Combining a diversion controller with a MPPT Solar controller

[GILow]

Hi Cruisers,

I just looked closely at the wiring diagram for the Morningstar TS-45 controller which I am about to purchase to manage my Aerogen wind generator, and I realised that it is not quite the "black-box" solution I had expected.

In the manual, the wiring diagram for the wind generator with diversion configuration (picture attached) connects the wind generator straight to the batteries. The regulator then appears to switch on the diversion load (resistor style heater elements in my case) as required to shed excess power. I suppose I had expected the wind generator to be connected to the regulator and the regulator would "divert" excess power from the wind generator as required to the resistors, depending on the calculated state of the battery bank.

Meanwhile I have a Votronic MPPT 420 controller managing the power from the solar panels, which I am going to assume will account for most of my power generation.

While I felt comfortable with the concept of the two controllers talking directly to the battery bank, and being smart enough to handle the variation in input power (let's face it, there are plenty of multi-regulator charging systems out there today) I am a lot less comfortable with the idea of the wind generator being connected directly to the battery bank and relying on the Morningstar to dump power as needed. Not least because I can see how the power dump might get activated by the Votronic putting solar power into the system if the two regulators are not in total agreement about the state of charge, float vs bulk vs absorbtion etc. OK, excess power is excess power but I don't want the dump resistors pumping out heat unnecessarily and messing with the brains of the Votronic which has been doing a great job to date.


Any ideas? I'm a bit stumped by this one.

[GILow]

Bump!


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[TMT2]

GiLow,

I have a similar conundrum wondering if you arrived at a solution? I have a Marine Kinetics 12v/450W wind generator with its own controller (no diversion load output terminals) and 12V/ 520W of solar (4x130 panels) managed by a Tristar 45A (with diversion charge control). I want to use the Tristar to manage power for both solar and wind to my bank of 6x6V AGMs serving as 3 x 12V units. I want to divert excess power to a 12V/600W water heater element when bank is full. Right now, each system (wind and solar) provide power to the battery bank from each respective controller. I'd like to have the Tristar control it all (since it has the diversion protocol available on it)? Is is a simple matter of connecting the wind controller 12V output to the Tristar input leads?...Then diverting excess to the aforementioned water heater element? I'd be happy to upgrade to a Tristar 60A unit to handle the combined max loads from both system inputs (Wind 27A/Solar 30A). Looking for any expert or learned advice?

TMT2



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[GILow]

Hello TMT2,


My solution involved making my own regulator from bits I had lying around I'm afraid. Picaxe 18 pin chip, i2c LCD panel and some Mosfets.


I certainly don't think you can combine the inputs of solar and wind onto the one input on the Tristar, that'll buggers something up for sure. Both have VERY different voltages at a guess, plus the windgen is a rectified unsmoothed AC wave form, while the panels are pretty smooth DC.


I think you face the same problem I faced, which is that the diversion load is on "the wrong side" of the regulator, to my mind. It is not a true "diversion" the way it is pictured in the tristar manual, but a drain load, and that is going to play havoc with the charging algorithms.


I just programmed the picaxe to divert power from the Aerogen to the dump load once the batteries reached 13.6 volts, and left the whole top end of the battery charge algorithm to the Vitronic reg on the solar panels. Have not yet actually tested it in anger because the boat has been in the pen since dinosaurs roamed the earth, but it worked perfectly on the garage bench with simulated inputs from a variable power supply. I only fitted the LCD to give me some sense of how much power I was getting over time from the Aerogen, one of those toys where the novelty will wear off pretty quickly I suspect. (We call it EFS, or Executive Fascination System, in my industry)


When I have time to play around, I will see if I can use a memory chip on the I2C bus of the picaxe to spot the final stage charging voltages from the Vitronic and contribute a bit of power if needed, but that is a lot of effort for little gain I suspect.


Sorry I could not come up with a better solution.


Matt

[TMT2]

Thanks GILow...I talked to a few other knowledgeable folks and their conclusions are similar to your insights here. I do not want to hoark-up the algorithms of the controllers as they were designed (just to get some use out of some spare power) - which is what I think could happen once the controller on the device producing 12V input has another controller between it and the battery bank. One tech-spert suggested that when the Tristar reads 13.8 and shifts inputs to the diversion load circuit...the "outside controller" may not get power (perhaps be damaged)? I also agree with you that there is something fishy about how the Tristar manual lays out the diversion load description?...and I concur that the smooth top-end curve of the solar is best to "finish" off the absorption for the banks. I am by no means an expert - just dangerous. But I can read a circuit schematic. I am not as comfortable as you appear to be building my own gadgets - I'm more of an "off the shelf" guy. I think my solution will be to leave it as is and double my Ah on the battery bank to hold more. Really appreciate your response and exchange.

TMT2

[GILow]

I am glad to be able to offer a little bit of input. Please report back on your final solution, I for one will be very interested.


Matt

[TMT2]

Will do Matt - Thanks.

TMT2