Need help making decision....

Ionelissy · Feb 24, 2012

Hi there,

I am about to buy 8 solar panels at 250w each to connect them with the Flexmax 80 charge controller and to the 24v battery bank system...

Will these 8 panels work ok if wired in parallel given that the Vmp is less than 36 volts which is the recommended value for the 24v system?

See pdf attached.

thanks in advance.

yellowvanman · Feb 24, 2012

Not sure what the flexmax spec is but running 8 panels in parallel will give you 8 times as much current at the controller. Don't know the Imppt of the module but would think its in the region of 6-7A - in which case your wiring will need to accomodate about 60A

Sorry, just seen your link. Imppt of module is 7.18A so current at your controller could be 57.44A

Ionelissy · Feb 24, 2012

Here is the MPPT flexmax 80 amp pdf, it says for 24v, max array is 2000w... I know it can handle all 8 panels... but the problem is...

in order for the controller to sustain a voltage higher than the battery voltage (which is 24v), panel Vmp needs to have a minimum of 36v... and this panel is 34,9v....

MorganPVI · Feb 24, 2012

It will work fine

moggy1968 · Feb 24, 2012

I think that is probably to cover drops in voltage over time and due to environmetal conditions.
If I look at the battery charge indicator on my old landcruiser, which is 24v, then it varies enormously depending on what else is going on (ancils on, environmental factors etc) but maxes out at over 30v, this is to ensure that with everything on and under all conditions it will still charge the batteries regardless of what you are using. IT's kind of the same with your system.

Interesting setup you've got. I presume this is to go off grid in a remote building or some such. How many batteries with how many AH, what are you intending to power with it?
You've tickled my interest, now you'll have to elaborate:smart:
keep us posted how it goes.

Ionelissy · Feb 24, 2012

moggy1968 said:
Interesting setup you've got. I presume this is to go off grid in a remote building or some such. How many batteries with how many AH, what are you intending to power with it?
You've tickled my interest, now you'll have to elaborate:smart:
keep us posted how it goes.

that's correct, system is for a new home built in a remote area where there is no electricity.

The battery bank I have, consist of 12x 12v batteries at 230ah each, wired in series and parallel to work at 24v. Total 1380ah @ 24v

For this setup I want to get the 2kw Sanyo panels (all 8 wired in parallel) and the MPPT Flexmax 80amp charge controller.

I just wanted to make sure these panels will work ok with this controller given the Vmp of 34,9v and controller recommends a minimum of 36v Vmp for a 24v battery system...