Converting 12v to 24v

WillAK

New Member
Joined
Nov 17, 2021
Messages
7
I'm trying to convert my battery bank into 24v but I'm doing something wrong!

My two 250aH batteries easily convert to 24v by changing the wires over and my 24v 3000w inverter works perfectly fine, but when I try and connect the batteries to my charge controller, the CC flashes rapid green light and a warning triangle next to the solar input.

My solar array is 4x100w panels wired in series producing 90v 5a and about 300w during the day here.

I'm either missing something very simple, such as wiring the panels wrong, or the Charge Controller which is 12v/24v 30A TRIRON Epever Modular MPPT Charge Controller is not working correctly?
 

JWLV

One Million Dollars!
Joined
May 27, 2020
Messages
88
Is the charge controller set to user-selected system voltage? If it is, then you should change it to 24v or automatic. When set to automatic, it should be able to detect the system voltage and automatically switch to 24v.

As always, charge controllers should be connected to the batteries first. Connect the solar input last.
 

WillAK

New Member
Joined
Nov 17, 2021
Messages
7
Thanks so much for your help.

I've no idea what i've done differently but I changed the settings of the battery type to flooded and then reconnected the solar array and now its charging perfectly fine at 24v. Batteries putting in 90v at 21c. I couldnt see any settings to change the voltage so i presume it's automatic.

One more question, I have 4 panels connected, 400w at around 90v. But i have a 5th panel which if I connect sends the voltage up to 113v which then makes the charge controller flash rapid green which indicates over pv voltage.
Is this because the inverter cannot cope with this much voltage or is it because 5 panels is an odd number? Even in series?

Thanks
Will.
 

chrisski

Solar Boondocker
Joined
Aug 14, 2020
Messages
2,700
Your charge controller has a limit. My guess is 100 volt limit. If that is a voltage limit on an SCC is exceeded, it can go bad quick, as in up in smoke.
 

WillAK

New Member
Joined
Nov 17, 2021
Messages
7
Thanks! I've just looked and the max PV open circuit voltage is 100v.
So that means if i want to add any more panels I need to get a larger charge controller or wire in parallel?
So essentially if the batteries are 24v, then anything more than 24v going into the batteries will charge them? So I could in theory put 6 panels with 600w and keep the voltage below 100w? Considering the Amperege is only around 4a at the moment.
 

littleharbor2

Solar Enthusiast
Joined
Sep 15, 2021
Messages
53
Charge controllers ratings refer to output (charging) current. If you series/parallel wire 3s2p you should be fine, provided your controller is 30 amps but better at 40 amps or higher. A 30 amp controller may be running at full throttle for part of the charging cycle. Many MPPT controllers can be over paneled to a certain extent without damage.
 

chrisski

Solar Boondocker
Joined
Aug 14, 2020
Messages
2,700
Also with the 100 volts, panel voltage goes up when it gets cold out. Check the all time cold of where you use this system and check the panel specs to see how this makes the voltage work. The 4S at 21 celsius may exceed voltage at freezing.
 
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