Is charger suitable for solar panels?

Sometimes I am asked if a charger is suitable for solar panes and until now my only advice has been to get a simple charger, they are more likely to work with a solar panel.

But this do not say everything, another parameter is if the charger locks up when voltage dips (Brown out) and it is possible to test for that.
I did a script for my test station that will reduce voltage a variable bit, then restore to full voltage to see if the charger still works.

It looks like this, it is a bit hard to read.

Using the data to draw a more simple curve it is much easier to see that this charger locks up when the voltage dips below 4.50V (Current = 0) and it will only reset if the voltage gets down to 2.0V. It do not change charge current but stays at the same current in all cases.

A charger that is good for solar usage would not have any brown out problems, but would always recover.

Are there any comments to this? Ideas to improvements? Ideas for a better title on the chart?

Much appreciated. I know at least a couple people who always want to know how a charger/powerbank functions with solar panels.

I have a solar setup for my chicken coops. It has a large farm battery also. Hooking up my Lii-500 with the car 12v adapter should juice up whatever li-ion I need.

I think I’m on the same page as you all, except mine has a large 12v battery. :smiley:

As long as you have a battery between the panel and the charger, there will not be any problems.

The problem is when the solar output drops some, but not fully, then the charger can lock up until the panel voltage goes very low.

Thanks for taking this problem into consideration.

We expect to lose grid power maybe for weeks after the big earthquake happens, and setting up for that needs the kind of help you’re offering.

I am interested in this type of testing. Look forward to your results.

I have hoped for you to do this for years now. I am a huge solar nerd and would love to have just the type of info you describe

Is it only relevant for 5V or do you also need it for 12V? I would generally expect that when using 12V a battery is included to buffer the solar panel.

Indeed 12 with a battery buffer is actually rather easy. I was hoping for 5 volt as I would like to try a setup using 6 volt panels for portability. These panels are readily available locally for fence chargers. I do not know if 6 volt would be too much for the chargers and I am not sure which charger would restart on its own after intermittent panel blockage. Really any info you care to share will be greatly anticpated and appreciated

I have been improving a bit on the curves today, including fixing a bug and added more samples.

Maybe using lines are better now:

But when the two curves overlap it is difficult to see (I cheated with the dots, one curve has a 0.02V offset).

Interested in these tests! Occupying the front row seats… :slight_smile:

Is there a ‘timeout’ time wherein the USB-powered charger will not recover? Or is it only due to drop in voltage? Possible to test that?

(Have some questions, let’s say when a small cloud passes by, the solar USB charger dips to 3.5v for a short few seconds, but quickly goes back up to regular 5v, will the charger recover? what if the (just as an example) 3.5v stayed for a longer time, like 1 minute, then maybe some chargers may recover but some may not? Does it work like that?)

In particular:

I would like to see the “solar charger simulation test” for these popular USB-powered chargers:
Lii-100, Lii-S1, Lii-202, Lii-S2, Lii-402, Lii-S4, Olight UC magnetic charger, Folomov A1 magnetic charger, Nitecore F1 charger, Opus BT-C100, other simple single-slot chargers like maybe those from Xtar…)

From other videos and some reading from the Internet, the Liitokala USB-powered chargers typically will not recover when USB voltage dips.
Based on my readings from the Internet, the Olight UC charger, Folomov A1, Nitecore F1 seems to work properly, but more controlled testing would be nice…

There may be time involved, but it will be charger dependent. I have selected to do a fairly slow test, letting the voltage drop over 40 seconds, stay down in 20 seconds, the restore full voltage for 40 seconds. This is slow enough that even slow chargers has time to recover.

It may even be more likely it locks up due to a short dip, it depends on the circuit in the charger.

I will check a few old chargers, but it is mostly for new tests. The charger I am used for the test above is the Lii-402

Another charger:

This looks fine for use with solar panels, the charger current will drop with voltage and then resume when voltage increases again.
The actual levels the voltage will drop at depends on the charge condition of the battery, for this test I started with an empty battery.

I prefer the dots for the graphic.

The above charger did fine for LiIon, but NiMH is another story, I had to modify my script to include it on the curve. During testing I noticed some noise (Full load hum) from my power supply, this is not supposed to happen with a USB charger. I modified the test to include maximum input current, but will only include it in the curves is there is problems, like here:

It looks like the charger has opened fully for the charge circuit due to the low voltage and is slow to turn the current down again. If there is enough current available it will probably destroy the charger (Not likely with a small solar panel). With the hole in the red line of dots, the charger is not suitable for solar panel usage when charging NiMH.

I see. Solar charger testing does seems like complicated to test for. Really appreciate your designing and doing the tests! Eagerly awaiting test results…

I hope you’ll make this a new column on your chart.

> If there is enough current available it will probably destroy the charger (Not likely with a small solar panel)

Are you using a charge controller between solar panel and charger?
This sort of thing:

I think that would be routine for anyone using a home-sized PV panel source to charge a home battery system.

I know that’s saved me from cooking batteries a few times.

I have done that now, but it will first be available with my next upload, i.e. next charger review.
The column will only be visible when selecting usb powered chargers.

The test here is for chargers that run directly on a solar panel with 5V output, how this output is made do not matter much. Exception being a output that always turn power completely off when the voltage drops (or recovers), they will not have this brown-out issue.

1 Thank

I have updated a few reviews with the information and added it to my main selection list as “Solar”, but only for “USB power input” selection.

1 Thank