A few silly and basic questions about diversion loads

[5 Minutes 2 Midnite]

I may start using a system full time that I have set up just for emergencies when the power goes out (COVID-19 may precipitate this need). Up until now the system has had only light use, but if it's going to go into full use I want to understand the concept of diversion loads, which I've read about only in passing. I perused some definitions and a few threads here before posting.

1) Somewhere in the back of mind there has been a slight perception that diversion loads may be necessary if the system is producing significantly more power each day then is actually used. In looking at some diversion loads videos there was even a mention of any excess power being burned off by the charge controller in the form of heat. That of course would be a concern in terms of possibly reducing the life of the controller due to higher temperatures.

But as best I can tell from looking at Classic threads, when the batteries are fully charged the charging circuit simply opens. Thus no power/heat to dissipate. Is that the way it works? Is it that simple?

2) There seems to be a philosophy of using diversion loads to avoid wasting power. That is not a concern here. I am currently adding more panels, simply to be able to gather more sunlight on cloudy days to insure being able to fully charge the batteries each day. I don't really think of the extra power on sunny days as being wasted. This brings me to my second question: If I wanted to charge, say, my electric car, is there any reason I would want to use a diversion load? Why not simply add the load along with all the other loads running off the inverter? It would seem the system would simply supply the additional power needed through the inverter. (It also seems that the question of whether there would be enough power to run the load as well as charge the batteries is the same whether the power is being supplied by the inverter or by a diversion load.)

The only reasons I can fathom to use a diversion load to satisfy the requirement to charge the EV would be:

a) the current draw of the EV is too great for the inverter

b) you want the load from charging the EV to be automatically disconnected when the charging source (say PV) wanes. You don't want charging the EV to take the batteries down.

So assuming in my case the EV draw is not too much for the inverter, and I don't mind unplugging the EV when the sun goes down, is there any compelling reason to go to the trouble and expense of adding a diversion load circuit?

thank you
jim

[ClassicCrazy]

Yes you don't need any diversion loads if you are only worried about over heating the Classic when the batteries are full.   
As  you said when the batteries are full the Classic doesn't have to do much ( it does not disconnect , it just puts in as much power as needed for loads )

You could do a couple of things to limit loads  on the inverter . Be around to monitor and manually shut EV charger off if  you don't have enough sun.  Or use a timer to limit the amount of time the EV charger would be on.

The other option is to use the AUX relays inside the Classic to control something . There are various ways to do that . The way I am using it now is I use the AUX to be able to turn a SSR solid state relay on and off - and that relay is controlling the power to an outlet.
There are a lot of different AUX logic options if you look in the manual. Or go to the first home page of the forum and search AUX because there are lots of posts about what you will want to know.

Since I have a Whizbang on my Classic I can't use AUX 2 since the whizbang uses that. So I am using AUX for the outlet and I have it so it will turn the power to that outlet on at  something like 95% and off at 94%   - just as example .  It could be 99% and 96% or anything . There are all kinds of other options in AUX to control things .

It is true that if you run large loads on your inverter and there is sun to charge the batteries then the Classic is going to run more amps through it and run warmer.  The Classic is designed to do this and also will cut it's output back if it gets too warm . But if your system is designed right you should be able to use all the power the Classic is capable of.

Some people want to get every last watt out of their system , others like me don't care about that and just what I need to use is fine. Like you my system has lots of PV for short winter and overcast days.  So when the sun is out -- lots of power available.

Larry

[boB]

Using an AC load off of the inverter is just fine.  It could still be considered a diversion load if it is being turned on after the batteries reach Absorb or if the unused power would be considered as "wasted".  The object though is to not discharge the batteries with this load.  At least not too much.


In fact the inverter  IS a DC load as far as the charge controller and batteries are concerned.

You can just turn on those loads manually OR you could get the Aux outputs of the Classic to control that AC load, whatever it turns out to be.

Could be to heat water or to pump water up hill...  One friend said he wanted to make and store hydrogen with the extra electricity.

[5 Minutes 2 Midnite]

Thanks CC and boB. That all confirms my hunches. But better facts than hunches, so thank you for replying.

[5 Minutes 2 Midnite]

By the way, boB's answer made me think about one possible config for diversion loads; Do some folks power a second inverter direct from the power source (PV or whatever), bypassing the batteries?

[ClassicCrazy]

By the way, boB's answer made me think about one possible config for diversion loads; Do some folks power a second inverter direct from the power source (PV or whatever), bypassing the batteries?

Easy answer - it won't work and would be no advantage to trying to do it anyway.

Larry

[5 Minutes 2 Midnite]

Very good. Thank you Larry.

[boB]

By the way, boB's answer made me think about one possible config for diversion loads; Do some folks power a second inverter direct from the power source (PV or whatever), bypassing the batteries?

Easy answer - it won't work and would be no advantage to trying to do it anyway.

Larry

It COULD work with some of these batteryless inverters that are out now.

But they would have to have their own PV array so that isn't really dumping extra power from the PV that is being wasted.

This is because a PV cannot be connected in parallel with another charge controller's input.  You COULD however have a separate switch to steer the once source PV but that would be kind of awkward

[bee88man]

There is a add-on after market diversion for grid-tied (battery or not) that is good enough to hold the poco meter suspended or held still with precision...no grid bought...no PV sold up to full PV production.
AC Resistance heated water storage is the diversion load and it never misses a coulomb..uses standard 120-240 volt immersion elements in properly sized storage..
With the  systems that do have the  battery bank the inverter will need to be smart enough to handle the battery regulation.
All  battery charging remaing throughout if having global charging from the inverter.Flluating house loads are constantly measured and adjusted for on the fly.
Whenever PV doesn't keep up then grid power is passed through only to whatever amount of the shortage is beyond PV available at the moment..
All measurement to choose whether to buy, sell or divert are made 120 times per second...it is all run by microprocesser same as an Aurdino.