Two Charge Controllers One Battery

[Archie42]

Hello There I have just found this website so i hope my question has the required information,
Anyway so my solar panel set-up is that i have one 250W 24V panel and one 100W 12V panel on my roof the 24V panel goes into a 20A charge controller and the 12V panel goes into a another 20A charge controller (the charge controllers are identical brands and everything). From here the two charge controllers feed into one 150Ah 12V battery bank.

Now too my issue...

The 250W panel charge controller is the only one feeding power into the battery bank, the other charge controller (with the 100W panel plugged into it) just sits here and float charges 1W all day. This means that even when the battery's are low the 250W panel is the only one supplying power. So is my battery bank too small? or Is my Charge controller set-up wrong? and would it make a difference if i had a bigger battery bank?

Also my charge controllers do not communicate with each other or read battery temp.

Thanks for any replies.

[Sunking]

The charge controller in a higher energy state always will be the one supplying power. Guess which one that is?

What you can try is setting the voltage of the 250 watt system lower than the 100 watt system. Likely result is you go from 20 amps charge current down to 8 amps. To work both controllers must be set to the exact same voltage.

[Archie42]

Wow Thank you for the quick reply,
So how would i get the voltage of the 24V panel down to 12V?

[Sunking]

Wow Thank you for the quick reply,
So how would i get the voltage of the 24V panel down to 12V?

Huh? If you are using a MPPT controller, they can work as 12/24 volt battery. There is nothing unusual about having two systems charging a common battery. What is unusual is the way you are going about it. Normally you would use two equal systems of same panels. wattage, and charge controllers that work as Master/Slave so they talk to each other and equalize outputs.

[Archie42]

Ok so is there anything i can do with my current charge controllers or will i have to get new ones?

[Sunking]

Ok so is there anything i can do with my current charge controllers or will i have to get new ones?

Already told you. Set the voltages to equal. If your controller do not allow you to do that will require new ones.

[Archie42]

I am really sorry i do not understand. Would i be changing the float, bulk and absorb voltages or the actual solar panel voltage and how would i do that?

[Sunking]

You set the Bulk, Absorb, and Float the same in both controllers.

[Mike90250]

The better charge controllers have a way to calibrate their internal voltage sensor just for this reason, Without the ability to calibrate and truly share charging duties, one controller will hog all the charging. This even works well across brands, I have a Morningstar and a Midnight Classic, and they both share charging power - AFTER I calibrated one to match the other.