solar panel sizing question

[goboatingnow]

variants of this questions are asked regularly , so bear with m

e I have 2x Victron SPM100-12 panels , nominal 12v 100w panels, was going to replace them with SPM041751200 , 170 watt , 12V nominal

But I can fit all four

So I was thinking of two parallel strings of a 100W and a 170W and a MPPT 100/50 controller

shading isnt in general a big issue , as the panels are clear of the bimini etc , I could split the two series strings into sperate controllers

any comments ( boat is 12V )

[Pete7]

Wouldn't you get a similar amount of power of out a pair of SPM 175s from Victron? then sell the 100s off. Also you could get away with two smaller chargers which will be cheaper than 2 x 150 MPPTs.

If you have the room then stepping up to the SPM042152400 raises the voltage much higher with more cells so thinner wire and again small chargers.

I went for a single 60 cell 300w panel to keep it simple.

Pete

[Dsanduril]

I think you are saying you will keep the existing 100W pair and then add a new pair of 175W for a total of four panels?

For paralleling panels (or strings of panels), the key is that the Vmp (and also the temperature coefficient thereof) be very close to the same. Victron's current SPM datasheet includes a 90W panel and a 115W panel but not a 100W. Both of those are listed at Vmp of 19.xV, would guess a 100W is similar. The 175W is listed at 19.4V, so should be compatible. Any size above the 175W moves into the 30+V range and would not be compatible.

For the series portion you want the Imp to be identical, this is best done by using identical panels but you can mix-match if current is very close.

Whether or not two controllers would be better depends on shading and how you feel about redundancy, certainly one controller could easily handle that load.

[Edit] just found an older SPM100-12 datasheet that lists Vmp as 18V. If you use a single controller the MPPT sweep will likely settle near that voltage (or double if series string), meaning that you might lose 1.4/19.4~=7% of production from the 175W panels. Temperature coefficients are similar. This complicates things slightly, you have to balance that hit to production against cost and against the static losses that a second controller will add.

[hlev00]

I divided my four panels into two sets with separate controllers to improve shading issues, but I like the redundancy aspect too. The Victrons can be configured in sets as well, with one picking up as leader, to deliver the right charge as a system, assuming of course they are all being used to charge the same bank.


https://www.cruisersforum.com/forums...no-238690.html


harry

[goboatingnow]

Thanks

It’s been suggested that I series the panels of same wattage and then parallel ( optionally two controllers ) ie 2x100w paralleled with 2x170W

Did Victron ever implement the shared mppt controller conceit over VE.direct

[goboatingnow]

Originally Posted by Dsanduril

I think you are saying you will keep the existing 100W pair and then add a new pair of 175W for a total of four panels?

For paralleling panels (or strings of panels), the key is that the Vmp (and also the temperature coefficient thereof) be very close to the same. Victron's current SPM datasheet includes a 90W panel and a 115W panel but not a 100W. Both of those are listed at Vmp of 19.xV, would guess a 100W is similar. The 175W is listed at 19.4V, so should be compatible. Any size above the 175W moves into the 30+V range and would not be compatible.

For the series portion you want the Imp to be identical, this is best done by using identical panels but you can mix-match if current is very close.

Whether or not two controllers would be better depends on shading and how you feel about redundancy, certainly one controller could easily handle that load.

[Edit] just found an older SPM100-12 datasheet that lists Vmp as 18V. If you use a single controller the MPPT sweep will likely settle near that voltage (or double if series string), meaning that you might lose 1.4/19.4~=7% of production from the 175W panels. Temperature coefficients are similar. This complicates things slightly, you have to balance that hit to production against cost and against the static losses that a second controller will add.

Can you post the link to the older data sheets thanks

[noelex 77]

Originally Posted by Dsanduril

I think you are saying you will keep the existing 100W pair and then add a new pair of 175W for a total of four panels?

For paralleling panels (or strings of panels), the key is that the Vmp (and also the temperature coefficient thereof) be very close to the same. Victron's current SPM datasheet includes a 90W panel and a 115W panel but not a 100W. Both of those are listed at Vmp of 19.xV, would guess a 100W is similar. The 175W is listed at 19.4V, so should be compatible. Any size above the 175W moves into the 30+V range and would not be compatible.

For the series portion you want the Imp to be identical, this is best done by using identical panels but you can mix-match if current is very close.

Whether or not two controllers would be better depends on shading and how you feel about redundancy, certainly one controller could easily handle that load.

[Edit] just found an older SPM100-12 datasheet that lists Vmp as 18V. If you use a single controller the MPPT sweep will likely settle near that voltage (or double if series string), meaning that you might lose 1.4/19.4~=7% of production from the 175W panels. Temperature coefficients are similar. This complicates things slightly, you have to balance that hit to production against cost and against the static losses that a second controller will add.

Great advice

[Dsanduril]

Originally Posted by goboatingnow

Did Victron ever implement the shared mppt controller conceit over VE.direct

Yes. Noelex, who just posted here has far more hands on experience than I. What I have seen/configured it seems to work very well.

Originally Posted by goboatingnow

Can you post the link to the older data sheets thanks

Found the same value two places; Victron’s MPPT calculator spreadsheet (go to “Modules” tab:
https://www.victronenergy.com/upload...-Calc-2_2.xlsx
Or this old catalog:
https://www.yumpu.com/en/document/vi...s-solar-bazaar

[noelex 77]

Originally Posted by goboatingnow

Did Victron ever implement the shared mppt controller conceit over VE.direct

The inexpensive ($50 or so) Victron SmartBattery sense will synchronise the charging between the the solar controllers. It also sends accurate battery voltage and battery temperature. It communicates via Bluetooth, which is perhaps not ideal although this makes installation easy.

If the Bluetooth range is inadequate, as it is on some larger vessels the unit can easily be mounted next to the the solar controllers. This will invalidate the temperature function, but the other features will still work. It is well worth the small cost. Buy the newer blue long range version rather than the old black model.

I believe there are some other ways of achieving the same thing. For example, via the Victron colour control panel. This is a more expensive solution and as I do not have this installed I am not sure of the features available.

[Sailing Ohm]

I thought that much like batteries, solar panels in parallel or series should all be the same ratings...

If you can fit four you obviously have room so why not just get two larger panels in the 200-300watt range? Usually these are high voltages also so your mppt will love It. (So will you wallet in wiring costs)
Two is always less complicated than four.
Why buy new small panels and a new controller to set up some not ideal system? Why not just upgrade the panels to ones that meet your needs and use your existing set up.

[hlev00]

My pair of Victron 75/15 MPPT controllers connect themselves to manage charging without the need of another module. You have to be sure the battery profiles are configured the same because they don't exchange settings. They decide which one should be the leader themselves and then the leader manages the charging levels. I've had the pair for over a year but only noticed, or implemented the feature this summer. So far, so good.

[goboatingnow]

Originally Posted by Sailing Ohm

I thought that much like batteries, solar panels in parallel or series should all be the same ratings...

If you can fit four you obviously have room so why not just get two larger panels in the 200-300watt range? Usually these are high voltages also so your mppt will love It. (So will you wallet in wiring costs)
Two is always less complicated than four.
Why buy new small panels and a new controller to set up some not ideal system? Why not just upgrade the panels to ones that meet your needs and use your existing set up.

I don’t have room for the larger panels per se , I need to split up the mounting

My thinking was to re-utilise the older panels rather then selling them

I think the best might be the two 170 W in series and the two 100w in series and two SmartSolar controllers which will handle being paired, can’t see much point in the blue solar range as price is nearly identical. I might just get away with the 75/15 units, though the two 170w panels will probably need a 100/20 unit

As I understand it , the SmartSolar MPPT will handle parallel MPPT controllers over Bluetooth without anything else needed , That still leaves me VE.direct to feed into my system monitoring software

[noelex 77]

Originally Posted by goboatingnow

I think the best might be the two 170 W in series and the two 100w in series and two SmartSolar controllers which will handle being paired, can’t see much point in the blue solar range as price is nearly identical. I might just get away with the 75/15 units

Assuming you have a 12v system, the 75/15 is unfortunately much too small for 2x170w panels.

Originally Posted by goboatingnow

As I understand it , the SmartSolar MPPT will handle parallel MPPT controllers over Bluetooth without anything else needed , That still leaves me VE.direct to feed into my system monitoring software

The two controllers will work OK together, but there is no communication or synchronisation between the controllers via Bluetooth unless the optional extras I mentioned are installed.

This lack of communication causes minimal problems in practice, but there are occasional conflicts that cause the charging algorithm to be less than optimal in some situations. The low cost of SmartBattery sense removes these conflicts and at the same time eliminates the problem of voltage drop and (often, depending on Bluetooth range) incorrect temperature between the batteries and the controller. These factors can have a significant effect the charge algorithm.

Especially if you are contemplating two controllers, the Victron Smartbattery sense is a bargain for the extra functionality it provides.

[zstine]

The 2 different panel types must be on different controllers since they output differnent voltages.. you must use 2 controllers or will have very, very poor performance.

[Quadrille in JB]

I have never heard of the Victron Smart Sense until now but it sounds like it will work great with my 2-360w Sunpower PV panels and my 2-100/30 Victron mppt controllers.
I just ordered one on Amazon for $39 with free next day delivery.
My system works great now but things can always br improved. BTW I have screen shots of my controllers showing 385 watts output on a nice sunny day