A quick and maybe stupid question

dapago · October 2017

Hello,

I have a 2480W array. I leave bulk charge generally at 11am meaning my CC enter Absorb mode at 11am and float mode at 1pm with still 2 good sun hours to go.

Either the bulk, absorb and float modes limits the current entering the batts below what are producing the panels per hour. Can the extra current be used for my day load? I have seen somewhere that when in float mode the load is taken directly from the panels and not the bank but is it the same in bulk and absorb modes when my PV is producing more than what the CC needs to properly charge the bank on those modes?

thank

Photowhit · October 2017

In general, yes.

The charge controller doesn't limit the current, but does limit the runaway voltage that happens when batteries are 80-85% full (flooded lead acid). There are several ways to end the absorb cycle, timed is the most common. after a hour or 2 the charge controller switches to float. Many battery banks can stand a longer time in absorb than the standard timed.

So loads will either be in noticed if less than the incoming current, or some charge controllers, will restart or move back to bulk if a load is larger than the in coming current can support.

Sophisticated charge controller, like your midnite classic can also switch based on end amps, switching when the battery is only accepting 1-2% of it's capacity. I think this can be done with it's on board shunt or using the Whiz Bang Jr attached to a shunt at your battery. The onboard shunt can only measure the current passing through the charge controller, so the Whiz Bang Jr it will measure the current passing to the battery rather than to the system, which would include loads.

dapago · October 2017

Photowhit said:

In general, yes.

The charge controller doesn't limit the current, but does limit the runaway voltage that happens when batteries are 80-85% full (flooded lead acid). There are several ways to end the absorb cycle, timed is the most common. after a hour or 2 the charge controller switches to float. Many battery banks can stand a longer time in absorb than the standard timed.

So loads will either be in noticed if less than the incoming current, or some charge controllers, will restart or move back to bulk if a load is larger than the in coming current can support.

Sophisticated charge controller, like your midnite classic can also switch based on end amps, switching when the battery is only accepting 1-2% of it's capacity. I think this can be done with it's on board shunt or using the Whiz Bang Jr attached to a shunt at your battery. The onboard shunt can only measure the current passing through the charge controller, so the Whiz Bang Jr it will measure the current passing to the battery rather than to the system, which would include loads.

So basically if I want to use the extra voltage for my load, I have to:
- use the CC special feature (end amps? Water not?)
-install the Whiz Bang Jr to measure the current passing to the bank

But in any case the extra power produced need to pass first through the bank before to be useable by the load?
And if so, how do I configúrate my CC to do so?
thanks

Raj174 · October 2017

Dapago,
The Whizbang jr. is really a battery monitor that measures the amp hours that go in and out of the battery. So, it can give you a fairly accurate measurement of the state of charge (SOC) of the battery. The Wihzbang jr. comes with instructions on how to install it and configure the Classic to use it.

The charge controller's job is to charge the battery. It applies current at the battery terminals. The inverter is also connected to these cables. If the load by way of the inverter draws current from it's connection to the battery, the charger will try to compensate by increasing the current. If it can't supply enough current, then the battery will make up the difference. When the load drops, more current will flow into the battery than the loads. This can happen in any charging stage, bulk, absorb or float. This will happen without any configuration change.

Rick

Photowhit · October 2017

dapago says;

So basically if I want to use the extra voltage for my load, I have to:
- use the CC special feature (end amps? Water not?)
-install the Whiz Bang Jr to measure the current passing to the bank

But in any case the extra power produced need to pass first through the bank before to be useable by the load?
And if so, how do I configúrate my CC to do so?
thanks

No, first it's extra wattage, voltage is not power. Your MPPT type charge controller will track the most effective incoming voltage and convert the incoming wattage to the correct voltage, maximizing your current (amperage)

In general, just don't worry about it, unless it's a huge load that you will be using often and for long periods every day.

dapago · October 2017

Raj174 said:

Dapago,
The Whizbang jr. is really a battery monitor that measures the amp hours that go in and out of the battery. So, it can give you a fairly accurate measurement of the state of charge (SOC) of the battery. The Wihzbang jr. comes with instructions on how to install it and configure the Classic to use it.

The charge controller's job is to charge the battery. It applies current at the battery terminals. The inverter is also connected to these cables. If the load by way of the inverter draws current from it's connection to the battery, the charger will try to compensate by increasing the current. If it can't supply enough current, then the battery will make up the difference. When the load drops, more current will flow into the battery than the loads. This can happen in any charging stage, bulk, absorb or float. This will happen without any configuration change.

Rick

Thanks Rick. So all the power is taken from the bank and the extra wattage produced by the panels if basically wasted. Unless you add extra batteries. I just wanted to try to optimize my batteries cycling.

dapago · October 2017

Photowhit said:

dapago says;

So basically if I want to use the extra voltage for my load, I have to:
- use the CC special feature (end amps? Water not?)
-install the Whiz Bang Jr to measure the current passing to the bank

But in any case the extra power produced need to pass first through the bank before to be useable by the load?
And if so, how do I configúrate my CC to do so?
thanks

No, first it's extra wattage, voltage is not power. Your MPPT type charge controller will track the most effective incoming voltage and convert the incoming wattage to the correct voltage, maximizing your current (amperage)

In general, just don't worry about it, unless it's a huge load that you will be using often and for long periods every day.

Great. What do you call a huge load? What about a diary 1200W/h load?

Raj174 · October 2017

Only wasted if it is not used by the loads.

Estragon · October 2017

If I'm understanding what you're thinking of doing, it's an opportunity load. To do this, you would typically connect an aux terminal on the controller to a relay appropriate for powering the load. There are various ways of setting the aux terminal behavior, eg power the aux terminal (which triggers the relay to change state) when transitioning to float. On classics, the aux1 and aux2 behave differently for different needs. Details in the classic manual.

dapago · October 2017

Estragon said:

If I'm understanding what you're thinking of doing, it's an opportunity load. To do this, you would typically connect an aux terminal on the controller to a relay appropriate for powering the load. There are various ways of setting the aux terminal behavior, eg power the aux terminal (which triggers the relay to change state) when transitioning to float. On classics, the aux1 and aux2 behave differently for different needs. Details in the classic manual.

Yes this is what I want (would like) to achieve. But I want the aux terminal (1 or 2 I will check the manual) to deliver 110V witch I think is not possible. So can I get an opportunity load directly connecting my 110V load to the inverter?
What kind of relay are you referring to?
thanks.

Estragon · October 2017

You can't get AC from the controller, it's all DC. The aux ports are also limited in the current they can supply, so only very small loads can be powered directly.

To power an AC load (eg), a normally open relay is wired into a circuit coming from the inverter or AC panel to the load to be switched. The controller could be set to supply DC voltage to the relay signal terminal on transition to float, which closes the relay and turns the load on.

The exact type of relay needed depends somewhat on the load.

dapago · October 2017

Estragon said:

You can't get AC from the controller, it's all DC. The aux ports are also limited in the current they can supply, so only very small loads can be powered directly.

To power an AC load (eg), a normally open relay is wired into a circuit coming from the inverter or AC panel to the load to be switched. The controller could be set to supply DC voltage to the relay signal terminal on transition to float, which closes the relay and turns the load on.

The exact type of relay needed depends somewhat on the load.

Thank you. Well then if I can’t get a 110V, the opportunity load is no use for me. Thank you for your help and explanations. Have a great day.

Estragon · October 2017

You CAN get 110vac from the inverter. A small DC wire from the controller can trigger a 110v relay to control your opportunity load.

bfitzgerald · October 2017

You can buy a relay that turns on a 120v, 1500 w.a.c. load (like a water heater). You can trigger it on or off with a 12v "signal" sent from your charge controller. You program the aux port signal. I do exactly that and about 90% of my hot water needs (spring and summer) are supplied by opportunity charging. It is reasonably automatic and won't allow too much power from the batteries to to be used for heating water. And the best part, the relay from Sparkfun costs less than 10 bucks. Easy and cheap.

Brian

nickdearing88 · October 2017

Opportunity loads are a great bonus. I really focused on mine this season and you'd be amazed at the extra power that would otherwise go "unused". Not only are you using "extra power" that would be wasted -- any opportunity load doesn't add to wear and tear on your batteries because you're not cycling them! This can add up a big $$$ savings with an off-grid system, since batteries wear and age. On my small system, I just use manual opportunity loads such as charging batteries of other devices, bread maker, laundry load, etc. I would use an automatic process on a larger system, like water heating.

As you study and get more familiar with the charging patterns of your system, you will learn the points at which to begin loads, through absorb and float, and how much of a load will safely avoid discharging your batteries.

Photowhit · October 2017

Please understand that an off grid system, must be wasteful! to have enough energy to charge your batteries and reach full charge once or twice a week even during cloudy weather the array size must be larger than your needs. I ran through some numbers a while back, if you use 1 Kwh of electric, it takes roughly 3 times the array size for an off grid system compared to a grid tied system.

Something else you Midnite charge controller can do is start a relay for you to run, say a electric water heater or pre heater, once the battery is full.

A large load will be different on different systems. a 1200W/h load on my 4000 watt array while in direct sun, will not change it's charging profile, on a 3000 it would be marginal, on a 2000 it would likely reduce the available voltage enough to change charging modes.

dapago · October 2017

I am totally lost hehehe. Unfortunately I can not rely on “profesional” here because there is none (welcome to the “third world”). Maybe someone can make me a little and simple diagram?

Estragon · October 2017

Classic DC aux terminal -----> relay DC control terminal {Relay} <------ 120Vac from inverter to relay ACin
} -------> switched ACout output to 120Vac load

The relay is just a switch controlled by the DC voltage instead of a toggle or whatever on a manual switch.
Hopefully this makes sense?

A quick and maybe stupid question

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