Frying Solar Charge Controllers

Thread Starter

jackfrost2

Joined Dec 17, 2015
5
Hello,
I have (6) 100w panels wired parallel for 18vdc /30amps approximately. This comes in and I have wired (3) 12/24vdc/30amp controllers in parallel with the PV panels. Each controller is then wired to a 12vdc battery. Simple enough. But there is an issue: I also need these batteries to provide a series output of 36vdc for an actuator motor. The series connection of the batteries is an immediate short condition. How do I protect the controllers and get the required 36vdc I need. I am using each batteries output at 12vdc for brushless motor blowers. The actuator circuit at 36vdc is also needed to maximize solar energy gain.
Kind regards,
Jim
 

Kermit2

Joined Feb 5, 2010
4,163
Short answer is, you cannot parallel batteries AND get a series connection volt age level out.
You MUST break the parallel connection to get a series output voltage.
This was done in days of old with one of those multiblade knife switches.
You could charge in a 12 volt parallel arrangement and discharge in a series mode. Your 12 volt motors CAN be connected in a voltage floating method across individual 12 volt batteries while the batteries are in series. Those connections will have to be broken for parallel charging.
 

ErnieM

Joined Apr 24, 2011
8,010
You start with 6 panels in parallel to drive 3 controllers you want to wire in series.

Go back and rewire the panels so 2 panels drive one controller. That way all the outputs should be floating and able to connect in series. Sloppy but may work with your existing parts.

A preferred solout on would be to get a 36 volt controller to charge the all the batteries in series as you use them. That should eliminate any charge in balance.
 

N11778

Joined Dec 4, 2015
174
ErnieM Hit it on the head.
2panels one charge controller one 12v battery then the three batteries can be in series.
Again sloppy but it will work

Keep in mind everything only does half of what the manufacture says it will
 

Thread Starter

jackfrost2

Joined Dec 17, 2015
5
To Everyone:
Thank you so much for your quick responses. I realize this setup is frugal/ sloppy. The two panel idea does work, as they float, but they lack the current. While I gave this more thought waiting and hoping for help from you, I ordered 12vdc motors. The total current draw will be 20% less than what is available from the panels. I will let the charge controllers fight over which battery gets what as the batteries will discharge at varying rates.
Kind regards
Jim
 

N11778

Joined Dec 4, 2015
174
I'm getting lost. .
So now you are only going to have 12volts for everything???
Are the batteries going to be in parallel ???
Why would they discharge at varying rates ???
Scribble out a simple diagram and post it . . . . .. Please i think i smell smoke :)
 

Thread Starter

jackfrost2

Joined Dec 17, 2015
5
Hi N,
I'll post the schematic of this project soon. The PV panels are in parallel as are the three chargers. The batteries will be treated/ charged separately This system is designed to run an actuator and a brushless 12vdc blower per battery. The variability of discharge comes from a thermistor controlled PWM controller for the blower.
Three chargers, three separate systems per battery. I started this project last year and am adding to it. I'm looking for heat during the winter and hopefully not smoke.
 

N11778

Joined Dec 4, 2015
174
If you put the charge controllers in parallel one will hog the load and all the current will go thru that one
To charge the lowest voltage battery.
Its ok if the charge controllers are all good for carrying the load of the 6 panels
I burned up an 80 amp controller putting just 30 amps thru it. Im in the dessert and its hot in the summer
 

ErnieM

Joined Apr 24, 2011
8,010
Winter can be a problem for PV systems too. Panels produce a higher voltage the colder they get. In some systems not designed for the worst case an over voltage may result.
 

Thread Starter

jackfrost2

Joined Dec 17, 2015
5
When this system is completed, it should provide 90K btu's per hour at peak averaging 64K on cloud irradiance times during daylight, My biggest hurdle prior to the series parallel battery charging fiasco, has been finding the correct voltage divider using a thermistor added to a pwm controller controlling the duty cycle of the blowers. The panels are AP-100's about 10 yrs old. I doubt that the voltage can climb higher than 22vdc. And also banking on a 20% reduction in total current available due to the panels' useful lifespan.
Just as an FYI, the system is for solar air heaters.
 
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