Charge controller for each solar panel?

[jbinbi]

just did a solar install. 2 285 W solarworld panels. 2 ecoworthy controllers.

https://www.amazon.com/ECO-WORTHY-Ch.../dp/B00FF1KGT4

my issue (see thread running on battery monitors) is that these controllers are located where i can't see the displays easily. I am going to purchase either 1 50 A or 2 25A analog current meters to put where i can see them. I like the idea of having 2 monotors to see what each panel controller is doing. I also like have 2 controllers for redundancy. If I had 4 panels, I would probably put 2 panels per controller.

[SailFastTri]

When using multiple controllers; does the output of one controller "fool" the others into sensing that the battery charge state is higher than it really is (by raising the voltage on the common buss)? If so, doesn't that cause them each to reduce their output accordingly?

[noelex 77]

Originally Posted by SailFastTri

When using multiple controllers; does the output of one controller "fool" the others into sensing that the battery charge state is higher than it really is (by raising the voltage on the common buss)? If so, doesn't that cause them each to reduce their output accordingly?

No, but you can end up with a longer absorption time which can overcharge the batteries. It is not a practical problem with just a couple of controllers, but can become an issue with three or more controllers.

It is more of problem with batteries that are sensitive to overcharging such as gel batteries. You can prevent this problem by reducing the automatic absorption time or manually forcing the controller onto float, but this adjustment tends to only be available on the larger more expensive controllers and these are not commonly used in a system with one controller for each panel.

[ramblinrod]

Originally Posted by Privilege

I had read this somewhere else so prior to installation I spoke to the tech's at Morning Star corporation. They told me that the controllers don't recognize the voltage output from the other controller and misinterpret this to be a charged battery. It's the battery that controls the acceptance rate of the controller, not the controller itself.

Correct, the charge controller doesn't care what the battery voltage is. They only care about the amount of current it will accept.

[mitiempo]

Originally Posted by noelex 77

You can prevent this problem by reducing the automatic absorption time or manually forcing the controller onto float, but this adjustment tends to only be available on the larger more expensive controllers and these are not commonly used in a system with one controller for each panel.

Victron's MPPT controllers are fully adjustable with a cable and free software or with their MPPT monitor. Their 75/15 will handle 200 watts and is not expensive.

[noelex 77]

Originally Posted by mitiempo

Victron's MPPT controllers are fully adjustable with a cable and free software or with their MPPT monitor. Their 75/15 will handle 200 watts and is not expensive.

The Victron products look good on paper for a lower cost controller, but I have not had much to do with them in practice. There has been some criticism of the start up voltage if using lower voltage panels, but this not a problem if using higher voltage panels.

You mention that they fully adjustable, but from a quick read of the handbook I cannot see a way to adjust the absorption time which is important when multiple controllers are used. Is this possible?

[mitiempo]

Originally Posted by noelex 77

The Victron products look good on paper for a lower cost controller, but I have not had much to do with them in practice. There has been some criticism of the start up voltage if using lower voltage panels, but this not a problem if using higher voltage panels.

You mention that they fully adjustable, but from a quick read of the handbook I cannot see a way to adjust the absorption time which is important when multiple controllers are used. Is this possible?

It is not in the manual. Details can be found here:
https://www.victronenergy.com/live/ve.direct:mpptprefs

Here is a list of the options:

[mitiempo]

Victron introduced the MPPT monitor about a year ago, shown below. It allows full adjustment of their MPPT controllers as well as status including 30 days of historical data.

https://www.victronenergy.com/panel-...g/mppt-control

[noelex 77]

Originally Posted by mitiempo

It is not in the manual. Details can be found here:
https://www.victronenergy.com/live/ve.direct:mpptprefs

Here is a list of the options:

Thanks. The absorption time is adjustable which makes the controller a good option if contemplating a single controller for each panel.

The ideal system is to adjust the absorbsion time for each cycle based on the "battery return amps". Only the most expensive controllers will do this.

The Victron does not have this system but at least has a manually adjustable absorption time and makes some attempt to to automaticly modify this manual adjustment based on the battery voltage. If adjusted correctly it looks like a good system and should work well even when multiple controllers for each panel are used.

[seandepagnier]

I wanted to suggest, that I put some panels on a controller and some directly to the battery. This way I can use a smaller controller, but my load is always high enough to saturate the panels not on a controller. Maybe mppt has more power but the difference is slight and the cost much higher and wiring far more complicated.

[masonc]

The rule on MPPT charge controllers and panels is - one controller per co-planer array, within the current and voltage limits of the controller. If you want to use multiple CC with a display, many will allow chaining, some will require a hub, depends on the brand.
I like to drive solar equipment hard, as so much of the time the insolation levels are well below rated. If you look at the power curve for a grid tied system, there's only a short amount of time the equipment is at maximum.
The main thing is the read the ratings and calculate for your temperature range. Solar panels put out less power as the temperature rises. For residential installations, we calculate the lowest temperature at that location and adjust accordingly. For boats, I would use a conservative rating in case you decide to sail to Canada and survive the winter there.

Co-planner means facing the same way. If you have two panels facing forward tilted at 15 degrees and two facing to starboard and tilted at zero degrees, you need to use two charge controllers.

[ramblinrod]

Originally Posted by boat_alexandra

I wanted to suggest, that I put some panels on a controller and some directly to the battery. This way I can use a smaller controller, but my load is always high enough to saturate the panels not on a controller. Maybe mppt has more power but the difference is slight and the cost much higher and wiring far more complicated.

This will cause a higher than normal float voltage causing batteries to gas excessively and loose water rapidly. The combination of controller float and unregulated solar shouldn't put in more than 1 A per battery.

[Maine Sail]

Originally Posted by ramblinrod

This will cause a higher than normal float voltage causing batteries to gas excessively and loose water rapidly. The combination of controller float and unregulated solar shouldn't put in more than 1 A per battery.

Here's a 400Ah bank that only requires 0.1A to maintain 14.4V... At this current the battery should have been "floating" at 13.5V and should be taking a few hundredths of an amp..... 1A would push this bank well over 15.0V at this SOC..




A solar panel capable of even 0.6A to 0.7A can push a 200+ Ah bank to well over 15V if left unattended. Leaving a 1A capable panel connected to a most typical battery banks, for periods of unattended time, can eventually cause it to destroy the battery. I have seen numerous banks destroyed by unregulated solar systems...

[ramblinrod]

Originally Posted by Maine Sail

Here's a 400Ah bank that only requires 0.1A to maintain 14.4V... At this current the battery should have been "floating" at 13.5V and should be taking a few hundredths of an amp..... 1A would push this bank well over 15.0V at this SOC..




A solar panel capable of even 0.6A to 0.7A can push a 200+ Ah bank to well over 15V if left unattended. Leaving a 1A capable panel connected to a most typical battery banks, for periods of unattended time, can eventually cause it to destroy the battery. I have seen numerous banks destroyed by unregulated solar systems...

Yes we are on the same page, but a 15W unrrgulated panel is OK on a group 27. While it can apply 1 A to a fully charged battery, it is typically only going to try to put in about 2.5 A-hr / day average.

[Maine Sail]

Originally Posted by ramblinrod

Yes we are on the same page, but a 15W unrrgulated panel is OK on a group 27. While it can apply 1 A to a fully charged battery, it is typically only going to try to put in about 2.5 A-hr / day average.

If the battery is being used regularly, so that it never actually attains 100% SOC then this can work. If however you leave it unattended the voltage will get pushed well beyond 15V regularly and eventually destroy the battery.