Diverting (Waste Not Hi) During Bulk

[DEinME]

Is the Classic supposed to be diverting (waste not hi) during bulk charging?

One of the two Classics has AUX2 connected to an SSR for diverting AC from the inverter. Sometimes the Classic will turn on AUX2 with Waste Not Hi during bulk charging. It keeps the battery voltage about 1.7 volts below the set point for absorb. There's plenty of power for full absorb voltage if I shut off waste not hi. It is configured with volts -0.2V, width 1V. The two classics are configured to follow and both have software Rev 2193. The problem only happens when I'm running other loads of about 2kW from the inverter.  Turn off the loads and the Classic will bring the batteries up to Absorb.

I'm going to abandon the idea of diverting 110VAC. The waveform is pretty rough with this diversion and causes flickering lights. The setup for this is diverting 110VAC from the breaker panel powered by a Magnum 4448 PAE split-phase inverter. AUX2 powers an AC SSR which is then connected to a 220V 9.5 ohm dryer coil. Even though I'm abandoning this now, I do plan to use diversion for hot water once I have water.

I could understand if the relay was on in Bulk with the voltage 0.2V below the Absorb setpoint, but 1.7V low seems odd.

With Waste Not Hi turned off, both Classics charge normally.

-

There's another oddity too:

In Absorb, the whole thing works OK although it leaves lots of power unused. For example, with both arrays in full sun, one Classic is almost idle while Waste Not Hi gives a duty cycle of about 50%. I can change the Waste Not Hi parameter volts to -0.3V and the dryer coil gets hotter although my multimeter  always says about 50% duty cycle. I can turn off Waste Not Hi, take the 2 wires off the "load" terminals of the SSR and connect them to each other. When I turn on the breaker for that circuit, the dryer coils get much hotter than they ever do with the SSR and Waste Not Hi. These could just be things I need to learn how to configure. It's clear that my Extech multimeter is not up to measuring the duty cycle. I don't have a clamp-on ammeter; should probably get one that measures DC as well as AC.

Thanks for your help.

Edit to add: The control board in this Classic is one I got from FNG. SN: CL30XXX

[boB]

I was going to say to reduce the voltage from -0.2V to something even lower but if you are seeing it divert at -1.7 volts below then maybe try raising the reference to + 0.5 volts or something and see what happens ?

Usually for a 48V system you can go more than 0.2 volts below absorb just fine.  It's that -1.7V part that is kind of confusing.

boB

[DEinME]

When the sun returns I'll try that.

Thanks.

[DEinME]

I was going to say to reduce the voltage from -0.2V to something even lower but if you are seeing it divert at -1.7 volts below then maybe try raising the reference to + 0.5 volts or something and see what happens ?

Usually for a 48V system you can go more than 0.2 volts below absorb just fine.  It's that -1.7V part that is kind of confusing.

boB

I tried +0.5V and voltage improved some while still diverting in Bulk and keeping the battery about a volt low.

You said "or something" so I increased the AUX2 "volts" to +0.8V and it increased the voltage a little more and still diverts during Bulk.

So I tried +1.2V and the Classic doesn't divert during Bulk but does divert pretty early in Absorb and it keeps the battery voltage pretty close to the Absorb voltage with t-comp on and Waste Not Hi off.

I left the volts at +1.2V but turned off Waste Not Hi because I am abandoning 110VAC diversion. I don't have a correctly-sized DC SSR.

Thanks.

edit to clarify one convoluted sentence: "So I tried +1.2V and the Classic doesn't divert during Bulk but does divert pretty early in Absorb and it keeps the battery voltage pretty close to WHAT the Absorb voltage WOULD BE with t-comp on and Waste Not Hi off.

[boB]

Thanks DE !

Great  information !

[DEinME]

Waste Not Hi is still acting strange.

A neighbor/engineer/solar guy stopped by yesterday. I turned on Waste Not Hi to show him the diversion load and the classic didn't divert. I had to turn down the volts to .9 to get it to divert. The Classic was in Float at the time.

This morning, I tried while the Classic was in Absorb and it was keeping the battery voltage low and I could turn volts back up to 1.2 while still diverting.

I can also change the actions of Waste Not Hi by changing the loads on the inverter but they work backwards of the way I'd expect. When I turn on a 1500W heater, the Classic diverts more. When I turn off the 1500W heater, the Classic diverts less or turns diversion off. This is not a heater connected as a diversion load, but a "milk house" heater plugged into a normal outlet. So when the inverter is drawing more current from the battery, the Classic also diverts more current. This happens in Absorb or in Float.

It seems like I have to find a value for volts that works with either Absorb or Float and also works with variable loads on the inverter. I'm still not regularly using Waste Not Hi because I don't want the flickering LEDs but I will want it to divert DC in the future.

You are welcome to doubt anything I've written and I can check again. Sun for the rest of the week.

Thanks.

edit 2. Edit 1 is wrong. Some clouds have moved in recently and I didn't notice from the basement. Trying again, turning on 2.7kW of 120V load decreases battery voltage by 0.5V to 0.7V when skies are partly cloudy and both Classics are in Float. I'll leave edit 1 there but it's wrong.

edit. Turning on the milk-house heater causes the battery voltage to drop by about 1 volt while both charge controllers are in Float with full sun on the arrays. The battery voltage and the Whiz-bang are the only connection between the 110V loads and the charge controllers. (At least the only connections I can think of.)

[boB]

OK...   Something's rotten.

Will look into it.

boB

[kitestrings]

That is strange.  I'll be curious to learn what you find.

We use Waste-not Hi for pre-heating DHW using DC elements via SS relays.  Ours is set at -0.2V with a 1V Width.  I've play with other settings, but this seems to work pretty well for us.

The DC diversion works well, but you do have oversize the relays quite a bit and make sure to have ample heatsinks.  Overwise, heat kills them.

An AC/DC clamp on meter is really handy for this RE stuff as you mentioned, but also for the car electrical, the garden tractor, end-use equipment, so many things - I would be without one now.

Good luck, ~ks

[DEinME]

OK...   Something's rotten.

Will look into it.

boB

Any thoughts?

[boB]

OK...   Something's rotten.

Will look into it.

boB

Any thoughts?

No, not yet, sorry.

boB