Is it possible to connect a PWM charge controller with another PWM charge cont......

[Hasan]

Hello Guys,
I've been trying to figure out if this thing is gonna work. i've drawn a sketch of my idea. i know the simple answer to my typical question is "GET AN MPPT Charge Controller" But i can't get it from where i live. i hardly get my hands on a proper PWM charge controller after 3 years of my first Solar Panel Installed. so i'm gonna skip this talk and get to the Real Topic.
I've Two 12v Solar Panels (300Wh) connected in Parallel connected to A 12/24v 30Amp PWM charge controller which is connected to Two 220Amp (apprx 5280Wh) Batteries in Parallel which are also 12v (obviously) i want to make that system a 24V. only problem i've is i dont want to get a 24v inverter because i already have Two 12v inverters 1000W inverters each. i also have a 20amp 12/24v PWM charge controller and a 100Amp 12v battery spare. so what i was thinking if it is possible to connect them all together and hook them up like in the picture? what do you think what are the side effects/advantages.
please review linked picture for better understanding, before making any comments.
Thanks

IMG-20150503-WA0003.jpg

[Mike90250]

No, to charge a 12v battery from a 24V battery, you need to limit the amps the 12V controller will be able to pass. Or use a MPPT controller for the 12V charger.

[Hasan]

Thanks

No, to charge a 12v battery from a 24V battery, you need to limit the amps the 12V controller will be able to pass. Or use a MPPT controller for the 12V charger.

i guess i will find a reasonably priced MPPT charge Controller. Thanks

[Amy@altE]

Why do you want to make it 24V? If you are not planning on getting a 24V inverter, what are you going to do with the 24V battery bank? What is your end goal? Are you just trying to wire the panels in series to reduce voltage drop, and still keep the batteries and inverter at 12V?

[gertvanzyl]

I have the same question but different application. I live in isolation and have different size panels which is arranged in two arrays, each with its own pwm controller. They WERE charging in parallel tot my 48v battery bank with a 3kw inverter. HOWEVER a link in the battery bank came loose, dropping the bank to 36v and blowing my inverter. I have a spare 96v 10kw inverter which will have to bail me out for the next 4 weeks. So i made changes to the battery bank. I've split the bank in two 48v banks and linked them in series to supply the 96v inverter. However now the banks are charging unballanced and one bank is drained at night way before the other. I need to balance the PV arrays. My idea is to connect the two pv arrays in parallel onto bars and feed from this "balanced" connection to the two PWM controllers in order to charge the banks at equal rate! Will this work? Will the 96v not "feed" back through the controllers and create a dead short die to the series 96v connection on the battery banks? Can this be done? Or is there another way to balance the charging to independant banks?

[jflorey2]

My idea is to connect the two pv arrays in parallel onto bars and feed from this "balanced" connection to the two PWM controllers in order to charge the banks at equal rate! Will this work? Will the 96v not "feed" back through the controllers and create a dead short die to the series 96v connection on the battery banks?

Yes, you will get a dead short. PWM controllers do not provide isolation, so the two negative outputs will remain connected together through the solar array, thus shorting out the lower bank.

Or is there another way to balance the charging to independant banks?

Options are:
1) Rewire the solar array to provide >96V
2) Switch the output of the solar system between the two banks, spending an equal time on both banks. NOT recommended, and difficult to do; it would have to be a custom design.

[gertvanzyl]

Ok tx. Rewiring the solar array wil necessetate replacing the current 48v 60A contollers?

[jflorey2]

Ok tx. Rewiring the solar array wil necessetate replacing the current 48v 60A contollers?

Definitely. The Midnite 250KS (250 volt in, 120 volt out, 35 amp) would be a good choice.

[Amy@altE]

Midnite discontinued that product last year. Not sure if you can find used ones online somewhere.

[gertvanzyl]

Tx Jflorey2 - I am trying to bridge the next 4 weeks without alternative hardware....

[TST]

Pls can mppt SCC work with pwm SCC in charging a power bank at thesame time? And is it proper to series 3 24v panel for 48v pmw SCC?

[inetdog]

Pls can mppt SCC work with pwm SCC in charging a power bank at thesame time? And is it proper to series 3 24v panel for 48v pmw SCC?

An MPPT CC can work in conjunction with a PWM CC to charge the same battery bank, BUT they will have to have totally electrically independent panel arrays connected to them. The MPPT algorithm will not be able to work properly if a PWM CC is drawing current from the same panel array.

[TST]

Hi, is it proper to connect in series 3 24v panel for 48v pwm SCC?

[Mike90250]

Hi, is it proper to connect in series 3 24v panel for 48v pwm SCC?

It will work with minimal loss. 48V batteries need up to 65V applied to properly charge/EQ 72V is not a bad PWM voltage. Beware though, 3 panels is not likely to be enough to recharge a depleted bank. 3 panels could be considered a trickle charge.

[TST]

Yes, I have 8 panel 300w 24v for 48v battery bank with 48v pwm SCC, my question is, is it proper to series 3 panel out of the 8 which gives you about 108v for 48v pwm SCC? Won't it burn for high volts? Note. IS NOT MPPT SCC. Thanks.

[Mike90250]

Of course your charge controller needs to be rated for the voltage and amps you are supplying it. That's rule # 1