What are the rules for mixing panels of different wattage or even brand?

[Gueyog8a7]

I have two of these from renogy in series. 12v, tracer bn 4215 controller.

Could I add more of these to existing array so that 200 would give more mileage on the same surface area?

I would actually prefer to buy elsewhere than renogy since I do not like that they are sneakily shipping from states and don't say that anywhere on their site. Would prefer to buy domestic from another website but what would be the rules in this case to mix and match with the above two linked in the first link?

If it would be best to buy all the same then 5x more of those (at most) I would just buy from renogy again. So is it best to do that or will other wattages and or brand be fine. These are what I would like clarification on to know how to proceed.

I know it seems to have been asked a few times before, I did search but no simple answer from replies I read yet.

So for my case, if 5x 100w more would be enough would I be better sticking with the same ones I got already?

If those 200w ones would also work it would probably be better then I would not have to mount them on the sides and get 2 x 200w, one roof on remaining space and 1 on hood of van. With the 100w ones I would do that and plaster 2 or 3 at 90 degrees on the side of the van without the door. I do prefer the all black design of the 100s though so might even prefer it if most other calculations work out similar.

 

[scrubjaysnest]

Panels in series Imp plus or minus 10%. Lowest panel current is what you get.
Panels in parallel Vmp plus or minus 1 volt.
Imo flexible panels are a very poor choice.

 

[John.DS99]

I think they are like batteries. Best to combine identical batteries to make a battery bank. Best to combine identical panels to get the most out of them. Otherwise you are making a compromise. It's your decision to combine them as you like if you are happy with the result (and don't burn down your house).

 

[MattiFin]

Panels in series Imp plus or minus 10%. Lowest panel current is what you get.
Panels in parallel Vmp plus or minus 1 volt.
Imo flexible panels are a very poor choice.

I'd rather use the 10% rule also for Vmp, 1 volt requirement is too tight especially with higher voltage panels like 600W panels with Vmp close to 45 V

 

[scrubjaysnest]

I ran a 16 volt Vmp with 18 volt Vmp panels. When you get into the bigger wattage panels many will be 3 or 4 volts for 10%. Also need to watch Voc.

 

[mikefitz]

Panels in series limit the current to that generated by the smaller panel, voltage is the sum of the panel volts. Thus panels in series should have similar current outputs.
Panels in parallel deliver the sum of the currents, panel volts for maximum power need to to be similar , +/- 1 volt on 20 volt panels, +/- 2 on 40 volt panels.
If you have strings of panels connected, each string ideally should have the same total volts, a variation up to 10% is possible with a slight loss.
Conside the options, for a 12v battery system, existing 100 watt panels, 19v, 5 amps, in series 5A , 38 volts
To add 200 watt panels, 20v 10 amps.
Option 1, reconnect the existing 100 watt in parallel , in effect producing a 200 watt panel, 19v, 10 amps. Connect this in parallel with the additional two 200 watt panels. Fit a series 15 amp fuse in the feed from the each panel.
Option 2, as Option 1, connect the two 100 watt in parallel, then add in series the 200 watt and then the second 200 watt in series .
Options 3, leave the two 100 watt in series, connect the two 200 watt in series and then add in parallel to the existing series 100 watt.

Using 100 watt panels only.
These can be connected is series or parallel combinations. It's practical to have an even number of panels. Assuming 4 off 100 watt panels are to be added.
Option 4, leave the existing panels in series, make up two more strings of two 100 watt panels and add in parallel to the existing. Fuse each string at 10 amps.
Option 5, add one 100 watt to the existing two in series, connect the remaining 3 off 100 watt in series and then add in parallel.

There are few alternatives for flexible panels, many of the low cost units have a short life. Renogy panels are better than most and have a useful warranty.