PWM charge controller

[eeefreakians]

I have 135 watt Kyocera panels with a rated output of 17.7 volts at 7.63 amps. Using Ohm’s Law:

17.7 volts x 7.63 amps = 135.051 watts

However, 17.7 volts is not useful to the amateur radio operator. The voltage needs to be converted down to approximately 13.5 volts to support a 12 volt battery and run amateur radio gear. Keep in mind that on a PWM solar controller, the output current will never exceed the input current:

13.5 volts x 7.63 amps = 103.005 watts.

my question

why doesnt the current change??? say in a boost converter ,will reduce the current and boost voltage. what am i missing here??

why the current isnt altered in PWM charge controller??

 

[KlausST]

Hi,

Ohm's law (R = V / I) is how you calculate resistance, not power.

Your shown values for V and I: be sure they are the full load values.

Keep in mind that on a PWM solar controller, the output current will never exceed the input current:

This may be true for linear regulators. But this is not true for switching step down regulators (with PWM and inductor).
For switching regulators the output current can be higher than the input current.

--> If you want to discuss this in more detail, then you need to show us your circuit.

Klaus

 

[FvM]

The question is what do you consider a "PWM charge controller"? If it implements a buck converter with inductor, it can of course increase the current. But if it only periodically interrupts the panel current without a storage inductor, it reduces the power delivery from the panel instead of converting voltage and currents.

 

[mtwieg]

The question is what do you consider a "PWM charge controller"? If it implements a buck converter with inductor, it can of course increase the current. But if it only periodically interrupts the panel current without a storage inductor, it reduces the power delivery from the panel instead of converting voltage and currents.

Apperently many cheap "charge controllers" work by basically connecting the panel directly to the battery via a FET which is controlled via a low frequency PWM. So they can charge a battery okay, but can't implement MPPT. These cheap types are often referred to as "PWM charge controllers," but sometimes they are also incorrectly referred to as MPPT controllers. A scam preying on ignorant consumers, basically.