solar panel sizing question

[Dsanduril]

Originally Posted by 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.

They don't output different voltages, they output nearly the same voltage even though one set is 100W and the other is 175W. They are both 36-cell panels with monocrystalline cells and thus have a nominal 0.5V/cell Vmp.

As noted above, the newer panels are about 1.4V higher Vmp than the old panels, but because of the nature of the I-V curve the loss in production will not be greater than 1.4/19.4=7%. Actual loss will be a bit less because when the voltage drops below Vmp the current increases (slightly).

The knee of the I-V curve is fairly broad on decreasing voltage side, for 36-cell panels operating 1V lower than Vmp will result in very little loss of power production. For a 60- or 72-cell panel this widens to about 2V. Going the other way, operating above Vmp the current dropoff is very steep and power production goes way down immediately.

Here's a typical I-V curve for a 12V (nominal) panel - probably 32-cell.


At Vmp the power is 42.75W (17.1x2.5), at 16V it is ~42.35W (16.1x2.63), A loss of 1% in power production even though the voltage drop was 5.8%.

[Adelie]

I would put a small MPPT controller on each panel rather than 1 big controller.
A. Redundancy
B. Better production: Any shading or overheating of 1 panel will not drag the production by all the panels down or half the panels if you go with 2 big controllers.

The Victron 100/50 is $320 OR $295 (Smart vs Blue).
The Victron 75/15 is 114 x 4 = $456 OR $88 x 4 = $352.
To me doing so will cost modestly more in wiring and slightly more in controllers.

Also, at about $100, bringing a (5th) spare controller becomes conceivable.

[Shoalbay]

Originally Posted by 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

When deciding on panels I also went with only one (260W in my case). Lower parts count increases reliability. The engine alternator is the backup charging system.

[goboatingnow]

I don’t believe the smart battery sense unit is needed if using the Smartsolar moot range

[noelex 77]

Originally Posted by goboatingnow

I don’t believe the smart battery sense unit is needed if using the Smartsolar moot range

The Smartsolar MPPT controllers have built-in Bluetooth so you may reasonably expect these to communicate and synchronise with other Smartsolar controllers within range. Unfortunately they cannot do this.

To form a network, additional hardware is needed and the Victron Smartbattery sense is the cheapest and easiest way of accomplishing this.

[Quadrille in JB]

I just ordered a Victron Smart Sense last night and I'm wondering where to install it as my battery bank is located in 2 adjacent but different locations.
I have 6-105 ah AGMs located under the quarter berth and an additional 2-105 ah AGMs located in the engine compartment. While underway the temperature in these two compartments will differ greatly but most of our solar charging is done at anchor.
So...should I monitor the battery temperature in the engine compartment or under the quarterberth?
thanks for your opinions in advance,
Bill in JB

[noelex 77]

Originally Posted by Quadrille in JB

So...should I monitor the battery temperature in the engine compartment or under the quarterberth?
thanks for your opinions in advance,
Bill in JB

There is no perfect solution, but it would be better to use the higher temperature so I would put the Smart Sense on the batteries in the engine compartment.

Keep in mind that the Bluetooth range on the Smart Sense is not great, even with the newer “long range” blue module so check the communication between the solar controllers and Smart Sense is reliable in the chosen location before permanently sticking the unit onto the batteries.

[Quadrille in JB]

Originally Posted by noelex 77

There is no perfect solution, but it would be better to use the higher temperature so I would put the Smart Sense on the batteries in the engine compartment.

Keep in mind that the Bluetooth range on the Smart Sense is not great, even with the newer “long range” blue module so check the communication between the solar controllers and Smart Sense is reliable in the chosen location before permanently sticking the unit onto the batteries.

Thanks, that is exactly what I was thinking. The range from the Smart Sense to the Victron controllers is only about 4 feet.

[MJH]

Originally Posted by 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 )

I installed 4x140 panels in 2015 with a single controller for each pair with each pair going to a separate 8D Gel house battery...I have not had a problem. I suggest you put a single controller on the 100s and a separate controller for the 170s. Any future upgrade would be done via the pairs already established.

~ ~ _/) ~ ~ MJH

[goboatingnow]

Strangely that contradicts what Victron themselves said. Why would a simple voltage /temp unit be needed to enable synchronised charging ?

[noelex 77]

Originally Posted by goboatingnow

Strangely that contradicts what Victron themselves said. Why would a simple voltage /temp unit be needed to enable synchronised charging ?

My understanding is that a “hub” or central device is needed to set up the synchronisation between the Smartsolar controllers. The Smart battery sense is one device that can function as this hub.

It is always possible I have this wrong, but I have owned and used 3 Victon Smartsolar MPPT controllers for a couple of years and the charging state was definitely not linked or synchronised before installing the Smart battery monitor.

I cannot find any information from Victron that indicates that synchronisation is possible with multiple Smartsolar controllers alone, without any additional hardware. Nor is there any information on how this can be set up if it is possible. Victron do explain in detail how this can be done once the Smart battery sense is installed.

Could you possibly post a link to where Victron has indicated this is possible? It would be great if owners of Smartsolar controllers can achieve synchronisation of the charge state without purchasing any extra hardware.

[noelex 77]

This link on the Victron forum provides some insight, although this may be wrong or out of date:

https://community.victronenergy.com/...ncronized.html


The answer given is:

“No, only if you use a Smart Battery Sense, or a BMV networked to your battery.”

[goboatingnow]

Well the smart battery sense only aids the process in that it discount voltage drops in the mppt to battery cables , which you can easily mitigate

Here’s the answer from the Victron community

“Justin Cook - Bay Marine Supply USA answered · 10 hours ago EXPERT ANSWEREXPERT ANSWER
Hi @goboatingnow , welcome to the Community!

A Smart Battery Sense, SmartShunt, or BMV-712 is only required should you want the chargers to take into account battery voltage, temperature, and/or current (in the case of a SmartShunt or BMV-712) and is advised but not necessary. For basic synchronized charging, you don't need any additional hardware - just create a VE.Smart Network while connected to one MPPT, then connect to the other and click "join VE.Smart Network" and select the network that you set up through the first controller, and you're done!

As noted in the manual, it is critically important to ensure that both controllers have the same battery settings.”

[noelex 77]

Originally Posted by goboatingnow

Here’s the answer from the Victron community

“Justin Cook - Bay Marine Supply USA answered · 10 hours ago EXPERT ANSWEREXPERT ANSWER
Hi @goboatingnow , welcome to the Community!

A Smart Battery Sense, SmartShunt, or BMV-712 is only required should you want the chargers to take into account battery voltage, temperature, and/or current (in the case of a SmartShunt or BMV-712) and is advised but not necessary. For basic synchronized charging, you don't need any additional hardware - just create a VE.Smart Network while connected to one MPPT, then connect to the other and click "join VE.Smart Network" and select the network that you set up through the first controller, and you're done!

Thanks for that.

It certainly looks like it is possible exactly as you indicated.

Victron have lots of software updates and I suspect this capability has been added in one of these updates. That is a great feature of Victron controllers. The software updates have significantly improved the controllers‘ charge algorithm and adjustability compared to the units I purchased a couple of years ago.

Has anyone enabled this synchronisation with just the controllers themselves? It would be nice to know exactly what is meant by “basic” synchronised charging. Hopefully that means the controllers will jump to the same charge state. Without the smart battery sense for a single voltage reference, presumably the voltage of one solar controller is used as the reference.

[noelex 77]

If anyone is checking, it is this “synchronised charging” indication that you are looking for: