Trying to match solar panels to previous purchased SCC

[JWWRadio]

I have already have the Victron MPPT 150 | 45 SCC.

I was looking at (2) 250 watt panels wired Parallel.

Specs on each are:

250 watt
Max V: 18.7v
Max Current: 13.3a
VOC: 22.5v


So if wired parallel (please check me):

509 watt
Max V: 18.7v
Max Current: 26.6a
VOC: ?


Will my Victron SCC be oversized? Will the 45a accommodate me with the 26.6a from panels. A third 250 watt panel would bring current to 39.9A.

Thoughts?

My power bank is 12v - 280ah.

Forgive me, just trying to come to an understanding.

Jeff

 

[Drunkin Solar]

I would definitely recommend to overpanel that setup depending on your situation and also to wire the panels in series instead of parallel.
A third panel will help with unproductive days unless your usage only calls for very light loads.
What do you plan to power up?

 

[chrisski]

Victron allows over amperage and you are under spec. 540 watts for a 12 volt 45 amp MPPT.

Also, it’s not the just the amps in limited to 45 amps, it’s the amps out. 45 amps x 12 volts = 540 watts.

I’d go with the two panels for a while, and if max daily output is less than 540 watts, I’d add another. I would not want to overpanel by more than 20%.

Check the manual, but likely says max PV input is 20% more than VOC of panels. You could go 2s2p and still be within specs.

I used to overpanel by much more, but I recently had a Victron MPPT die that had been overpaneled for years. I will never know why it died.

 

[DIYrich]

You need a minimum voltage for panels (in series) of battery voltage plus 5v, so around 60v for a 48v battery to charge at 55v.

 

[Q-Dog]

That controller can pass through up to 650 watts at 12 volts, so you are not overpanelled at all with the 150/45.

 

[Wibla]

The limits you have to worry about:
Max Voc: 150V (145V max operating voltage)
Max Isc: 50A

I would recommend 3x250W in 3s or 4x250W in 2s2p.
Would not recommend 3p unless you have shading issues.

 

[Mattb4]

The limits you have to worry about:
Max Voc: 150V (145V max operating voltage)
Max Isc: 50A

...

The Victron SCC rating is 150Voc and maximum charging amperage of 45A. Do not confuse PV amperage in as part of that rating other than obviously you can not get 45 A out without sufficient wattage from the panels. W=VA Watts from panels must equal (with some loss) the watts charging. 45A at 12vDC = 540W

Panels wired to develop higher voltage than the battery will see the amperage much lower. Say you wire in series the 2 OP panels to deliver ~36vDC. 500W/36vDC= 13.89A going to SCC. Charging amperage from SCC would be 500W/12vDC=41.67A

 

[Wibla]

The Victron SCC rating is 150Voc and maximum charging amperage of 45A. Do not confuse PV amperage in as part of that rating other than obviously you can not get 45 A out without sufficient wattage from the panels. W=VA Watts from panels must equal (with some loss) the watts charging. 45A at 12vDC = 540W

I am not confusing it, are you?
My post only referred to connecting up panels to his MPPT, not output. This should be self evident based on the units I used, Voc and Isc.
See also: Victron datasheet.

Panels wired to develop higher voltage than the battery will see the amperage much lower. Say you wire in series the 2 OP panels to deliver ~36vDC. 500W/36vDC= 13.89A going to SCC. Charging amperage from SCC would be 500W/12vDC=41.67A

As an industrial automation engineer, I always appreciate being schooled in the use of Joule's law.

In his case, if he adds enough panels to max out his charge controller, he will be looking at 45A output current from his MPPT controller at 13.2 - 14.4 volts depending on state of charge (and when his BMS kills charging unless the Victron is configured correctly). That means roughly 590 - 645 watts.

E: at 500W output power, we're looking at ~35-37A depending on state of charge, not 41A...

 

[Mattb4]

I am not confusing it, are you?
My post only referred to connecting up panels to his MPPT, not output. This should be self evident based on the units I used, Voc and Isc.
See also: Victron datasheet.


....

No I am not confused. Sorry to upset your feelings. Emotional people are hard to deal with.

 

[JWWRadio]

Thanks all. Let me chew on this info for a bit. I live in Hurricane alley and essentially will keep storage charged up ahead of storms. Typically we can be without power for up to 2 weeks. I really want to keep frig cool and maybe some fans. I know Air Conditioning is off the table but we deal with it every couple of years.

South Louisiana

Jeff

 

[Q-Dog]

3 of those panels you mention in your first post would work well in series with that 150/45 charge controller. Would be OK in parallel at 12 volts, but you may have to add fuses to the panels.

 

[DIYrich]

Rough numbers, you need 2kWh per day to run the fridge, and 1kWh for an inverter (unless you have a 12v fridge).

750w of panels is cutting it close. Do you have a generator to recharge the battery? If not, I would get 10kWh of battery, and 2kW of panels for 2 weeks of grid down.

 

[Wibla]

You don't necessarily have to run the inverter 24/7 to keep the fridge cold (enough) in an emergency... if the fridge isn't completely shit it will keep temp for a while as long as you don't open it.

 

[Q-Dog]

The battery only has to carry your loads through the night. You can use solar panels and/or a generator to recharge the battery and carry loads during the day.

 

[JWWRadio]

Rough numbers, you need 2kWh per day to run the fridge, and 1kWh for an inverter (unless you have a 12v fridge).

750w of panels is cutting it close. Do you have a generator to recharge the battery? If not, I would get 10kWh of battery, and 2kW of panels for 2 weeks of grid down.

I do have a 6500 watt gas powered Generac. Hate running it 24 hrs per day and oil changes every 100 hrs of use. But not opposed to running periodically in the hurricane aftermath scenario.

 

[JWWRadio]

The battery only has to carry your loads through the night. You can use solar panels and/or a generator to recharge the battery and carry loads during the day.

Absolutely.

 

[DIYrich]

I do have a 6500 watt gas powered Generac. Hate running it 24 hrs per day and oil changes every 100 hrs of use. But not opposed to running periodically in the hurricane aftermath scenario.

0.5c charge rate is at the upper limit for lifep04 battery, or 1600w for a 12v@280a battery. 2 hour run time per day when the sun is not shining.

 

[JWWRadio]

I would definitely recommend to overpanel that setup depending on your situation and also to wire the panels in series instead of parallel.
A third panel will help with unproductive days unless your usage only calls for very light loads.
What do you plan to power up?

I have three Eco Worthy LiFEPo batteries. (1) 12v 280Ah and (2) identical 12 v 100Ah. I guess I am mis-match on the batteries. So I guess I was thinking I had to stay at 12 volts by wiring the batts in parallel.

Don't I need to wire the two (or three) panels to match the voltage of the batteries?

 

[Drunkin Solar]

The panels need to produce at least 5v more than battery voltage to start charging. That said the controller takes care of matching voltage for the batteries (charging profile) you will probably have better charging efficiency with the panels in series (higher voltage).

Those mis-match of batteries should be okay in a 12v configuration if properly wired.

 

[Q-Dog]

Don't I need to wire the two (or three) panels to match the voltage of the batteries?

No. That is the magic of MPPT. The MPPT finds the Maximum Power Point and adjusts/manages the voltage to produce whatever the batteries need. You just have to make sure you don't overvolt the Victron and you do that when you figure out how to wire the panels.

 

[JWWRadio]

No. That is the magic of MPPT. The MPPT finds the Maximum Power Point and adjusts/manages the voltage to produce whatever the batteries need. You just have to make sure you don't overvolt the Victron and you do that when you figure out how to wire the panels.

Ah! Got it.

Jeff

 

[JWWRadio]

The panels need to produce at least 5v more than battery voltage to start charging. That said the controller takes care of matching voltage for the batteries (charging profile) you will probably have better charging efficiency with the panels in series (higher voltage).

Those mis-match of batteries should be okay in a 12v configuration if properly wired.

Thank you sir....

Jeff

 

[JWWRadio]

How bad did I foul up by purchasing two 12v 100ah batteries and one 12v 280ah battery. They are all EcoWorthy. I will need one more 12 volt to be able to wire them for 48v.

 

[Wibla]

280 Ah + 100 Ah + 100 Ah + ??? Ah in series ... that's a bad idea.

 

[CaliSunHarvester]

How bad did I foul up by purchasing two 12v 100ah batteries and one 12v 280ah battery. They are all EcoWorthy. I will need one more 12 volt to be able to wire them for 48v.

Can you still return them?