How to charge a battery with A solar panel?

Is the power coming from solar panel more to charge or less or is perfect.

  • Power is more

  • Power is Perfect

  • Power is less


Results are only viewable after voting.

Thread Starter

Pranav Sant

Joined May 12, 2021
1
Hii Everyone,

I want to make a project in which I want to charge my 12V--7.2Ah SMF(Sealed Maintenance Free ) Battery. I have a solar panel which has Vmp of 18V
, Isc of 0.75A and rated power of 12W. I personally think that this solar panel is generating much more power than to charge the battery. So please could anyone help me to how to regulate the power supply coming from Solar panel and not damaging the battery.

Thank you!!
 

Ian0

Joined Aug 7, 2020
2,235
The maximum charge current will be 0.25C, or 1.8A (0.25 x the capacity)
Your solar panel will give an output current of between 0.65A and 0.75A in full sunshine when connected to the battery, so that will not a problem.
You must limit the charge (not the power) so that it doesn't overcharge the battery, and that depends on how you are going to use the battery.
Is it for standby power (so that it is kept on charge all the time and used just occasionally) or is it discharged every day?
Note that there are different sorts of VRLA battery depending on the application. Those intended for standby power won't last long if discharged every day (cyclic use); and those intended for cyclic use will fail if left for a long period of time on continuous charge.
 

LowQCab

Joined Nov 6, 2012
557
You need to determine what your Load-Character will be first,
then choose a Battery that is design for that type of usage.
Then consult the Battery Manufacturers Data-Sheet to
determine the most appropriate Charging-Scheme and
the Exact Charging-Voltage,
and the Maximum allowable Charging-Current,
for the intended usage.

Of course, if you are just tinkering around, and
are not really too concerned with the Life-Expectancy of the Battery .............

Just get a 497-5376-5-ND Voltage-Regulator from DigiKey-Electronics, ~$1.58,
no other supporting parts are required,
but it should be screwed to a 4" X 4" piece of Aluminum (or larger) for cooling,
the Aluminum must be connected to the Common Ground.

It will charge the Battery at exactly 13.7-Volts, and
limit the Current to ~1.5-Amps Max. before automatically shutting-down.

This should not do any harm to the Battery,
but it is not adequate for Fast-Charging or Heavy-Cyclic-Loads.
Since you are using a Solar-Panel, over-Charging the Battery will not be an issue,
since it will be "On" for less than 12-hours, and "Off" for more than 12-hours.
.
.
.
 

LowQCab

Joined Nov 6, 2012
557
SLA( sealed lead acid) batteries are charged at constant voltage of 13.8V for a 12V battery.
The Ideal Charging Voltage varies with the Battery-Core-Temperature.

With Higher-Temps a lower-Voltage is needed, and vice-versa.

13.8V is slightly high for a continuous Float-Voltage at average Room-Temps (~20-C ).

There is an excellent reason why exactly 13.7V was chosen as
the permanently designed-in-Voltage of this Regulator.
.
.
.
 

Ian0

Joined Aug 7, 2020
2,235
You’re correct, 13.8V is a cool battery! different manufacturers recommend just slightly different voltages.
Yuasa has a graph of float voltage vs. service life.
10AF346F-6064-48BE-9B57-812D85AA6210.png
 

BobaMosfet

Joined Jul 1, 2009
1,776
Hii Everyone,

I want to make a project in which I want to charge my 12V--7.2Ah SMF(Sealed Maintenance Free ) Battery. I have a solar panel which has Vmp of 18V
, Isc of 0.75A and rated power of 12W. I personally think that this solar panel is generating much more power than to charge the battery. So please could anyone help me to how to regulate the power supply coming from Solar panel and not damaging the battery.

Thank you!!
Well, you need to view datasheet for solar panel, and datasheet for battery. Battery may also have special requirements (expansion, thermal, voltage or current) for charging which must be taken into account. Many factors.
 

Mussawar

Joined Oct 17, 2011
74
MPPT charger is also a considerable option to fetch maximum power from a solar panel (even in weaker light). Search if you can find one with low power specifications, since your system is at a small scale.
 
Top