3 differant panels to one charger

System

Question, I have three different panels, 12v 60w, 12v 75w, and 12v .5 w.
can I simply add all the positives and all the negitives to a bus bar and then run one wire ( from each) to the controler?
Thanks

BB.

Re: 3 differant panels to one charger

More or less, the answer is yes... If the 60 watt and 75 watt have much different Vmp readings (say one is 15 volts and the other is 18 volts)--depending on the controller, the power output may not add up...

MPPT type controller may set the Maximum Power Point (Tracking) to the 18 volt panel and the other lower voltage panels may hardly add any current/power.

A PWM controller would work better in this case, because the controller, during maximum charging, will simple connect the battery directly to the panels--so the operating voltage will be closer to 15 volts (+/-) and all panels will output maximum current.

Normally, MPPT type controllers are the "better" and more "efficient" charge controllers to use... But in some cases, PWM will work as well (or better) at lower cost. If this is a small system and all of the components are close together (no long wire runs from panels to charge controller + battery shed)--then an MPPT may not be worth the extra costs.

Adding the 5 watt panel may not even be worth the effort/wiring/mounting. It will probably have the lowest voltage and contribute little additional power to the system.

-Bill

System2

Re: 3 differant panels to one charger

Thank you,
it is becoming a small system and the panels are just outside the wall where the controler and batteries are located. Maybe 5' of wire!

What's the PWM controller?
I'll have to look at which one I already have.

BB.

Re: 3 differant panels to one charger

Here is a list of controllers from one company (Morning Star)... All of them are PWM type controllers (Pulse Width Modulation--basically just turning an "electronic" switch on and off 10's to 1,000's of times per second).

All of the above are PWM, except for this one which is, arguably, the best small MPPT type charge controller (for 200 watts of panels at 12 volts, or 400 watts maximum of solar panels on a 24 volt battery bank) presently available at this time.

Otherwise, the larger, more expensive charge controllers (Outback, Xantrex, and others that are 800 watts and above) are typically MPPT type charge controllers (MPPT type are basically "buck mode switching power supplies"... They use a little bit more power to run the electronics, but are much more efficient at match Solar Panel Voltage/Current output to the battery system--sort of like the DC equivalent of a variable AC Transformer... Much better for larger system, and systems that run in Hot and Cold climates where solar panel's output higher voltages in cold weather. Also, very handy to allow high(er) voltage from the solar panel to charge controller wire run (can use smaller gauge wires to lower costs because Power=Voltage*Current -- if you can double the solar panel voltage, the current requirement is cut in 1/2 allowing smaller guage wire for long runs).

-Bill

niel

Re: 3 differant panels to one charger

you may have to watch it because if the voltage output between those pvs are different enough and there's no blocking diodes in the pvs that one higher voltage pv can pump some of its power into the smaller voltage one. this also holds even more true for all of the pvs when no blocking diodes are present that with some cheap quality controllers you could find the power being drained from the battery and into the pvs. when using a blocking diode in a pv be sure that the diode is rated for the current capability of the pv it's being used in.
ps putting the diode in backwards will show 0 output, but will not usually harm the diode.