Equipped To Survive Equipped To Survive® Presents
The Survival Forum
Where do you want to go on ETS?

Topic Options
#292488 - 06/13/19 06:11 PM Cell phones & Other Electronics
hikermor Offline
Geezer in Chief

Registered: 08/26/06
Posts: 6853
Loc: southern Cal
Russ posted OT in another thread about his evaluation of backpackable solar panels and their utility in keeping a cellphone running. This probably deserves a thread of its own.

Cells, especially the smarter variety, are becoming ubiquitous and increasingly useful, so that providing power for them is more and more important. Other items, like headlamps, GPS and radios, also need juice. What else? What is the most compact and portable rig?

If a vehicle is involved, usually plenty of juice is available. If not, one is probably dependent on solar power, at least until they turn the lights back on.

I have a couple of Goal Zero solar panels and about four of their lanterns which can function as power banks as well. Apparently the GZ panels do not do all that well in comparison with other brands. I will be very interested in Russ's conclusions when he finishes testing.

Gotta keep them electrons in the corral!!
Geezer in Chief

#292489 - 06/13/19 07:00 PM Re: Cell phones & Other Electronics [Re: hikermor]
Russ Offline

Registered: 06/02/06
Posts: 5097
Okay, I raised the topic in the other thread, my subconscious mind was probably anxious to get the info out there. So here is what I have so far. This is a sample of the backpackable solar panels available on Amazon.com, there are others I donít have so didnít test. Since I didnít test every panel available (and there are a lot of them) Iíve decided to simply remove the brand names from some of the panels because theyíre pretty much generic panels and there are many very similar.

Itís one thing to say a solar panel can charge a phone (all the panels tested can charge a phone which only need <5 watts); itís another to quantify power output in raw volts, amperes and watts (ie., power) terms.††So I decided to test that.

Watts in a name? The other thing I was curious about was the wattage number in every panelís model name. What does that number represent? As far as I can determine, itís the max theoretical wattage of the solar cells, not to be confused with the entire systemís output.

Without further ado:
Renogy 21W ó Output = 14.3 watts
USB X: 4.96 volts, 1.03 amps = 5.1088 watts; and USB D: 4.91 volts, 1.87 amps = 9.1817 watts. Total 14.3 watts
One USB port into both power banks: 4.91 volts & 2.88 amps = 14.1408 watts.

XXX 16W ó Output = 8.4 watts
USB X: 4.72 volts, .91 amps = 4.2952 watts; and USB D: 4.74 volts, .86 amps = 4.0764 watts. Total watts 8.3716
One USB port into both power banks: 4.74 volts, 1.54 amps = 7.2996 watts

YYY 14W ó Output = 8.5 watts
USB X: = 4.74 volts, .84 amps = 3.9816 watts; and USB D: 4.72 volts, .96 amps = 4.5312 watts. Total 8.5128 watts
One USB port into both power banks: 4.79 volts, 1.77 amps = 8.4783 watts

ZZZ 10W ó Output = 6.1 watts
USB X: = 4.67 volts, .50 amps = 2.335 watts; and USB D: 4.70 volts, .80 amps = 3.76 watts. Total 6.095 watts
One USB port into one power bank: 4.97 volts, 1.04 amps = 5.1688 watts

Goal Zero Nomad 7 ó Output = 4.6 watts
USB out: 4.73 volt, .98 amps = 4.6354 watts

Renogy E.Flex5 ó Output = 4.1 watts
USB out: 4.71 volt, .88 amps = 4.1448 watts

A couple comments:
I didnít test any of the panels for durability/ruggedness.

One of my original panels functioned much worse than the others (percentage output) and that company sent me a new one, no charge at all and it was immediately apparent that it was a newer model. The solar cell configuration was different and the power out was 2.5x the original.

In general the panels with Sunpower cells did better, but since I didnít test them all, that may be an incorrect perception.

The Goal Zero Nomad I tested is a few years old and it seems really well built. I only tested the 5V USB port, I have no use for its 15V(?) port and no way to test it.

I liked both of the Renogy units. The Renogy 21W had the highest raw output and one of the highest by percentage. The Renogy E.Flex5 seems to be a very solid product. Itís small enough that it doesnít need to fold so no moving parts, itís rigid and that probably contributed to its efficiency.

#292492 - 06/13/19 08:17 PM Re: Cell phones & Other Electronics [Re: hikermor]
Russ Offline

Registered: 06/02/06
Posts: 5097
Besides backpacking, another reason to have one of the backpackable solar panels is for emergency power following a natural disaster ó hurricane, earthquake, et al. The primary threat here is the recent earthquake swarm just east of LA near Fontana, CA.

After the testing I did on small (21W and less) panels, I bought a 100 watt panel and a 10 Amp 12V/24V Solar Charge Controller. The system would primarily be used to keep a Goal Zero Yeti 400 charged, keeping it available to recharge batteries, lights, radios, cell phones...

A lot of homes in my neighborhood have solar panels on their roofs connected to the electric grid. In the event of a wide spread power outage where the grid is down, all those solar panels are essentially useless. Mine is off-grid and independent of other system failures.

FWIW, $.02 and all the other disclaimers.

#292493 - 06/13/19 08:41 PM Re: Cell phones & Other Electronics [Re: Russ]
hikermor Offline
Geezer in Chief

Registered: 08/26/06
Posts: 6853
Loc: southern Cal
Is thee an way those panel could be easily switched to an independent battery system. It certainly is worthwhile to be able to achieve independence rom the grid...
Geezer in Chief

#292494 - 06/13/19 09:50 PM Re: Cell phones & Other Electronics [Re: hikermor]
Russ Offline

Registered: 06/02/06
Posts: 5097
Donít know, not sure. Looking at my neighborís set-up, the panels are wired into a panel which hooks it to the grid. I see no way of taking it off-grid without dismantling parts of it. Iím not sure how their contract reads, Iím not sure they really ďownĒ the panels. You donít know what you donít know.

That said, there are optional battery systems that could be installed so the panels could still be useful during a grid outage. But that optional battery installation comes at a price ($$) and you need a place to install the battery bank. Most people who have these systems installed do it to save money on their monthly electric bill. Paying more out of pocket to have electricity when the grid shuts down is not part of the plan.

Eventually Iíd like to get a system big enough to keep the refrigerator running during a power outage. That alone would be huge, no need to power everything.

#292495 - 06/14/19 02:08 AM Re: Cell phones & Other Electronics [Re: hikermor]
AKSAR Offline
Old Hand

Registered: 08/31/11
Posts: 1134
Loc: Alaska
Outdoor Gear Lab ran some tests of solar panels: The Best Portable Solar Panels and Chargers of 2019. Goal Zero did not come out all that high in their rankings.

I'm not all that knowledgable on solar panels. I don't always care for Outdoor Gear Lab's methodology and conclusions, however on some things they get it right. I'd be curious to see how Russ's conclusions compare with theirs?

I know some folks with remote cabins, who have extensive solar set ups. Some of them run large items like freezers, etc, but they all seem to supplement their solar power with generators, for times when either demand on the system is high, or solar output is low (like in winter).
"Toto, I've a feeling we're not in Kansas any more."
-Dorothy, in The Wizard of Oz

#292497 - 06/14/19 06:59 PM Re: Cell phones & Other Electronics [Re: AKSAR]
Russ Offline

Registered: 06/02/06
Posts: 5097
Overall, I liked Outdoor Gear Labís Solar Panel test. OGL tested a lot more panels than I did and they looked at more attributes of those panels. They tested for things like durability and ruggedness so I wouldnít have to. IIRC OGL did their testing in an area of the desert SW that has better sun than SOCAL.

My goal was to take a small sample of panels and see how much actual power they made available through their respective USB ports measured in watts. Compare that output with the number in the panelís name and see if it matched ó in general, none were close. Iím not going to say which of my panelís is best or even rank them, they all have their place. If I had to choose one, it would be the 21 watt panel simply for the power output under less than ideal conditions.

Testing was conducted using a pair of USB multimeters and a pair of Anker PowerCore 10000mAh power banks. I had both power banks at ~ <50% power. Then I read out the volts and amps from the multimeters. Since I intend to use the panels to charge a power bank while I have sun available this seemed like a valid testing method. Keeping the power bank(s) charged means you have power when you need it, even at night when the panels donít work.

My only conclusion is that the watts in a panelís name do not reflect the power output on a nice sunny SOCAL day at noon; in all cases the actual output was something less than their names implied. Clouds and low sun angle will further reduce the output. Thatís the main reason the Renogy 21W came out well for me; it has enough reserve power output to charge a cellphone under less than ideal conditions. Donít buy a 10 watt panel thinking you can get 2 amps out of its USB ports to charge your tablet, youíll be disappointed.

One other point that applies to all the panels except the Renogy E.Flex5. In my opinion, in ideal conditions multiple USB output ports are nice to have if you need to charge multiple devices, but how often does that happen and does the panel have the total output to charge two cellphones in a timely manner? Iíd much rather have a panel with streamlined electronics to reduce the power loss that comes from splitting the power between multiple ports. None of these panels has a lot of power to start with and itís too bad they chose to squander it on multiple ports. OTOH, the Renogy E.Flex5 has a single USB port and itís fairly rigid ó no moving parts. It had the highest efficiency (percent output/watts in the name) of the panels I tested; still, it starts out small and the power out was limited to only 4.1 watts.

Along this line of thinking, one of my tests looked at the difference between charging devices using both ports versus charging using one port with the second port empty (thanks to haertig for this suggestion). When both of my power-banks drew power from the same port, the total output was slightly reduced from when both ports were used. So while one USB port had no current running through it, the other USB port had a significant increase, but the total output dropped ó not a lot, but it did drop. This was one data point that led me to think there may be some efficiency to be gained in the electronics, probably at the expense of marketing (thinking 2 ports is better than 1 for sales)...

Note: Of the dual USB port panels, one has a pair of single USB ports on pigtails, while the others have a single dual USB port fixed to the panel usually in an enclosure (pocket). Itís nice to pull a USB port out of the panelís pocket and hook it up, but the price is power. The dual USB port systems seemed to be more efficient than the 2x single USB port system; the dual port systems seem to split the power more efficiently between the 2 outputs.

#292501 - 06/16/19 06:36 PM Re: Cell phones & Other Electronics [Re: hikermor]
teacher Offline
Old Hand

Registered: 12/14/05
Posts: 751
I also recommend a variety of small, inexpensive batteries; everything from salt shaker sized to fat book sized.

#292513 - 06/19/19 04:28 AM Re: Cell phones & Other Electronics [Re: hikermor]
Burncycle Offline

Registered: 09/16/04
Posts: 525
My 28W Bigblue was only able to manage 15-17 W under the best conditions in my area, but I expected that going in


Moderator:  Alan_Romania, Blast, cliff, Hikin_Jim 
Su M Tu W Th F Sa
1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30 31
Who's Online
0 registered (), 214 Guests and 3 Spiders online.
Key: Admin, Global Mod, Mod
Newest Members
NickChurick, Willie, Pierdolec89, willpo, Mollerstrom
5287 Registered Users
Newest Posts
Remains of actor found in remote area
by Phaedrus
Today at 04:10 AM
A very humbling 'survival' experience!
by Phaedrus
07/14/19 09:05 PM
New Orleans flooding / T.S. Barry
by wildman800
07/13/19 04:43 PM
Potassium Permanganate Crystals
by Phaedrus
07/13/19 06:30 AM
Extended gaucho knot tutorial - zipper pull, key
by TonyE
07/13/19 04:15 AM
How do you update your first aid kit?
by Ren
07/11/19 05:36 PM
2 strand gaucho knot tutorial
by Phaedrus
07/11/19 06:16 AM
fanny pack sized kit
by teacher
07/10/19 05:18 PM
Newest Images
Tiny knife / wrench
Handmade knives
2"x2" Glass Signal Mirror, Retroreflective Mesh
Trade School Tool Kit
My Pocket Kit

WARNING & DISCLAIMER: SELECT AND USE OUTDOORS AND SURVIVAL EQUIPMENT, SUPPLIES AND TECHNIQUES AT YOUR OWN RISK. Information posted on this forum is not reviewed for accuracy and may not be reliable, use at your own risk. Please review the full WARNING & DISCLAIMER about information on this site.