PWM controller - 12 / 14 volts selection - how does it work

[mghunter]

A question re 12/24 volt PWM controllers.

Attached is a manual for a ebay one with LCD display plus USB.

It says it can handle up to 50 volts solar input and is self detecting on 12 or 24 volts.

Second try

Can I assume that if you connect to 12 volt battery (eg manual says to connect battery first anyway), the unit defaults to 12 volt operation regardless of the voltage of the solar panel ? eg is you have a 36 volt panel the controller will still handle that and still only charge the battery to 12 volts (actually the float at 13.7 volts)

My set up seems to do this okay (albeit I have two controllers feeding off one panel via diodes on the solar inputs, each one charges a 1100CCA battery)

The good thing with these PWM's is that you can always see the voltage on the LCD display and set the charge and cut off voltage (I run some ultrasonic transducers to minimise barnacles).

I've also seen one that shows incoming amps.

[tanglewood]

Yes, but in your example you will be losing a huge portion of the available power from your 36V panel. That panel puts out max power at 36V. If you run it at 13V (or whatever you actual battery voltage is) you will only get about 1/3 of the panels power output. This where an MPPT controller comes into play by operating the panel at 36V where it will produce max power, and converting that to the actual charge voltage of your battery via a DC/DC converter. Power loss in the conversion is 10% or less., as opposed to about 60% if you run with a PWM controller.

[slowpoker]

I agree with tanglewood's reply. Make the best use of the voltage your panels are producing.
How well are those ultrasonic barnacle things working for you? Keeping the bottom clean? Are they consuming a lot of power from your panels?
The MPPT controlers will make a big difference. Not all advertised from China are true MPPT, get a name brand; Blue Sky, Morningstar, Outback, etc. Do some research and wire them properly. You can always test their output with a simple meter or gauge and do not really need a display built in.