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# Solar panel diode and battery ? Answered

Hello,

I have 5V solar panel which will charge my 18650 3400mah Panasonic 3.7V battery. I will use Voltage step up to 5V and I don't know which diode should I use between panel battery? I have all these diodes.
IN4148 Diodes
IN4007 Diodes
IN5819 Diodes
IN5399 Diodes
FR107 Diodes
FR207 Diodes
IN5408 Diodes
IN5822 Diodes

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## Discussions

First you want a low fwd voltage schottky diode.

Drop the 1N400x which are plain GP diodes.

Next you want the current ability to equal or exceed solar current..

You've probably never looked at a specification sheet.. Open the 1N4148.pdf first page it is a Switching Diode NSC (not a solar candidate)

originally manufactured by Vishay_Semiconductors .

Still pp1 under ABSOLUTE_MAXIMUM_RATINGS see the line Average_forward_current If(avg) = 150 ma MU (means using) 100 ma very low..

On the second page see the Forward_voltage Vf = 1V too high (NSC) ..

So X cross this diode off your list.

The 1N5819 has a forward drop of 0.9v and an average current of 1 ampere

that is a better diode..

Here are variations on a circuit for a very low forward voltage drop of

only 0.04 Volts and less reverse leakage then a Schottky diode !

You will need to click on the pics to see the whole ckt..

thank you. I didn't know what should I look or do. Now, I can easily understand.

Yeah. The same thing DU35 said: A diode with current rating greater or equal to the current you will be pushing through, and a low forward voltage drop.

By the way, the reason small forward voltage is desired, is because you will necessarily lose some power through the diode. How much? Answer: the diode's voltage drop multiplied by the current flowing through it. P=V*I

https://en.wikipedia.org/wiki/Diode#Forward_bias

But, you know, it is like my grandmama always used to say:

You have to waste electric power to make electric power.

At least I think she was talking about electric power...

http://www.phrasemix.com/phrases/you-have-to-spend...

;-)

Anything with a low voltage drop and able to handle the current will do.

Sorry, I stepped on your line, will pull if you want ?

Just did not want to cause any bad feelings, as a duplicator of your answer, and was offering to remove my comment.. Now Jack has chimed in too...

Live where you like, read what you like, think what you like and
Like the wisdom you acquire.