Splitting a solar suitcase

jrhamel

I posted on the Tag Forum with no success so I thought I would try hear. We've downsized from a Tab 400 to a Tag XL. I have a Renogy 200w solar suitcase. It was great for the 400 but over kill for the Tag, and it is heavy. My thought was to take them apart and use just one rather then dealing with selling and buying a 100W suitcase. Renogy, without explaining why said don't do it. Looks fairly easy, unplug one panel, disconnect it form the other, and move the leg from the unused panel to the other. 
Has anyone done this or see a reason not to?
Thanks

AnOldUR

Just guessing, but could it have something to do with the Renogy controller?

pthomas745

I'm sure it can be done.  I've never seen a straight answer from any company when something involves any "can I do this" question.  Not that I blame them.

How is the back of the panel (s) wired?   That would seem to be the hangup.

jrhamel

@pthomas745 Their a is a set of connector wire that goes from a power box on one panel to the other panels power box then a another set of connecter wires that connect from the second panel to the controller. It looks like can just disconnect the one panel from the other with out doing any rewiring. 

AnOldUR

jrhamel said:

Their a is a set of connector wire that goes from a power box on one panel to the other panels power box ....

Wired in series or parallel?

Denny16

One way to find out, unplug the one panne, that is not connected directly to the controller and see if the remaining connected one still outputs voltage through the controller.
 Cheers 

jrhamel

@AnOldUR I think in series but not sure.

@Denny16 Thanks, I will try that

AnOldUR

Perhaps someone could school me in solar. I know that a panel that's rated at 12V can vary quite a bit. But could these be 6V panels in series to make it similar to a 12V? Would a controller that expecting an average of 12V function properly if fed something in the area of 6V?

edit to ask, or am I completely off base?

Denny16

No, Solar Panels used for RVs are not 6VDC or even 12VDC, they are more like 15-35 VDC, depending on the sun hitting the panel.  Right now with low winter sun on front of the TaB (wrong side from solar panels on the rear), the solar panels are outputting around 16VDC.   The controller output voltage to the battery is 13.25VDC at 0.6 amps (battery is mostly charged).

The solar controller reduces the voltage to match what the battery needs for charging, which is why you need a solar panel controller.
 Cheers 

Bayliss

@jrhamel, I would recommend calling Renogy directly and talking to one of their techs. When they wrote, "don't do it," it may simply be because splitting the panels will void the warranty.  If not, I tend to agree that it may have something to do with the controller, or the fuse size (which you can change.)

CrabTab

jrhamel said:

@AnOldUR I think in series but not sure.

You're right @jrhamel the Renogy briefcases come wired in series (at least mine did, two 50W panels).
I would expect to lose half your voltage if you split them. Don't know if they would push the current into the battery.

pthomas745

I noodled around with this, just...because.  You have a 200 watt suitcase.  Each panel is 100 watts.  Both panels have "junction boxes" on the back.  The junction boxes appear to be identical across many different panels.  I couldn't find anything special about them at all.  The wiring of the two panels seems pretty straightforward.

I'd have to study this more closely with a multimeter, but it certainly seems that each panel could be set up with the connectors of your choice simply by cutting the cables that connect them and adding new terminations.

CrabTab

You should test it with a multimeter @pthomas745. I really think you'll find that the panels act like batteries do in series, the voltages add.
Given that the Renogy suitcase panels combine for an output around 20V (in my experience) and are equal, each will probably produce around 10V individually. Just my understanding of electricity mind you, so looking forward to someone proving me wrong. 

Dutch061

Actually, Solar Panels can be configured in parallel or in series. So as mentioned a multimeter will be a must.

The photo posted above appears they are wired in series.

Brad

jrhamel

@CrabTab Wouldn't each panel act as a 100w panel? Does a 100w panel produce more than 10v? I have no idea, just going on logic, although that often proves to be wrong.

Dutch061

Each panel is 100 Watts but understand that Watts equals Voltage x Amps. So, you could have a 10-volt panel that will output 10 amps in full sun, or you could have a 20-volt panel that outputs 5 amps in full sun, or you could have a 30-volt panel that outputs 3.33 amps. All 3 are examples of 100 Watts.

Which is why you also need a Solar Charge Controller as it will set the voltage and also control the amperage going into your battery bank.

Brad

CrabTab

@jrhamel
As explained by @Dutch061, a 100W panel can be engineered to output different combinations of Volts and Amps.
My hypothesis has been the 100W panels in your suitcase do not have the same design values as the 100W panels Renogy sells as an independent panel. The individual cells are joined in different combinations of series and parallel circuits within the panel.
Since your panels are purpose built to be joined with a hinge, Renogy chose to attach them in series. This allows for a higher amperage output in each panel at the cost of a lower voltage. The lower voltage is made up for by the combination of the panels, voltage in power sources add when they are placed in series.
Nothing trumps actual visual data, so measure it with a multimeter if you can. I haven't pulled my briefcases out. But I have looked at the photos provided by @pthomas745 It looks like the covers readily come off the black boxes. You should be able to place a meter probe on the exposed wiring before the little cylinder object (looks to carry the markings of a diode) and the other probe in the adjacent MC4 connector to measure the voltage across one panel. Compare that to the voltage from MC4 to MC4 (both panels).

jrhamel

Thanks @CrabTab I will give it a try. 

Denny16

If the two panels are engineered to work together in series, than the controller may have a minimum voltage it will work at also, split the panels, the total voltage to the controller drops, and you not get any charge current out of the controller.  

We had this issue arise on a customer, who’s older solar setup was a series setup, and when one panel died, he tried to add a jumper cable to bypass the dead panel, but this brought the output voltage of the system be,ow the required minim voltage for the controller, which is a fixed program setup.
 Cheers 

jrhamel

@Denny16, Seems like that might be the issue. I think I will sell the 200w and buy a 100w. 

Denny16

Sounds like a good plan to me jr.
 Cheers