Charge controller for wind

[Shadow]

After searching right up to the last page on the Internet for a charge controller that might handle my 110 volt DC Jacobs to charge my 48 volt battery bank I came across this one.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270547146502&ssPageName=ADME:X:RTQ:US:112



3

The Jacobs is rated at 140 volts DC max at 20 amps . If I cant find a decent charge controller I'm left with rewiring the Jacobs to a lower voltage.

I've been waiting for the Midnite Classic to come out, but after emailing the company I'd be looking at over $2000.00 (1700.00 for the clipper to be used with wind).

Hopefully some of you electrical gurus can evaluate this controller for me... Thanks

[Flux]

Not sure I follow what you want to do.

If you are using a 48v battery bank then you need a 48v charge controller if you are just connecting the Jacobs to the battery. Even then you only need the controller if you are not prepared to watch the state of charge manually.

I doubt that the performance connected to 48v will be very good but with pitch control you won't loose control of it.

If for some reason you are wanting to use a 48v battery in place of the 120v one and keep the same performance you need a controller incorporating a buck converter, this would fit in with your idea of using the classic. I am not sure whether it would work better using its mppt tracking or whether you could fix the conversion to 2:1 step down and let the machine work as Jacobs intended.

With pitch control you can set the maximum open circuit volts and if you set it low enough you shouldn't need the clipper. ( not sure how many volts the classic can handle).

Using it as a fixed ratio converter many of the solar controllers should work as long as you can override the mppt tracking and stop them sampling open circuit volts.

Basically you are looking for a big 2:1 step down dc converter that can handle over 120v in and 20A.

If you run it directly into the 48v battery it will be low on field and would probably work better with reconnecting the field coils. It will mess up the cut in speed and performance generally but with pitch control you can limit the peak current to a safe value.

Rewinding the whole thing to 48v is a drastic move and hardly worth it unless the windings are in poor condition. Unless it was intended for this sort of change you may have to watch commutator and brush limitations but these were built like battleships and are pretty robust so that may not be an issue.

Flux

[dbcollen]

It is just a simple diversion controller, no voltage conversion. You would still have to rewire the jacobs mill. Also, I would never consider a relay (solenoid) based controller, it WILL FAIL, only use solid state switching.

Dustin

[TomW]

I am with Dustin here. Relays will fail.

I am not too keen on "Bang Bang" controllers, either.

ghurd's controller can drive large IGBT or FETs to dump almost any amount of power.

Still not the conversion you need to get good use of 120 volts into 48 volts.

Just opinions.

Tom

[ghurd]

I am with you guys.

Relays in controllers are evil.

"Uses the same relay as the SEA-440".

That cracks me up.

G-

[Shadow]

Yeah sorry guys I jumped the gun before reading this through.

 At first I thought it was like the mppt controllers that would step down the voltage.  I've looked into almost every kind of mppt controller out there ,none will accept the input voltage the Jacobs could be capable of.

I've also looked into Dc-Dc converters, same problem  input voltage.

 i'm ready to reconfigure the field coils, but wanted to leave it factory so I could just switch to 110 volt water heat elements for a diversion.

I'm finding its a tough conversion to do.

 I also looked into a DC-AC inverter I found one but same thing the 110 volt input had to be stable.If I could find a way to switch it to AC I could feed it into my tel. co. rectifiers.

 

[Flux]

The Jacobs is pitch controlled and if you set the pitch control to a lower speed you will limit the open circuit volts. Your 140v is based on enough to bring a 120v battery to gassing volts with some to spare.

I am sure there are mppt converters that will accept over 100v and if necessary I suspect you can screw the speed down to keep volts to this level. As long as you can prevent the mppt converter unloading to sample then it never need to see open circuit volts so maintaining 100v should be possible. If the mppt converter will take 120v then even more chance of doing it.

Not so simple but perfectly possible you could build a field regulator to limit armature volts to a set value. It will shed load as you limit volts but no problem with a speed controlled governor.

If you reconnect the field coils then I see your problem with water heaters but I think you have other issues just changing over to a resistive load instead of batteries. A shunt machine is not going to be very stable into resistors unless you have a controller to change the load with wind speed, I am not sure it will work that way as it stands, most shunt machines shed load at low speed, it is mainly the battery volts that keeps you working under those conditions. If you used such a controller you could make sure you didn't let volts exceed about 70v and that would still be within the field capability. Running into a mppt tracker at 70v it would probably work perfectly well but with slightly reduced full load capacity.

[Shadow]

Thanks Flux,

 I'm going to go with the Xantrex mppt controller, from what I can gather about it it dosent sweep looking for changes it just stays connected. It also has 150 volt input with over voltage protection.

My next question is How many volts do the field coils need to perform at full capacity? If hooked to a 48 volt battery bank  is that the voltage they will see? or if hooked to the charge controller will thier voltage climb as the wind turbine climbs?

I think I read the field coils draw 1 amp, So that would be 100 watts at 100 volts, but only 50 watts at 50 volts.

Next , blocking diode? Will I need one using a charge controller? Or will the charge controller keep it from back feeding?

Thanks

[Flux]

I don't know anything about the controller so I really can't answer this.

In normal operation the dynamo would build up to about 120v to reach battery volts at cut in, the battery then holds the field volts and it stays in the 120/140 v region, I think it is fairly well saturated in this region so the flux is near constant.

With only half volts on the field I don't think you will get much power at the normal props speeds for the available wind speed.

If you can set the converter to a fixed step down ratio ( near 2:1) then the machine will just work much the same as into a 120v battery and the converter will double the current into 48v.

If the converter ratio can't be fixed then the issue is complicated. If the converter is a solar converter I am not sure what it will do, the input voltage is normally set by the number of cells. I don't think it will deal with a variable voltage dynamo.

If the converter is meant for wind then it will have been designed for a PMA with voltage proportional to prop rpm. I don't think it will sort out the field if connected normally, you will add another variable in the system.

In this case I think you will have to re connect the field for 48v and feed it from the battery. The armature circuit will then feed the converter input much as if it was a rectified PMA. I don't think 48v to the fields connected for 120v will do a lot of good. You will need something to disconnect the field from the battery when wind is below cut in but that is not a major problem.

You may need a blocking diode, the buck converter can back feed if the input mosfets are on, with an alternator the bridge rectifier would prevent this.

Flux

[scoraigwind]

With all due respect to you guys a relay is extremely reliable if used correctly.  A relay that is used within its rating will do the job for years and on the whole I have found them a lot more reliable than FETs.  Of course they will fail.  So will everything eventually.

Relays switching on the AC side are great.  Relays switching 48 volts DC need to be very carefully chosen.

Switching with relays is nice and quiet compared to PWM.

Using relays you can choose to dump off the inverter into Ac loads such as water heaters in a very convenient way.  Or directly off a high voltage windmill before the transformers is a good option.

Relays are great.  Just read the small print before using them.

[halfcrazy]

Most likely the Jacobs will go over the voltage limit of the Xantrex and burn it up. The XW will sweep the voltage at times and this will allow the Jacobs to make higher voltage.

The thing we need to keep in mind here is that we will need some sort of voltage clamp period my 10ft Otherpower turbine will generate 240 volts OC. I figure we need to consider the cost of a voltage clamp or clipper as part of the cost.

In your case if the issue is cost of electronics than I give you 2 options:

Pay some one to rewind the Jacobs for 48vdc

Build an Otherpower turbine and sell the Jacobs

[hydrosun]

Apparently there is a way to program the XW not to sweep. Or to go open circuit after 24 hours. I haven't done it but I worked on  hydro system that is using the XW at high voltage.

Chris

[zvizdic]

Switching with relays is nice and quiet compared to PWM.<p>
.

I used relays and FETs and I like FETs.
Modified space heater as a dump woos noisy(clicking)but whit old dryer heating element no sound.

Using GHURDs 48V controller set at 54v nominal and 62V for dump trough  6 FETs parallel works like charm.

PS: 10' windmill 4.5ohm dump .

[fabricator]

With all due respect to you guys a relay is extremely reliable if used correctly.  A relay that is used within its rating will do the job for years and on the whole I have found them a lot more reliable than FETs.  Of course they will fail.  So will everything eventually.<p>
Relays switching on the AC side are great.  Relays switching 48 volts DC need to be very carefully chosen.<p>
Switching with relays is nice and quiet compared to PWM.<p>
Using relays you can choose to dump off the inverter into Ac loads such as water heaters in a very convenient way.  Or directly off a high voltage windmill before the transformers is a good option.<p>
Relays are great.  Just read the small print before using them.

I'm glad I not the only nut job using a relay based controller, I can't remember the amount of threads just one this one board about solid state stuff frying.

[ChrisOlson]

With all due respect to you guys a relay is extremely reliable if used correctly

I agree with Hugh.  I'm using an Allen-Bradley three-pole contactor to drive my water heater with the inverters, with the one contactor handling the output from two inverters, and the conactor operated by a simple voltage monitoring board with a five minute timer on it.  They are so dead reliable that it's beyond belief.  That relay has contacts rated at 20 hp three-phase and I'm only driving twin 1,500 watt elements with it.  If the contacts do get burned eventually I can put a new contact set in the contactor for about $7.  A new coil for it is $20.  And the coil in those things gives ample warning if it's failing because it starts to buzz when its energized.

Those contactors cycle thousands and thousands and thousands of times in industrial applications and they so rarely fail that nobody even looks at them or thinks twice about them.  Sure, they make a big satisfying "THUNK" when they engage, but that's just the audible indicator that your water is being heated.
--
Chris

[zvizdic]

To use relays you need big battery bank .
I used relays on a 50AH 48V bank and at low voltage wind gust would rise voltage quickly so relay would go wild.
This one survive other ones are in garbage.

[ChrisOlson]

To use relays you need big battery bank .

Those little DC relays are toys.  This is is what the guts of a real relay looks like:



The one in the photo is over 20 years old and I rebuilt it before I started using it on my system to drive my water water.  I stole it off a 480 volt, 20 hp three-phase wet bin motor on a grain dryer.  In that application it cycled on and off every three minutes, three months out of the year, 24 hours a day for over 20 years, with a starting surge load of 28 kW and a continuous running load of 13.8  kW.  When I tore it down to rebuild it for my off-grid system there was absolutely not one thing wrong with it.  It had a 208 volt coil in it, which I replaced with a 120 volt coil, and since a new contact set was only $7 I put that in too.

On my 4,360 amp-hour bank it starts cycling at about 11:00 AM on any good day, and it cycles 5 minutes on and about 2 minutes off all afternoon driving a 3 kW load.  It heats 55 gallons of water from well temperature to 150 degrees every single day for us, operating like that.  If we get no wind or sun then I throw the switch and engage it manually and run the generator to keep the bank up until we get the water heater up to 135.

20 years from now this thing will still be operating flawlessly.  I guarantee it.

I tried every DC power dumping scheme known to man and not any of them could heat 55 gallons of water for us every day at anywhere close to the efficiency that I get now.  I still got a big collection of worthless DC heating elements that couldn't heat their way out of a paper bag once you factor in the losses in the copper transmitting low voltage DC power.
--
Chris

[Antero]

There is a Finnish company which has controller for charging with high voltage and using powerfull windgenerators, to charge 24-48V etc battery systems;

http://www.finnprop.fi/index6.html

http://www.finnprop.fi/pdf/windmill_power_controllers.pdf

Hugh Piggot has wrote about this in his blog;

http://scoraigwind.co.uk/?p=205

Antero

[cardamon]

Why is using the classic out of the picture?  I understand the need for overvoltage protection but couldnt you just build your own device to throw some resistance in the line if the voltage reaches a certain threshold?  Where is their clipper so ungodly expensive?

[ghurd]

Throwing resistance in the line will allow the turbine to go faster.

It can be done.  I have done it experimentally.  Hugh has done it for heat, and may have the schematics on his site.
I imagine the furling may need adjusted a bit different.

The battery voltage will still need some kind of control or baby sitting because the charging amps are still charging.  Hugh's circuit may take care of that with the same schematics.  My experimental circuit would have basically been 2 ghurd controllers set at slightly different voltages.

Good solid reliable fast clippers are made for big power.  Big power parts are expensive.
Cutting corners to save a buck is why there are stories about solid state stuff frying.
I claim the ~55A rated mosfets I sell for $1 are good for a bit over 6A.
But a mosfet actually good for 25A is not $4, it is $50, and it needs a $25 heat sink!
G-

[rossw]

Good solid reliable fast clippers are made for big power.  Big power parts are expensive.
Cutting corners to save a buck is why there are stories about solid state stuff frying.

Absolutely.

I claim the ~55A rated mosfets I sell for $1 are good for a bit over 6A.

Here's where "reality" hits "theory"!
The rather optomistic "device specifications" as published are achievable - under absolutely perfect conditions. Check their heatsinking and ambient temperature conditions for their test conditions. They're far from real-world for most of us
Also, how many "DIY" guys have the right thermal transfer compounds, and can apply them perfectly? And have the right bolts and mounting hardware, and torque them up properly? And how many people take the care to drive the device exactly as it wants?

I see many of my friends go get 55A, 100A, 167A rated devices and think they'll handle 50% of their rated current - then look all surprised when the device lets out the magic smoke on half that!

I think your call (saying it's "an honest 6A") is comfortably achievable by most DIY types!

[ghurd]

LOL!  Yes, I know what you mean.
People ask about my fancy $2 fet (FDP7045L), and why I do not recommend it for the 100A or 300A it is rated.
I point out #0000 (11.684mm dia) copper wire is rated for 302A for power transmission, or #000 (10.4mm dia) rated for 328A in chassis wires.
Next I point out the tiny little legs on T0-220 devices will 'blow like a fuse' with that kind of amps.

My rule of thumb for TO-220s is I^2*Rds=<1W.
Works for me.
G-

[cardamon]

Throwing resistance in the line will allow the turbine to go faster.

Right, that makes no sense.  Meant to say add a load, resistance in parallel!

[ghurd]

Throwing resistance in the line will allow the turbine to go faster.

Right, that makes no sense.  Meant to say add a load, resistance in parallel!

That is exactly what a decent dump load controller does.
From the fanciest to the ghurd controller, the load is in parallel with the battery.
G-

[Steve Trumann]

Ghurd,
 As you know, I chose the wrong the wrong FETs  a while back. Would you explain your formula a little bit more for me. I understand I messed up on resistance and heat dissipation. I could us a little more discussion on this.
Thanks, Steve Trumann

[rossw]

Ghurd,
 As you know, I chose the wrong the wrong FETs  a while back. Would you explain your formula a little bit more for me. I understand I messed up on resistance and heat dissipation. I could us a little more discussion on this.
Thanks, Steve Trumann

My name isn't Ghurd, but he's probably sleeping now

FETs have a number of parameters, one is their "On resistance". This is their minimum resistance from drain to source when fully saturated with appropriate gate drive.

As you will know, heat is a function of current and resistance.  Amps squared times ohms gives power in watts.

If you have a fet that has Rds (Resistance drain-source) of say 8 milliohms, and you are passing a current of 10 amps, the power the fet has to dissipate internally is 10 squared (100) times 0.008 (8 milli-ohms) = 0.8 watts.

Why this is an issue is because the chip itself has to have some way to get the heat out. There is a "thermal resistance" from the junction to the case of the device (often a metal face or tab). That resistance is fairly low usually, and is measured in "degrees C per watt". Say it's 0.5 deg/W, they're saying that the chip is going to be half a degree hotter than the case, for every watt the device is dissipating. (In our example above, thats 0.4 degrees hotter)

Next comes the thermal resistance of "case to air". Without a heatsink, this is often 40 degrees/watt or more. So add another 32 degrees there. This is temperature *RISE* above ambient. So if it's say 30 degrees air temperature, your 0.8 watts dissipation means the actual silicon inside is 30 + 32 +0.4 = 62.4 degrees.

Adding a decent heatsink and properly thermally bonding all the bits so you can get the heat away from the silicon is the only way you can save the life of most of these power fets!

[ghurd]

I never sleep.

Ghurd,
Would you explain your formula a little bit more for me.

Sure.
I do not do it very conventionally.  Someone will do it fancier than I do it. (Ross)
This is simplified.

The fet data sheet will have Rds listed  Resistance from Drain to Source in Ohms while fully saturated.
Fully saturated, to me, is either 6V for logic level gates, or 12V for standard fets.  Usually. 

Depending on how old you are, or how old your books are, 'I' is Amps.

Ohm's Law say Amps multiplied by Amps multiplied by Ohm's = Watts.
For this discussion, Watts is heat in the fet, and I like it below 1W in a TO-220 package (physical size of the fet).

I^2 = Amps Squared = Amps times Amps = A x A

Watts of heat in the fet are I^2 x Ohms.  We know the amps.  The data sheet shows the Ohms while fully saturated.

The 1W is what I use for a T0-220 package.  A bit more for a fet with a small heat sink, a bit less without.

Example A.
IRFZ44N mosfet.
The data sheet, right there at the top, show the resistance as 17.5milliohms.  0.0175 Ohms.
The desired load is 4A.
Watts (heat) in the fet are I^2*R.  Amps x Amps x Ohms.
4A x 4A x 0.0175 Ohms = 0.28 Watts

Example B.
Same fet.  Load is 8A.
8A x 8A x 0.0175 Ohms = 1.12 Watts

The Point, Part #1:
A small increase in amps increases the watts in the fet exponentially.
Doubling the amps increases the watts in the fet exponentially.

The Point, Part #2:
My fancy $2 fet, FDP7045L, has a resistance of 0.0035 Ohms.
17A x 17A x 0.0035 Ohms = 1 Watt
1 Watt is OK in my rule of thumb math, but 17A in those little tiny fet legs is an awful lot of amps.


Another issue regarding heat in the fet is frequency.
Fets have higher resistance while in 'between' fully On and fully Off.  Fast switching fets switch more often, so they spend more time in a higher resistance state.
The time a fet spends in the "between" state is almost a fixed value. 
A fet switching a 6A load at 500,000 cycles per second at a 50% duty cycle will run hotter than a fet switching 6A at 1 cycle per second at a 50% duty cycle, because it is spending 500,000 times more time in a high resistance state.
I slowed the ghurd controller down to a lower frequency so it is not an issue.

That's it in a nut shell.
G-

[Steve Trumann]

Thank you rossw and ghurd,

 Those examples and explanations explained it in a nut shell. That's what I needed to get it wrapped in my brain. That explains why they worked under partial load, then burnt up under full load. Who says an old dog can't learn new tricks?
Thank You much, Steve Trumann

[cardamon]

That is exactly what a decent dump load controller does.
From the fanciest to the ghurd controller, the load is in parallel with the battery.
G-

Sorry guys if this is getting off the original thread topic a bit, But when we talk of a "clipper", arent we generally referring to a device to prevent overvoltage from damaging the controller? That was always my impression but perhaps I was wrong.  If we have a turbine connected directly to batteries or thru a transformer, we can regulate the charge on the batteries with diversion and all is good.  However when we start throwing in fancy mppt controllers, we lose that definitive coupling of battery to turbine voltage and therefor need to assure the turbine doesnt damage the controller.  I believe midnites clipper does both of these tasks - regulates battery voltage and assures voltage doesnt rise beyond the classsic's specs.  Is that correct?  So I was thinking that the classic is the ideal controller for this dilemma,  but the deal breaker seemed to be the price of the clipper.  I was proposing to use just the classic, regulate batts with a few tristars, and build a simple device connected to the line side of the classic to prevent possible overvoltage.  I am considering doing this as well and was not clear on whether the clipper was recommended/required for using the classic with wind.

[rossw]

Sorry guys if this is getting off the original thread topic a bit, But when we talk of a "clipper", arent we generally referring to a device to prevent overvoltage from damaging the controller? That was always my impression but perhaps I was wrong
.....
So I was thinking that the classic is the ideal controller for this dilemma,  but the deal breaker seemed to be the price of the clipper.

Depending on the powers involved, there are devices "transorbs" that are basically high power zener diodes. My local stores have them in a variety of voltages, currents and AC or DC operation.

Even quite smallish devices can handle 30A peaks (only an amp or two continuously) - for about a buck a piece. If you could get some of the very large ones, they'd be great for the job, but I think they might be excessively expensive.

For reasonable size turbines, I think a very simple voltage-sensing system and a decent contactor to bring in a suitably sized dump-load would be a more cost effective solution. As long as you are not using it to *shutdown* the turbine by shorting all 3 phases, running the contactor coil directly across two phases might even be enough. The right choice of contactor coil voltage should get you where the contactor will pull in above the normal operating region of the turbine but safely below the maximum voltage of your controller. When it operates and pulls the dumpload on, there will probably be enough voltage there to keep the contactor held in until the wind drops or the MPPT takes back over etc.

The main thing is, you want something simple, reliable and effective. A contactor and dumpload probably meets all those requirements

[Volvo farmer]

My understanding is that Halfcrazy has been using a Classic with an Axial flux turbine for quite some time now. There is a PDF over on the Midnite forum of his homerew "clipper" device.  It basically uses the Classic's Aux output and a relay that throws a contactor to directly short all 3 phases if the voltage starts to get close to the maximum allowed.  It does not seem pretty nor elegant, but it does seem  to work.  I am planning on copying his design to protect my Classic from over-voltage.

[boB]

However when we start throwing in fancy mppt controllers, we lose that definitive coupling of battery to turbine voltage and therefor need to assure the turbine doesnt damage the controller.  I believe midnites clipper does both of these tasks - regulates battery voltage and assures voltage doesnt rise beyond the classsic's specs.  Is that correct?  So I was thinking that the classic is the ideal controller for this dilemma,  but the deal breaker seemed to be the price of the clipper.  I was proposing to use just the classic, regulate batts with a few tristars, and build a simple device connected to the line side of the classic to prevent possible overvoltage.  I am considering doing this as well and was not clear on whether the clipper was recommended/required for using the classic with wind.

 A contactor would be pretty "clicky" wouldn't it ??  And was that going
to be for AC or DC ??  That will make a difference on how long it lasts and how it needs to be
connected up. A relay can certainly work though.

I think a better way to go is to use triacs if it's on the AC side
 (my favorite clipping method if the turbine has AC output)

Trransorbs will not dissipate enough heat for continuous clipping.

Cardamon...
You are right that the Clipper limits the input voltage to the Classic to help it live longer as
well as reduces RPMs in higher winds, reduces noise and hopefully increases turbine life....

As for the price of the Clipper, we have reduced its complexity (AC and DC versions)
quite a bit by letting the Classic's Aux output do the PWMing as
well as reduce the need for a microprocessor and separate communications.

There are certain advantages to having communications though, such as increased
info from the Clipper (RPM, dump current, etc). The new one also runs the switches
slower (in the hundreds of Hz range)  now.  As Ghurd mentioned, this helps reduce
the switching losses of the switches.

That old Clipper design may have ended up being around $1700 (too much !)  and
the newer version will still be expensive, but it will be way less than that.  A Clipper will
increase the life of the Classic... Or any other wind MPPT controller unless it just has
a huge voltage headroom.

Some people can design and build their own clippers just fine...  But some have had trouble.
There are some important design and construction issues that have to be
considered, such as inductance of the load resistors, mainly.   Some times these
problems aren't found out until it's too late.

It would be nice if folks on this forum can eventually come up with a  less expensive
and reliable  working option for clippers.  Choosing the proper load resistance and
making sure that the load is not going to get too hot and disconnect (like a water
heater) is very important.  Resistors with good ratings and good cooling is
also very important of course.

There is also the clipper method like Kestrel uses...   A whole BUNCH of bridge rectifiers
in series mounted to a heat sinking backplate.  The only problem with this is that
the clip voltage is fixed and not adjustable for varying conditions.

Anyway, for now, a clipper will be necessary to keep things working smoothly for wind mppt.

boB for now.

[fabricator]

My understanding is that Halfcrazy has been using a Classic with an Axial flux turbine for quite some time now. There is a PDF over on the Midnite forum of his homerew "clipper" device.  It basically uses the Classic's Aux output and a relay that throws a contactor to directly short all 3 phases if the voltage starts to get close to the maximum allowed.  It does not seem pretty nor elegant, but it does seem  to work.  I am planning on copying his design to protect my Classic from over-voltage.

Something you might want to consider, use a dpdt contactor to disconnect the DC side at the rectifier and short the DC side of the rectifier, it makes for a softer stop for the turbine.