Hello everyone,
I want to power a 3.3V Microcontoller AND a 6V Motor with the help of rechargeable batteries. I got 5 1.2V 1100mAh batteries in series and want to recharge them with 2 3V solar panels in series. My problem is that I don't now how to select the right charge controller for my project. I want the solar panels to charge the batteries AND simultaneously power the Microcontroller and the Motor. I heared about the TP 4056 but I also heared that this charging controller isn't suitited for charging the batteries and output power simultaneously.

schematic:
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so my questions is: Which charge controller would you suggest and is my wiring even correct?

Thanks in advance
Felix

 

You can’t fully charge a 6V battery from a 6V source. PV panels are very unreliable sources of power. The output is related in full sun and that‘s not the common case. You can’t expect to charge an 1100mAH battery and power a motor which two PV cells, you need a lot more capacity to manage anything like that.

Also, your schematic shows +12V input to the L298N, how does that work?

 

I forgot, the TP4056 is for Lithium Ion batteries, not NiMH. You will need a chip that is designed for the right chemistry.

 

You can’t fully charge a 6V battery from a 6V source. PV panels are very unreliable sources of power. The output is related in full sun and that‘s not the common case. You can’t expect to charge an 1100mAH battery and power a motor which two PV cells, you need a lot more capacity to manage anything like that.

Also, your schematic shows +12V input to the L298N, how does that work?

Actually I got 8 Pannels, but want to wire them in parallel so at the end there are 6V but with more power.

schematic:


And yes I got NiMH batteries. Do you know any chip which is suitted for these kinds of batteries?

 

There is a rigorous and complicated process to do the analysis for solar powered projects. I have no idea if your 8 PV panels are going to be enough. You should research this particular topic and do the analysis yourself to avoid disappointment.

The MAX712 can handle 1 to 16 cells in series and has a “linear” mode which will let the charging supply power the load while charging.

 

Thanks for the answer and the recommendation. In order to better understand the electronics and the values behind my parts
I did some calculations:




Note that I use the european period and comma symbol.
So according to my calculations the panels wouldn't produce enough current to destroy the battery. In this case do I even have to use a charge regulator?

Thanks in advance
Felix

 

Your calculations are missing some things. First of all, you need to look up the average solar radiation at your location. The rating of the PV panels is a best case which you are unlikely to achieve very often in Europe. If you were in Saudi Arabia, for example, you might have a better chance at it.

Second, PV panels have a voltage-current curve that’s not linear. Solar chargers are designed to use the MPP (Maximum Power Point) where the combination of voltage and current produce the most power. Without it, your PV panels will get you even less power. Investigate MPP so you understand this effect and optimization.

As far as characterizing the power requirement of your system, did you make empirical measurements? Because if not your numbers are not better than guesses. You really need to profile your system to understand the power requirements. The pattern of power usage will also have an effect on battery life.

I can recommend, at least for an introduction to the problems and working on them, videos from Andreas Spiess. He’s quite good and very thorough. Here’s an example that might be helpful:

He has others, and while he mostly focuses on LiPo and other lithium chemistries powering MCUs, the fundamentals are the same.

 

Thanks for the answer and the additional informations. I was just wondering, because this project was intended to be low budget, if a MPPT is necessary. Additionally I think I should also add that I only intended the project to run in the summer months (it is a outdoor watering system). So even though it isn't very effective, do you think I could just use the panels, without the additional charge controller or MPPT, to load the batteries?

 

Thanks for the answer and the additional informations. I was just wondering, because this project was intended to be low budget, if a MPPT is necessary. Additionally I think I should also add that I only intended the project to run in the summer months (it is a outdoor watering system). So even though it isn't very effective, do you think I could just use the panels, without the additional charge controller or MPPT, to load the batteries?

I really don‘t know. The MPPT controller is pretty much required because you have to limit the current you try to draw based on the incident light or you will drag down the PVs to the point that their output will be pitiful. You have a very large battery to charge (relative to PV capacity).

It might work. It’s the kind of thing that requires empirical testing. The MAX712/713 is the right chip for your NiMH cells, though.