Frequently Asked Question

NOTE: There may be a bug in certain firmware that causes erratic operation.  It will be fixed in a future release.
 
HOW DOES AUX2 "WASTE NOT HIGH" PWM DIVERSION WORK?

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% to 100% in 10% steps. 0.1v=10%, 0.2v=20%, 0.3v=30% and so on.

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 and OFFSET is = 0.
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)
WIDTH=1v gives you 10 of 10% steps, WIDTH of 2v gives you 20 or 5% steps. (leave it at 1v unless you know what you are doing)


Now, this is not going to do any diversion UNLESS some other charging source pushes the voltage ABOVE the Classic's settings.
So, if we want to divert, we must use a negative offset.
Say -0.2 volts. This allows up to 20% diversion capped at 20% unless something pushes it ABOVE the Classics settings.

And, since we are diverting power starting at a -0.2v, we might want to set the Classic's voltages an extra 0.2v higher to insure we are getting a proper charge. (Up to 0.5v higher is not going to hurt most lead-acid batteries.) The voltage tolerance in the Classic is only plus or minus 0.1v anyhow so being a bit higher is good.

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. (Solid State Relay)
SSR because it is at around 500 Hz. A relay with contacts ain't gonna buzz that fast very well.

(This document was interpreted and re-written from an engineers notebook with an attempt to simply into understandable terms, if you do not understand what is being said here then you probably should not be attempting to use diversion. Diversion done wrong may result in battery damage and Midnite Solar is in no way responsible)