Solar panel to battery charger

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Solar panel to battery charger

As I was camping last week, I found that having all the family out with me for more than 2 days, devices start to die. Usually, we’re at a spot with power, but this time we were not.

I have 5 flashlights using 18650, cell phones and kindles and flashlights that charge off USB, and a few headlamps with AAA eneloops (we’ll leave those for now).

I would like to dip my toe in to solar, and I’m not clear what goes between the panel and any of those things,

I did a search here, but came up with 2018 and before threads, so assume recommended gear has changed.

I have an Xtar WP2H. It charges 2 18650s to my satisfaction. It has a USB out. It wants 12v in. Can I just put the correct barrel on any dumb solar panel, and start charging 18650s and my USB powerbank? If not, is there a cheap (under $15) thing I would wire between the two? I understand some panels and some chargers basically shut down if the voltage drops too low.

For all the USB stuff I see a thing called a wide voltage usb regulator, for $10 ish, which appears to convert 12v to 5v with a USB port. So I could wire that to the solar panel. If that’s the way I go, then I would have to buy a new charger for the 18650s (xtar x4 seems to accept usb in, feed usb out, and looks like it would charge the AAAs as well). WP2H would stay home.

ChrisGarrett's picture
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Joined: 02/12/2014 - 22:03
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Location: Miami, Florida

If your stuff is 5vdc USB, then stay in that format and get a good power bank that allows you to interchange cells, like my older Tomo V8, or my newer Xtar PB2S (21700, 20700, or 18650 only.)

Charge that during the day with your solar panel and than charge your stuff during the night. Carry a few pair of 21700s and charge them when needed.

12vdc systems need a digital charge controller if the panels are 20w or greater, so while they’ll provide more power, they’re also more cumbersome to employ in the field.

I just got a 28w USD Blue Sky USB panel for just under $100 and it gets very good marks on the survival/camping sites.


Last seen: 4 hours 20 min ago
Joined: 06/14/2012 - 13:48
Posts: 629
Location: Virginia

Welcome to the forum.

One thing I would recommend (which doesn’t answer your question) is to test out whatever you buy in partly cloudy and overcast conditions. Thats when thing get interesting.

You probably want to put your solar panel (whatever you get) and some kind of battery (probably a usb power bank) in the sun to charge all day, then you can use the power bank to charge your devices at night.

TimMc's picture
Last seen: 21 hours 36 min ago
Joined: 06/26/2020 - 02:22
Posts: 536
Location: Melbourne, Australia

I got an XTAR ANT MC1 Plus charger with the hope that it’ll be more resilient to dips in power coming from a portable solar panel and not suddenly stop working. There are a few YouTube videos… I need to get around to buying some solar panels. Silly

Interested to see some recommendations.

Last seen: 5 months 2 days ago
Joined: 10/26/2020 - 20:34
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Location: upstate NY

I think it would be cheaper to buy a USB-powered charger than to buy the solar charge controller that would be necessary to use to get the proper output for your 12V charger.  My charge controller cost half as much as the solar panel.


I use a Bioenno 28W foldable panel, a 12V 9ah LiFePO4 battery and their solar charge controller suitable for LiFePO4 batteries.

Last seen: 4 months 2 weeks ago
Joined: 12/17/2017 - 21:16
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Location: United States

Thanks for the replies

Last seen: 14 hours 35 min ago
Joined: 12/05/2012 - 13:35
Posts: 34
Location: Hudson Valley, NY

“5 flashlights using 18650, cell phones and kindles and flashlights that charge off USB, and a few headlamps”

That’s a lot of stuff to charge, even if only half of them a day.

You can’t connect a solar panel directly. There has to be a controller in between, either separate or internal to the solar panel.
When I camp off grid, I use a deep cycle battery, power inverter, phone and 18650 chargers and charge the battery with solar panel.
The solar panel charges the battery during the day while we’re out and about.

I upgraded to this panel the other day because it was 50% off. I haven’t used it yet, but it appears to have every thing you need.
There’s probably something similar around for Black Friday or other holiday sale.

I just ordered this too to eliminate all the clutter and have it in one package.

Good Luck

Corey Webb
Last seen: 6 months 2 weeks ago
Joined: 04/13/2020 - 08:15
Posts: 11
Location: "2167 West Virginia Avenue Albany, NY 12204"

I’m using SOLPERK 20W solar panel charger. They work quite well.


wle's picture
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Joined: 01/07/2015 - 13:49
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Location: atlanta ga

the kindle(s) would be the big problem
then cell phones

a panel 1 foot square in full sun collects 100 watts
panel is 15% efficient
15 watts

sun is out for 4 hours
60 watt hours

charge[power bank] and discharge[power bank] then charge again (devices) maybe 40% efficient
24 watt hours

that is 2 flashlights at full charge
or 2 cell phones

kindles might need 25 watt hours each for full charge
a cell phone 10
flashlight 5-10

now assume the day is cloudy
output is cut by 75%
you see the problem

you may end up with 25 square feet of panels
not something you can really hike with

also charging another cell type like eneloop or nimh just adds more equipment for not much energy storage capacity
consider converting to all li-ion


"You never have the wind with you - it's either against you, or you're having a good day."
    Daniel Behrman, "The Man Who Loved Bicycles".
It never gets easy, you just go faster.   
-Greg Lemond.

xtarflashlight's picture
Last seen: 6 hours 23 min ago
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Location: Shenzhen

Glad that you like our chargers! Thanks for your kind supports. Beer

lampliter's picture
Last seen: 2 days 12 hours ago
Joined: 07/31/2017 - 16:06
Posts: 303
Location: Paradise

I use this-
120 W panel
300 W power bank
Various USB hook-ups (see pics)
!P1210003 P1210004 P1210005 P1210006 P1210007!

It's only true if you believe it.

helicoil's picture
Last seen: 6 months 1 week ago
Joined: 06/29/2020 - 12:46
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Location: the Netherlands


I am testing these .... and the Yeti / GoalZero-Nomad 20W is allready way better than the Xtorm / WakaWaka 10W but that's also a bit to be expected .....


The Yeti / GoalZero-Nomad is more for camper / camping and the Xtorm / WakaWaka is more aimed at backpacking / cyling ...... 


The Fenix E28R was a free gift on Black Friday along with a 20% discount on the Yeti / GoalZero-Nomad combination ....


The Yeti in action .... a real multi-tasker ..... 2 x USB + 12V + 220V all at once ...... just enough to load all 4 ....





Last seen: 9 hours 59 min ago
Joined: 02/22/2020 - 14:27
Posts: 89
Location: idaho

Im off grid solar for 6 years now.

Whats needed no matter how big or small.

Solar panels
Charge controller
Battery for storage

How I do it

I have a big system 48v 120a

My Cc converts 60v coming in to amps/volts for batteries.

From 48v batteries i use 12v converter to give car aux sockets. That way i have 12v when needed. I plug auto adapters into 12v aux sockets.

From 12v aux sockets i run usb power panels. I can then charge all devices. I have over 10 usb slots.

Power draw varies

Laptop 3ah
8× 18650 charging 1ah
Tablet and 2 phones 1ah
Blf lanterns 1ah

Two ways to do it while camping.
Use cqr battery as bank or…
Bring external 40ah lipo 12v bank.

Car as bank
Lay foldable 100w panel on car roof
Use genasun mppt 12v charge controller
Clip leads to car battery
Buy anker usb power 12v aux strip
Plug anker strip into car aux.
Charge devices on car floor.

Use lipo 40ah 12v bank
Same as above but using external mobile battery pack.
Make sure your lipo bank has a bms.

Or use yeti and car aux to charge.
Much simpler. If needed bring foldable panel. Clouds and trees block solar.
Also can wire car aux to stay on even if no key in ign.

RandyGolden's picture
Last seen: 2 weeks 1 day ago
Joined: 05/29/2021 - 06:12
Posts: 7

Using solar panels as a charger for devices is a very convenient solution, especially if you go with tents on a small trip far from the city. It’s a great vacation, right? At the expense of solar panels, I can recommend you to look at the ones that I found at this link. I think you’ll have plenty to choose from.