Solarpanel

hello guys,

I'm trying charge a lithium battery with a solarpanel. This is the solarpanel that i'm currently using(12V;50mA: https://www.budgetronics.eu/index.php?item=zonnecel-12-volt-50ma&action=article&group_id=14&aid=330&lang=NL

The is the mppt solar charger that I use: https://nl.aliexpress.com/item/1-Cell-Lithium-Battery-Charging-3-7V-4-2V-CN3791-MPPT-Solar-Panel-Regulator-Controller/32900911894.html?spm=a2g0z.10010108.1000016.1.4e537e19V6jqZz&isOrigTitle=true

But the problem is that when I connect the solarpanel to the mppt, the voltage of the solarpanel decreses to 4 V. When the solarpanel isn't connected is produces 9,6V. Because of the 4 V input the mppt won't work. It only works with a minimal voltage of 9 V. My question is why does the voltage decrease so much?

The mppt is not broken I first tried it with a power supply unit and it works with an input of 9V and 0,005 mA. This gives an ouput of 4,2V and 0,04A.

I hope you guys can help me

with kind regards,

Bram

by Bram12
November 20, 2018

1 Answer

Answer by mikerogerswsm

This is the datasheet:

https://datasheetspdf.com/pdf-file/1257610/CONSONANCE/CN3791/1

It looks like the series combination of R3 and R4 in Figure 1 is too small in your application. It is permissible to increase them in the same proportion, say to two or three times the existing values. If this doesn't work, increase or remove R1. The CN3791 takes 1mA into the Vcc pin.

+1 vote
by mikerogerswsm
November 20, 2018

PS - First check the output current of the solar panel. Are you getting a suitable current out of it? Is it in direct sunlight as requited in the spec?

If you don't know how to measure the current ask your teacher.

by mikerogerswsm
November 21, 2018

Your Answer

You must log in or create an account (free!) to answer a question.

Log in Create an account


Go Ad-Free. Activate your CircuitLab membership. No more ads. Save unlimited circuits. Run unlimited simulations.

Search Questions & Answers


Ask a Question

Anyone can ask a question.

Did you already search (see above) to see if a similar question has already been answered? If you can't find the answer, you may ask a question.


About This Site

CircuitLab's Q&A site is a FREE questions and answers forum for electronics and electrical engineering students, hobbyists, and professionals.

We encourage you to use our built-in schematic & simulation software to add more detail to your questions and answers.

Acceptable Questions:

  • Concept or theory questions
  • Practical engineering questions
  • “Homework” questions
  • Software/hardware intersection
  • Best practices
  • Design choices & component selection
  • Troubleshooting

Unacceptable Questions:

  • Non-English language content
  • Non-question discussion
  • Non-electronics questions
  • Vendor-specific topics
  • Pure software questions
  • CircuitLab software support

Please respect that there are both seasoned experts and total newbies here: please be nice, be constructive, and be specific!

About CircuitLab

CircuitLab is an in-browser schematic capture and circuit simulation software tool to help you rapidly design and analyze analog and digital electronics systems.