Solar Power Bank and Librem 5

After my brief experiment with a lower-spec’ed solar power bank, I decided to buy this ToughTested Solar ROC16 16,000 mAh with PD Power Delivery model and test it over several days.

Results follow.

Day 1

  • I connected the newly purchased power bank to an electric outlet and charged to full, in accordance with the instructions. Then I disconnected it from the outlet and left it exposed to fairly direct sunlight at a window.

  • (1st Charge) I connected the powered-on Librem 5 to the power bank using the L5’s cable (USB-C to USB-C). The L5’s charging light illuminated, and the phone started charging.

  • I left the L5 powered on and connected to wifi only, with no other applications running.

  • From a starting charge level of 41%, the L5 reached 99% in 3 hours, at which point I disconnected it and allowed it to drain over several hours to 41% again.

  • (2nd Charge) I connected the powered-on L5 to the power bank again (still next to the sunny window, no electrical connection), this time with only the mobile network connection running, and it again charged to 99% in 3 hours.

Day 2

  • (3rd Charge) Connected L5, mobile network enabled, wifi disabled.
purism@pureos:~$ cat /sys/class/power_supply/tps6598x-source-psy-0-003f/uevent

Start level: 41%
After 1 hour: 73%
After 1 hour, 16 minutes: 80%
After 1 hour, ~52 minutes: charging stopped (apparently no juice left), ~86%

purism@pureos:~$ cat /sys/class/power_supply/tps6598x-source-psy-0-003f/uevent

So that was 3 acceptable, adequate charges from the unplugged power bank, presumably from just the stored energy added during the original electrical outlet charging. The power bank had about 6 hours of constant, bright sun exposure on Day 1, but conditions over these first 4 hours on Day 2 were gray and overcast.

Day 3

  • I charged the power bank overnight to full (via electrical outlet)
  • drained the Librem 5 during the morning
  • then connected the L5, powered off, and started charging until the LED was extinguished
  • disconnected and powered on

(1st charge:)
Starting charge level: 25%
Ending charge level: 99%
Time elapsed: 3 hours, 40 minutes

After charging, the power bank’s remaining charge was at 3 out of 4 LEDs.

(Are those graphs helpful? I don’t know.)

Day 4

(1st charge:)
Libem 5 powered on, mobile network and bluetooth active. (Bluetooth not linked with any other devices.) Wifi off.

Librem 5:
Starting charge level: 40%
Ending charge level: 99%
Time elapsed: 3 hours, 5 minutes (charging stopped by me)

Power Bank:
Charge level start: 3 blue LEDs out of 4 (left over from Day 3)
Charge level end: 1 blue LED out of 4

Temperature readings at 99% charge:

(2nd charge:)
As the power bank’s LEDs were down to just one illuminated, I took the opportunity to let it accumulate some solar energy, although it probably still has residual power from the last plug-in charge.

Power bank
Solar charge time: 6 hours, indoors (3 in bright sunlight, 3 in ambient sunlight, positioned in or near a window

Librem 5
Charge level start: 35%

purism@pureos:~$ cat /sys/class/power_supply/tps6598x-source-psy-0-003f/uevent

Then I powered down the phone and continued charging.

The phone’s charging LED extinguished after 1 hour.

Charge level end: 70%

So, less effective charging than on Day 1.


(…to be continued…)


Does the powerbank give an indication of its own charge level and/or whether it is fully charged? e.g. LED?

How long does it take to charge the powerbank from empty to full using only the solar panel? My guess would be > 2 days of sun - so you may not have the patience for that test. :wink:

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Yes. I checked the manual after the fact. Pressing the power button twice illuminates blue LEDs. A display of only one blue LED (out of 4) indicates depletion, and the necessity of recharging the unit. (I confirmed it was depleted after I wrote “apparently no juice left.”) The unit turns itself off when depleted.

The manual reads:

  • Solar charging is best used for emergency purposes only.
  • 5 hours solar charging will provide enough power to charge a smartphone about 30%.

(Unclear if the power bank can accumulate a greater charge after a longer period of sun exposure.)

I’ll be testing solar replenishment soon, and then see how well it can charge the L5.

The user guide is available online at the product link, if anybody is interested. It’s fairly minimal, though.


There’s also a higher capacity unit, by the way: Solar Chargers

About double the price, though. The one I bought was US$56 on sale.


I got one of those about 5 years ago, about the same time I ordered my L5 but order to delivery time was less than a week. It didn’t last more than a year. It cost 15 bucks. Different brand, but with the same casing, right down to the orange trim. My guess it comes out of the same chinese factory with a steady whomp, whomp, whomp that makes chinese army messkits.

Althought when it worked, the best place for it was on my vehicle’s dashboard, in the Sun of course.


The manual for mine says:

“Note on solar charging: Avoid prolonged exposure to heat as it may damage the battery, do not place on a car dashboard or other surfaces that can become hot to the touch.”

Did it have a name similar to, say, “NCEHGVBOWWQPSE?” :rofl:

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Ach, I should have read the manual!

Should I to mount a heat sink on my dashboard? Or maybe that’s what the little loop on one corner is for, to hang if from my rear view mirror?

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I think it’s probably OK to frequently expose it to sunlight, but probably not good to let it bake in the sun on a hot dash full-time. If the car’s interior is going to be extremely hot, maybe take the unit inside or shade it appropriately.

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I noticed that too.

I think what they are trying to say is:

Don’t leave it on the car dashboard on a sunny day in an unattended car or put it on the dashboard immediately after getting into the car on a sunny day.

If you yourself are in the car and the temperatures in the car have come down to “reasonable” then it should be fine to charge it on the dashboard.

But then when in my car and driving I just charge using the in-car charger connected to the “cigarette lighter”.


Day 4: results not great. See OP.

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I’m wondering whether it would be better “design” to decouple power generation (the PV panel) from power storage (the powerbank). Since the powerbank can be charged by any suitable USB-C input (unclear specifications) or a microUSB input (unclear specifications) … what if you could get a more potent PV panel setup just to generate USB power?

The model that you have talks about “280mA fast recharging solar panel” but that is actually horrendously slow, and must be much slower than what is being negotiated when you charge the powerbank from the mains.

The current design inherently limits the size of the panel to relate to the size of the powerbank.

The relevance of these comments depends on whether the powerbank itself is the more important aspect to you or whether the solar charging is the more important aspect.