Classic with Separate Diversion Controller

[keyturbocars]

If I am understanding things correctly, the Classic will work like other MPPT controllers from the standpoint that when the battery is fully charged, then the Classic will shut off power to the battery bank.  In the case of wind, then this means that the wind turbine would be disconnected and freewheeling (unless a Clipper type device applies the brakes).

In my set up, I have a separate diversion controller that I use to divert power to an auxillary 80 gal hot water heater (pre-heater) which feeds into my primary hot water heater.  I've got around 90 amps @ 48V diversion load in DC hot water heating elements.  I use a diversion controller made by a small company known as Coleman Air.  It's an OK controller, but I wouldn't recommend it for most people.  I chose it because it can handle bigger loads and because it was easy to integrate a thermostat into the circuit, so I can have the diversion load shut down when the 80 gal hot water heater reached 125F. 

Anyway, the way that I am envisioning it is that I would have a Classic set up to charge my battery bank, and I would use my diversion controller to actually regulate battery bank voltage.  That way, the Classic is always ON and providing efficient MPPT power conversion of incoming wind power.  I would have the voltage set points such that when the battery bank voltage is nearly "full", then the diversion controller would start diverting power to the hot water heater before the Classic shuts down charging.

I see it sort of like a bathtub.   The tub is the battery bank.  The Classic is like the spout feeding water into the tub.  My diversion controller is like a valve that controls the drain on the tub.  When the water level in the tub approaches full, the diversion controller begins draining to keep the bathtub level constant.  This prevents the water level from getting too high which would trigger the Classic to shut off charging. 

In effect, I'm trying to keep my battery bank in float mode and utilize incoming power to heat hot water.  It's the way I've had my system set up for the past year and it has worked quite well.  I currently have a 125F thermostat on my auxillary 80 gal hot water heater.  If the hot water heater trips the 125F thermostat, then wind power is then dumped to air heating resistors/elements.  I've never had this happen because we use a lot of hot water.  I've got a family of 9 (7 kiddos) and we do a LOT of dishes, laundry, showers/baths, etc...  The only time I could even imagine having the hot water heater thermostat trip is if the wind was roaring for days and perhaps then the hot water heater would reach max temp during the night.  If the wind was really sustained, I could also use some extra power by running some loads on my inverter.

All that to say... am I thinking about this correctly?  Will the Classic work well with this separate diversion controller that keeps "draining" power from the battery bank, so that the Classic is always on and the wind turbine is always connected and loaded?

Edward
   

 

[Westbranch]

Hi Ed, I know you have 'too much of a good thing ' frequently, but what happens when there is NO wind???

Eric

[keyturbocars]

Hi Eric,

I live out in the boonies, but we're still on grid.  I use the alternative power to help reduce our power bill some and also to provide a back up means of power for my family.  This time of year is fairly calm.  When Spring comes, then things will really start to blow around here for an extended time.  Winter is usually the calmest time of year around here apart from an occasional wind storm.  That's why I'm trying to get everything working the way I want it now, before the big winds come. 

Thankfully, we've got reasonably price hydro power because of the dams.  Although, they keep raising the rates and plan to continue to do so over the next few years.  The power rates around here are so reasonable that big names like Microsoft and others are building huge datacenters, because the hydro power is so "cheap".

Edward 

[Westbranch]

Sorry about that, what I meant was what will happen to the batteries if there is no wind and the batteries go to 0% SoC?  what is your fail safe?

Eric

[keyturbocars]

OK, I see.  I have the Coleman Air diversion controller set to only dump when battery bank voltage reaches around 54V.  So, the incoming wind power basically just keeps the batteries in float mode, and most power is diverted to hot water heating.  The batteries are never really drawn down unless grid power goes down and I start running off battery power.  If we don't have wind for a while, I occasionally turn on a 50A Argus rectifier/charger to try to keep the batteries topped up.

If I run with the big APC Matrix 5000 UPS for split phase 120/240 power, then I can set the low voltage cut off.  My smaller Exeltech XP1100 has the fixed low battery cut off. 

Edward

[cdog]

I must not be understanding something here(most often the case)
I was under the assumption the classic would charge mppt and also regulate voltage to a dump load, I did not realize I would need a separate diversion controller?

[cdog]

I also cant understand how the clipper holds down the turbine without making huge heat in the stator if I wanted to go this route instead?

[cdog]

Edward, why would you not reccomend the coleman to most people, just curious, they seem very reasonably priced, and one model will handle 440 amps??

[keyturbocars]

cdog,

The reason I am not real fond of the Coleman Air controller is that it's sample rate is too slow (in my opinion). 

Depending on the battery voltage, the battery voltage is sampled once every 5 seconds or once every 1 second.  When battery voltage climbs and gets closer to trip point, the controller starts sampling once per second.  In my situation, if the wind is roaring and the turbine is cranking out higher amps (especially during a gust), the controller will be too slow to respond quick enough.  As a result, it overshoots the trip point much of the time.

In other words, when you set the trip point, it's not what you end up getting.  "What you see is not what you get."  Let's say I set the trip point of the controller to 54.0V (using a precise power supply), then the voltage might shoot up to 59V before the controller ever knows what's going on.  This happens frequently during strong wind gusts.  The problems with this is that then my secondary dump load is triggered inadvertently and the power goes to heat air.  The way I dealt with this is that I experimented with different trip point voltage settings until the wind gusts would not trigger my secondary dump load - except in very strong gusts.  As a result, I have to set the trip point so low that the batteries don't really stay at the float voltage that I want.

Another issue for me is when it diverts power, then the battery is drawn down enough that when the diversion ends, the battery voltage is low enough that the controller goes back to the 5 seconds sample rate.  Then a new wind gust comes and the controller is in "duh" mode and can't respond.  The Coleman controller is just too slow to respond.  Maybe for a lot of other people, it wouldn't matter.  But, the way I have my system set up, it matters.  I've got 2 stage diversion set up.  Primary is hot water heating.  Secondary is to heat air.  I don't like the secondary diversion being tripped constantly when it's not supposed to be tripped.

I've tried to discuss this with the creator/owner of the controller, but he doesn't want to change anything.  He said the 5 second sample rate is necessary so that a battery state of charge LED can blink.  In other words, he said that the IC can't sample battery voltage any more often than every 5 seconds when the SOC LED is blinking.  In my opinion, something should be changed so the controller can do better than sample once every 5 seconds! 

It might be a good choice for some people, but not ideal for my situation.  I have strongly considered switching over to 2 Morningstar TS-60 controllers set up as diversion controllers, but there are some issues for me that I won't go into now (because this is too long already).    I've got around 97A @ 48V worth of diversion load right now.  Actually, after writing all this, it makes me more motivated to come up with another solution!

Edward

[boB]

I also cant understand how the clipper holds down the turbine without making huge heat in the stator if I wanted to go this route instead?

Some turbines will have a problem with this.  Normally this is only a problem is the wind speed is high and you completely short the turbine and it does not slow down.  THEN you can have a big problem.

With a real AC clipper connected, we can tell if the turbine slowed down and in fact we don't have to completely short it...  We can semi-short it and vary its speed.  Sometimes we will be able to slow it down enough where it can eventually stop without burning up its stator.  Detecting current and RPM is a big plus for a real clipper.

PWM and tachometer are the magic words here.

boB

[cdog]

So it would seem that if you don't have a use for the diversion power, get a clipper, if you do, get a pwm diversion controller?

[cdog]

Could one of the aux spaces on the classic be used to operate a large solid state relay and divert power this way?

[boB]

Could one of the aux spaces on the classic be used to operate a large solid state relay and divert power this way?

Yes.   The problem can be that some people will not know how much of a load to attach and then there could be other problems, like diversion not working and hurting things.   This is why the Clipper will have its own loads.

Theoretically, of course, one could add their own diversion loads and be just fine...   Don't count on heating water necessarily though.  Water eventually gets hot and the water can either boil away or the thermostat shut off the load.

boB

[keyturbocars]

Don't count on heating water necessarily though.  Water eventually gets hot and the water can either boil away or the thermostat shut off the load.

boB

Very true.  That's why I set my system up so if the 80 gallon hot water heater (pre-heater to my main household water heater) hits 125F, then the thermostat turns off my primary diversion load.  When that happens, then the secondary diversion load comes into play and air is heated.  This 2 stage diversion is important for safety/redundancy.  In my unique situation, because I have 9 people in my household, I use a tremendous amount of hot water (baths, showers, dishes, laundry).  So, I've never had the 80 gal hot water heater reach 125F and trip off.  It could happen though given the right circumstances.  I could imagine a night of roaring wind and everyone's asleep and no water movement through water heaters... eventually it can/will hit 125F in that 80 gal pre-heater.

Edward

[cdog]

Would it be better to divert after the rectifiers or get a 3 phase str and divert the ac?
Would this change what the classic ''sees'' to do, the load being a resistor of some sort, instead of the battery bank?