Best array configuration for a 24 volt system

Hairfarm

Greetings,

I'm considering upgrading to 24 volt when I add two new panels to my array.

In the end I'll have 8 panels. They are 135 watt Kyocera. 17.7 volts, 7.6A.  I'm thinking two strings of four panels each in parallel for 70.8 volts, 15.3 amps.  Is this array config still too high for a 24 volt system?

thanks

Raj174

No, it's not too high as long as the MPPT controller can handle the VOC voltage, 4 per string will work fine.

vtmaps

Hairfarm said:

I'm considering upgrading to 24 volt when I add two new panels to my array.

In the end I'll have 8 panels. They are 135 watt Kyocera. 17.7 volts, 7.6A.  I'm thinking two strings of four panels each in parallel for 70.8 volts, 15.3 amps.  Is this array config still too high for a 24 volt system?

What controller are you using?  Many (most?) MPPT controllers will work OK with 4 of those panels to a string. 

Do you have room for 9 panels?  If so, 3 strings of 3 panels per string (string Vmp = 53.1) would be ideal.

--vtMaps

Hairfarm

What controller are you using?  Many (most?) MPPT controllers will work OK with 4 of those panels to a string. 

I'm using an Outback Flexmax 80. Max VOC for the CC is 150V I only have room to add two more panels for a total of eight.

thanks!

Photowhit

vtmaps is saying use strings of 3 panels so you won't have a problem with VOC. You should use try to limit incoming voltage to about 2x the system voltage, 24 volt x 2 = 48 volts. This will keep the charge controller from working as hard down converting the higher voltage to a lower voltage and losing some of your energy in the process of aging your charge controller quicker.

There is a string sizing tool for the Flex Max 80 here;

http://www.outbackpower.com/outback-support/string-sizing-tool

But in a 24 volt configuration, with an 80 amp output max, you should be able to handle 1900 watts of array minimum (1900 watts ÷ 24 volts = <80 amps) and cost effective to around 2500 (2500 x 75% normal output of array = 1875 watts), with the charge controller limiting output to 80 amps for those cool days.