Portable Solar System

DDiamondDDiamond Registered Users Posts: 3
How is it possible to have a portable solar array ( for backpacking ) capable of powering a lithium ion battery which has an input power of 19v at 1.6A DC ? I have looked at different ways to regulate power from solar panels but they always use different batteries, not lithium ion ones. If there is a tool to regulate the power could someone give me a name of this product and if not how could I make my own? 
I would be happy to get better informed on this matter so any help would come in handy, thank you in advance.


  • BB.BB. Super Moderators, Administrators Posts: 28,315 admin
    Are you trying to recharge a laptop computer?

    Solar panels have highly variable output voltage and current.

    Most battery chargers are designed for relatively stable output voltage (ac or dc). Powering chargers that are not designed for solar input can be a nightmare. Unreliable, damages to changer and/or batteries, etc.

    Knowing more about your application may help us help you.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 4,781 ✭✭✭✭
    As Bill eluded to, it sounds like a laptop sized load. That said "input power of 19v at 1.6A DC" is very large when you are looking at carrying everything on your back. In direct sunlight you would be looking at a pretty good sized solar panel and they would pretty much need to be stationary to not be shaded on and off...

    2 possibilities might help, a very low power computer, like the Raspberry Pi's or a small screen tablet. or just use your phone....

    As to lithium storage and charging, most lithium power banks and jump boxes have their own regulators. So you could send somewhat close voltage to them they will regulate it to charge the batteries, and they will do it with what current you can send them.

    If you can get down to a 5v (USB) world, things become pretty easy. Most/many smaller tablets will run off USB power supply. There are many USB power banks to choose from and they make solar chargers just for these banks or 5volt devices like this one;

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • DDiamondDDiamond Registered Users Posts: 3
    Thank you for your replies,
    I want to power a laptop computer and a drone using this portable battery pack which is powered by a solar panel like this (or two if necessary) that I could connect together somehow and strap onto my backpack whilst hiking. 
    I know there are systems that provide what I need but they seem to be a bit more costly like the goal zero sherpa 100 which can be charged by a solar panel. The goal zero products are basically what I would want but I'm wondering if there is a cheaper way to do the same thing.



  • BB.BB. Super Moderators, Administrators Posts: 28,315 admin
    edited May 2018 #5
    A lot of planning for solar power included figuring out your [email protected] volts and or kWH per day.

    Going with an ac inverter+battery back to charge your laptop and drone, is not bad if fixed or vehicle mount. Back packing, it would be nice to drop the AC inverter (more loses, more weight).

    Starting with your power requirements and some basic math can tell you what is practical or not. I will make some guesses...

    Standard laptop = 30 Watts * 10 hours per day (running drone/editing videos/flight planning = 300 WH per day
    Phantom DJI Drone = 4,480 mAH battery * 15 volts * 23 minutes * 1/60 minutes per hour * 2 hours flight time per day = 52 WH per day
    Cell phone+WIFI HOT SPOT = 3,000 mAH * 4 volt battery per day (~5-10 hours of use per day) = 12 WH
    300 WH + 52 WH + 12 WH = 364 WH per day

    From my first guesstimate--Your Laptop could use 5x as much power as the rest of your backpack equipment (assuming a relatively
    powerful laptop running the whole time). A tablet may use 8 Watts, or a lower power laptop (or fast laptop set for conservation) may use 8-20 Watts.

    Say you are using this in/around Zurich. The amount of sun with a solar array pointing at the sun during the day would see around:

    Continue next post due to technical reasons....
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 28,315 admin

    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel where the angle is adjusted each month to get optimum sunlight.
    Jan Feb Mar Apr May Jun
    Jul Aug Sep Oct Nov Dec
    So, not a lot of sun... But let us guess that this is mostly a non-Winter project and you are  looking at 4 hours of sun per day (solar panels need to be in sun from at least 9:00 to 15:00 hours (9am to 3pm) at least to gather most of the solar energy available.

    The size of solar array needed to recharge this usage every (average) day would be:
    • 364 WH per day * 1/0.61 AC system eff with Li Ion battery bank * 1/4.0 hours per day =149 Watt array "break even"
    Your 100 Watt array is not exactly "oversized" for this mythical system, but it is in the ball park (baseball colloquialism).

    Of course, this means that your solar array+whatever you are charging (local battery pack, computer, etc.) needs to be pretty much fixed during most of the daylight hours.

    If you are going to charge a battery pack during the day, and your equipment at camp during the evening/night, then the battery pack needs to be >~364 WH to recharge your tools. Looking at your first link:

    • Includes Goal Zero Sherpa 100 power pack, Nomad 20 watt solar panel, and Sherpa Inverter
    • 100 watt bolt-on inverter included
    • Sherpa Power Packs

      Offered in a 50Wh and 100Wh battery capacity, with removable AC inverter, the Sherpa power packs provide reliable, portable power at the push of a button.

    The system with 100 Watt AC inverter (probably "big enough" for your needs--check laptop AC input typically around 60-70 Watts or so charging), but only a 20 Watt panel and the largest single pack of 100 WH for AC inverter... Neither is really large enough to support a multi-day expedition with solar only--Need to go "much larger".

    For the second link:
    AC Power Bank, NOVOO 20100mAh AC Outlet Laptop Portable Battery Pack Travel Charger output with two USB Ports 60w Output, 72.36Wh Universal Travel Charger for Macbook, Laptops, Tablets and Smartphones
    60 Watt AC inverter--Might be a bit small. The 72 WH integral battery bank really is only enough power for 2-3 hours of Laptop Only storage.

    If you wanted "significant" battery storage to recharge your equipment at night, then something like this (I know nothing about website or product--Just informational):

    Length 12.75"
    Width 6.5"
    Height 8.7"
    Weight 28 lbs.
    Type LiFePO4
    12 volts * 100 AH = 1,200 WH or ~3-4 days of stored energy and no need for solar panels (for short trips).

    LiFePO4 is a "safer" Li Ion chemistry... But if you will be taking this equipment on commercial aircraft, you will have to check the rules about shipping Li Ion (and other batteries)--Many are considered fire hazards).

    Using a Kill-a-Watt type meter for your AC loads, and a DC AH/WH meter for DC loads will help you better understand your energy needs (links below are informational only--lots of mfg/models available):


    I will stop here before I go to far off from your real needs with my guesses.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DDiamondDDiamond Registered Users Posts: 3

    Thank you very much for your help Bill,
    As you said my laptop would consume five times more power than the rest of my equipment so I think I will ditch that idea and just go with my drone and do the editing later so that I can maximise my flight time. As for the battery that would be ideal but I don't have a big budget so I might stick to the cheaper lithium ion battery. Thank you again the information you gave me was very useful and I will take it into account. 
    Good day to you 
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