SanTan Solar T Series 250W & Epever Tracer-BN Series MPPT

[fafrd]

4 250W panels @ 12V would be 83.333 amps and I would need a 100a controller, no?

I’ve got 380W panels with Isc of 10A, so something sounds off.

250W panels should have Isc under 10A for total input current of under 40A in 4P string.

These 250W panels are used, correct, so they’ve actusllly degraded (as much as 10% if they are 10 years old).

Despite whether the panels are effectively rated for 250W or 225W, they are rarely going to exceed 90% of rating, even during the highest-productivity part of the day.

So new 250W panels will pretty much never exceed 225W of actual output while 10-year-old 250W panels will rarely if ever exceed 202.5W of actual output.

A 4-panel array of these panels will max out at 900W if new or 810W if old.

The SCC is only about 97% efficient, so 900W max in = 873W max out (if new) or
810W max in = 786W max out )of old)

So charging a 12V battery, you’ll never exceed 73A with 4 new panels or 66A with old panels.

With a 60A SCC you’ll lose a maximum of ~18% power generated during the peak part of the day so paying a bit more for an 80A SCC might make sense.

With old panels, you’ll rarely lose more than 10% of generated power and only for the hottest ~1 hour of the day, so figure a maximum of 10% of 25% of a full days production might be lost, or ~2.5% per day. So a 60A SCC is probably more sensible with old panels.

My 250A Microinverters are powered by 335W panels (34% overpanelling) and I rarely max out and lose power.

If an 80A SCC costs the same as a 60A, it’s a no brainer to build in some headroom for future expansion and get the larger SCC.

But if there is much of any premium for the larger 80A SCC it will probably never pay off from the ~3kWh additional output it’s going to give you per year (or even the ~10kWh per year of additional output new panels would give you).

MPPT will increase string voltage to decrease input power whenever output current reaches maximum rating, so it’s purely a matter of some potential energy production that was not captured due to that output current cap coming into play…

 

[SDovey]

Looks like they are out of stock on these panels, anyone know where else I could get them?

I am putting these on a Sailboat and room is limited. What are the best output small footprint panels? I would like to get to a minimum of 1kwh with the least amount of room and/or panels possible.

 

[SDovey]

2S arrays do not require over-current protection. The panels are essentially self-fusing.

If you want a fuse or breaker between the panels and the MPPT. Most panels specify a maximum fuse size. If that info isn't available, select one that is at least 1.25X higher than the Isc value of the panel.

You'll need a 50A fuse or breaker between the MPPT and the battery.

Size all wires in accordance with awg specs and use a voltage drop calculator (select "Estimated resistance" tab) to confirm your wire gauge/length/current scenario is acceptable.

What are acceptable;
Voltage drop:
Voltage drop percentage:
Voltage at the end:

 

[sunshine_eggo]

What are acceptable;
(1) Voltage drop:
(2) Voltage drop percentage:
(3) Voltage at the end:

(2) is calculated from (1) and (3). (3) is determined from starting voltage, which is (1) + (3). Essentially, you only have one question.

"What is the acceptable voltage drop?"

Typically 3% or less, and that equates directly to power loss. In some cases, such as very long wire runs and/or expensive cable, one might choose to accept 5-10%.