Battery charging by Solar Panel

Dear All,

I need to charge batteries direct from solar panel with cost effective solution.

for that i guess a diode will work from positive supply of solar panel & negative is directly connected with battery & load.

I have following queries/

1. Please see the attached circuit & guide me will it work.
2. If the batteries are fully charged how will i cut off the charging.
3. Do i need to cut off the charging in this scenario.
4. what should be the diode rating.
5. What should be the add on in this circuit for proper working.

Thanks & Regards.

Please supply you circuit diagram
What is the specification of your PV panel?
What is the specification of you batteries?
Yes, you must protect your batteries from overcharging

There's no attached file.

I tend to think that when it comes to batteries, a cheap charging solution might be cheap in the short term, but can very easily lead to shortened life of the (expensive) battery and increased cost later.

Let's see your diagram.

Where is attachment?

You should not charge battery direct from solar panels, this should be done over regulator.

Each solar panel should have own bypass diode. Current ratings of diode depends from current needs and power of solar panels.

Examples (dont forget regulator) :



When one cells or part of cell is in shading that cell is bypassed via diode, without diode cell will behave like consument of power.

Diode make voltage drop, because that should choose schottky diode 0,2V drop instead 0,7V.


What is power of panels ?

asimraufawan said:

Dear All,

I need to charge batteries direct from solar panel with cost effective solution.

for that i guess a diode will work from positive supply of solar panel & negative is directly connected with battery & load.

I have following queries/

1. Please see the attached circuit & guide me will it work.
2. If the batteries are fully charged how will i cut off the charging.
3. Do i need to cut off the charging in this scenario.
4. what should be the diode rating.
5. What should be the add on in this circuit for proper working.

Thanks & Regards.

Click to expand...

Design is not good! There is no charging regulator, batteries will overcharge, first will loose water, then sulfatiosation will occur, and in last phase you will have dead cooked batteries.

How will i protect my circuit from overcharging in the same circuit i have provided,
what should be the diode rating or provide me the model number.

You must use regulator for charging, and diode current ratings depends from current which is flowing throught them.

What type of regulator please elaborate in detail.

Charge batteries as per the drawing

Regulator charges bat and when bat is full he can give power direct to devices, and battery can be puted on float charging. Charging regulator regulate voltage and current of battery charging. All of this depends from particular type and model of regulator.




Its very usefull to have power logger for such systems. To see how much solar panel produce energy.


Search google about solar regulators, and on edaboard there is many threads about solar tech.
We can talk about this few days, better is to give precize question.

can i use zener diode to avoid over charging in the same circuit that i attached.

I know about charge controllers but the problem is i need a cheap solution , precision is not required.

asimraufawan said:

can i use zener diode to avoid over charging

Click to expand...

Definitely NO!!! Will explode!!!

You should search 48V regulator circuit.

What if my total load is 50W , i use 80 W panel with output voltage of 12-17 Volt & battery voltage is 12 volt 100 AH.

Can i use zener in this case If yes , then how.

You cant, forget zener for that!!!

what else should be the better option how will i know my batteries are charged fully.

Voltmeter is instrument for that. When battery voltage reaches a certain level of voltage battery is full. Its a job of regulator.

With zener you cant measure voltage.


You should read some material about batteries (lead acid).

asimraufawan,

As everyone is telling you, you really must use a proper regulator for this job. It's not simple, not even as simple as charging the SLA bank from a fixed voltage. There are other issues to consider...

Have you studied how photovoltaic panels work, in relation to their voltage and current output curves with varying illumination and (very important! - temperature), peak-power, etc.? It's not trivial when you are dealing with large panels and a large battery.

The panel output might vary up to 70V (maybe more!) for a nominal 48V array. When it gets hot (and they get hot) it might drop to below 48V even in good sunlight. If your battery is going to be used anything more than minimally, then you need to take full advantage of all the power your photovoltaic panel can give.

Using a simple charger (by which I mean proper, but relatively simple charge control) might do the job if you have plenty of sun. Otherwise I really would recommend a MPPT (maximum power point tracking) charger. These use a switching regulator to draw just the right current from the photovoltaic array to keep it at its maximum power output - that does not coincide with just drawing as much current as you can.

The very least you need is a proper charge control circuit suitable for a large battery, and capable of handling a widely varying input voltage and available current. I'm not an expert on it (others here certainly are and can advise on actual design) but I do know that there are some good circuits on the web.

can battery indication IC like LM3914 help in status of battery ?

shahbaz.ele said:

can battery indication IC like LM3914 help in status of battery ?

Click to expand...

Yes, but for this job you need something better and more precize, like LCD monitoring of voltage, amperage, watage,...