Solar battery powered autonomous robot ...

Thread Starter

myked

Joined Oct 18, 2021
3
I'm trying to build a small wheeled robot that is powered by a battery that is charged by a small solar panel. The idea is that the robot stops trying to move until there is a sufficient charge and then moves until the charge drops. The solar charging needs to be itelligent so that it maintains the battery in good health and does not overcharge it or allow it to over-discharge. An Arduino needs to be powered as well as the two small electric motors for the wheels.

The main problem I'm having is finding a solar charging manager that can handle the load which I think might peak at 2A due to the elecric motors which I planned on driving through an H-Bridge circuit.

The very promising DFRobot DFR0535 module is perfect other than the fact that is can only provide 9V at 0.5A to the H-Bridge.

Any comments gratefully received.
 

BobTPH

Joined Jun 5, 2013
4,046
Do some calculations before proceeding with this project.

What is the capacity of the battery and the solar panel? How long will it take to charge? How long can the robot run on that charge?

My gut feel is that it will get a few minutes of operation per hour of charge in full sun. Is that your expectation?

Bob
 

Thread Starter

myked

Joined Oct 18, 2021
3
Yes thanks Bob... I'm new to all this and can only do rough calculations anyway.

I'm aware that the robot may not move very much but I have found a number of 3.7V LI-ION high capacity batteries that I think will do the job. If I could find some motors which drew very little power that might help. Ideally I'd want decent motors though so that they had some oomph albeit in short spurts.
 

Yaakov

Joined Jan 27, 2019
3,755
Yes thanks Bob... I'm new to all this and can only do rough calculations anyway.

I'm aware that the robot may not move very much but I have found a number of 3.7V LI-ION high capacity batteries that I think will do the job. If I could find some motors which drew very little power that might help. Ideally I'd want decent motors though so that they had some oomph albeit in short spurts.
Will this robot be outdoors?
 

BobTPH

Joined Jun 5, 2013
4,046
I'm aware that the robot may not move very much but I have found a number of 3.7V LI-ION high capacity batteries that I think will do the job
Its not the batteries that are likely the problem, it is the solar panel. And, as Yaakov hinted, indoors makes it pretty much impossible.

Bob
 

Yaakov

Joined Jan 27, 2019
3,755
Its not the batteries that are likely the problem, it is the solar panel. And, as Yaakov hinted, indoors makes it pretty much impossible.

Bob
Even outdoors is going to mean try extended charge times or very large PV. If it only needs to move a short distance every few hours, it might work but practically speaking I don't know where you'd use it. Application would help...
 

Janis59

Joined Aug 21, 2017
1,357
I am using the 5 USD worth Chinese modules like this https://www.banggood.com/12V-or-24V...lay-p-1766110.html?cur_warehouse=CN&ID=517856 In the aliexpress them are bit cheaper, they exist at ebay as well. PWM-type of semi-mppt, accu lower voltage, upper voltage controls, load shutdown at low battery, adaptive 12 or 24 V output determined by battery. Solar cells yet diifers drastic. The weakest are 1224x635 mm giving 50 W (price 8 Eur) whilst the most advanced insolated from both sides by means of mirror gives 830x1600 mm the 390W (price 140 Eur).
 

Janis59

Joined Aug 21, 2017
1,357
By the way, each solar battery, my physics is one extra large DIODE. Thus the term - i(R zero) ir full of meaning and practically may variate from tens of microamperes at 36V for brand new battery up to 10 mA for well used but still alive and 300 mA for panel staying with both feet in the semiconductor graveyard. Thus, in the bright sunshine both, old and new will give roughly the same harvest, but in the shade.... oh, they will differ very much. Thus, check all the panels as You buy with a diode tester - second and You have a prognosis of life expectancy.
 

MrChips

Joined Oct 2, 2009
24,620
How often will the robot be running per day?

Put it this way. Suppose the robot draws 25W and is expected to run for 8 hours. That is 200Wh.

Assuming that you can get 5 hours of full sunshine (which is never the case and depends on your location and daily weather), you would need a 40W solar panel.

When all the uncertainties and efficiencies are taken into account a 100W solar panel would be recommended.
 

Juhahoo

Joined Jun 3, 2019
250
You might find this interesting, for me at least it was somewhat hilarious how he managed to use Barbie car wheels for the project.
 

Thread Starter

myked

Joined Oct 18, 2021
3
Hey thanks to all of you for the great comments.

The project is outdoor and the whole point at this moment is just to see how much autonomous solar powered spurts of mobility I can get per day. The Chinese charging module looks promising so I'll pursue this. I'm enjoying learning all this new stuff I know I'm going to learn learn plenty more by getting it wrong.
 

Yaakov

Joined Jan 27, 2019
3,755
Hey thanks to all of you for the great comments.

The project is outdoor and the whole point at this moment is just to see how much autonomous solar powered spurts of mobility I can get per day. The Chinese charging module looks promising so I'll pursue this. I'm enjoying learning all this new stuff I know I'm going to learn learn plenty more by getting it wrong.
Have you sized your PV panel?
 
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