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Old 27-01-2021, 14:56   #1
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Help! Controllers for 2 solar arrays to 1 battery bank

I have a trawler with a hard top with a decent camber/arch. I am installing four 200W panels in two arrays as the two pairs will be tilted slightly resulting in a 10-degree difference between the two sets. Battery bank is 600AH LiFePO4.

Attached diagram ignores switches/fuses.

QUESTION: What type of controllers should I use? My first inclination was to get two MPPT charge/controllers such as these Victron Smart 100/20, but then it occurred to me that they might fight each other in modulating charge to the batteries. So perhaps there is an MPPT controller (no charger function), then a separate charge controller? I have a VIctron Smart 100/50 controller - if I can use it, great. If not, that's okay too.

I could use a knowledgeable suggestion on controller and charger selection.

Thanks in advance -

Peter

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Old 27-01-2021, 15:09   #2
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

I prefer two controllers and there is little risk (but it can happen) that they will fight with each other. This can happen when the batteries are very close to full, but it is generally not a problem.

If you are really looking at the Victron Smart 100/20 (Bluetooth version) then add the Victron SmartShunt into the mix. With the SmartShunt installed you can configure everything over Bluetooth, the shunt will provide battery information to the controllers, and one controller will become master and direct all your controllers so you avoid any conflicts.
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Old 28-01-2021, 01:26   #3
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

if they are both set to the same voltage they will work together.

if the panels are facing different ways having more controllers will be better.
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Old 28-01-2021, 03:12   #4
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

Two controllers can occasionally cause some minor conflicts, but these only have a small impact on the charging profile. Two controllers will track multiple panels more accurately and this advantage generally outweighs any slight problems from any potential conflict especially when the panels are subject to different conditions or installed at different inclinations.

However, multiple smart solar controllers can be linked to remove any conflicts.

So your best solution is two Victron Smart controllers. As you already have a 100/50 you only need to purchase one extra controller. The two controllers can be different sizes without creating any problems, although I would double check with Victron that different sized controllers can still be linked (synchronised). The 100/20 you were considering purchasing is a little small for two 200w panels if you have a 12v system (it would be OK if you 24v house bank).

Finally, your panels are shown in series. It is worth experimenting with a parallel configuration, as this normally produces a higher yield in the shady conditions encountered on a boat, especially with Lithium. This will require a suitable gauge wire for the higher current. This assumes the panels are conventional “12v” panels where the panel voltage (Vmp) would be expected to be higher than the 14v indicated on your diagram. It also assumes your house battery is 12v. If it is a 24v system the series connection is needed.
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Old 28-01-2021, 03:16   #5
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

Why not consider the two solar banks to be in parallel and run the combined positive and negative leads to one controller?
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Old 28-01-2021, 03:30   #6
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

Quote:
Originally Posted by mvweebles View Post
I have a trawler with a hard top with a decent camber/arch. I am installing four 200W panels in two arrays as the two pairs will be tilted slightly resulting in a 10-degree difference between the two sets. Battery bank is 600AH LiFePO4.

Attached diagram ignores switches/fuses.

QUESTION: What type of controllers should I use? My first inclination was to get two MPPT charge/controllers such as these Victron Smart 100/20, but then it occurred to me that they might fight each other in modulating charge to the batteries. So perhaps there is an MPPT controller (no charger function), then a separate charge controller? I have a VIctron Smart 100/50 controller - if I can use it, great. If not, that's okay too.

I could use a knowledgeable suggestion on controller and charger selection.

Thanks in advance -

Peter

Attachment 231414
Unless I am missing something, all you need is another Victron controller and the very cheap and simple Victron Smart Sense battery monitor.

With this setup the two controllers talk to one another via the battery monitor.

It's what I am running and it is super simple, very flexible and very, very stable.
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Old 28-01-2021, 03:32   #7
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

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Originally Posted by noelex 77 View Post
Two controllers can occasionally cause some minor conflicts, but these only have a small impact on the charging profile. Two controllers will track multiple panels more accurately and this advantage generally outweighs any slight problems from any potential conflict especially when the panels are subject to different conditions or installed at different inclinations.

However, multiple smart solar controllers can be linked to remove any conflicts.

So your best solution is two Victron Smart controllers. As you already have a 100/50 you only need to purchase one extra controller. The two controllers can be different sizes without creating any problems, although I would double check with Victron that different sized controllers can still be linked (synchronised). The 100/20 you were considering purchasing is a little small for two 200w panels if you have a 12v system (it would be OK if you 24v house bank).

Finally, your panels are shown in series. It is worth experimenting with a parallel configuration, as this normally produces a higher yield in the shady conditions encountered on a boat, especially with Lithium. This will require a suitable gauge wire for the higher current. This assumes the panels are conventional “12v” panels where the panel voltage (Vmp) would be expected to be higher than the 14v indicated on your diagram. It also assumes your house battery is 12v. If it is a 24v system the series connection is needed.
Noelex, am I missing something? I would have expected you to recommend the Smart Sense. Aren't you using one?
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Old 28-01-2021, 04:14   #8
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

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Originally Posted by sstuller View Post
Why not consider the two solar banks to be in parallel and run the combined positive and negative leads to one controller?
I was going to ask the same question, so following... With the two banks in parallel then even if one bank is shaded the other will continue to produce power, right?
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Old 28-01-2021, 05:29   #9
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

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Noelex, am I missing something? I would have expected you to recommend the Smart Sense. Aren't you using one?
Yes, you are right, the Smart Sense would be a valuable addition. It provides the correct voltage (compensating for voltage drop between the controller and the batteries) and (providing the range is adequate), the correct battery temperature. This is much better than using the controllers’ internal temperature. This latter feature is less essential (but still useful) on lithium batteries. The Smart Sense is only about $50 so it is a bargain for the features it offers, unless you have other Victron components that duplicate the features.

I was under the impression the Smart Sense was also necessary for synchronisation, but another forum member pointed out that with the latest software synchronisation can be achieved with the solar controllers alone. So the Smart Sense is very nice to have, but not essential.
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Old 28-01-2021, 06:14   #10
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

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I was going to ask the same question, so following... With the two banks in parallel then even if one bank is shaded the other will continue to produce power, right?
Yes, they will produce some power, but with multiple controllers (ideally one per panel) the power produced will be higher when the solar panels are subject to different conditions such as more shade on one panel.

When panels are subject to different conditions, the maximum power point voltage will be different for each of the panels. With multiple panels in parallel connected to a single controller, the controller must choose a power point (input voltage) that is the best compromise for all the panels.


When one controller per panel is installed the controller is free to select the maximum power point that ideally suits that particular panel. This will fluctuate as the conditions change and the controller will adjust the value to optimise the output of the single panel it is connected too.

Thus the total output will be higher and multiple controllers provide some redundancy enabling some power to be produced if one controller fails. As MPPT controllers are not the most reliable electronic devices, this latter feature is also valuable.

Multiple controllers have the drawback that the wiring is more complex and the cost is generally higher (although in some cases multiple small controllers are cheaper than one large controller of similar total capacity). Thus a compromise such as two controllers with four panels, as the OP is contemplating, is sometimes the best practical compromise. You also have to careful that the self consumption of multiple devices does not negate the gains from the higher output. This usually only becomes a concern when small panels are connected to older controllers (which frequently have high self consumption). Finally, the issue of charging conflicts can occasionally cause minor inefficiencies and slightly incorrect charging profiles if the controllers are not linked.
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Old 28-01-2021, 10:29   #11
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

Quote:
Originally Posted by noelex 77 View Post
Yes, you are right, the Smart Sense would be a valuable addition. It provides the correct voltage (compensating for voltage drop between the controller and the batteries) and (providing the range is adequate), the correct battery temperature. This is much better than using the controllers’ internal temperature. This latter feature is less essential (but still useful) on lithium batteries. The Smart Sense is only about $50 so it is a bargain for the features it offers, unless you have other Victron components that duplicate the features.

I was under the impression the Smart Sense was also necessary for synchronisation, but another forum member pointed out that with the latest software synchronisation can be achieved with the solar controllers alone. So the Smart Sense is very nice to have, but not essential.
Thanks so much to all - incredibly helpful information.

For posterity (or lurkers without much knowledge such as myself), here is a link to the Smart Battery Sense device from Victron. The embedded video is super helpful and gives set-up guidance.

https://www.victronenergy.com/access...e#pd-nav-video

Great resource here and thanks for being so generous with your time to respond in such detail.

Peter
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Old 28-01-2021, 10:58   #12
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

I'm curious why, with a new installation, you wouldn't consider the Smart Shunt rather than the Smart Sense? Yes, there is a $ component, but the Smart Shunt is basically the BMV 712 without the display. Means you get a full-on battery monitor without having to run any cables outside the battery box, the same data sharing as the Smart Sense, and the ability to view your battery monitor data from anywhere. It adds about USD80 to the whole thing but seems well worth it unless you already have a battery monitor in place with a sunk cost.
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Old 28-01-2021, 13:10   #13
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

Quote:
Originally Posted by mvweebles View Post
Thanks so much to all - incredibly helpful information.

For posterity (or lurkers without much knowledge such as myself), here is a link to the Smart Battery Sense device from Victron. The embedded video is super helpful and gives set-up guidance.

https://www.victronenergy.com/access...e#pd-nav-video

Great resource here and thanks for being so generous with your time to respond in such detail.

Peter
It is also worth noting (last time I checked a few months ago) there are two different Smart Battery Sense offerings: one with a 3 meter Bluetooth range (black in color) and one with a 10 meter BT range (blue in color)...

I have one of each because I didn’t know this when I ordered my first one ~3 years ago; or perhaps that was the only model available at that time?... (the 3 m unit was subsequently installed on the engine bank, so still proves useful even though not linked to the 3 Victron Smart MMPT Controllers.)

In case this spares anyone else from inadvertently owning 2...

Cheers! Bill
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Old 28-01-2021, 14:01   #14
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

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I'm curious why, with a new installation, you wouldn't consider the Smart Shunt rather than the Smart Sense? Yes, there is a $ component, but the Smart Shunt is basically the BMV 712 without the display. Means you get a full-on battery monitor without having to run any cables outside the battery box, the same data sharing as the Smart Sense, and the ability to view your battery monitor data from anywhere. It adds about USD80 to the whole thing but seems well worth it unless you already have a battery monitor in place with a sunk cost.
I actually have a magnum 3100 hybrid inverter and battery monitor as well as Blue Sea panel multi-gauges. Victron has decent videos on both. As cool as the shunt one is, I think I'll go with the basic one. Honestly, I'm trying to keep Bluetooth and wireless networks to a minimum, which contributed to my choice of Magnum.
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Old 28-01-2021, 14:08   #15
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Re: Help! Controllers for 2 solar arrays to 1 battery bank

Fair enough.

I actually think there's a market (although probably small) for your original sketch - charge devices with a separate charge controller. I think it would be great if we had a battery monitor that can manage your solar MPPT charge devices, your alternator regulator(s), your shore power charger(s), your wind generator(s), and any other charging sources and provide a consistent charge profile. With prioritization by operating cost so that when you are plugged in to shore power it still uses solar before shore power.

You can get close with some of the Victron equipment (and maybe even get all the way there?) but it isn't easy.
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