Exceeding recommended PV array wattage

[Bendesa1962]

Hi all,

I've a question about a Outback FlexMax 60 Amps. 150 VDC

I've a 12 VDC Battery bank and 4 x 300Watt panel.

The recommended PV array wattage for the FlexMax 60 in combination with a 12 VDC battery bank is 750 watt. What would happen if I connect the 4 x 300 Watt panel to the FlexMax 60? I will connect it in 2 strings of each 2 panels. I will stay within the maximum of the 150 VDC.

So I'm exceeding the recommended PV array wattage with 550 watt.

what will happen, how will the system behave?

Many thx

Regards

[SunEagle]

Hi all,

I've a question about a Outback FlexMax 60 Amps. 150 VDC

I've a 12 VDC Battery bank and 4 x 300Watt panel.

The recommended PV array wattage for the FlexMax 60 in combination with a 12 VDC battery bank is 750 watt. What would happen if I connect the 4 x 300 Watt panel to the FlexMax 60? I will connect it in 2 strings of each 2 panels. I will stay within the maximum of the 150 VDC.

So I'm exceeding the recommended PV array wattage with 550 watt.

what will happen, how will the system behave?

Many thx

Regards

There are two possible options.

One is that the inverter handles the extra wattage but "clips" it so you only get a maximum of 60amps output instead of 100amps (1200w / 12v = 100amp)

The second option is that the inverter fails due to exceeding the input wattage.

My suggestion is if you want to use all 4 300w panels then make sure 2 are facing in a different compass direction (East or West) then the other 2. That way you really only get about 600watt input to the inverter instead of the full 1200 watts but you get a longer time period for charging the batteries.

[Bendesa1962]

Hi SunEagle

thanks for your reply. I guess by inverter you mean chargecontroller right?

regards

[SunEagle]

Hi SunEagle

thanks for your reply. I guess by inverter you mean chargecontroller right?

regards

Yep. My bad on confusing the issue. The CC is the heart of a solar/battery system. You do not want to abuse it.

[Mike90250]

I concur with half the array aimed easterly, and half westerly. That spreads your peak harvest to be less peak, but a longer duration.

do plan to include a generator for backup charging, and to assist with monthly EQ charging.

Even with optimum sun & angle, the panels will seldom produce more that 960 watts / 14V = 68A, so the controller will clip a bit, but as long as it's well vented, it should survive.

[PNW_Steve]

A little different application but similar situation. I am putting significant solar on the roof of my RV. They will be flat mounted and will see use anywhere from Seattle in January to Yuma in July. My ability to collect will vary significantly depending on where I park so I have overpaneled significantly.

Someone pointed out a feature that the newer Midnite Classic charge controller when used in conjunction with the Whizbang Jr. You can set the maximum charge current supplied to the battery bank. That way I can have lights in Seattle without fear of boiling my batteries when I head to Yuma.

Prior to finding that nifty feature I was considering using the breakers in my combiner to selectively turn strings on and off depending on conditions. I think that would have been adequate as long as I never forget to turn one or more strings off before heading South. One senior moment could be disastrous for the batteries.

[Mike90250]

The output limit setting on a Midnight classic, does not need the whizbang to function

[PNW_Steve]

The output limit setting on a Midnight classic, does not need the whizbang to function

My understanding from talking with Midnite was that if you include the Whizbang jr that you can limit the current to the battery while still have access to the excess to support loads.

Without the Whizbang, you can set a hard current limit and anything the panels produce in excess of the set limit is wasted. Or, so says Midnite tech support. I do not have it in production yet.

[Mike90250]

Midnight support is right if you want other loads at the same time. Generally, I find that the batteries will only consume what they need, as they charge up, their amp draw reduces.