diy solar

diy solar

Which battery chemistry should I choose for a tiny beginner DIY solar system?

So I have decided to finally dive in and try to make a tiny system.

I am planning on taking either a NiMH or a Li-ion cell. A single cell will probably be enough.
Then wire it with a tiny solar charger in order to charge it. Literally trying to make one of those solar power bank chargers that people use for cellphones. But instead of buying it I wanna make it and learn stuff in the process.

For now I am questioning which battery to take. I saw on Reddit /r/batteries the other day, someone posted this guide https://techmoment.net/best-18650-battery/ about the 18650 li-ion batteries.

I initially thought of getting exactly that battery for my project but that article states that those batteries can be dangerous and I am afraid that if I need to solder wires to their ends that it might not be something I am capable of doing properly + the article says that you should never solder them. I find that hard to believe because those cells must be soldered together when they are used in some devices.

Either way those batteries seem like a potential trouble on one hand but on another they seem to have much higher capacity and voltage than the NiMH.

And from what I learned from a few people here on the forum is that I can get more Watt energy if I have higher voltage.

So if I use a 3000mAh li-ion with 3.6v I will get 10.8Wh if I am correct in my calculations.

If I use 2000mAh NiMH with 1.2v I will get only 2.4Wh.

I am inclined to work with the stronger battery but I am not sure if its smart considering my lack of experience.

I would still love to do this.

What are your suggestions? Maybe I am completely off here. Should I try something else or a battery with completely different chemistry??
 
hi,
i have soldered a 18650 pack without problem (iron around 350-360c) but because my pack become hard to debug (also it’s not a good idea to re-solder more than once), i have now a 4s2p done with 18650 Li-ion 3500ma on 4 pack batteries holder back to back (16.8Vmax output) with a cheap bridge rectifier 25amp to drop the output (only 2 diodes are used but it’s cheap and because i charge to 16.4v - 1.4Vdiodes drop = 15Vmax which most 12v appliances can work with, and add an other bridge for delicate ones).. so my output become 15Vmax to 10.6Vmin (for 3.0Vmin/cell) after one bridge (ideal for a tiny ac inverter?) or 13.8Vmax with two of them.. yes, a bit of power is loss by the diodes but it’s more useful than a 3s configuration which give only 12.8Vmax.. my diy pwm (fun project) is programmable and as i’m near the max power point of my 12v PV, i love it.. and because my battery pack output is near of 16v, i can use a cheap dc-dc step down converter for to charge any other tiny batteries or lower voltage appliances..
anyway, hope you have fun with your project!
Marc
 
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