Frequently Asked Question

Last Updated 4 years ago

WIDTH is the voltage range (usually 1.0 volts) that the PWM goes from full off to full on.
The Classic has a voltage resolution of 0.1 volts. That 1.0 volt width is divided up into 10 different PWM possibilities.
10% per 0.1V when set to 1 Volt Width, 5% per 0.1V when set to 2 Volts Width.

Every 0.1 volts, the PWM gets a bit wider or narrower depending on if the voltage is going up or down and if it is active high or active low.
Same frequency.... About 500 Hz

Pick a voltage "threshold"... Or, set point....

0% PWM is off all the time... 100% PWM is on all the time

50% PWM is off half the time and on the other half of the time etc...
Time here being 1/500 Hz or a period of 2 milliseconds
So, 50% would be on for 1 ms and off for 1 ms

So, if you want to limit something to 55.0 volts, that is your threshold voltage.

OK, battery V = 55.0 volts.
When the voltage is below 55.0 volts, the PWM is at 0%
When the voltage is at 55.5 volts, the PWM is at 50%
that is if the width is 1.0 volt
when the voltage is 56.0 volts, the PWM is at 100%
that is if the width is 1.0 volt

So, if you set the offset minus, you start below your charge setting.
For example, setting to -0.3 volts will give you 30% diversion up to and stop at your charge setting.
You will only get the other 70% if some other charging source tries to push the voltage past the setting.
It is suggested you set your target charge setting higher by 0.3V in this case so you always get to your needed voltage.
This diverts from your needed charge voltage to 0.3V above it to insure you get a full charge.
Most batteries will not be harmed with a voltage 0.3 or .4 higher.

Now you see ?
So, Waste-Not is simply where the threshold voltage is set to the Absorb or Float or EQ voltage

BUT it gets slightly more complicated than this because the CC wants to limit the battery voltage by raising the PV input voltage.

Same thing happens for when the Classic needs to limit the output current.
It has to raise the input/PV voltage closer to Voc to open it up and reduce output current
OR keep the battery output voltage from rising because the PV input voltage is higher than the battery voltage.

So, the Aux 2 would be switching a dump load on and off using a DC SSR of some sort
SSR because it is at around 500 Hz. A relay with contacts ain't gonna buzz that fast very well.

Ahhh.... Consternation turned to lucidation !  boB

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