Solar panel hook up to a power bank

Thread Starter

telerian

Joined Jul 19, 2010
57
Hi,

I have a 5000 mAh power bank that I need to charge using solar panel. The power bank is standard USB one, with micro USB charging port and I have 2 6V solar panels. Can I connect the 2 panels in parallel and connect them directly to the USB charging port or do I need charge controller ?
 

Dodgydave

Joined Jun 22, 2012
8,356
Most solar panels are connected all in parallel then fed into the charger, you can use diodes in series with each panel this prevents back feeding due to shadowing.
 

Thread Starter

telerian

Joined Jul 19, 2010
57
Most solar panels are connected all in parallel then fed into the charger, you can use diodes in series with each panel this prevents back feeding due to shadowing.
What about the 6V, would that be ok on the 5V USB charging port ?
 

Dodgydave

Joined Jun 22, 2012
8,356
Whats the spec on the usb charger say, if you want to drop some voltage put a diode in series with the solar panels.
 

Roderick Young

Joined Feb 22, 2015
408
A few thoughts.

When a small panel like that is advertised as 1 watt, it probably has far less output. It might be 1/10 watt.

If this was my experiment, I would put both panels in parallel, and also put a 100 uF capacitor in parallel. The capacitor is to supply surge currents, in the likely event that your power bank uses some sort of switching converter on its charger. Then I would hook it up. There are no guarantees when hooking something that is 6 volts to device designed to accept USB power, but my guess is that when the panels are hooked up, the voltage will drop, possibly to an unusably low voltage. If that happens, then you know that you need more or stronger panels.
 

Thread Starter

telerian

Joined Jul 19, 2010
57
A few thoughts.

When a small panel like that is advertised as 1 watt, it probably has far less output. It might be 1/10 watt.

If this was my experiment, I would put both panels in parallel, and also put a 100 uF capacitor in parallel. The capacitor is to supply surge currents, in the likely event that your power bank uses some sort of switching converter on its charger. Then I would hook it up. There are no guarantees when hooking something that is 6 volts to device designed to accept USB power, but my guess is that when the panels are hooked up, the voltage will drop, possibly to an unusably low voltage. If that happens, then you know that you need more or stronger panels.
What about this one ?
 

Roderick Young

Joined Feb 22, 2015
408
I have never ordered from AliExpress, but have a distrust of claims made by Chinese vendors. It says monocrystalline, but that's indistinguishable from a cheap amorphous panel in a picture. I use a 10 watts per square foot as a guideline to true power, but unfortunately, there is no dimension given. The hand in the picture gives an idea of scale, I suppose. When I look at a panel, I'm always suspicious when only a wattage is given - no open circuit voltage, no short circuit current, no CEC or PTC rating. The vendor can make up whatever number they like for the power.

Only way to know with such a thing is to get one and try it.
 
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