MPPT vs PWM with Voltage Down Controller circuitry

SLPx

Hi All,

I'm a Newbie here. But I do have a problem to ask and appreciate very much that If any of the seniors here could shed me a light.

I have a solar network of following
- 3 panels of 340W (36V, 47Vmp)
-Two PWM chargers of 30A/60A
-One MPPT charger with 60A
-Inverter 230V, 1500W with 12V input
-Two Lead-acid (car) batteries (at the moment).
-The network is on 12V off-grid
-Used to power the house, when the inverter power is available, the house connected to the inverter. when the juice is over, automatically switches to the grid. 
-at the moment, unable to grid tie the panels and buy new batteries (including deep-cycle) 

I have connected two solar panels parallel to MPPT and One panel to PWM
-When connected my PWM controller withdraw charging the batteries and let the voltage of the solar panel to flee
-MPPT charge controller got 20A and it did not charge the Lead batteries to full. Kept the maximum level at 12.5V (although the charge voltage is 14.2)

So I disconnect my MPPT controller and connect all to PWM.
PWM charges the batteries to 13.8V and batteries lasts to the night.

Now I have the following issues to tackle.
1. Since I'm not using a collosal amount of energy out of the panels and only the PWM controller is working,
With the least cost options and almost exclusively using existing peripherals,
 ---- can I use a 5-60V DC step down converter to 18V between solar panels and the PWM controllers, to utilize the missing voltage area of 18-46

2. Having two deep-cycle batteries with the MPPT controller at 24V (purchasing two deep cycle batteries) and convert the output with step down controller to either other two batteries to charge or, directly to the inverter and having an ac-dc charger to charge the rest of the batteries.
(use the battery storage to night use)

3. any other feasible solution to this.

Thanks and Best regards
Sanjeewa

Photowhit

Stop, put every thing in the closet/garage and read...

I suspect there is a language barrier, but please give specs on each individual solar panel. "- 3 panels of 340W (36V, 47Vmp)" makes no sense.

PWM charge controller rarely work with panels so far away from the charging specs. Using a PWM with panels with a VMP of 36 or 47 volts will likely damage them.

Please explain;

"When connected my PWM controller withdraw charging the batteries and let the voltage of the solar panel to flee"

and

"-MPPT charge controller got 20A and it did not charge the Lead batteries to full. Kept the maximum level at 12.5V (although the charge voltage is 14.2)"

SLPx

Above is the Panel Config.


*1,
I have connected Two panels to MPPT and One panel to PWM. Both connected to the same battery bank of 12V, 100AH, Two batteries connected parallel. 
MPPT charged the batteries at 21.2A, PWM charge current is 0.00, showing the panel voltage as 40.2V

*2.
MPPT when the battery got to the voltage of 12.5V, it drops down to 12.0V and restarts charging to 12.5
PWM, on the other hand, kept the battery voltage to up from 12.0 to 13.8v when connected the same panels.

Hope this helps.

Thanks

Wiring Diagramme

BB.

Your panels are fine for an PWM controller charging a 24 volt battery bank (38.7 Volts Vmp -- Voltage Maximum Power). If you are charging a 12 volt battery bank with a PWM controller, you are, roughly losing 1/2 of the solar panel output power (Watts):

• 8.79 Amps Imp * 14.7 volts charging = 129 Watts charging a 12 volt battery bank with PWM controller and your panel
• 8.79 Amps Imp * 29.4 volts charging = 258 Watts charging a 24 volt battery bank with PWM controller and your p

With an MPPT (Maximum Power Point Tracking) solar charge controller, the output power to charging a 12 volt battery would be:

• 340 Watt panel * 0.77 panel+controller derating (typical "real world output at noon") * 1/14.7 volts = 18 amps @ 12 volt MPPT charging
• 18 amps * 14.7 volts charging = 265 Watts charging 12 volt battery with MPPT and your solar panel

Your PWM controller should work charging your 12 volt battery bank with a Vmp~38.7 volt panel (if your charge controller is a 12/24 volt rated controller)--However, you will only get ~50% of the power (Watts) from your panel.

Your MPPT controller should work just fine. Make sure you connect the MPPT (and PWM) controllers to the battery bank first, then connect the solar panel(s). If you connect the solar panels first, then the battery bank, it can confuse the solar charge controlle
Your 12 volt battery bank should be "resting" at ~12.7 volts, and charging at 13.x to ~14.7 volts (when in "absorb" charging stage), then go back to "float" charging at ~13.6 volts (ramps up charging voltage from 12 or 13 volts to 14.7 volts and holds 14.7 volts for 2-6 hours, then ramps back down to "float" at ~13.6 volts).

It sounds like your have a broken MPPT charge controller or it is not being connected to the battery bank correction (backwards connections between Vpanel and Vbatt, connecting +/- incorrectly, etc.).

In general, your PWM and MPPT controllers can be connected to a 12 volt or 24 volt battery bank (with correct wiring). However, if you have a 12 volt AC inverter, then you need a new 24 VDC input AC inverter for use with a 24 volt battery bank... You cannot connect a 12 volt inverter to a 24 volt battery bank and get things to work well (for many reasons).

I guess you are somewhere around Colombo Sri Lanka?

Get your battery charging working correctly first. If the batteries are not charged correctly, you can ruin them very quickly (in a few days, worst case).

-Bill