What size epever MPPT?

[JayGuevara]

Guys.

I have 2 x 275w panels

What size MPPT is best?

It needs to be rated for 550w input right?

Cheers

 

[snoobler]

It needs to be rated for the charge current of the battery selected as well as the panel input voltage and current.

If you have a:
12V , 550/12 = 45.8A
24V, 550/24 = 22.9A
48V, 550/48 = 11.5A

The panel open circuit voltage needs to be well under the voltage rating as well as the PV amps input rating. Series/parallel affects this.

Your operating voltage of your panels, whether in series or parallel, needs to bet 50% or higher than the battery voltage.

SCC are often listed at a single 20, 30, 50A rating - that's the battery charge current. You need to dig into the specs to confirm:

1. Supports desired battery voltage
2. Supports desired panel configuration voltage
3. Supports desired panel configuration current
4. Has fully customizeable charging parameters compatible with your battery choice

It is also acceptable to "over-panel" a charge controller. This is sometimes done because panels rarely put out their true 100% rating for very long on any given day. I have a 6kW array, but my SCC can only handle 5.8kW. however, my panel configuration meets with the 150V and 70A INPUT limits on the SCC.

 

[JayGuevara]

It needs to be rated for the charge current of the battery selected as well as the panel input voltage and current.

If you have a:
12V , 550/12 = 45.8A
24V, 550/24 = 22.9A
48V, 550/48 = 11.5A

The panel open circuit voltage needs to be well under the voltage rating as well as the PV amps input rating. Series/parallel affects this.

Your operating voltage of your panels, whether in series or parallel, needs to bet 50% or higher than the battery voltage.

SCC are often listed at a single 20, 30, 50A rating - that's the battery charge current. You need to dig into the specs to confirm:

1. Supports desired battery voltage
2. Supports desired panel configuration voltage
3. Supports desired panel configuration current
4. Has fully customizeable charging parameters compatible with your battery choice

It is also acceptable to "over-panel" a charge controller. This is sometimes done because panels rarely put out their true 100% rating for very long on any given day. I have a 6kW array, but my SCC can only handle 5.8kW. however, my panel configuration meets with the 150V and 70A INPUT limits on the SCC.

Cool man. This is going on my van. Think run at 24v is more efficient and just get a step down 12v?

I'm in uk and our sunshine would hardly ever get panels to maximum effiency I guess.

Attached a pic with the spec off the back if the panels. I can get lots of these brand new at dirt cheap.

 

[snoobler]

24V is generally more efficient due to lower DC currents. DC-DC 24-12V converters are common. Those look like good panels and are fine for a 24V system.

 

[tictag]

Your choice of battery system voltage, imho, should depend on your expected load. As a rule of thumb:

• 1W to 3,000W -- 12V battery system
• ~3,000W to 5,000W -- 24V battery system
• >5,000W -- 48V battery system

What size MPPT is best?

If you want to optimise on cost, it's generally good practice to over-panel your array by around 30% so in your case an SCC with a nominal power output of around 385W would be cost-optimised e.g. 26A at 14.6V (so a 30A controller for a 12V nominal battery system) or 13A at 29.2V (so a 15A controller for a 24V nominal battery system).

At 2 x 38.5V you would need an SCC capable of supporting 100V if connected in series, or circa 75V if connected in parallel.

 

[JayGuevara]

Your choice of battery system voltage, imho, should depend on your expected load. As a rule of thumb:

• 1W to 3,000W -- 12V battery system
• ~3,000W to 5,000W -- 24V battery system
• >5,000W -- 48V battery system

If you want to optimise on cost, it's generally good practice to over-panel your array by around 30% so in your case an SCC with a nominal power output of around 385W would be cost-optimised e.g. 26A at 14.6V (so a 30A controller for a 12V nominal battery system) or 13A at 29.2V (so a 15A controller for a 24V nominal battery system).

At 2 x 38.5V you would need an SCC capable of supporting 100V if connected in series, or circa 75V if connected in parallel.

Went for 12v in the end and bought a Epever BN-Series Tracer 40 amp MPPT... the one Will likes!
Says maximus panel array of 525w and mine are 550w but I cant ever imagine them pumping out full cap here in the UK?

 

[tictag]

You'll probably be fine, just don't chance it with the input voltage and remember that in cold, sunny weather array Voc can rise by as much as 10%.