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Parraling up mismatched panels.

Gros21

New Member
Joined
Jun 23, 2021
Messages
36
Basically my toy hauler has 1 panel of unknown spec, which is hidden under a shade sail.

So I'm wanting to put a 200w on the front of the trailer.

Also then can I parral it with my 300w (when camping) my voc will be the same as the 200w but the vmp is ~1w different.
 
I think you probably meant that the Vmp is 1 volt different?

In general paralleling modules with different voltages is fine. If youre charging with an MPPT then getting a second one for the new module would eliminate any mismatch loss due to the difference in Vmp, but it's not going to be that big a deal either way.
 
Yes it will be with a mppt.

Basically 1 unknown panel permeantly installed.

I'll grab a few 200w units which will be parralled with unknown unit all the time.

Then 300w unit which is vmp is close to 200w units.
 
When you say you're adding the new modules in parallel with the unknown one do you mean with a new MPPT or by connecting them to the inputs of an existing MPPT? If the former then no problem.

If the latter then you should check the operating voltage of unknown module.You can do that with a multimeter at the MPPT terminals with the MPPT operating. Also you'll need to be sure the exusting MPPT can handle the additional current.
 
When you say you're adding the new modules in parallel with the unknown one do you mean with a new MPPT or by connecting them to the inputs of an existing MPPT? If the former then no problem.

If the latter then you should check the operating voltage of unknown module.You can do that with a multimeter at the MPPT terminals with the MPPT operating. Also you'll need to be sure the exusting MPPT can handle the additional current.
Existing unknown panel is hooked up to pwm controller and a n200 battery (dozer battery)

The pwm and n200 is getting replaced with a 400ah 12v batt set up and a 40a mppt controller charger.

But don't want to simply throw the current panel.

But were trailer lives is under a shade sail so I definitely need a panel up front that won't be shaded.

Plus I don't want to hook up a 2nd mppt just for unknown panel.

But I can measure volts on unknown panel and check specs on pwm controller.

Plus batts can definitely use that extra panel.
 
go BIG or go home

check your roofs ditch the baby stuff and start by looking at 370w panels
I put 2 x 370 panels side by side on the roof or my trailer... still had ROOM for a walkway between them

my panels ... measured 39wide x 70 long
if you have to ... put panels over top of a sewer vent and/or move antennas out of the way!
they charge my 200ah lithium just fine! Have never had to plugin shorepower for battery charging


I do not see any reason to try and save/use a 100w panel on a RV install
everything is against us already ... flat mounted... smallish panels with limited roof space
chuck the 100w ... I bet a 200w will fit in it's place (if you cant fit bigger 370w)

not hard to fill up any holes ... use eternabond tape


PS I bought a $85.00 Amazon 50amp MPPT just to prove it can be used
and got panels NEW from local Facebook Market place $150.00 EACH no shipping
 
Existing unknown panel is hooked up to pwm controller and a n200 battery (dozer battery)

The pwm and n200 is getting replaced with a 400ah 12v batt set up and a 40a mppt controller charger.

But don't want to simply throw the current panel.

But were trailer lives is under a shade sail so I definitely need a panel up front that won't be shaded.

Plus I don't want to hook up a 2nd mppt just for unknown panel.

But I can measure volts on unknown panel and check specs on pwm controller.

Plus batts can definitely use that extra panel.
If the new battery is lead acid you can just leave the unknown module connected through the pwm controller and put your new modules through your new MPPT. That way you don't need to be concerned about any mismatch between the old and new modules.

Otherwise since it's a pwm controller you'll need to disconnect the wires from the old module and measure it's Voc. If you leave it connected you'll usually just see the battery voltage so it won't tell you much. If its Voc is pretty close to the new modules' then it shouldn't be a problem connecting them up in parallel to the input of the new MPPT.
 
1 panel of unknown spec,
Disconnect from the PWM and measure the panel volts with the panel in the sun. If its in the region of 22 volts you can connect panels in parallel with similar open circuit voltage.
Another option is to use the existing panel with a Victron Smart 75/10 controller and use the additional 200 watt plus external, In parallel, with a Victron Smart 100/30

A further oprtion is to use each panel with its own controller, a 75/10 for the existing roof panel, a 100/15 for the 200 watt and a 100/20 for the 300 watt.
 
but will you be wasting valuable roof realestate ?
keeping a small panel in a spot where possibly a larger one could fit?

maximize what little space there is ...
minimize any possible losses especially mismatched panel can drag the whole system down) can

lets say you got an older 100w panel producing 17v (old and tired panel)
Plus 2 newer 200w panels ..... 20v @ 8 amps
instant 48w lost on the 2 panels due to the 100w only producing 17v
may as well not have it ..... as that panel may only be producing 70w


Large array on the roof of a house multiple stings ... you can afford a bit of loss
small RV you may as well see if another better panel fits in that spot

Keep the 100w and the pwm .............. for ground panel array .... deploy it when you are in a bad location
 
go BIG or go home

check your roofs ditch the baby stuff and start by looking at 370w panels
I put 2 x 370 panels side by side on the roof or my trailer... still had ROOM for a walkway between them

my panels ... measured 39wide x 70 long
if you have to ... put panels over top of a sewer vent and/or move antennas out of the way!
they charge my 200ah lithium just fine! Have never had to plugin shorepower for battery charging


I do not see any reason to try and save/use a 100w panel on a RV install
everything is against us already ... flat mounted... smallish panels with limited roof space
chuck the 100w ... I bet a 200w will fit in it's place (if you cant fit bigger 370w)

not hard to fill up any holes ... use eternabond tape


PS I bought a $85.00 Amazon 50amp MPPT just to prove it can be used
and got panels NEW from local Facebook Market place $150.00 EACH no shipping
Can you provide sources for the panels? And is shipping exorbitant for panels of any substantial size?
 
I looked local...
Facebook market place ... craigs list
or contact local solar companies they may have extras or be willing to add some extra panels for you on their next order from distributors

shipping and prices ONLINE often a problem ...they want minimum order of 10 or more (pallets)

I would think in NV you can pick up some panels fairly easy
 
I looked local...
Facebook market place ... craigs list
or contact local solar companies they may have extras or be willing to add some extra panels for you on their next order from distributors

shipping and prices ONLINE often a problem ...they want minimum order of 10 or more (pallets)

I would think in NV you can pick up some panels fairly easy
Not in my part of NV. 400mi + from LV, 250 - 300 from Reno, Boise & SLC
 
go BIG or go home

check your roofs ditch the baby stuff and start by looking at 370w panels
I put 2 x 370 panels side by side on the roof or my trailer... still had ROOM for a walkway between them

my panels ... measured 39wide x 70 long
if you have to ... put panels over top of a sewer vent and/or move antennas out of the way!
they charge my 200ah lithium just fine! Have never had to plugin shorepower for battery charging


I do not see any reason to try and save/use a 100w panel on a RV install
everything is against us already ... flat mounted... smallish panels with limited roof space
chuck the 100w ... I bet a 200w will fit in it's place (if you cant fit bigger 370w)

not hard to fill up any holes ... use eternabond tape


PS I bought a $85.00 Amazon 50amp MPPT just to prove it can be used
and got panels NEW from local Facebook Market place $150.00 EACH no shipping
Issue here is trailer is under a shade sail with just its nose sitting out. So im looking at adding a large panel on the front of the trailer on the 45% pitch (inefficent but wanting it to keep it topped up). 40A is 480W of pannels.

I want a 200W on front of trailer and i have a 300w folding set up which will be used when out and about.
Once i upgrade my solar on my house ill end up putting those panels onto the trailer (making sure mppt can handle the volts)

I spose i could hop up there and check the specs of the current panel its on a slight tilt so im hoping i can get a camera and check its name plate
 
If the new battery is lead acid you can just leave the unknown module connected through the pwm controller and put your new modules through your new MPPT. That way you don't need to be concerned about any mismatch between the old and new modules.

Otherwise since it's a pwm controller you'll need to disconnect the wires from the old module and measure it's Voc. If you leave it connected you'll usually just see the battery voltage so it won't tell you much. If its Voc is pretty close to the new modules' then it shouldn't be a problem connecting them up in parallel to the input of the new MPPT.
Im building a "portable" 400AH lithium battery box ill get rid of the n200 as its good as dead as the current solar panel has been hidden under a shade sail.
 
Just checked it's a 250w house panel hooked up to the cheapest pwm controller that does not do lithium.

So it's a fair difference.

Maximum Power (P)

250W

Maximum Power Voltage (V)

30.3V

Maximum Power Current (Imp)

8.27A

Open Circuit Voltage (V)

38.0V

Short Circuit Current (1)

8.79A
 
What are the Vmp's and Imp's of the other modules you want to use with that one?
20.4v

But my DC charger only accepts up to 30v which isnt really enough for my house panel.

When the time comes lll likely upgrade my home solar (going bigger) so I'll likely simply throw on a 60-80a mppt and cover the caravan with panels. It's a caravan/toy hauler with plenty of roof space.

Then move the 250w to front edge of trailer and keep it on mppt or similar. Just to keep battery trickled up
 
Yeah the max 30V input charger is too low. Check your module Imps also.

If you get a new MPPT that works at a higher voltage you might be able to connect your various modules in series first then in parallel to get the voltage in the right range for the new MPPT.

Modules in series: Imp's need match. Modules in parallel: sum of Vmp's need to match. By match I mean within 5 to 10 percent or so of either voltage or current.

Or you can get a dual channel (or two single channel) MPPTs.
 
Yeah the max 30V input charger is too low. Check your module Imps also.

If you get a new MPPT that works at a higher voltage you might be able to connect your various modules in series first then in parallel to get the voltage in the right range for the new MPPT.

Modules in series: Imp's need match. Modules in parallel: sum of Vmp's need to match. By match I mean within 5 to 10 percent or so of either voltage or current.

Or you can get a dual channel (or two single channel) MPPTs.
My mppt is a dc to dc charger.
So I'll leave that one there plus 400ah and 300w is enough for camping.

Only time it will cop.a hiding is in caravan so will wire that mppt into a Anderson plug that will go into batts.

I also throw a energy meter on trailer and see just how much the AC pulls while it's plugged into 220v

I'm likely over thinking it.
 
sounds like you got a permanent site?

ditch the sail ............. make a frame and put panels over the top for shade
or use a ground array
while at home are you living in it or just storing


any restrictions on being allowed to put up structures ?
gazebo style... can be used for relaxing shade and solar production?

-------------------------------------------------------------
how long do your trips last ... weekend or weeks?

weekend... just get bigger battery any solar you collect is a bonus

weeks.... optimize the roof with as much as possible
2 strings if possible so the SHADED back panel at home does not affect the rest of the panels
ditch any mismatched panels.... work out best layout panels are cheap(ish)
 
sounds like you got a permanent site?

ditch the sail ............. make a frame and put panels over the top for shade
or use a ground array
while at home are you living in it or just storing


any restrictions on being allowed to put up structures ?
gazebo style... can be used for relaxing shade and solar production?

-------------------------------------------------------------
how long do your trips last ... weekend or weeks?

weekend... just get bigger battery any solar you collect is a bonus

weeks.... optimize the roof with as much as possible
2 strings if possible so the SHADED back panel at home does not affect the rest of the panels
ditch any mismatched panels.... work out best layout panels are cheap(ish)
Trailer sits at my house. It's just a toy hauler but set up with beds (to get wife approval) nothing fancy.

I'll be running AC non stop when I go away likely 4 day trips.

When at home it's just sitting there.

Here is a pic, trailer goes back about ~8 more feet (so drawbar is 2ft on foot path), solar panel starts at front of the trailer and is shaded.

I'm darned if I do darned I don't.

If it helps that's a Touareg and it's a 18ft/5.5m body.
 

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mine TT is at home I just run a extension cord from garage 20amp to an 30amp adapter
can run all the stuff in the TT ... but one LARGE item at a time

I store it with the a/c ON ....... set to 85 which controls the humidity
can even use the converter if I wanted to

one solar panel can keep battery maintained ... since you not living/camped in it
 
mine TT is at home I just run a extension cord from garage 20amp to an 30amp adapter
can run all the stuff in the TT ... but one LARGE item at a time

I store it with the a/c ON ....... set to 85 which controls the humidity
can even use the converter if I wanted to

one solar panel can keep battery maintained ... since you not living/camped in it
Yes it would keep it maintained but it currently gets no soalr hence me wanting to put one the front.

Then issue is when i take it out its often ion 100-110f weather so want ac to run the whole time.
 
getting the a/c to run off battery , inverter and solar
on a 18ft trailer ... NOPE not gonna happen

you will have to swap out the air conditioner for a variable speed inverter model
decent battery at around 400ah
and around 800w of panels
Then you got a good chance to run the a/c for a few hours, depending on where you camp

buy a generator !
 

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