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Topic: How to modify the voltage of solar charger? (Read 2502 times) previous topic - next topic

wvmarle

By and large Schottky diodes work the same as a normal diode - key differences are switching speed (very fast), forward voltage drop (low) and reverse current leakage (high - for a diode, that is, in the order of µA normally).
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

falexandru

Then I can mount a Shotky to prevent back-current to the PV panel and a Zener + resistor to regulate voltage to a value more than 4 V (to charge my 3 x 1.2 V NiMH AAA in series), right?

1steve

I have no idea what the 6 volt name means. My best guess is that the panel has enough over head that it will work with a solar controller to deliver 6 volts. I am more familiar with 12 volt panels and I know the no load voltage will be anywhere from 18 to 24 volts. Also the power rating is at the higher voltage. So a 100 watt 12 volt panel will not give 8.33 amps. (100w/12v=8.33a) It will be more likely (100w/18v=5.55a) 5.5amps.

falexandru

I brought the components:

1) 1 N 5822 Shotky diode -  1 pc
2) Z 4 V 3/0.5 W Zener diode  - 1 pc
3) resistor metal oxid 47/1 W 5%- 1 pc
4) resistor 200 Ohm/ 0.25 W - 1 pc
5) white LED 8mm -1 pc
6) Photovoltaic panel (poli-crystal) 1.1W/6V/200mA (note it is a much smaller one than the initial one)- 1 pc
7) 3.5 mm barrel jack - 1 pc
8) 3.5 mm barrel socket - 1 pc
9) black and red 2 wire (the type used for the speakers) - 2 m
10) perfboard  6 mmx4.5 mm - 1 pc
11)1.2 V 800 mAh AAA NiMH batteries - 1 pc
12) the case for the NiMh batteries (3 in series) - 1 pc
13) commuter 2 ways (2 throws?) - 1 pc

+ various PVC stripes, glue and screws, hooks.

Now, first problem to solve is to pick the right Zener out of the pile of diodes I got. I ordered a range of nominal voltages Zeners and  the seller packed all values together (Zeners are some 2 mm length => [emoticon punches to (my) head].

I will post the schematics asap - I am drawing it by hand.





 

falexandru

#34
May 26, 2018, 09:09 pm Last Edit: Jun 01, 2018, 10:32 pm by falexandru
and here it is the shematics

Parts as in the previous list:

R1 = 47 Ohm 1 W
R2 = 200 Ohm 0,25 W

C1= 4.7 uF (not sure I really need it, I know it may protect the active components from voltage spikes, but I cant figure out whether spikes have any chances to occur).

This time I am planning to solder components on the perfboard, in a clear design, components at some distance one to another.

I would be extremely happy if somebody more experienced than myself could spend some time to check the circuit. Thank you very very much!

I am going to first breadboard components and once everything is OK, I will proceed to the case and wiring design.

+++

The PV panel I use to prototype is smaller (200 mA) and less efficient (poly-ristal vs. mono-crystal) than the one I posted in the beginning. Reason ist double:
- it is three times cheaper - nice in this risky phase
- if Ok, then I can make more circuits than in the case I used the expensive one - that is good for demo purpose.





falexandru

Correction: there are 3 pcs NimH units. Sorry!

ted

Look ok, you don't need C1 for solar panel.

ted

I brought the components:


Now, first problem to solve is to pick the right Zener out of the pile of diodes I got.

 
Just put any diode and measure voltage on it.

Wawa

Why R1. A solar panel is a current source (you can short it).

The whole idea of a schottky backflow diode is that you can leave the panel connected to the battery,
so why a SPDT switch.

Why not use a zener on the solar panel side of the schottky diode (post#28),
so the batteries are not drained by the zener leakage when the sun goes down.
Leo..

falexandru

Thank you guys, for your kind decision to have a look on my circuit!

Why R1. A solar panel is a current source (you can short it).

The whole idea of a schottky backflow diode is that you can leave the panel connected to the battery,
so why a SPDT switch.

Why not use a zener on the solar panel side of the schottky diode (post#28),
so the batteries are not drained by the zener leakage when the sun goes down.
Leo..
R1 is paired with the Zener downhill

Without the switch, the circuit will light the LED during the day as well.  In a later stage of the project, the same battery will be charged by a Savonius wind turbine, so I am planned to replace the switch by an Arduino board to drive the charging.

falexandru


falexandru


falexandru

To keep it as simple as possible and easy to explain, I rather refrain to use a transistor.

Wawa

Try to draw this:

Zener (4.7volt) across solar panel.

Schottky diode from solar panel to battery(+).

Switch between battery(+) and LED circuit (R2).
Leo..

falexandru

#44
May 27, 2018, 09:56 am Last Edit: May 28, 2018, 02:02 pm by falexandru
Thank you @Wawa! I followed your advise - see following.

-----------------

Here it is the simplified version of the solar charger from (6V;1.1W;200 mA) Photovoltaic panel to 3 series NiMH battaery units (1.2 V; 800 mAh).

The list of components for this simplified version (see picture attached) is the following:

+++++++++++++++++++++
+ Demonstrative solar charger  +
+++++++++++++++++++++

Components's list

1) Shotky diode: 1 N 5822 -  1 pc
2) Zener diode: Z 4 V 3/0.5 W - 1 pc
3) Resistor: 200 Ohm/ 0.25 W - 1 pc
4) LED: white,  8mm -1 pc
5) Photovoltaic panel: poli-crystal 1.1W/6V/200mA - 1 pc
6) Barrel jack:  3.5 mm  - 1 pc
7) Barrel socket: 3.5 mm  - 1 pc
8) Connection wires:  black and red (the type used for the speakers) - 2 m
9) Perfboard:  6 mmx4.5 mm - 1 pc
10) Batteries: 1.2 V, 800 mAh, AAA, NiMH - 3 pcs
11) Case for the 3 units NiMh batteries: 3 in series - 1 pc
12) Switch: 1 pole - 2 throws - 1 pc

+ various PVC stripes, glue and screws, hooks (drawing pending).

+++++
+END +
+++++




(note that PV is a much smaller one than the initial one)

No more R1, no C1
for this simplified version.

Not sure if I correctly followed:  "Schottky diode from solar panel to battery(+)".


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