What Solar Controller would you recommend for 4 of these panels on top of my RV?

brichards · February 2019

I am mounting 4 of these Sunpower 435 watt panels on my RV roof.

48 Volt Lithium Battery Bank

1) What controller would you use for my 48 volt battery bank and these type panels.

2) Wire in Series / Par.

1 of 4

2 of 2

3) In addition I am wiring 2 additional of these panels - mounted on the side of my RV that will be able to tilt up like a small awning over a window, but these 2 panels will be on a smaller separate controller.

Panels being used for this system.

Sunpower

https://us.sunpower.com/sites/sunpower/files/media-library/data-sheets/sunpower-e-series-commercial-solar-panels-e20-435-com-datasheet-521912-revb_1.pdf

SPR-E20-435-COM

Rated Power - 435 W

Nominal Power (Pnom)6 435 W

Power Tolerance +5/−3%

Avg. Panel Efficiency 20.3%

Rated Voltage (Vmpp) 72.9 V

Rated Current (Impp) 5.97 A

Open-Circuit Voltage (Voc) 85.6 V

Short-Circuit Current (Isc) 6.43 A

Max. System Voltage 1500 V UL & 1000 V IEC

Maximum Series Fuse 15 A

Power Temp Coef. −0.35% / o C

Voltage Temp Coef. −235.5 mV / o C

Current Temp Coef. 2.6 mA / o C

Operating Condition And Mechanical Data

Temperature −40° F to +185° F (−40° C to +85° C)

Impact Resistance 1 inch (25 mm) diameter hail at 52 mph (23 m/s)

Appearance Class B

Solar Cells 128 Monocrystalline Maxeon Gen II

Tempered Glass High-transmission tempered anti-reflective

Junction Box IP-65, MC4 compatible

Weight 56 lbs (25.4 kg)

Max. Load Wind: 50 psf, 2400 Pa front & back

Snow: 112 psf, 5400 Pa front

Frame Class 2 silver anodized; stacking pins

BB. · February 2019

Vmp~72.9 volts is in that "gray zone" for 48 VDC battery bank... For an MPPT type charge controller, you really want >~78 volts. And for a standard 150 VDC MPPT controller, they take Vmp~100 VDC (if you are in a cold climate that gets well below freezing).

So, you are "stuck" with getting a higher input voltage charge controller (roughly ~200 VDC minimum).

Or possibly, using a PWM type charge controller (MPPT controllers require somewhat higher voltage to work "as designed").

It does also depend on the charging voltage of your Li Ion battery bank (number of cells, chemistry type). Nominally, a flooded cell lead acid battery bank runs around 59-62 volts (charging and float charging).

And Li Ion batteries typically do not use a temperature voltage offset--You have to be able to set (or configure) the charge controller for 0 volt per degree C per Cell offset (none).

For an RV, especially if you will be working/sleeping/etc. during the day... I suggest that you choose a solar charge controller that does not have a fan(s). They can be pretty noisy during the day (controller needs to be in a well ventilated space so that it does not overheat).

-Bill

jonr · February 2019

The Midnite Solar Kid is a good choice. No gray area with all panels in parallel.

Ohwinniepooh · September 2019

Could I run 2 in parallel and drop the voltage to 36v and use a good MPPT around $200? To charge an AGM gel bank 24v.

Raj174 · September 2019

@Ohwinniepooh

Yes, but 36V is the bare minimum for the MPPT controller in this case, leaving almost no headroom for the MPPT to work effectively. So yes, if you must, but you could see about a 10% increase in production with a higher voltage.

Rick

Ohwinniepooh · October 2019

So then it's just better to run in series?

Raj174 · October 2019

Are you considering the 435 watt Sun Power panel in the first post here? Or another panel.

Ohwinniepooh · October 2019

I'd use the same panel 435. Or even a higher like 460 or 470w x21 series sunpower.

Raj174 · October 2019

Ok, so panel VMP is 72.9 volts and should be wired in parallel with a MPPT controller for a 24 volt battery bank.

Ohwinniepooh · October 2019

If anyone can sell me of these 460w or 470w X21-470-COM please contact me by sunpower.

What Solar Controller would you recommend for 4 of these panels on top of my RV?

Comments

Categories