Solar panels series vs parallel

[prairiecamper]

Has anybody ever heard of any 12 volt type solar panels not being able to wire them in series? Not physically of course but technically? I have 4 Coleman 100 watt panels and nowhere on the box or on the enclosed manual does it say to only wire in parallel or not to wire in series! Talked with a Coleman customer support rep, tech I think, and was told they can ONLY be wired in parallel??
I have been all over the Internet and cannot find anywhere, where there is some explicit instructions on any panel that I have seen to only wire them in parallel.
Now I am not looking for pros and cons over series vs. Parallel I am aware of all that. Just whether there are panels made that must be wired in parallel only?

[KRedburn]

Can't say for sure regarding Colman panels. I cannot think of any real reason why they cannot be wired series/parallel either.

I have home panels (30) that are connected series/parallel that output 389 volts dc. Inverter has multiple mppt connections and it is grid tied. 8800 watts output max. Been working for couple of years without any issues.

I would contact Coleman and get the spec sheet on the panels.

[KRedburn]

forgot to say that a lot depends on your charge controller for the batteries.
If it is 12v only then you could only wire 12 volt panels in parallel to the charge controller up to the rated power of the controller.

[timfromma]

If you wire 12V panels in series the voltage increases by 12V for every panel in the series. Your 4 panels wire in series will produce 48V which will most likely blow up your controller. Wire them in parallel to keep the voltage at 12V.

[kfergiez]

I don't know the specs of the Coleman solar panels, but if they are the standard 100W panels, they are most likely manufactured by somebody else and are just fine being wired in series.

To answer your question in short:

Right now, wiring them in series is best due to the efficiency of MPPT controllers and you'll be able to generate higher voltages a lower levels of light. These controllers can also take a much higher voltage, convert them to 12v with more amps.

If you wire them in parallel, you'll get more amps at 12v but the PWM controllers are less efficient. In addition, the when wired in parallel, it will take longer for the charge to actually start because the panels must generate more voltage than the battery has in order to start charging. This requires more light. If the panels are wired in series, you'll get more voltage with less light, just at a lower amperage... but your batteries will still begin to charge.

Originally Posted by timfromma

If you wire 12V panels in series the voltage increases by 12V for every panel in the series. Your 4 panels wire in series will produce 48V which will most likely blow up your controller. Wire them in parallel to keep the voltage at 12V.

Maybe with SOME controllers, but not all. And with open circuit voltage, you're looking at 72v, not 48v.

I would recommend wiring ALL 4 panels in series (yes you heard that right). The Victron BlueSolar MPPT 75/15 controller can handle up to 75v of open circuit charge directly from the panels. Your 100w panels most likely produce 18v at open circuit which translates to 72v at full capacity. Plus the Victron will auto-limit if anything is exceeded.

Victron Solar Controller

I've done a few solar installs, and if you have any questions, feel free to PM me.

[Kaadk]

I haven't done anything Solar yet, but it makes sense that some panels might only be available in parallel. To wire in series you need to have two connectors right? An input and an output. If the panel manufacturer only puts one connector, you'd only be able to wire in parallel. I could see a company like Colman, whose panels I see mostly marketed as trickle charge battery maintainers, doing something like that.

Course, I haven't actually bought any panels yet, just looked at them lovingly while the DW stands by saying "Come along dear, we don't need those.", so what do I know?

[kfergiez]

Originally Posted by Kaadk

I haven't done anything Solar yet, but it makes sense that some panels might only be available in parallel. To wire in series you need to have two connectors right? An input and an output. If the panel manufacturer only puts one connector, you'd only be able to wire in parallel. I could see a company like Colman, whose panels I see mostly marketed as trickle charge battery maintainers, doing something like that.

Course, I haven't actually bought any panels yet, just looked at them lovingly while the DW stands by saying "Come along dear, we don't need those.", so what do I know?

You actually don't need an input and output... in the terms your speaking.

All solar panels have a (+) and (-) terminal which is your "input and output." To wire things in series, you simply connect the (+) of one panel to the (-) of another panel and you're left with a single (+) and (-) to connect to your controller.



To wire in Parallel you wire the panels (+) to (+) and (-) to (-). Easy peasy.

[Skyliner]

Can't think of any reason why you can't wire them in series either.

Lots of folks think that 12 volt panels are 12 volts. Nope, most are between 18-21 volts. I'm pushing 42.2 volts with my system when the sun is shining.

[prairiecamper]

Thanks for all the replies! Again I have to say this isn’t about series vs parallel or mppt vs pwm. I know about voltages amps ohms etc.
My question is simply are there panels that have to be wired series only or parallel only? I personally am only aware of panels that can be wired either series, parallel, or a combination thereof.
Technical replies from electrical engineering folks and or links to articles would be most appreciated.

[kfergiez]

I have never heard of solar panels that need to be wired in parallel only. I can't think of any reason they would be set up that way, unless they are lacking in some diodes or something like that.

Do you have these panels sitting in front of you?

[prairiecamper]

Originally Posted by kfergiez

I have never heard of solar panels that need to be wired in parallel only. I can't think of any reason they would be set up that way, unless they are lacking in some diodes or something like that.

Do you have these panels sitting in front of you?

They are Coleman model 38100. Specs 100 watt 5.8amps.
Can be seen on the internet.

[prairiecamper]

Ok just received this email from Sunforce products, they are the people that manufacture the panels for Coleman.

“On May 3, 2018, at 12:35, Michael Carpenter <michael.carpenter@sunforceproducts.com> wrote:

Hello Donald, thank you for your message.

Our panels are designed to go in parallel (positive to positive, negative to
negative)
The components of the panels are not designed to go in series.

Best regards,
Michael Carpenter
Customer Service Technician
Sunforce Products Inc.
1-888-478-6435 ext. 121”

I find this extremely hard to believe, thoughs? I need a drink.

[kfergiez]

Originally Posted by prairiecamper

They are Coleman model 38100. Specs 100 watt 5.8amps.
Can be seen on the internet.

Okay.... I found some documentation, but it is woefully incomplete. I couldn't find open circuit voltages or anything. If you have that info on hand, let me know.

SUNFORCE PRODUCTS (this may be the manufacturer)

User manual for your panel

One thing I did learn is that your panels have an integrated blocking diode. This may cause issues if you wire them in series. If you have the 1st or 2nd panel in the series producing less voltage than panels 3 and 4 (maybe they were dirty or are more shaded), those diodes MAY open the circuit which would halt charging the battery because the potential on panels 3 & 4 is greater. This is not a definitive scenario, so I'm not 100% certain how they would behave.

That being said, if you wired them in parallel, the blocking diodes would work in your favor by not draining the battery after the sun goes down.

So disregard what I told you earlier, the safe bet is to wire these in parallel.


EDIT:

Prairie, I just posted my reply before I saw your post!
It seems that these blocking diodes WOULD cause an issue if they only recommend wiring them in parallel. My guess is that they originally designed these to be used without a controller one panel at a time.

Originally Posted by prairiecamper

Ok just received this email from Sunforce products, they are the people that manufacture the panels for Coleman.

“On May 3, 2018, at 12:35, Michael Carpenter <michael.carpenter@sunforceproducts.com> wrote:

Hello Donald, thank you for your message.

Our panels are designed to go in parallel (positive to positive, negative to
negative)
The components of the panels are not designed to go in series.

Best regards,
Michael Carpenter
Customer Service Technician
Sunforce Products Inc.
1-888-478-6435 ext. 121”

I find this extremely hard to believe, thoughs? I need a drink.

[prairiecamper]

Originally Posted by kfergiez

Okay.... I found some documentation, but it is woefully incomplete. I couldn't find open circuit voltages or anything. If you have that info on hand, let me know.

SUNFORCE PRODUCTS (this may be the manufacturer)

User manual for your panel

One thing I did learn is that your panels have an integrated blocking diode. This may cause issues if you wire them in series. If you have the 1st or 2nd panel in the series producing less voltage than panels 3 and 4 (maybe they were dirty or are more shaded), those diodes MAY open the circuit which would halt charging the battery because the potential on panels 3 & 4 is greater. This is not a definitive scenario, so I'm not 100% certain how they would behave.

That being said, if you wired them in parallel, the blocking diodes would work in your favor by not draining the battery after the sun goes down.

So disregard what I told you earlier, the safe bet is to wire these in parallel.


EDIT:

Prairie, I just posted my reply before I saw your post!
It seems that these blocking diodes WOULD cause an issue if they only recommend wiring them in parallel. My guess is that they originally designed these to be used without a controller one panel at a time.

I just purchased them, have not installed them! Making sure what I want to do is doable. If not they will be returned.

[kfergiez]

Originally Posted by prairiecamper

I just purchased them, have not installed them! Making sure what I want to do is doable. If not they will be returned.

Well, you won't be able to install them in series. If you're okay with that, buy a good quality controller and you're set.

[Flybob]

How you wire panels, is totally dependent on the controller you use. Most RV controllers are 12V so they need to be in parallel. There are some that are 24 or 48 V so they need to be 2 or 4 in series then paralleled in sets of 2 or 4. The controller will specify the input voltage.

[kfergiez]

Originally Posted by Flybob

How you wire panels, is totally dependent on the controller you use. Most RV controllers are 12V so they need to be in parallel. There are some that are 24 or 48 V so they need to be 2 or 4 in series then paralleled in sets of 2 or 4. The controller will specify the input voltage.

This is true for PWM controllers.
MPPT controllers have a range.

[prairiecamper]

Originally Posted by Flybob

How you wire panels, is totally dependent on the controller you use. Most RV controllers are 12V so they need to be in parallel. There are some that are 24 or 48 V so they need to be 2 or 4 in series then paralleled in sets of 2 or 4. The controller will specify the input voltage.

I already have a 30 amp mppt controller, hence the desire to wire solar panels in series. My logic for the 4 - 100 watt panels was that at approx 17 volts each I would be feeding the charge controller with approx 68 volts under ideal conditions. Also at higher input voltages to the controller I could use lighter electrical wire. I intend to use 8 ga wire. This would probably still provide power to the batteries even in low light conditions if the voltage even dropping to say 20 volts into the charge controller. Whereas I could use 1 residential type panel supplying approx 300 watts at 30~ volts and lose out on power in low light conditions perhaps!

[Flybob]

is 68V within the input range of your controller.

[prairiecamper]

Originally Posted by Flybob

is 68V within the input range of your controller.

It’s a victron 30 amp 100 volt.