from your panels in less than ideal sunlight.
Consider a LiFePO4 12V pack rather than Lead Acid if you want long life and can afford it.
Lots of useful threads in BLF.
I use this for a very good solar compatible usb power bank/18650 charger. it also works as a UPS a rare feature. which means you can solar charge batt and leave usb device pluged in. it will power the device from the solar and charge the 18650 cell too. if the solar/source is disconnected/too low it will use its batt to power usb device connected automaticly. like a pc computer power supply. fancy and very useful feature to have. unlike nice anker usb power banks that will only charge and not power devices while charging.
The more I think on the OP question, I would generally move into 18650 direction for a very simple reason - on battery 18650 holds much more energy than AA and still needs one slot for charging, so with a Tomo/other DYI powerbank or Lii-402 you can leave 4 batteries and 1-2 other devices to charge from a single solar charger. Same is valid for 26650, it is a matter if one has enough devices with one or the other battery type.
Below is a video how 2 Tomo models and 1 Xiaomi battery go along with the solar charger as UPS and what the device afterwards sees from them. Sorry for the sound level (low) and also I have made initially a mistake with the setup of the battery - I cannot connect directly the meter to it, as the ports are very close, so had to be creative
Models are :
- Tomo S4 - In: micro USB, USB-C or Apple, out: 2xUSB 2A+1A, contains up to 4 18650 batteries
- Tomo 26650 - In: Micro USB and USB-C, out: 2xUSB 2A+1A, contains up to 2 26650 batteries
- Xiaomi PLM03ZM - In: USB-C, out: USB 2A, 10000 mAh
I also tested Xiaomi PLM09ZM - in micro USB, out 2xUSB, but on the “blackout” it also resets its out port, so the next device is also experiancing restart, not really UPS feature.
I used Blitzwolf ampcore cables, so no big resistances coming from there.
re lead vs lithium
from when i have researched costs, my conclusion was that one is better off with li-ion than lead, around the same price, wieghs a lot less. hmm maybe similar amount of cycle life, i forget details…
note that with lead a 20ah batt is not 20ah cus you can only use was it something(? check, i forget) like 60% of its capacity if you want it to last for rated cycles. so in reality then a 20ah lead acid batt is 12ah of real power.
with li-ion you can make it last more than 500cycles by not fully charging it to 4.2v. 4v end charge voltage is used by http://electrodacus.com/ for a compromised between capacity and extra longer life.
I used ££ lifepo cus its easy to get large cells, I don’t have to worry about trying to balacne a dozzen little 18650 li-ion
arr whats the point, why am writing such tech detail when its not relevant to your question. you dont want to diy make your own large pack and thats ok, im just responding to others…
well ive written it, so ill post it, maybe this is of help to someone.
basicly if you have been put off my prices you have seen of li-ion or lifepo4, then search harder. there are a lot of over price shops/sellers. search aliexpress,banggood, gearbest or https://eu.nkon.nl/ for real prices.
ready made products come at a premium. thats what your paying for. all the extra features or the fancy drill pack case and the fact that its a batt pack for drills. drill packs are quite over priced.
I first tried a xtar MC1 Plus and I found it didnt like working with my solar panel
I ended up trying a Olight magnetic charger and it worked very well