64 w solar panel without a charge controller or battries but using a buck converter for direct regulated power?possible?

Greetings and thanks in advance for all the help.
i shall start with explaining the situation. 
i am going to be in the remote himalayas for about 2 months with a expedition team and for all our charging needs  we are going to carry a few solar panels, most of them are small 5-15 watt ones .
the problem comes in when i introduced the 64 w thin film roll able panel.
the specifications for the panel are as follows
Model PVL-64
Rated Power 64 (Watts)
Rated Voltage 16.5 (Vmp)
Rated Current 3.9 (Imp)
Open Circuit Voltage 23.8 (Voc)
Short Circuit Current 4.8 (Isc)

i intend  to use 3 LM2596 ebay buck converters to get 12 volts and 2 5V USB Output Converter DC 7V-24V To 5V 3A Step-Down Buck KIS3R33S Module KIS-3R33S for usb power.

All of these will have a common source of power (the solar panel) and have separate outputs as i need to charge multiple things at once.
 will this setup work or i need to think of something else.?

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Well the panel will already be putting out 12V with a load on it. So no
need to use buck converters to get it to 12V. But yes you can connect
those items to the panel for charging.

You do realize the panel your looking at is a 9 foot by 15 inch wide role that weighs almost 9 lbs.


Your talking something that is going to take up as much space as a moderatly priced 40 degree sleeping bag and weighs 4 times more. If you try cutting it down then the panels ability to produce the rated power drops considerably. This is not something you'll want to have on your pack. You'll want to stick with the small pack panels for your trip. This this is designed for roof applications not packing.

1st rover (author)  mpilchfamily2 years ago

1) actually the panel put out around 16.5 volts and that would fry my chargers. thats why the buck converters to get a stable voltage.

2)yes i do realise that this is a 9 foot long and is only to be used at the base camp to charge the power banks and other electronics.

this will be carried in by porters/ sherpas/mules/horses or yaks and will only be deployed at the basecamp.

If it has no load and you test it with a meter yes it will put out
16.5V. That is the open voltage with no current draw. As soon as you
have a device on it drawing current it will only be putting out about 12V under full sun.

Yeah sorry but most solar panels that are designed for Real "Off Grid" work will output a good 16.5v if not higher. Smaller panels and ones designed for Trickle Charging will have a more reasonable Voltage cap.

Btw Rover, This might be a good page for you to read over !

No, the RATED voltage is 16.5 V The OC voltage is 24. The rated current is ~4A

I'd find a higher rated buck regulator, and save weight and size. I'd also want a reputable supplier, because this could be a life saving decision.


If size and weight is the primary concern check "Kraftwerk".
It is a "generator" that uses a fuel cell, but unlike normal ones, this runs on normal lighter gas refills.
Like your lighter you fill it up and have enough energy to charge for several hours.
The gas canisters are quite light in weight and with two or three Kraftwerk chargers you should be good to go.
The amount of gas you will need depends on the usage, so a preliminary check and calcluation would be advisable.

Is it already on the market?

It is, the Kickstarter was a success.

For 149 bucks one of the best products in this area I have seen.
Still pricey but considering it runs on butane or propane gas instead of hydrogen and the tiny size make it perfect for things like an expedition.
I think if the author offers to take some nice shots in the mountains for product placements, together with a review they would even sponsor a few devices.

Not according to their website it isn't. "To be delivered February 2016"

Sorry, my bad!
I only followed their progress on the project and it seems I was only focussed on the sale date missing the delay in the delivery time.
Still might be worth contacting them for a prototype or two to test out, you never know.
Just thought it would be the perfect addition in terms of size and weight.

Try this: Its a PSU from MeanWell, who make some reliable kit. Its rated at 60W out of the box, it runs from 9-18V input, so we need to do some input monitoring which is straightforward enough.

fmarquis2 years ago

Weight is your primary concern and I understand you want to drop as much dead weight as possible. To answer your question, it should work. But you have to consider a few things : You will have the panels on your back while bucking, so the orientation to the sun will vary and will be less than optimal, so don't expect to get too much amps and to charge 7 devices at the same time. To address the fluctuations in lighting, I would strongly consider adding a few supercapacitors or hybrid ones on the pannel side to make sure all the power,even through brief illumination, is available for charging.

Also, you will need to protect those circuits. None of them will survive a trek being exposed the way they are!

Hope that helped!

1st rover (author)  fmarquis2 years ago

you got that right weight is my primary concern and that is why i asked the question or else i would have carried it along with a charge controller and a heavy battery .

but i wont be carrying this on my back while packing /hiking in

this will be carried in by porters/ sherpas/mules/horses or yaks and will only be deployed at the basecamp.

Well, you still consider the capacitors as they are light. You don't need tons of capacitance, just enough to smooth the charging. You can 3d print enclosures for the small boards.

And take some time to test your package before leaving, under different lighting conditions, just to be sure it will work as intended.

And btw, I happen to have colleagues who climbed the Everest, and ton encourage as much sherpas as possible, they requested to have a table and four chairs to be carried along. So, if you are not on a tight budget, maybe the lead batteries are not such a bad idea!