Connecting Solar Panel Question.

[Guest]

I currently have a 200W folding solar kit with a regulator on the back of the panel (not the most efficient and cost effective I know, but suits our requirements very well.) This simply connects to my battery bank via a fuse and works faultlessly.

Now the question: If I buy another kit like this, can I just parallell the controller outputs across the batteries, or will the controllers not get along? I will upgrade to a MPPT in time to come, but not just yet.

Many thanks.

 

 

edit these are the type: http://www.ebay.co.uk/itm/251384818382?_trksid=p2060353.m1438.l2649&var=550489870767&ssPageName=STRK%3AMEBIDX%3AIT

Edited December 26, 2016 by Guest

[nicknorman]

You can just get another kit and parallel it onto the batteries if that is what suits you.

[Guest]

You can just get another kit and parallel it onto the batteries if that is what suits you.

Cheers Nick, that is what I had hoped for. Not the most technically advanced system I know, but suits what I am doing for now. We can add a batter controller later.

[BEngo]

Cheers Nick, that is what I had hoped for. Not the most technically advanced system I know, but suits what I am doing for now. We can add a batter controller later.

Presumably you are intending to have a solar powered chip shop?

 

N

[Guest]

Presumably you are intending to have a solar powered chip shop?

 

N

Aye well spotted

[stegra]

Hi. A little late with this but; I'm not sure that the controllers will get on alright. It's possible that each one will sense the voltage from the other one and they'll just switch between themselves meaning you're only ever getting the power from one of the panels. If you can bypass the controllers, it may be preferable to connect them in parallel into a separate controller. Controllers are cheap nowadays and an MPPT will be more efficient.

[WotEver]

Hi. A little late with this but; I'm not sure that the controllers will get on alright. It's possible that each one will sense the voltage from the other one and they'll just switch between themselves meaning you're only ever getting the power from one of the panels. If you can bypass the controllers, it may be preferable to connect them in parallel into a separate controller.

I've seen that written a few times but never with any justification.

 

When the batteries are sufficiently discharged to demand whatever the chargers can throw at them (Bulk) both chargers will run flat out. Once the voltage has risen to Acceptance level (14.4V or whatever) then one of the chargers might cut out but if it does it's no big deal as the demand from the batteries is constantly decreasing at that time.

 

It's no different to having the solar connected while the engine is running and charging the batteries with the alternator.

 

Interesting article here from Morningstar: http://www.morningstarcorp.com/parallel-charging-using-multiple-controllers-separate-pv-arrays/

[stegra]

The solar charger on my motorhome cuts out when the split charge is running from the alternator.

[nicknorman]

The solar charger on my motorhome cuts out when the split charge is running from the alternator.

Sure, but that is because the alternator can supply all the current that the batteries can take, and its voltage is set a little higher than the solar charge voltage.

[stegra]

Yes. I was responding to the previous post. I should have included the quote: "It's no different to having the solar connected while the engine is running and charging the batteries with the alternator."

The concern with having two solar controllers is that one will sense the power of the other one and cut out its own panel; in the same way that solar controller senses the alternator. I'm not sure about all this but I do recall it coming up on a self-build motorhome forum several years ago.

[WotEver]

Yes. I was responding to the previous post. I should have included the quote: "It's no different to having the solar connected while the engine is running and charging the batteries with the alternator."

The concern with having two solar controllers is that one will sense the power of the other one and cut out its own panel; in the same way that solar controller senses the alternator. I'm not sure about all this but I do recall it coming up on a self-build motorhome forum several years ago.

Read my post again. In the Bulk phase both controllers will be working flat out. That's when you need them both.

 

If your batteries were sufficiently discharged and if the bank were big enough then the solar controller wouldn't cut out when the engine is running, it's only cutting out because the batteries don't need it - they're getting everything they need from the alternator.

[nicknorman]

Yes. I was responding to the previous post. I should have included the quote: "It's no different to having the solar connected while the engine is running and charging the batteries with the alternator."

The concern with having two solar controllers is that one will sense the power of the other one and cut out its own panel; in the same way that solar controller senses the alternator. I'm not sure about all this but I do recall it coming up on a self-build motorhome forum several years ago.

No this won't be a problem. When charging batteries that are in at low SoC from solar, the limiting factor is the solar's ability to supply current - the batteries can take far more current than the solar can supply, and thus the system voltage will be relatively low, both controllers will be in bulk mode. There will eventually come a point when the charge current that the batteries can take decreases to the point that the system voltage rises to the regulated value and the controllers thus start to supply less current. Presuming they are both set to the same regulated voltage, they will both start to decrease their current similarly. Eventually they will both go into float mode, or possibly one will go into float mode first, but by then the other is more than capable of supplying all the current the batteries can take.

 

I appreciate that you have read something that someone said somewhere on the internet. Trouble is there is a lot of BS written on the internet! I had the same problem when there were discussions about mixing alternator charging with charging via a Travelpower and Combi. A few folk, who purported to be "professionals", told me that it wouldn't work, the alternator and Combi would fight each other, probably a large crevasse would open up under the canal and I'd be sucked down into hell etc etc. But in truth it works fine, these "professionals" had heard somebody talking in the pub about their granny's pet gibbon who had a boat and all hell broke loose when they tried to mix charging sources. Of course there was absolutely no evidence for it. What is commonly known as an "urban myth".

[WotEver]

I appreciate that you have read something that someone said somewhere on the internet. Trouble is there is a lot of BS written on the internet! <snip> What is commonly known as an "urban myth".

I'm not sure why, but in boating circles there appear to be far more of these myths about electrical issues and in particular battery charging than there are about any other subject.

[Guest]

I'm not sure why, but in boating circles there appear to be far more of these myths about electrical issues and in particular battery charging than there are about any other subject.

I wouldn't be too sure, there is a lot of similar talk re engine oil and filters

I appreciate all comments and will see how the panels get along. As Stegra states, if they squabble, i could easily change the regulator, a job I intend to do anyway in due course. I will report back eventually.

[stegra]

I had to look into this a bit because I was pretty sure it wasn't as simple as 'urban myth'. Connecting more than one MPPT controller is where problems can arise. Some manufacturers make sync leads to overcome this and some units can be configured in master/slave modes. Admittedly, it's likely that where panels have built-in controllers they will be PWM which are little more than a voltage controlled switch so no processor to get confused.

 

Going back to the original post. You can buy a 40A MPPT controller for under £50. The difference between MPPT and PWM is very significant, especially in low light conditions and lower temperatures. (MPPTs tend to lose much of their advantage higher temperatures.) Unless there is an urgent need to double your solar capacity, it might be worth upgrading first to an MPPT controller large enough to handle a second panel and see how it works. An increase of 30% would not be surprising. Also, the panel you linked to is polycrystalline which is less efficient than monocrystalline. Not sure how well a combination of poly and mono works into one controller or whether 12v parallel would work better than 24v or 48v series configuration which would normally be considered preferable; stepped down to 12v by the controller of course.

[Guest]

I had to look into this a bit because I was pretty sure it wasn't as simple as 'urban myth'. Connecting more than one MPPT controller is where problems can arise. Some manufacturers make sync leads to overcome this and some units can be configured in master/slave modes. Admittedly, it's likely that where panels have built-in controllers they will be PWM which are little more than a voltage controlled switch so no processor to get confused.

 

Going back to the original post. You can buy a 40A MPPT controller for under £50. The difference between MPPT and PWM is very significant, especially in low light conditions and lower temperatures. (MPPTs tend to lose much of their advantage higher temperatures.) Unless there is an urgent need to double your solar capacity, it might be worth upgrading first to an MPPT controller large enough to handle a second panel and see how it works. An increase of 30% would not be surprising. Also, the panel you linked to is polycrystalline which is less efficient than monocrystalline. Not sure how well a combination of poly and mono works into one controller or whether 12v parallel would work better than 24v or 48v series configuration which would normally be considered preferable; stepped down to 12v by the controller of course.

Cheers, will give it some thoguht. I hadn't realised MPPT were available at that sort of price.

[nicknorman]

Cheers, will give it some thoguht. I hadn't realised MPPT were available at that sort of price.

However one should bear in mind that not all MPPTs are born equal. There are a variety of "ways of doing it" with some being crude and cheap, some being clever and more expensive. And of course some cheapo controllers advertised as MPPT are nothing of the sort!

I had to look into this a bit because I was pretty sure it wasn't as simple as 'urban myth'. Connecting more than one MPPT controller is where problems can arise. Some manufacturers make sync leads to overcome this and some units can be configured in master/slave modes. Admittedly, it's likely that where panels have built-in controllers they will be PWM which are little more than a voltage controlled switch so no processor to get confused.

 

Going back to the original post. You can buy a 40A MPPT controller for under £50. The difference between MPPT and PWM is very significant, especially in low light conditions and lower temperatures. (MPPTs tend to lose much of their advantage higher temperatures.) Unless there is an urgent need to double your solar capacity, it might be worth upgrading first to an MPPT controller large enough to handle a second panel and see how it works. An increase of 30% would not be surprising. Also, the panel you linked to is polycrystalline which is less efficient than monocrystalline. Not sure how well a combination of poly and mono works into one controller or whether 12v parallel would work better than 24v or 48v series configuration which would normally be considered preferable; stepped down to 12v by the controller of course.

I'll admit to not having experience of an MPPT controller but I'm still sceptical about this. Can you point us to a specific report of how two MPPTs haven't worked well together, giving details? As opposed to comments that they might not? I'm pretty sure we have folk on here who have two MPPTs and haven't had a problem.

[WotEver]

I had to look into this a bit because I was pretty sure it wasn't as simple as 'urban myth'. Connecting more than one MPPT controller is where problems can arise.

Can you point us to the source of this information?

 

I posted the link above to the one manufacturer comment that I found with a quick Google (Morningstar) and that confirmed that there was no problem, so it might be interesting to see which company disagrees.

[stegra]

Can you point us to the source of this information?

 

I posted the link above to the one manufacturer comment that I found with a quick Google (Morningstar) and that confirmed that there was no problem, so it might be interesting to see which company disagrees.

Well the actual article you've linked to explains that there can be problems. The point of that article is to indicate that Morningstar have overcome those problems as long as the correct installation procedures are followed. The paragraph; Key Factors of Parallel Set-up explains what conditions need to exist for the system to function. To quote:

 

Since Morningstar uses voltage based State of Charge (SOC) for voltage regulation, no direct communication between the controllers is necessary to ensure they charge correctly in tandem. The controllers will transition to and from the different charging states at approximately the same time if all of the following conditions exist:

• All of the controllers are set with the same charging profile
  • Use the same DIP Switch settings for matching the charging control.
  • If creating a custom setup in MSView, save the custom setup configuration by using “Write to File” in the Setup Wizard to program all of the controllers with the same settings.
• There is a connection from the battery bank to each controller’s Voltage Sense Terminal pair. This ensures each controller is measuring the same battery bank voltage. Note: paralleling between controllers’ Voltage Sense terminals, in order to share a single connection to the battery bank is an acceptable practice.
• A battery Remote Temperature Sensor (RTS) is used with every controller. This ensures all controllers will be measuring the same temperature for regulation charging, voltage temperature compensation. If the batteries are located indoors in a climate controlled area it may be acceptable to omit an RTS. Note: An RTS is included in the TriStar MPPT box, but not with the TriStar. If using TriStar controllers, RTS’s must be purchased separately for each controller. A single RTS CANNOT be paralleled or shared between multiple controllers.

 

That's a lot more complex than simply connecting them in parallel at the battery.

[nicknorman]

Well the actual article you've linked to explains that there can be problems. The point of that article is to indicate that Morningstar have overcome those problems as long as the correct installation procedures are followed. The paragraph; Key Factors of Parallel Set-up explains what conditions need to exist for the system to function. To quote:

 

Since Morningstar uses voltage based State of Charge (SOC) for voltage regulation, no direct communication between the controllers is necessary to ensure they charge correctly in tandem. The controllers will transition to and from the different charging states at approximately the same time if all of the following conditions exist:

 

• All of the controllers are set with the same charging profile
  • Use the same DIP Switch settings for matching the charging control.
  • If creating a custom setup in MSView, save the custom setup configuration by using “Write to File” in the Setup Wizard to program all of the controllers with the same settings.
• There is a connection from the battery bank to each controller’s Voltage Sense Terminal pair. This ensures each controller is measuring the same battery bank voltage. Note: paralleling between controllers’ Voltage Sense terminals, in order to share a single connection to the battery bank is an acceptable practice.
• A battery Remote Temperature Sensor (RTS) is used with every controller. This ensures all controllers will be measuring the same temperature for regulation charging, voltage temperature compensation. If the batteries are located indoors in a climate controlled area it may be acceptable to omit an RTS. Note: An RTS is included in the TriStar MPPT box, but not with the TriStar. If using TriStar controllers, RTS’s must be purchased separately for each controller. A single RTS CANNOT be paralleled or shared between multiple controllers.

That's a lot more complex than simply connecting them in parallel at the battery.

Not really. It just says that they need to be set up in the same way as each other. If the OP installs a second controller of the same model "out of the box" those criteria will have been met. And to be honest even if they are not exactly identical it's not going to matter too much - one controller will just go to float before the other one.

[WotEver]

Not really. It just says that they need to be set up in the same way as each other. If the OP installs a second controller of the same model "out of the box" those criteria will have been met. And to be honest even if they are not exactly identical it's not going to matter too much - one controller will just go to float before the other one.

Absolutely. On both points.