Question by Brandon: What’s the minimum wattage for a solar panel to need a charge controller?
I have a 10 watt 12v, 0.5 amp solar panel (apparently 10 because it could reach 21 V). I want a charge controller, but I read that a 5 watt panel had too low of an amperage to actually make the charge controller work, so i was wondering if a 10 amp 12 volt charge controller could work, like the type found on ebay. If not, what is the mnimum wattage you’d reccomend
Best answer:
Answer by steven
The best way is to determine what type of electrical load that you need to power and the capacity of the batteries that you will need to power that load for the duration of time (hours).
From that you will know that voltage and the current that will give you the wattage of the load for the time duration and thereby determine the battery capacity and ultimately the charge controller.
A charge controller for the batteries is somewhat tricky since the battery capacity cannot be charged all at one time. e.g. a 15Amp*hour battery cannot be supplied 15A to charge it in one hour. Doing so will overheat and possibly damage the battery.
It is best to recharge a battery at the slowest possible duration and then ‘float’ the voltage and current to top off the battery and keep it at full charge. Charging is at a fraction of the Amp*hour Capacity and is typically C/x where x is in hours. e.g. a 15Amp*hour battery charged to full capacity in 10 hours would be a 15/10 or 1.5 Amps per hour.
So again, find out the loading conditions for powering up your electrical loads (e.g. lights, motors, electronics), and then select batteries, then a charge controller for the batteries, and finally the solar panels to support that charge controller at a specific charge rate (C / hours).
http://en.wikipedia.org/wiki/Battery_charger
What do you think? Answer below!
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roderick_young says:
May 25, 2013 at 9:29 pm (UTC 0)
For a panel that small, just connect the panel straight to the battery through a diode. A charge controller would prevent overheating of the battery when full charge is achieved, but with such a small current (0.5 A max), that is impossible.
If your battery is like a car battery size, a charge controller starts to make sense with a 60 to 100-watt panel.
There is another type of charge controller that tracks the maximum power point of the panel. That type starts to make sense at about 300 watts.