Solar battery device


I had a question that my device uses 130mA at 6 to 7V and i am trying to use solar battery system for my device to power it in a day with sun and with batteries in day.

can anyone tell me what is the best components to use in this?

meanwhile i use 9v 220mA solar panel with linear voltage regulator to charge batteries and provide power to my device. bu it works just for short time and after couple of hours one of my battery in a battery bank goes dead 0V. while one remain ok. i had two lithium ion batteries in series in my battery pack. what will be the possible problem?


Hi @faizan57701,

Welcome to Core Electronics! Sounds like a couple of issues with the setup:

  • The LiPo batteries appear to be unbalanced. This can happen if different batches of LiPo are in use, or, they have not been managed correctly when charging. It might even be a bit of both.
  • Perhaps the panel you are using does not output 9V @ 220mA. This could be due to the type of sunlight it is receiving, the quality of the panel, or both.

Your project is likely to use 7 x 0.130 = 0.91 Watts per hour. Over 12 hours, that’s 10.92 Watts. The 9V 220mA Solar Panel should come close to being able to charge the circuit during the day if it truly performs as rated. You could always measure it.

You mentioned your project uses 6 to 7V; that’s a bit unusual. Is it perhaps powering a 5V or 3.3V regulator?

With your insight on the above question, I can recommend some hardware.


Yeah my device uses atleast 6V. Not more then 7V for nominal performance and it needs 110 mA current. So what you suggest me for nicely working my system as a self powered from solar and battery?

What hardware you could suggest me ?
And if I use lithium ion battery charger to charge one battery from solar and on its output i can connect boost converter to boost voltage to 6 volts for my device. What do you think?

Thanks alot


Ph: 0420281112


I am using 9V 220mA solar panel and 2 lithium ion 18650 batteries in series as a battery bank but it’s not working at all. Neither charging and one battery discharged to zero volts.

Really confused over this.

Faizan Qader Cheema

Hi @faizan57701,

You are going to need a proper Solar Charger between the Solar Panel and the LiPo. Consider this:

You are also going to need an efficient step-up regulator, such as this (to go from 3.7V to something higher)

Hi Graham!

So you think these hardware would solve my problem? did you get my problem fully? I tried to explain my best

This is the actual schematic of my system,

Until the diagram you just shared, you hadn’t described any of those other parts so I was operating on the context that you had nothing between the Solar Panels and the Batteries.

If you already have those parts shown in the diagram, then, by all means, list what they are.

Hi graham!

Both are voltage regulator of the same type with different output voltage set. other is just diode to block reverse current towards solar panel when batteries discharge.

and why my second battery fails? two batteries are in series. first one always remains stable but second one drops to zero. can’t understand the chemistry of lithium ion batteries. both are infact the same type.

one more thing, the device you mentioned as a MPPT solar battery charger, can it be used while running the load and also charging battery in sun and when there is no sun then battery will provide power to the load? it seems like that it can be used with load and battery together.

I’ve shared how I would go about this project, I wouldn’t recommend your setup given what has been described.

Use a single cell battery that is adequate for your project along with a step-up voltage regulator. Also use a proper Solar Charger to avoid all of the issues you are facing.

The products I linked go into more detail for hookup guides, etc.

So, with what system I have, you suggest to used MPPT with one battery with step up boost converter to power my device completely? this system will completely power my device from sun as I need this to test my device in a remote area for several days to month where there is no mains power at all

A 4400mAh LiPo (Single Cell) would work just fine given what you have described. That’s around 16 Watts of energy.

If your soalr panel doesn’t output what you say, then you’ll be in for trouble.

This is well worth the read

my solar panel averaging 9V open circuit voltage with 220mA current. I bought that from core electronics.

here it is;


Solar Panel (9v 220mA) Australia - Core Electronics
Introduction Need a clean energy source for your project? Check out this compact,high quality,high output endurable solar panel.The peak power output is around 9V at …

half of its current goes for powering up the sensor. while remaining goes for charging the batteries.

I was referring to more than just the product specs; it’s how you’ve mounted it and how much sunlight it actually gets throughout the entire day (under all conditions and locations of the sun).

To be sure, do the math with real-world figures. Measure how much energy your solar panel will generate throughout the day, and subtract the amount of energy your circuit will use (for both day and night).

If you want to bake in safety, then take off 30-50% of the solar panel power to accommodate cloudy/rainy days. Or, use a larger battery pack to store more energy from “normal” days so your project can endure a couple of less than perfect days.

Either way, it’s just energy in, energy out, with a buffer for efficiency.


Another problem is that i do not have more options in solar panel for voltage greater then 9 Volts which i already shown you from core electronics. most of the solar panels are with 6 volts. where as, sunny buddy needs
at least 6 volts to work its charging circuit. so for that i need small solar panel with voltage greater then 6 volts. Thus, this was the only option. which produce 9 volts averaging with 220 mA current.

Can i ask you if this solar panel produces 220 mA current. does it be boosted to 450 mA for battery charging by sunny buddy?

i looked through sunny buddy’s manual. i could not find this answer.

To save the copy paste here, it is explained in wonderful detail in this guide. I’m not sure how to word it in another/better way.

There are many solar panel variants. Perhaps add “Sparkfun” to the search to ensure you are keeping within the same brand of the charger module.

Hi graham!

I just want to reconfirm and reassure that can you please confirm me while using sunny buddy with solar panel, i can power my load and charge my battery at the same time in day and when voltage from solar panel drops
during evening or early day time then sunny buddy will not charge my battery then and battery will then provide power to my load?

is that right?

I just meant that my load will just keep on and will not disconnect as i had to keep my load on every time as i am testing it in a remote area.

Thanks a lot. please remove my this confusion

Yours sincerely,

Faizan Qader Cheema

Mob: +61 420 281 112

The load is essentially powered via the battery. If there is charge, then the load is powered.

Solar Buddy just so happens to charge the battery if sufficient energy is available from the Solar Panel. This doesn’t interrupt or affect the load.

This picture from the guide I shared shows the setup:

There’s also good technical narrative within the guide. You can’t just “hook it up” - follow the guide, step by step.

From this picture, it is obvious that load can be powered continuously while charging a battery in a day time and while discharging a battery in night or cloudy time.

Thanks a lot.

I am about to order this sunny buddy with a boost converter to provide enough voltage for my load. Actually i am designing a portable self powered system as i need to test it in a remote site for months. So, this is why
i am quite curios.

Yours sincerely,

Faizan Qader Cheema

Mob: +61 420 281 112