Wiring Panels

Re: Wiring Panels

And the short answer is probably you cannot do it very well or cheaply...

With most solar charge controllers, you need to properly match the Vmp/Imp (within ~10%) in series/parallel setup so that the Vmp of the array is >32 volts or so for proper battery charging.

With pairs of "12 volt panels" (really ~17.5 volt Vmp panels)--You can put pairs of them in series to get ~Vmp=35 volts.

And with MPPT type charge controllers, you can run the Vmp of the array around 35-100 VDC (for the larger, more expensive charge controllers). However, the Vmp of all the individual panel series strings need to match their Vmp too (you cannot put a 12 volt + 35 volt + 49 volt mix of Vmp together in parallel and expect very efficient power output to charge the battery bank).

In some cases, where you have 8 of one brand of panels and 8 of another brand/model of panels, it may be worth while to purchase 2 different solar charge controllers to connect in parallel and charge the same battery bank.

But, for your smaller panels, it may make more economic sense to purchase a couple new high power/higher voltage panels and a good MPPT charge controller.

Otherwise, the best you can probably do is, assuming all panels have Vmp~17 volts:

• connect the two 100 watt panels in series
• connect three of the 50 watt panels in parallel (make a 150 watt panel)--And connect those three in series with the 120 Watt panel.

It may work OK behind a PWM or MPPT controller.

If you are concerned about fire (shorted panel or wiring)--You should place fuses in each of the positive leads of the 50 watt panels that is equal to ~2*Isc (2x short circuit current rating of panels).

The above is probably the cheapest way you can get your system running... It won't make 370 watts output because of the power mismatches--but it should come reasonably close (again, assuming these are all Vmp~17 volt or so panels).

-Bill

Re: Wiring Panels

You need to wire them in series/parallel to charge a 24 volt battery bank (assuming they are ~17.x volt panels).

The Combiner Box is typically where the fuses or breaker reside... For something like yours? I am not sure if a commercial combiner box makes sense because they normally are designed to bus the wires together for your +/- bus connections (as I understand---My system is a Grid Tied so my experience does not cover the details of these setups).

Is it worth ~$100 for a DIN box plus $xx dollars per breaker/fuse per circuit? Is this system going to be "good enough" with a home made wooden box where you make your own 12 volt automotive fuse connections and such? Really your call.

The problem with "mixing" various panels together like this is there is not cheap, nice, and easy to code way of doing this stuff (that I see--others may be able to give you a better answer).

If this is a 12 volt system--then you could put all of the panels in series and connect them behind a PWM controller... Use a combiner box for the protective devices (you need different ones for each size of panel)--again assuming all panels are "12 volt" panels.

-Bill