Solar Panel Matching

[gypsydan]

I currently have one 175 watt Newpowa solar panel, and one 100wh Battle Born. Wanting to add another panel and Battle Born.

It has been said that it is required for solar panels to be matched when using more than one. I am not sure what matching means?  Do you need to have the panels match exactly, with each panel being exactly 200 watts, or can there be 5-10 watts difference between panels?

Any clarification would be useful.

[Darryl&Rita]

You want to match the voltage and amperage as closely as possible. If those are matched, the power output will be matched, but matching power output won't necessarily yield the most energy harvested.

[gypsydan]

1 hour ago, Darryl&Rita said:

You want to match the voltage and amperage as closely as possible. If those are matched, the power output will be matched, but matching power output won't necessarily yield the most energy harvested.

I can understand with that.  My question, though, is what specifically happens when there is 5-10-15 watts difference in output between panels?

[pjstough]

My understand is that your amp output will be the lowest rated amp hour panel, and the voltage will be limited to lowest voltage rated panel.

Perhaps, Chad will come along and give a definitive answer.

[GlennWest]

You could install separate controllers.

[KodiakJack]

Was researching this recently myself and found this site helpful.

Later,

J

https://www.alternative-energy-tutorials.com/solar-power/connecting-solar-panels-together.html

[Randyretired]

The best is to use identical panels.  If not then the voltage or the amps need to match depending on how the panels are wired.  If in parallel if there is a diffence in voltage the lower voltage panel will drag all the others to that voltage.  If in series the amperage needs to match or the lower amperage drags down all of the panels.  Separate controllers is a good answer to panels that don't match.  

[oldjohnt]

Dan I'm an electrical engineer but NOT any solar expert or installer, so see what the experts have to say: In general as you already know, its best if multiple panels are the same ....As far as matching WATTS of power, if both are 24 volt panels but one is higher watts, that means it can pump more current IE it would have a DIFFERENT/HIGHER current rating...So see below the consequences of using different current (even if same voltage)  rated panels..

   1) Its my understanding its best if panels wired in PARALLEL are the same voltage.

I'm sure you understand the problem if one were say 24 volts and another higher (say 30), the voltage wouldn't be higher then the lowest (24) voltage panel. 

2) Its my understanding its best if panels wired in SERIES are the same current.

 If they are different amperage the current is limited to that of the lowest current panel  

 Sure voltage is additive if different voltage panels are wired in series HOWEVER current is limited to the lowest current rated panel

 Sure current is additive if different panels are wired in parallel HOWEVER voltage is limited to the lowest voltage rated panel 

 In my system I used series parallel with matched panels in parallel in series with two other matched panels. 

 If you're stuck with different panels but its possible, I would use different solar charge controllers 

 As far as I know you can parallel two same voltage battleborns to double the Amp Hour energy storage capacity but not sure (but youre not doing that anyway) if they approve series if you were building a higher voltage bank...

 Cant you buy another panel of the same voltage and current of the one you already have ????

  If so then you need to decide between series (higher voltage less current) or parallel (higher current same voltage) . As long as your solar charge controller is adequately rated I like the higher voltage/less current that a series connection would give you. 

  Again check with the experts don't take my word for it

 John T

 

 

[Kirk W]

I am another experienced electrical person who doesn't have solar experience, so rather that give a lot of advice, I suggest that you visit Heiser RV Solar & Electric who does know the subject. Chad is always happy to help but must be busy since he has not yet been here.

[oldjohnt]

2 hours ago, Kirk W said:

I suggest that you visit Heiser RV Solar & Electric

AMEN I agree, you can't beat a professional installer. Looks like all the rest of us pretty much agree, it will be fun to see if we were right or wrong  ???????????????

Hapy New Year everyone

John T

[GlennWest]

Separate controller for each different should not be costly. Low amperage controllers can be bought at low prices

[lenp]

Also have many years of electronics experience but not a solar expert.  However, my experience tells me multiple controllers would not work well with each other.  If one (attached to the highest voltage panel) is charging the battery bank with 14.3 volts then the other controller(s) will see the 14.3 as a fully charged battery and throttle back their charge current or totally shut down.  I could be wrong but I can tell you from experience that trying to charge a battery with two battery chargers will result in only one really doing the charging.  Isn't a charge controller just a fancy battery charger?  Unless there is a controller out there that is designed to work with others I just don't see them working well together.

Just my two cents......

Happy New Year!!!

Lenp

[Randyretired]

1 hour ago, lenp said:

Also have many years of electronics experience but not a solar expert.  However, my experience tells me multiple controllers would not work well with each other.  If one (attached to the highest voltage panel) is charging the battery bank with 14.3 volts then the other controller(s) will see the 14.3 as a fully charged battery and throttle back their charge current or totally shut down.  I could be wrong but I can tell you from experience that trying to charge a battery with two battery chargers will result in only one really doing the charging.  Isn't a charge controller just a fancy battery charger?  Unless there is a controller out there that is designed to work with others I just don't see them working well together.

Just my two cents......

Happy New Year!!!

Lenp

Multiple controllers is a common and acceptable method of charging.  I have 3 different solar chargers on my RV battery bank.  Solar charge controllers are voltage regulated and as the batteries reach the regulated voltage no additional power can be fed to the batteries.  It is true that one controller may dominate near the end of charge, additional power would lift the voltage beyond the regulated maximum so more can't be used anyhow.  In practice I typically see the controllers sharing the load as maximum voltage is reached.  Some large solar/battery systems may have many controllers.  That is needed because the controllers are amperage limited.  Large solar arrays can produce a significant amount of power.

[Chad Heiser]

KodiakJack posted a good link.  I have some very similar information on my website.  Here are the highlights:

Both in series and parallel connection, plugging a panel of a lower power rating to the array drags the whole output power down.  The lower the rating, the higher the loss of solar generated power.

This, however, is much more evident for panels connected in series.

If you want to get the maximum power from your solar array, you should only connect similar panels.

Mixing different panels, whether connected in series or in parallel, ALWAYS reduces the installed wattage.

If you don’t have any other option than wiring dissimilar panels, you should know:

For series connection – the same current rating of the panels is more important.

For parallel connection – the same voltage rating of the panels is more important.

Mixing panels with close ratings is not horrible, but when you start mixing panels with large differences, you will greatly affect the overall output of the array.

[oldjohnt]

Chad, HUGE THANKS for your inputs, looks like all of us here pretty well agree on this one yayyyyyyyyyyyyy team...I really appreciate your knowledge and willingness to share it with us...

Randy, FWIW  I agree if different NON MATCHED solar arrays are used separate charge controllers is a good method. I will only add if I had my preference any solar charge controllers would be the same brand/design/style (talking their charging output) and used the same charging parameters    VERSUS     different brands, styles, designs and charging algorithms (even though sure can still work). And compared to the cost of Lithium batteries and panels, charge controllers aren't all the expensive and correct use could possibly ??? add to a batterys lifetime.    

 If the OP were to find a matched panel and his charge controller (assuming appropriate??) can handle the combined energy and specs THAT WOULD BE GREAT.....If he has to use non matched panels, I vote for separate controllers and even better if both had the same specs !!!!!!!!!! while sure even if not the exact same they can still work and the batteries internal BMS has control over those type of things also    

 Fun sparky chat for us techy types lol

Happy New Year everyone

John T  NOT a solar expert so listen to them versus me

 

Edited January 3, 2022 by oldjohnt

[Randyretired]

1 hour ago, oldjohnt said:

Chad, HUGE THANKS for your inputs, looks like all of us here pretty well agree on this one yayyyyyyyyyyyyy team...I really appreciate your knowledge and willingness to share it with us...

Randy, FWIW  I agree if different NON MATCHED solar arrays are used separate charge controllers is a good method. I will only add if I had my preference any solar charge controllers would be the same brand/design/style (talking their charging output) and used the same charging parameters    VERSUS     different brands, styles, designs and charging algorithms (even though sure can still work). And compared to the cost of Lithium batteries and panels, charge controllers aren't all the expensive and correct use could possibly ??? add to a batterys lifetime.    

 If the OP were to find a matched panel and his charge controller (assuming appropriate??) can handle the combined energy and specs THAT WOULD BE GREAT.....If he has to use non matched panels, I vote for separate controllers and even better if both had the same specs !!!!!!!!!! while sure even if not the exact same they can still work and the batteries internal BMS has control over those type of things also    

 Fun sparky chat for us techy types lol

Happy New Year everyone

John T  NOT a solar expert so listen to them versus me

 

John, Since charge controllers are voltage limited even controllers from different companies work well.  I have mixed scc on my system and it has performed flawlessly.   I have also combined AC powered chargers to supplement my solar when needed and that has also worked well.  I have even used 2 AC chargers along with the solar with great success.   I could add here that the charging parameters need to match the batteries but that is needed for any chargers. 

[oldjohnt]

Randy, you and I agree different controllers still work. If I had to buy two because of mis match solar arrays my first choice would still be the same brand and type etc., (no harm in that) but hey if you're upgrading and modifying that may not be possible, it seems anytime I repair or upgrade Im told THOSE ARE NO LONGER AVAIALBE AND ARE OBSOLETE GRRRRRRRRRRRRRRRRRR

  In a "perfect" world I would still prefer different charge methods/equipment be identical in all respects and parameters BUT HEY how often do we get that opportunity lol so we go with whatever works which Im sure and you have experienced will be fine.............At times I may have BOTH my smart converter/charger as well as my solar charge controller (different brands alltogether) running charging my Lithium bank and Ive experienced no problems same as you report. Once 100% SOC is reached I think the BMS also exerts a degree of control and limiting regardless how many different chargers are running.. but I have so specs or data to confirm that just observation...

The OP may NOT have a choice and have to go with whatever he can find which will still work. 

 Nice chatting with you now take care.

John T Also retired

Edited January 3, 2022 by oldjohnt

[Randyretired]

Since non of the arrays on my RV are the same size as you said using the same controllers isn't always practical.  You mentioned BMS's and I have seen some bad things when the charge parameters exceed the BMS parameters.   Once a BMS cuts out during charging a voltage spike is likely.   Suddenly removing the load of the battery causes the voltage to spike until the scc can react.  I have seen spikes in excess of 20v on a 12v system.  Additionally scc can be adversely affected when solar charge voltage is present without a battery.  It is usually best to keep charging parameters well below the BMS parameters.

[oldjohnt]

22 minutes ago, Randyretired said:

It is usually best to keep charging parameters well below the BMS parameters.

I can't argue against that.......Hopefully a QUALITY SCC or Converter/Charger will control and limit charging voltage and current so the BMS never has to perform drastic measures......Typically I don't run my scc and Converter at the same time (never a problem if I do AND NO THEY ARE NOTTTTTT THE SAME BRAND OR DESIGN LOL) but regardless, if one or both are up n running charging current pretty well shuts down as near 100% SOC approaches, so far so good KNOCK ON WOOD...........

Best wishes Randy I appreciate your expertise, Im never too old to learn I hope !!!

 John T

 

[gypsydan]

On 1/3/2022 at 1:11 AM, Chad Heiser said:

KodiakJack posted a good link.  I have some very similar information on my website.  Here are the highlights:

Both in series and parallel connection, plugging a panel of a lower power rating to the array drags the whole output power down.  The lower the rating, the higher the loss of solar generated power.

This, however, is much more evident for panels connected in series.

If you want to get the maximum power from your solar array, you should only connect similar panels.

Mixing different panels, whether connected in series or in parallel, ALWAYS reduces the installed wattage.

If you don’t have any other option than wiring dissimilar panels, you should know:

For series connection – the same current rating of the panels is more important.

For parallel connection – the same voltage rating of the panels is more important.

Mixing panels with close ratings is not horrible, but when you start mixing panels with large differences, you will greatly affect the overall output of the array.

My initial question concerned matching 2 Newpowa panels, one @ 175/watts, and the other @ 180 watts. Since I don’t have the 180 panel (they aren’t marketing 175s) I don’t know it’s specs. I can’t trust them anyway, as I initially purchased a 180 Newpowa from Amazon, but didn’t realize till several years later I had a 175 watt - hence my concern should I order another one and this time do get a 80 panel. 

can that 5 watts make a difference ?

[Lance A Lott]

You wont see much with 5 watts, you will basically have 2 175 watt panels. In my opinion that's not worth a second charge controller.  If you had several 180 panels and then added a 175 it would be a different  story.

[Lou Schneider]

You have to know the voltage and current each panel produces.  If they're connected in parallel, a higher voltage panel will be reduced to that of the lower voltage panel.  

If both panels have the same number of cells, you can assume they'll produce the same voltages and you'll have no problem connecting them in parallel.  If there was a significant voltage difference between them, say one panel put out 36 volts while the other put out 18 volts, the 36 volt panel would be drawn down to 18 volts, losing half of it's output power.  But if both panels have the same working voltage you can connect them in parallel without any problems.

[Chad Heiser]

As others have already stated, minimal differences in panel specifications won’t make a significant difference in output.  If the panels have major differences, then the output will be negatively affected.