Help with solar 🙏

[seanwinder22]

Hi everyone
Some help needed please to help understand more if it’s worth fitting this extra panel
Ok I have at the moment 3x120 solar panels which are wired in parallel the specs are
Open Circuit Voltage: 21.6V
Short Circuit Current: 7.13A
Max Power Voltage: 18.5V
Max Power Current: 6.49A
I have room for another solar which is my old one I didn’t want to waste also the only room I have is for this size I can’t get 120w this size it’s A renogy 100w which I will post also
The specs
Optimum Operating Voltage 18.9
Open-Circuit voltage 22.5V
Optimum OperatingCurrent 5.29A
So… Can I wire these up in series or wouldn’t there be any point
I understand in parallel the drop be too great. or better still would my Victron mppt 30 amp power this much also ? I understand from a little reading I wouldn’t get the whole 460w of solar , but at the moment I have 360w of solar so getting anything over this mark with the little space is still a bonus and I’m not wasting the solar I have. Any help appreciated

 

[BouncyBoatFolk]

Dedicate it to engine battery ?
Mike.

 

[I2C]

I wasn’t going to reply as I don’t think I can add much but as you’ve only had one reply I’ll give it a go

Your charge controller should handle the amps as it can do 30amps, though reading the specs it says it can handle only 440 watts. As you’ll have different sized panels I don’t think it’ll reach 460w but you’d have to do the calculations to confirm. This site explains the values you’d get with a different sized panel/configuration if that helps.

Is it worth the risk/hassle I can’t answer, don’t know how you use your van - we only have 160w and that does us fine for how we use our van. As BouncyBoatFolk says, maybe you could wire it to a cheap PWM controller and use it to keep the vehicle battery happy.

 

[seanwinder22]

Dedicate it to engine battery ?
Mike.

Dedicate it to engine battery ?
Mike.

I can’t buddy I use a Victron b2b and any solar of 100w going into the starter battery would keep turning the b2b on as I’ve also got the battery master hooked up as a trickle charger
Thanks tho

 

[seanwinder22]

I wasn’t going to reply as I don’t think I can add much but as you’ve only had one reply I’ll give it a go

Your charge controller should handle the amps as it can do 30amps, though reading the specs it says it can handle only 440 watts. As you’ll have different sized panels I don’t think it’ll reach 460w but you’d have to do the calculations to confirm. This site explains the values you’d get with a different sized panel/configuration if that helps.

Is it worth the risk/hassle I can’t answer, don’t know how you use your van - we only have 160w and that does us fine for how we use our van. As BouncyBoatFolk says, maybe you could wire it to a cheap PWM controller and use it to keep the vehicle battery happy.

Thanks
Yes I understand I won’t get 460w as I said above
At the moment I’m pulling 360w
I do have a spare pwm controller too! I may leave this solar panel off of this system and wire alone to the. Pwm and also run this to my battery bank
I do understand it won’t connect and work together with the mppt
But it’s a extra 100w of charge hitting the battery bank

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[seanwinder22]

Thanks
Yes I understand I won’t get 460w as I said above
At the moment I’m pulling 360w
I do have a spare pwm controller too! I may leave this solar panel off of this system and wire alone to the. Pwm and also run this to my battery bank
I do understand it won’t connect and work together with the mppt
But it’s a extra 100w of charge hitting the battery bank

Scrap the pwm it won’t be any good with lithium

 

[autorouter]

The voltages look reasonably well matched, it's probably worth a try. Since you already have the extra solar panel, maybe you could just place it on the roof and connect up some wires to try it. You would just need a couple of 2-way or multiway adapters. If the power goes up when you connect it up, then you're not losing anything.

In terms of power, the 460W of panel won't overload the controller. It's designed to take 440W as you say, and anything a bit over that it will just not use. When the batteries are full, it will be 'not using' 360W of power with your existing arrangement, so it's no big deal. Also when panels are flat on the roof and not tilted to the optimum angle, you'll be lucky to get much more than 70 to 80% of the nominal power anyway.

 

[seanwinder22]

The voltages look reasonably well matched, it's probably worth a try. Since you already have the extra solar panel, maybe you could just place it on the roof and connect up some wires to try it. You would just need a couple of 2-way or multiway adapters. If the power goes up when you connect it up, then you're not losing anything.

In terms of power, the 460W of panel won't overload the controller. It's designed to take 440W as you say, and anything a bit over that it will just not use. When the batteries are full, it will be 'not using' 360W of power with your existing arrangement, so it's no big deal. Also when panels are flat on the roof and not tilted to the optimum angle, you'll be lucky to get much more than 70 to 80% of the nominal power anyway.

Thanks buddy
Yea this is what I thought they are very similar
I have just set up this morning but for some reason the mppt is showing off in the state
I have wired in series but I’m getting nothing My 3 panels was connected parallel
All I did was disconnected everything then wired positive to negative on each panel then the first panel positive to the mppt and the last panel negative Also to the mppt
I’m getting nothing . I can not understand why

 

[autorouter]

I have wired in series but I’m getting nothing My 3 panels was connected parallel

Not a good idea. The MPPT will have an input voltage limit. You didn't say exactly which MPPT you have, but the first number is the voltage limit, probably 75V or 100V. Not normally a problem because panels are usually wired in parallel, so the total voltage is the same as the panel voltage, about 22V max. But in series the voltages add together, so the total voltage will be 4 x 22V = 88V maximum. Chances are it won't have exceeded 4 x 19V = 76V which is the maximum power voltage. so if you disconnect them the controller will probably be OK.

If you are using standard solar connectors (MC4) then you can get 2-to-1 and 3-to-1 adapters to parallel them together - that's probably how they were originally wired. You only need another couple of adapters to connect your 4th panel in parallel.

 

[seanwinder22]

Not a good idea. The MPPT will have an input voltage limit. You didn't say exactly which MPPT you have, but the first number is the voltage limit, probably 75V or 100V. Not normally a problem because panels are usually wired in parallel, so the total voltage is the same as the panel voltage, about 22V max. But in series the voltages add together, so the total voltage will be 4 x 22V = 88V maximum. Chances are it won't have exceeded 4 x 19V = 76V which is the maximum power voltage. so if you disconnect them the controller will probably be OK.

If you are using standard solar connectors (MC4) then you can get 2-to-1 and 3-to-1 adapters to parallel them together - that's probably how they were originally wired. You only need another couple of adapters to connect your 4th panel in parallel.

I have actually got it all working . A wire had pulled a little out the back of a panel . I crimped again now it’s. Fine
So I can’t have these in series ? I have the Victron 100/30 controller
So x3 120 w and x1 100w in series will be too much ? I have to go parallel
Then all my solar will basically go to the lowest being the 100w panel so in total 400w ?
Thanks

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[seanwinder22]

Not a good idea. The MPPT will have an input voltage limit. You didn't say exactly which MPPT you have, but the first number is the voltage limit, probably 75V or 100V. Not normally a problem because panels are usually wired in parallel, so the total voltage is the same as the panel voltage, about 22V max. But in series the voltages add together, so the total voltage will be 4 x 22V = 88V maximum. Chances are it won't have exceeded 4 x 19V = 76V which is the maximum power voltage. so if you disconnect them the controller will probably be OK.

If you are using standard solar connectors (MC4) then you can get 2-to-1 and 3-to-1 adapters to parallel them together - that's probably how they were originally wired. You only need another couple of adapters to connect your 4th panel in parallel.

I believe I’m still under 100v and 30amp even having these wired in series isn’t that correct
I just was lead to believe going in series with this is the best option with these being very similar volts wise
Or as I said above in parallel I’m definitely getting 100w on each panel anyway

 

[I2C]

I believe I’m still under 100v and 30amp even having these wired in series isn’t that correct
I just was lead to believe going in series with this is the best option with these being very similar volts wise
Or as I said above in parallel I’m definitely getting 100w on each panel anyway

Correct, your controller can take 100v. I’ve used series on our setup (I know there are others here who wouldn’t), a) because I have no obstacles on the roof or park under trees and b) the wire sizes can be smaller as there’s less amps just more volts which doesn’t affect the wire size compared to amps.

 

[seanwinder22]

Correct, your controller can take 100v. I’ve used series on our setup (I know there are others here who wouldn’t), a) because I have no obstacles on the roof or park under trees and b) the wire sizes can be smaller as there’s less amps just more volts which doesn’t affect the wire size compared to amps.

Thanks for this buddy you really helped I too have nothing in the way
Everything seems to be working great

 

[autorouter]

The series panels should be OK with a voltage limit of 100V, I was concerned because many of the smaller Victron MPPTs are 75V, which is a bit too low for 4 panels. That voltage limit is a hard limit, not a soft limit like the power handling.

In series, the voltage matching is not important, it's the amps matching that is. All 4 panels will be limited to the amps of the lowest panel, so basically you are losing 20W from each of the larger 3 panels. That's still an overall gain, but not much. In parallel, if the voltages match (which they do) the amps add up, and you will gain most of the power from the 4th panel while leaving the 3 larger panels as they were. Worth a try, it's only a matter of reconfiguring the plugs.

A safety note - with parallel panels the voltages stay below the 50V threshold where they can become dangerous. If you are wiring in series remember that a voltage of 80V or more is enough to give you a shock, and if you are working on the roof of the MH that might precipitate an accident. Not a big deal, but worth bearing in mind as you are wiring up, with the panels in sunlight.

 

[Raul]

Your only best shot is 2S2P, two in series then parallel the two series. You will loose only 1A on ONE of the series due to the 100w panel being lower amps. The other two will not be dragged down as they are on separate string. Trust me, I’ve coupled mismatched panels many times. Your proposal is doable with minimal loss, only noticeable when you reach full power harvest. All of the time when solar is below max output, will be no loss.

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[Billy192]

i would leave the setup you have, just add a second MPPT (small one) just for the 100w panel. then you get all the 460w, if the soalr controller's were both victron it give s you a total reading of both.
Billy

 

[seanwinder22]

Your only best shot is 2S2P, two in series then parallel the two series. You will loose only 1A on ONE of the series due to the 100w panel being lower amps. The other two will not be dragged down as they are on separate string. Trust me, I’ve coupled mismatched panels many times. Your proposal is doable with minimal loss, only noticeable when you reach full power harvest. All of the time when solar is below max output, will be no loss.

Thanks buddy I was just looking into this myself

 

[Raul]

Yes you got it.

 

[seanwinder22]

Yes you got it.

This way apparently if the volts are very similar you don’t lose out

 

[Just smiffy]

Lots of good advice here and I’m learning all the time… but, are you a heavy user of the power you have? I used to have 300w feeding two agm’s and never ran low…

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[seanwinder22]

Lots of good advice here and I’m learning all the time… but, are you a heavy user of the power you have? I used to have 300w feeding two agm’s and never ran low…

Yea buddy we have a 300ah lithium and now 460w solar which I guess still won’t cut it lol we only do off grid