Inverter Capacity from Solar Panels???

[vanidasen]

Hi All
I am planning on scaling up my solar inverter system.
I have:
1. Open Range Solar Inverter 3KVa / 2.4Kw
2. 2 X 105Ah batteries
3. 2 X 415W Canadian solar panels (Approx. 50V and 10A)
Solar Charger:
4. Max PV voltage is 80V
5. Max PV amps is 50A
6. System voltage: 24V DC

I already have two 415W panels in parallel. So 50V and about 20A max here.
My plan is to put another two 415W panels and have them all in parallel. So theoretically 50V and 40A max

Does anyone foresee any problem on this potential setup?
My plan is to get a 5KW inverter at a later stage so i dont want to add further panels later. Just change their configuration.

 

[TheChamp]

Hi All
I am planning on scaling up my solar inverter system.
I have:
1. Open Range Solar Inverter 3KVa / 2.4Kw
2. 2 X 105Ah batteries
3. 2 X 415W Canadian solar panels (Approx. 50V and 10A)
Solar Charger:
4. Max PV voltage is 80V
5. Max PV amps is 50A
6. System voltage: 24V DC

I already have two 415W panels in parallel. So 50V and about 20A max here.
My plan is to put another two 415W panels and have them all in parallel. So theoretically 50V and 40A max

Does anyone foresee any problem on this potential setup?
My plan is to get a 5KW inverter at a later stage so i dont want to add further panels later. Just change their configuration.

Can't tell if we don't know the specs of the inverter in regard to the solar limitations.

 

[vanidasen]

Can't tell if we don't know the specs of the inverter in regard to the solar limitations.

i assumed that point 4, 5 and 6 gave those limitations.
I have also attached the specs from the manual.

 

[itareanlnotani]

Looks ok to me.

20A is under the limits, and 50V is well under 80V - whats the open circuit voltage on those panels to double check?

 

[TheChamp]

The only issue for now is that your panels Vmp is out of the inverter's range, but besides not reaping the full benefits of the solar no harm will come of it.

I see it's a PWM inverter so you are really going to lose out on valuable amps from the panels.

 

[vanidasen]

I have attached datasheet portion of the panels. Yes it is PWM. Hope to get an MPPT controller when I upgrade inverter.

I just wanted to make sure that nothing would blow/short when i have 4 of these panels in parallel. So it will be 50V and possibly 40A max from these 4 panels.

 

[agentrfr]

You are going to pop those batteries if you add any more current. You're already at about 0.2 C (105Ah/20A) which is twice what you should be at to prolong the lifespan of the batteries (0.1C assuming they are lead-acid)

Consider adding more batteries in parallel first

 

[agentrfr]

Using an mppt will bump up that amperage even more, so just be careful

 

[vanidasen]

Very interesting. I never thought of the current going to the batteries.
Okay, will consider 2 X 200Ah batteries .
Thanks to all for the great advice.

 

[vanidasen]

@agentrfr: Just been paging through manual. There is a setting for max charging current which i set to 30A. Range for this is (20, 30, 40 and 50A). Manual says, Max charging current= utility charging current + solar charging current.
Then there is a setting for max utility charging of which the range is 20 or 30A. I set it to 20A.
Does this not mean that the inverter will only allow 10A from PV to charge the battery?
And balance of PV amps will feed directly to circuit if required.

My inverter is set to solar powering load first and when there is no light it automatically switches to utility in the evenings. So no unnecessary cycling of the batteries in the evening.

 

[TheChamp]

Very interesting. I never thought of the current going to the batteries.
Okay, will consider 2 X 200Ah batteries .
Thanks to all for the great advice.

Because it doesn't necessarily mean it's going to the batteries, the batteries will get what you have set on the inverter and the excess current will be consumed by your load.

 

[TheChamp]

@agentrfr: Just been paging through manual. There is a setting for max charging current which i set to 30A. Range for this is (20, 30, 40 and 50A). Manual says, Max charging current= utility charging current + solar charging current.
Then there is a setting for max utility charging of which the range is 20 or 30A. I set it to 20A.
Does this not mean that the inverter will only allow 10A from PV to charge the battery?
And balance of PV amps will feed directly to circuit if required.

My inverter is set to solar powering load first and when there is no light it automatically switches to utility in the evenings. So no unnecessary cycling of the batteries in the evening.

Set the maximum charging current to 20A. What it all means is that if solar is not available utility will supply all the 20A needed to charge the batteries, if however your solar is performing exceptionally well on a particular day and can supply all the 20A then it will do just that, you will get all your charging current from the solar.

If solar can only supply half the charging current then utility will pick up the slack for the remainder.

 

[TheChamp]

You are going to pop those batteries if you add any more current. You're already at about 0.2 C (105Ah/20A) which is twice what you should be at to prolong the lifespan of the batteries (0.1C assuming they are lead-acid)

Consider adding more batteries in parallel first

The inverter will control what amount of current goes to the battery.

 

[vanidasen]

Thanks for the breakdown.

 

[agentrfr]

The inverter will control what amount of current goes to the battery.

The charge controller controls the charge going to the battery.

@vanidasen
Reading between the lines, OP is using a PWM charge controller. Most PWM charge controllers have an output to an inverter, such that the inverter is connected to the charge controller instead of directly to the batteries.

The job of the charge controller is to ensure that the battery is not overcharged either by voltage or current, as well as ensure that the battery does not go down too low in voltage to damage the electrodes' surfaces. (Some inverters dont come with a low voltage cutoff since it is assumed batteries are protected on the battery end as the inverter does not know the chemistry of the attached voltage supply. Of course fancier inverters allow you to tell it what the chemistry of the batteries are, but I assume that is not the case here)

PWM works by lopping off the voltage supplied by the solar that is too high for the battery, up to the set current.

Example here, OP has 50 V panels and a 24 V battery system. Max charge for the batteries is around 29.2 V, so the PWM must cut away about 20 V of the supplied 50V, for a charge supply efficiency of 60 % (assuming Imax is reached)

An MPPT charge controller bucks the excess voltage into more current to maximise the charge efficiency of the solar supply. MPPTs get to be around 95% charge supply efficenct.

The problem here with OP's setup is that he only has 105 Ah @ 24 V. In theory he should only charge the batteries at 0.1 C, or about 10 A. He is already charging at 0.2 C. This is the weakness in the current setup, so this must be upgraded first before anything else.

@agentrfr: Just been paging through manual. There is a setting for max charging current which i set to 30A. Range for this is (20, 30, 40 and 50A). Manual says, Max charging current= utility charging current + solar charging current.
Then there is a setting for max utility charging of which the range is 20 or 30A. I set it to 20A.
Does this not mean that the inverter will only allow 10A from PV to charge the battery?
And balance of PV amps will feed directly to circuit if required.

My inverter is set to solar powering load first and when there is no light it automatically switches to utility in the evenings. So no unnecessary cycling of the batteries in the evening.

It sounds like a poor chineese translation, but I am going to assume that "utility charging current" is the current permitted to battery itself (since solar current = current to battery + battery to load). May you link to the manual / take a couple pictures as well as a picture of the wiring of the charge controller?

 

[agentrfr]

The inverter will control what amount of current goes to the battery.

unless the charge controller is built into the inverter xD

OP what is the model of the inverter/charge controller?

 

[TheChamp]

unless the charge controller is built into the inverter xD

OP what is the model of the inverter/charge controller?

Yes it is, it's one of the Axpert type models. He seems to be looking past the inverter anyway and planning ahead, a PWM inverter is a non starter for anything serious.

 

[deweyzeph]

The inverter is powered by the batteries, not the solar panels. The solar panels charge the batteries. So really the question is not whether your solar panels are sufficient for your inverter, but whether your solar panels are sufficient to charge your batteries.

 

[vanidasen]

The charge controller controls the charge going to the battery.

@vanidasen
Reading between the lines, OP is using a PWM charge controller. Most PWM charge controllers have an output to an inverter, such that the inverter is connected to the charge controller instead of directly to the batteries.

The job of the charge controller is to ensure that the battery is not overcharged either by voltage or current, as well as ensure that the battery does not go down too low in voltage to damage the electrodes' surfaces. (Some inverters dont come with a low voltage cutoff since it is assumed batteries are protected on the battery end as the inverter does not know the chemistry of the attached voltage supply. Of course fancier inverters allow you to tell it what the chemistry of the batteries are, but I assume that is not the case here)

PWM works by lopping off the voltage supplied by the solar that is too high for the battery, up to the set current.

Example here, OP has 50 V panels and a 24 V battery system. Max charge for the batteries is around 29.2 V, so the PWM must cut away about 20 V of the supplied 50V, for a charge supply efficiency of 60 % (assuming Imax is reached)

An MPPT charge controller bucks the excess voltage into more current to maximise the charge efficiency of the solar supply. MPPTs get to be around 95% charge supply efficenct.

The problem here with OP's setup is that he only has 105 Ah @ 24 V. In theory he should only charge the batteries at 0.1 C, or about 10 A. He is already charging at 0.2 C. This is the weakness in the current setup, so this must be upgraded first before anything else.


It sounds like a poor chineese translation, but I am going to assume that "utility charging current" is the current permitted to battery itself (since solar current = current to battery + battery to load). May you link to the manual / take a couple pictures as well as a picture of the wiring of the charge controller?

I have set the max charging current to 20A. So neither the solar nor the utility will surpass that current. The setting for Utility max is also set to 20A.
The PWM charge controller is built in.
I have set battery low voltage cut off to 23V.
But there is another setting that allows batteries to suspend supplying the load at 24.5 as long as there is either solar or utility available. Batteries dont work at night as long as there is Utility power available.
Remember there are TWO 105Ah batteries. Not sure if that is still 0.2C or will now be 0.1C because of two batteries.

All spec sheet pages from manual is attached. I have the 3KVa/2.4KW version.

I just wanted to ensure that when i add two 415W panels to my existing two 415W panels, that nothing will fry or blow. All 4 panels will be in parallel of course to stay under inverter maximums for voltage and amps from PV.

Also, this application will be temporary as i am going to upgrade to a 5KW inverter with an MPPT charge controller and possibly better battery capacity like maybe 2 X 200Ah or even a 2/3KW lithium battery.

 

[Geoff.D]

Why are you wanting to buy more panels if they are not needed?
The batteries care in series connected as a 24 volt bank with one string. The current flowing is this the same through both batteries, assuming balanced charging of course.