Problem with solar panel charger

[adwnis123]

Ok, If I use this:

https://energypower.gr/wp-content/uploads/2015/12/epsolar-ls0512r-manual.pdf

with a 40Watt, 12Volt solar panel,

3 Li-Ion batteries connected to "3S 25A 18650 Li-ion Lithium Battery BMS Protection PCB Board 12.6V With Balance" and connect it to the EPSOLAR

https://www.ebay.com/itm/3S-25A-18650-Li-ion-Lithium-Battery-BMS-Protection-PCB-Board-12-6V-With-Balance/332212297624?epid=933998449&hash=item4d59655f98:g:-7gAAOSwzppaMl4L

and as a load a circuit that maximum consumes 500 mA,

will it work?

Sorry for the many messages, it is the first time I use solar panels + batteries +chargers, and I want to figure out how it is going to work.

Thank you...

 

[c_mitra]

The link :

**broken link removed**

DOES NOT WORK!!

 

[BradtheRad]

The charging source must deliver higher voltage than battery voltage, so it can push current into the battery. Your circuit is also exposed to that higher voltage during battery charging. It's one more thing you need to consider.

 

[adwnis123]

The right link:

https://www.ebay.com/itm/3S-25A-18650-Li-ion-Lithium-Battery-BMS-Protection-PCB-Board-12-6V-With-Balance/332212297624?epid=933998449&hash=item4d59655f98:g:-7gAAOSwzppaMl4L

After many days/weeks of searching I conclude that I should use a solar panel with the below characteristics:
40Wp/12V
Watt 40W
Vmp 18V
Imp 2,2A
Voc 22,1V
Isc 2,4A

with this EPSOLAR LS0512E

https://www.smart-cover.gr/wp-content/uploads/2018/03/Epsolar-series-LS_E-manual.pdf

am I correct? Please your opinion...

Thank you...

 

[betwixt]

My opinion:

Yes it will work but it will be very inefficient and the battery will never properly charge to full capacity. What you are proposing is to connect a lead acid charger to a cell balancing circuit then to individual Li-ion cells. The charging voltage and current will be wrong, that doesn't mean it won't store charge, it means it may never reach a fully charged state.

The board in the Ebay link is not a charger, it is a load balancer. The idea is it limits the voltage across each cell individually so that if they are at different states of charge or if one or more fails, it doesn't cause a cascade failure of all the others. You can achieve almost the same effect by wiring a Zener diode across each cell but doing it that way would cost more.

You have never described exactly what you need. I think what you are asking for is a circuit that takes power from a PV panel and converts it to a stable 12V output for your equipment and diverts any surplus power to a battery. When the PV is unavailable, the battery provides the 12V output instead. Am I correct?

Brian.

 

[adwnis123]

My opinion:

Yes it will work but it will be very inefficient and the battery will never properly charge to full capacity. What you are proposing is to connect a lead acid charger to a cell balancing circuit then to individual Li-ion cells. The charging voltage and current will be wrong, that doesn't mean it won't store charge, it means it may never reach a fully charged state.

The board in the Ebay link is not a charger, it is a load balancer. The idea is it limits the voltage across each cell individually so that if they are at different states of charge or if one or more fails, it doesn't cause a cascade failure of all the others. You can achieve almost the same effect by wiring a Zener diode across each cell but doing it that way would cost more.

You have never described exactly what you need. I think what you are asking for is a circuit that takes power from a PV panel and converts it to a stable 12V output for your equipment and diverts any surplus power to a battery. When the PV is unavailable, the battery provides the 12V output instead. Am I correct?

Brian.

Sorry for the misunderstanding. I just posted the link for the user that said he can't find it. I am not going to use it anymore....

To my last post, I will use entirely new approach, meaning that I will use only:

the solar panel with the characteristics above + the EPSOLAR charger I posted above + 12 Volt, 2,4 A, Sealed Lead Acid + supplied circuit that consumes max ~500mA

Will this scheme work? That is what I am asking.

Thank you...

 

[betwixt]

Yes, that should work. I have no experience of that EPSOLAR module but the specification suggests it will be suitable.

Brian.

 

[adwnis123]

For a solar panel like the one I posted, that works for 12-18 Volts, what size of cables do I need? Assume 3 Amps current for safety and 2 meters length. I found this form here, that gives me 2.5 mm^2

https://www.solar-wind.co.uk/cable-sizing-DC-cables.html

but on the store I asked they didn't know for sure...!!!

And what happens if the solar panel goes to 6 Volts if there is not sun? The form gives me 4mm^2

What should I choose?

Thank you....

 

[KlausST]

Hi,

And what happens if the solar panel goes to 6 Volts if there is not sun? The form gives me 4mm^2

--> then there will be about no current. Thus this is no critical situation you have to care for.

On the calculator site they ask about "system voltage", not any actual voltage. And your system voltage is 12V.

--> use 2.5 mm^2.

Klaus

 

[c_mitra]

And what happens if the solar panel goes to 6 Volts if there is not sun...

Basically, the solar panels are const voltage devices. The current produced depends on the light intensity. The more the sun, the higher the current. But the voltage will not increase.

But that is all theory. In reality there is some leakage and you have some load. So they specify a short circuit current for the panel.

So, with less sun, the voltage will drop a little but the current will drop more. I see that the open circuit voltage is 22V whereas the nominal voltage is 18V.

The cable size you can use depends on the loss you can accept.

 

[BradtheRad]

Assume 3 Amps current for safety and 2 meters length.

I tried the calculator and clicked 5 percent as acceptable loss. It recommends 18 gauge.

Below are links to charts of wire gauges showing safe amp-carrying capacity.
To carry 3A they recommend 16-18 gauge (AWG).

http://amasci.com/tesla/wire1.html

http://www.powerstream.com/Wire_Size.htm

 

[adwnis123]

I tried the calculator and clicked 5 percent as acceptable loss. It recommends 18 gauge.

Below are links to charts of wire gauges showing safe amp-carrying capacity.
To carry 3A they recommend 16-18 gauge (AWG).

http://amasci.com/tesla/wire1.html

http://www.powerstream.com/Wire_Size.htm

I bought 4mm^2 because I didn't find 2.5mm^2. But it is too coarse to fit to the solar panel charger's plugs. If I cut a few of the small cables it has inside so as to reduce its width and fit it to the solar panel charger's plugs, will it work? (I have no experience of solar panels and their currents they consume as you see...)

Thank you...

 

[BradtheRad]

If I cut a few of the small cables it has inside so as to reduce its width and fit it to the solar panel charger's plugs, will it work?

Yes, that's okay. It sounds as though you purchased 6 gauge wire, 4mm diam.