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Panels in parallel - can I add a slightly different wattage panel (410W vs 405W JA Solar)


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I'm hoping that the site guru's can assist with a question around panels in parallel. I bought and installed a small simple system: EasySolar 16oo 24V Victron and 2 X JA Solar 405W panels to run a fridge and LED lighting in an off grid cottage. The system has worked extremely well from onset. But I find I need to add an additional panel to deal with a bit more load during daylight and when overcast. So the EasySolar has a PV Voltage limitation so the panels needed to be in Parallel. Now I need a third panel, I cant find a 405W JA Solar panel for love or money. It has been suggested that while not ideal I could add a JA Solar 410W panel which operates at a slightly higher voltage. So my question is, is this advisable in a parallel array? The spec sheets attached say there is a 5W variance but this could equate to 10W between the panels. I'm desperate as I dont want to buy 3 new panels of the same. I would really appreciate some expert advise here. 

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11 minutes ago, Gremlin said:

I'm hoping that the site guru's can assist with a question around panels in parallel. I bought and installed a small simple system: EasySolar 16oo 24V Victron and 2 X JA Solar 405W panels to run a fridge and LED lighting in an off grid cottage. The system has worked extremely well from onset. But I find I need to add an additional panel to deal with a bit more load during daylight and when overcast. So the EasySolar has a PV Voltage limitation so the panels needed to be in Parallel. Now I need a third panel, I cant find a 405W JA Solar panel for love or money. It has been suggested that while not ideal I could add a JA Solar 410W panel which operates at a slightly higher voltage. So my question is, is this advisable in a parallel array? The spec sheets attached say there is a 5W variance but this could equate to 10W between the panels. I'm desperate as I dont want to buy 3 new panels of the same. I would really appreciate some expert advise here. 

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This will be fine. The panels will all be at the voltage of the panel delivering the lowest voltage. 

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2 hours ago, Speedster said:

This will be fine. The panels will all be at the voltage of the panel delivering the lowest voltage. 

Not quite - they are current sources so open circuit voltage will be the higher voltage. The max power point could be harder to find with dissimilar panels, but these are so close that it is hardly worth considering. The difference is barely 1% - the only reason they are binned so close is to maximize profits.

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29 minutes ago, Gremlin said:

Thanks - I appreciate the input!! Now to find the 410W!!

A simple rule of thumb.  You panels in parallel will always be equal to the lowest voltage and current.  In series it will add but will not deliver more than the lowest current.

Parr   you calculate  if you have 4 panels 8.9A, 9.1A 9.1A , 9.7 = 4 x 8.9A   If the V are equal then you can say 8.9 + 9.1 + 9.1 + 9.7A  very seldom this happens therefor the rule of thumb is simple V = lowest V and I = lowest x panels without getting to technical

Edited by Erastus
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Just put the 3 panels in parallel.

The panel has a Vmpp of 42V and Voc of about 50V . 

 Your 100/50 can handle 1400 W max and can handle 100V MAX and require 5 V above Battery voltage to start the mppt - so that should be about 29-30V . The panels will operate well. Your amp limit is 50A and the three panels will operate at about 33A max . So you are ok . The  two panels in series are vary close to the max limit if open circuit and on cold days you would probably exceed it . 

With the three panels in parallel you also have 1200w  available that is within the spec of the MPPT . You are also limited by the original choice - a better option would have been 4 panels of 340 W probably but this should be still a ok setup .

Dont worry about the 5 W difference between the panel rating - panels derate over time and you will find on new panels that this is within the tolerance anyway you probably have on randomly selected panels . All those panels are assembled on the same line and with the flasing test at the end  the rating is assigned anyway . That is why you have families of panels with the same number with only the rating different. The component combination of the silicon wavers give the difference . In large solar panel installations such as PV grid installations this do become important . Not in this case .

Hope this help and good luck .

 

 

 

 

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16 hours ago, branderplank said:

Strange that you could not find a 405 watt. Have you checked with the major distributors?

Ja you would think!!!??? This is the list of outlets I tried. All had a 405W on their sites:

Segen Solar

Cape Solar Supplies (lekker oke but no stock, is keeping an eye out for me)

Sonop Solar

Tika Solar

Mega Solar (also a lekker oke and super helpful!)

ArtSolar

GCSolar

BKSolar

Civic

SolarWorld

Rubicon

PowerForum (Steve is going to help me out with a 410W when they arrive)

Im really not sure who the major distributors are? Some of the above seem big, some small.

 

 

 

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12 hours ago, mikemidrand said:

Hi Gremlin. Your Easy Solar 1600VA 24V inverter i assumed has a built in Blue Solar MPPT 100/50. If this is the case your 2 panels JA Solar 405W having Voc at 49.86V X 2 = 99.72V would have nearly maxed out the 100V max of the charge controller.  It would therefore be impossible for you to add a 3rd panel in series. However you can add 2 more panels in series as a 2nd string and the 2 strings be connected in parallel on busbars with your batteries.

Fyi, my supplier expect stocks of JA Solar 410W to arrive in JHB on or about 30th April 2021 (594 pcs).

If you can consider 2 X JA Solar 395W, stocks are currently available.

Thank Mike, appreciate the heads up. Steve from the Powerforum shop also advised the same and will hopefull get one of the 410W for me.

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2 hours ago, 1ougat said:

Just put the 3 panels in parallel.

The panel has a Vmpp of 42V and Voc of about 50V . 

 Your 100/50 can handle 1400 W max and can handle 100V MAX and require 5 V above Battery voltage to start the mppt - so that should be about 29-30V . The panels will operate well. Your amp limit is 50A and the three panels will operate at about 33A max . So you are ok . The  two panels in series are vary close to the max limit if open circuit and on cold days you would probably exceed it . 

With the three panels in parallel you also have 1200w  available that is within the spec of the MPPT . You are also limited by the original choice - a better option would have been 4 panels of 340 W probably but this should be still a ok setup .

Dont worry about the 5 W difference between the panel rating - panels derate over time and you will find on new panels that this is within the tolerance anyway you probably have on randomly selected panels . All those panels are assembled on the same line and with the flasing test at the end  the rating is assigned anyway . That is why you have families of panels with the same number with only the rating different. The component combination of the silicon wavers give the difference . In large solar panel installations such as PV grid installations this do become important . Not in this case .

Hope this help and good luck .

 

 

 

 

Thanks - Indeed it does help. Appreciate your advice and information as well as all the others before. Learning as I go along and this explains the families of panels! Regarding the original choice of panels I am restricted to 4m2 of panels due to the sectional title rules hence the two (at the time) largest wattage panels available. But as I said I need a third so going to stretch the rules a bit!!

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2 hours ago, branderplank said:

Can you mix for example JA Solar with a Canadian Solar? probably not

Also can't mix a poly with a mono?

Found a 405watt canadian solar

 

 

You can mix and match to your heart's content. The same voltage and current principles apply

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