One more kick at this topic....
I searched the forum and found a few posts about connecting a generator/mains to a Classic.
The general answer was to avoid it.
Well.... In my case I have no AC mains, but a generator as a backup to my solar system.
I currently do have a battery charger which I have occasionally used to charge my batteries - but it's output is limited to 30A or so.
I'm now eyeing my Classic 250 which can put out 79 amps. To buy a charger with this performance - I'm going to spend as much as I would on a Classic!
Instead of buying a new expensive charger, it seems to make sense to just rectify/filter the generator output, feed that into my Classic and all is good.
So, instead of hearing "don't do it" - maybe we can get a bit more technical and understand exactly why not, or better yet, how to do it.
There was talk of making sure the supply was "soft." Well, how soft is soft? "Soft" isn't very specific.
Is there an optimal mode for the Classic - something other than solar? Maybe Micro? Maybe Wind with a table specifically populated to optimize performance with the generator.
Any technical feedback would be greatly appreciated!
rob
Rob;
I am just tossing this on the wall to see what sticks:
Wondering if you could get away with programming a Wind curve that maxes out at XX amps and YYY volts with XX amps well below The Classic's current limit?
Tom
Depending on efficiency demands you could stick a resistance in series with the batteries to "soften" the supply by limiting current. Pretty nasty power waste but could maybe work? Not very elegant I guess that comes from my vacuum tube and brute power origins in herding electrons::)
I will shut up now.
Good Luck.
Tom
Rob
Isn't the best solution to get an inverter that will also charge ? You connect your generator to the inverter and it will charge the batteries and also run your AC loads without the generator.
Do you just run pure DC loads and don't have an inverter ?
Larry
Quote from: cabinrob on March 25, 2016, 03:26:58 PM
One more kick at this topic....
I searched the forum and found a few posts about connecting a generator/mains to a Classic.
The general answer was to avoid it.
Well.... In my case I have no AC mains, but a generator as a backup to my solar system.
I currently do have a battery charger which I have occasionally used to charge my batteries - but it's output is limited to 30A or so.
I'm now eyeing my Classic 250 which can put out 79 amps. To buy a charger with this performance - I'm going to spend as much as I would on a Classic!
Instead of buying a new expensive charger, it seems to make sense to just rectify/filter the generator output, feed that into my Classic and all is good.
So, instead of hearing "don't do it" - maybe we can get a bit more technical and understand exactly why not, or better yet, how to do it.
There was talk of making sure the supply was "soft." Well, how soft is soft? "Soft" isn't very specific.
Is there an optimal mode for the Classic - something other than solar? Maybe Micro? Maybe Wind with a table specifically populated to optimize performance with the generator.
Any technical feedback would be greatly appreciated!
rob
8) I like your thinking!
Quote from: ClassicCrazy on March 25, 2016, 05:57:52 PM
Rob
Isn't the best solution to get an inverter that will also charge ? You connect your generator to the inverter and it will charge the batteries and also run your AC loads without the generator.
Do you just run pure DC loads and don't have an inverter ?
Larry
Just a thought, maybe trying to work with what is available for now and work into a perfect system as the time permits! Not everyone can set up everything today, sometimes it takes time and we work with what is available for today. JMT
Walt
Rob what size of AC gen do you have ?
bank voltage & size also please .
VT
Some answers to the questions that were asked:
I do have an inverter (Xantrex 2000W Pure Sine) but I don't use it very much.
Most of my cabin runs off of 12V. (Lights are 12V LED, fridges are both 12V, radios 12V, water pump 12V etc.)
I only turn on the inverter if I need to run things like power tools.
Battery bank is 10 x 6V Golf Cart batteries wired for 12V and giving me a capacity of about 1000 Ah.
I don't see that getting an inverter/charger is going to gain me much. (Typically high quiescent currents.)
I do have an Iota 12v charger - but the output voltage is not high enough. It starts charging with a reasonable current, but this soon levels off and I waste a lot of gas without much charging going on.
The generator is a 2500 watt gas unit.
For completeness, I have a Classic 200 (mis-typed in the original email.) Solar has 6 x 305W panels set up as a virtual tracker. One series string of 3 points SE, and the other series string of 3 points SW.
Needed a Classic 200 to handle the Voc at the cold temps that we get.
The added benefit of a Classic 200 is that the Voc of the rectified generator output would in the neighbourhood of 170V. A Classic 150 wouldn't handle this. The other interesting thing about this setup is that the panels give me close to the RMS equivalent of line voltage - so I anticipate diverting extra power to an electric water heater.
Back to my original thought - the Classic already knows about temperature compensated charging, and has set-points adjusted for my battery bank. It is all wired and set to go - with the exception of the input.
Why get another charger?
I could max out the Classic 200 and would only load the generator at 50%.
Everything seems like a slam-dunk - except for the matching of the generator to the input of the Classic....
Hi .....rob,
There have been a number of Threads on this subject here, and elsewhere.
MidNite Engineering has said that this is NOT RECOMMENDED.
As Tom noted, adding some reasonable resistance in series with the Vin to the Classic will help 'soften" the input, but would waste a lot of power.
It was also mentioned here, that having the battery voltage close in voltage to the external Power Supply would help protect the Classic -- this was in the context of an external PS, and your situation seems far from this recommendation.
Also, a simple bridge/filter capacitor would seem to present a poor Power Factor to the Genset.
One way that many MPPT CCs protect themselves is that they reduce the load on the input power source, which causes the input voltage to rise. In Solar Mode, the Classic "knows" that the input source IS from PV, and this operating point WILL reduce the input power to the CC. With your direct output from the filter to the CC, this is not really the case.
It was also noted in that same Thread, that running the Classic in Legacy P&O would probably be the preferred Mode for these relatively risky approaches.
Your comment, "I do have an Iota 12v charger - but the output voltage is not high enough. It starts charging with a reasonable current, but this soon levels off and I waste a lot of gas without much charging going on", probably indicates that the Bulk charging has finished, and the Absorption voltage has been reached, so the battery charge current will continue to taper.
This apparent battery charge current taper, could also be that with FIVE STRINGS (!!!) of batteries, that there could be poor current charge current sharing between all of those batteries, and the one or two batteries that are hogging much of the current have gotten to Absorb ... just guessing.
Your thoughts are common ones, at least about using an external PS that feeds an MPPT CC input. Direct rectification for this input is also risky, as there is NO isolation between the genset AC output, and DC side of the system ... this is often risky in its own right, for Safety reasons.
To determine the approximate value of the "softening" resistor, you could look at the Vmp verses Voc curves of the PVs that you are using, and figure out about what is the output impedance is of the String of PVs that you are using, this could possibly guide you. BUT, this will become a bit of a heater.
And so on, GOOD LUCK ! Vic
Some comments:
There have been a number of Threads on this subject here, and elsewhere.
MidNite Engineering has said that this is NOT RECOMMENDED.
>> It's is still not clear to me why! I hate being told that I can't do something - without a solid explanation.
As Tom noted, adding some reasonable resistance in series with the Vin to the Classic will help 'soften" the input, but would waste a lot of power.
>>Well, having a generator run at a light load is also just wasting gas - hence wasting power.
It was also mentioned here, that having the battery voltage close in voltage to the external Power Supply would help protect the Classic -- this was in the context of an external PS, and your situation seems far from this recommendation.
>> My panels run at 130V. This is far from the battery voltage. No-one is telling me I shouldn't being doing this. What exactly am I protecting?
Also, a simple bridge/filter capacitor would seem to present a poor Power Factor to the Genset.
>>Since I would be drawing less than half the rated power from the generator, this should be a non-issue.
One way that many MPPT CCs protect themselves is that they reduce the load on the input power source, which causes the input voltage to rise. In Solar Mode, the Classic "knows" that the input source IS from PV, and this operating point WILL reduce the input power to the CC. With your direct output from the filter to the CC, this is not really the case.
>> Maybe "many" CC do this? Is this what the Classic does? As far as I can tell, the Classic is just a DC-DC converter. I would think that it would be more sophisticated in managing currents than picking a different panel operating point in order to manage input current/power.
It was also noted in that same Thread, that running the Classic in Legacy P&O would probably be the preferred Mode for these relatively risky approaches.
>>Why not hydo mode? Isn't a hydro generator just a, well, generator connected to a water turbine? From the point of view of the Classic, how is this different from a gas generator. It's just a "generator" being run by a gas engine instead of water. No?
Your comment, "I do have an Iota 12v charger - but the output voltage is not high enough. It starts charging with a reasonable current, but this soon levels off and I waste a lot of gas without much charging going on", probably indicates that the Bulk charging has finished, and the Absorption voltage has been reached, so the battery charge current will continue to
This apparent battery charge current taper, could also be that with FIVE STRINGS (!!!) of batteries, that there could be poor current charge current sharing between all of those batteries, and the one or two batteries that are hogging much of the current have gotten to Absorb ... just guessing.
>>I have measured the current going to my batteries - and the strings are quite balanced. The issue is that the Iota does not have a high enough output voltage. It does not understand temperature compensated charging. I have boosted the output voltage to its maximum - and it's just not high enough.
Your thoughts are common ones, at least about using an external PS that feeds an MPPT CC input. Direct rectification for this input is also risky, as there is NO isolation between the genset AC output, and DC side of the system ... this is often risky in its own right, for Safety reasons.
>>I don't see how this is any different from having the same power/voltage/current coming from my panels??? I don't know the design of the classic, but I would have expected that it's basically just a transformer. On the input side there is a power oscillator converting DC to high frequency AC. This goes to a transformer and then on the output side there is a rectifier/filter. I would think that other than a common ground there should be isolation???
To determine the approximate value of the "softening" resistor, you could look at the Vmp verses Voc curves of the PVs that you are using, and figure out about what is the output impedance is of the String of PVs that you are using, this could possibly guide you. BUT, this will become a bit of a heater.
>>I would rather start from the input impedance spec of the Classic and then work back to my power source. So far, I've only read about "soft." This really does not help me.
>>For what it's worth, there may be another approach to this problem that could do away with resistor to massage the characteristics of the supply. Most generators have some sort of feedback look to manage throttle vs. load. As the load increases, the "throttle" of the generator is increased. If one disables this feedback mechanism, then the generator will probably start to look a whole lot like a solar panel. Just thinking out loud.....
And so on, GOOD LUCK ! Vic
>> I was really hoping to avoid luck and maybe throw in some science/engineering!!!
>> I do appreciate the input. Thanks.
Quote from: cabinrob on March 26, 2016, 12:15:29 PM
Some answers to the questions that were asked:
Everything seems like a slam-dunk - except for the matching of the generator to the input of the Classic....
Iotas are adjustable & have smarts , what is your model , I have 12,24,V in 45a&90&120A in 24V .
Gen set is it a screamer or the inverter style , if so inverter tap within , screamer use Iotas (2) on 220 split phase & balance gen , and croon amps in thru shunt bypassing classic , let classic finish & monitor .
VT
Quote from: Vic on March 26, 2016, 03:25:25 PM
Hi .....rob,
There have been a number of Threads on this subject here, and elsewhere.
MidNite Engineering has said that this is NOT RECOMMENDED.
As Tom noted, adding some reasonable resistance in series with the Vin to the Classic will help 'soften" the input, but would waste a lot of power.
It was also mentioned here, that having the battery voltage close in voltage to the external Power Supply would help protect the Classic -- this was in the context of an external PS, and your situation seems far from this recommendation.
Also, a simple bridge/filter capacitor would seem to present a poor Power Factor to the Genset.
One way that many MPPT CCs protect themselves is that they reduce the load on the input power source, which causes the input voltage to rise. In Solar Mode, the Classic "knows" that the input source IS from PV, and this operating point WILL reduce the input power to the CC. With your direct output from the filter to the CC, this is not really the case.
It was also noted in that same Thread, that running the Classic in Legacy P&O would probably be the preferred Mode for these relatively risky approaches.
Your comment, "I do have an Iota 12v charger - but the output voltage is not high enough. It starts charging with a reasonable current, but this soon levels off and I waste a lot of gas without much charging going on", probably indicates that the Bulk charging has finished, and the Absorption voltage has been reached, so the battery charge current will continue to taper.
This apparent battery charge current taper, could also be that with FIVE STRINGS (!!!) of batteries, that there could be poor current charge current sharing between all of those batteries, and the one or two batteries that are hogging much of the current have gotten to Absorb ... just guessing.
Your thoughts are common ones, at least about using an external PS that feeds an MPPT CC input. Direct rectification for this input is also risky, as there is NO isolation between the genset AC output, and DC side of the system ... this is often risky in its own right, for Safety reasons.
To determine the approximate value of the "softening" resistor, you could look at the Vmp verses Voc curves of the PVs that you are using, and figure out about what is the output impedance is of the String of PVs that you are using, this could possibly guide you. BUT, this will become a bit of a heater.
And so on, GOOD LUCK ! Vic
.....rob,
This is obviously is something that you really want to do.
On this Forum, MidNtie Engineering said that this is not recommended -- a polite way of saying DO NOT DO THIS.
There may not be enough time in a day to discuss this in detail, at least there is not enough time in my days.
I have no horse in this race. You seem to have the answers, so who am I to try to dissuade you from your task.
Vic
My thought about building the ideal generator rectifier like you are talking about is that by the time you engineer to put in all the parts and design to consider all the details you will have something like what you see in an inverter charger or the better Iota chargers mentioned above.
I am not an electrical engineer so couldn't begin to design such a device like you want. I watch tear downs of devices on EEV blog on youtube and he explains in detail all the engineering and design details of devices - there is so much to consider. Check out that youtube channel - he can spend 45 minutes just scratching the surface on what thoughts went into some electronic device.
And as mentioned above by vic - no matter how big your generator capacity is , for lead acid batteries once they reach the Absorb setpoint the current is going to taper back. If you want a battery pack you can quickly dump a lot of power into then you should consider getting lithium batteries .
Larry
So the "Real" issue is the stiffness of the generator, The Classic (like other MPPT controllers) is used to working with things it can through around in voltage. So if it tries to sweep all the way down to battery caboom goes the FETs.
That said I have a set up just like this, 120vac generator rectified and filtered slightly with capacitance fed through a resistor and then fed to a classic. I use Hydro mode with a low voltage limit of like 145 and current limit set to 40 amps. The Resistor acts as a shock absorber. I use 2 ohms and it seems ok.
Of course tech support will tell you this is "Unsupported" and will "Void your warranty"
I can agree with them on both parts as it can be a large consumption of time to walk some one through making it work and then they have the liability if the Classic blows up. So long story short, yes it can be done, Yes it is slightly tricky and YES it can blow up the classic if not done right
Quote from: Halfcrazy on March 27, 2016, 09:58:03 AM
So if it tries to sweep all the way down to battery caboom goes the FETs.
Gotta love those
Fire
Emitting
Transistors!!
Some responses to the responses!
Iotas are adjustable & have smarts , what is your model , I have 12,24,V in 45a&90&120A in 24V
>> I have a DLS-45. In dual voltage mode - it puts out 14.2V and 13.6V.
>> In Smart mode: Bulk:14.8V, Absorb:14.1V and Float 13.6V
>>At cool temps, these voltages are too low. The Bulk needs to have the ability to be about a half volt higher than it is.
This is obviously is something that you really want to do.
>> Yes!
On this Forum, MidNtie Engineering said that this is not recommended -- a polite way of saying DO NOT DO THIS.
>>I can understand the liabilities that some have explained. I also understand that MidNite may not want to spend time explaining how to do this.
>>I'm willing to accept the responsibility it I destroy my Classic. I was hoping that someone on the forum had experience.
There may not be enough time in a day to discuss this in detail, at least there is not enough time in my days.
>> Understood. On the other hand, if others have done this - then the answer could be fast and simple.
I have no horse in this race. You seem to have the answers, so who am I to try to dissuade you from your task.
>>If I had the answers, I wouldn't be asking for help or suggestions!
My thought about building the ideal generator rectifier like you are talking about is that by the time you engineer to put in all the parts and design to consider all the details you will have something like what you see in an inverter charger or the better Iota chargers mentioned above.
>> I think that people are over analyzing this problem. The answer should be as simple and a few diodes, a capacitor and maybe a resistor. If the Classic had a mode that does not sweep, we would be all done.
I am not an electrical engineer so couldn't begin to design such a device like you want. I watch tear downs of devices on EEV blog on youtube and he explains in detail all the engineering and design details of devices - there is so much to consider. Check out that youtube channel - he can spend 45 minutes just scratching the surface on what thoughts went into some electronic device.
>> I do have a background in electronics. Really, really, it's not all that complicated....
And as mentioned above by vic - no matter how big your generator capacity is , for lead acid batteries once they reach the Absorb setpoint the current is going to taper back. If you want a battery pack you can quickly dump a lot of power into then you should consider getting lithium batteries
>>Correct. But if the Bulk and Absorb voltages are too low, then one is not putting as much current into the batteries as one could. This means that the generator ends up running longer than it should. Even a completely unloaded generator eventually runs out of gas. Where I have my cabin, it is very difficult to get fuel - not to mention the philosophic issue of wasting something that you don't have to.
So the "Real" issue is the stiffness of the generator, The Classic (like other MPPT controllers) is used to working with things it can through around in voltage. So if it tries to sweep all the way down to battery caboom goes the FETs.
That said I have a set up just like this, 120vac generator rectified and filtered slightly with capacitance fed through a resistor and then fed to a classic. I use Hydro mode with a low voltage limit of like 145 and current limit set to 40 amps. The Resistor acts as a shock absorber. I use 2 ohms and it seems ok.
>> Thanks for the data. I'm not sure where you got the 145V from? The rectified, filtered, unloaded voltage should be around 170V. But as you put a load on the output, you're going to come back down to the 120 RMS voltage. I guess if you are lightly loading your generator, you could be at 145V?
Of course tech support will tell you this is "Unsupported" and will "Void your warranty"
>>I accept the consequences.
I can agree with them on both parts as it can be a large consumption of time to walk some one through making it work and then they have the liability if the Classic blows up. So long story short, yes it can be done, Yes it is slightly tricky and YES it can blow up the classic if not done right.
>>Having said that - I would think that Midnite Solar could get some marketing mileage out of being able to use their CC in such a mode. Heck, they could even build the interface box and add a mode that does not sweep the input. They might sell even more CC's.
Quote from: cabinrob on March 27, 2016, 06:53:13 PM
Some responses to the responses!
Iotas are adjustable & have smarts , what is your model , I have 12,24,V in 45a&90&120A in 24V
>> I have a DLS-45. In dual voltage mode - it puts out 14.2V and 13.6V.
>> In Smart mode: Bulk:14.8V, Absorb:14.1V and Float 13.6V
>>At cool temps, these voltages are too low. The Bulk needs to have the ability to be about a half volt higher than it is.
This is obviously is something that you really want to do.
>> Yes!
On this Forum, MidNtie Engineering said that this is not recommended -- a polite way of saying DO NOT DO THIS.
>>I can understand the liabilities that some have explained. I also understand that MidNite may not want to spend time explaining how to do this.
>>I'm willing to accept the responsibility it I destroy my Classic. I was hoping that someone on the forum had experience.
There may not be enough time in a day to discuss this in detail, at least there is not enough time in my days.
>> Understood. On the other hand, if others have done this - then the answer could be fast and simple.
I have no horse in this race. You seem to have the answers, so who am I to try to dissuade you from your task.
>>If I had the answers, I wouldn't be asking for help or suggestions!
My thought about building the ideal generator rectifier like you are talking about is that by the time you engineer to put in all the parts and design to consider all the details you will have something like what you see in an inverter charger or the better Iota chargers mentioned above.
>> I think that people are over analyzing this problem. The answer should be as simple and a few diodes, a capacitor and maybe a resistor. If the Classic had a mode that does not sweep, we would be all done.
I am not an electrical engineer so couldn't begin to design such a device like you want. I watch tear downs of devices on EEV blog on youtube and he explains in detail all the engineering and design details of devices - there is so much to consider. Check out that youtube channel - he can spend 45 minutes just scratching the surface on what thoughts went into some electronic device.
>> I do have a background in electronics. Really, really, it's not all that complicated....
And as mentioned above by vic - no matter how big your generator capacity is , for lead acid batteries once they reach the Absorb setpoint the current is going to taper back. If you want a battery pack you can quickly dump a lot of power into then you should consider getting lithium batteries
>>Correct. But if the Bulk and Absorb voltages are too low, then one is not putting as much current into the batteries as one could. This means that the generator ends up running longer than it should. Even a completely unloaded generator eventually runs out of gas. Where I have my cabin, it is very difficult to get fuel - not to mention the philosophic issue of wasting something that you don't have to.
So the "Real" issue is the stiffness of the generator, The Classic (like other MPPT controllers) is used to working with things it can through around in voltage. So if it tries to sweep all the way down to battery caboom goes the FETs.
That said I have a set up just like this, 120vac generator rectified and filtered slightly with capacitance fed through a resistor and then fed to a classic. I use Hydro mode with a low voltage limit of like 145 and current limit set to 40 amps. The Resistor acts as a shock absorber. I use 2 ohms and it seems ok.
>> Thanks for the data. I'm not sure where you got the 145V from? The rectified, filtered, unloaded voltage should be around 170V. But as you put a load on the output, you're going to come back down to the 120 RMS voltage. I guess if you are lightly loading your generator, you could be at 145V?
Of course tech support will tell you this is "Unsupported" and will "Void your warranty"
>>I accept the consequences.
I can agree with them on both parts as it can be a large consumption of time to walk some one through making it work and then they have the liability if the Classic blows up. So long story short, yes it can be done, Yes it is slightly tricky and YES it can blow up the classic if not done right.
>>Having said that - I would think that Midnite Solar could get some marketing mileage out of being able to use their CC in such a mode. Heck, they could even build the interface box and add a mode that does not sweep the input. They might sell even more CC's.
Wow :o ! That's heavy and not sure how to absorb it all, I'm not very smart here but will try to follow along! We have a lot of knowledge here and I'm grateful for that!
Quote from: Vic on March 26, 2016, 11:42:41 PM
Quote from: Vic on March 26, 2016, 03:25:25 PM
Hi .....rob,
There have been a number of Threads on this subject here, and elsewhere.
MidNite Engineering has said that this is NOT RECOMMENDED.
As Tom noted, adding some reasonable resistance in series with the Vin to the Classic will help 'soften" the input, but would waste a lot of power.
It was also mentioned here, that having the battery voltage close in voltage to the external Power Supply would help protect the Classic -- this was in the context of an external PS, and your situation seems far from this recommendation.
Also, a simple bridge/filter capacitor would seem to present a poor Power Factor to the Genset.
One way that many MPPT CCs protect themselves is that they reduce the load on the input power source, which causes the input voltage to rise. In Solar Mode, the Classic "knows" that the input source IS from PV, and this operating point WILL reduce the input power to the CC. With your direct output from the filter to the CC, this is not really the case.
It was also noted in that same Thread, that running the Classic in Legacy P&O would probably be the preferred Mode for these relatively risky approaches.
Your comment, "I do have an Iota 12v charger - but the output voltage is not high enough. It starts charging with a reasonable current, but this soon levels off and I waste a lot of gas without much charging going on", probably indicates that the Bulk charging has finished, and the Absorption voltage has been reached, so the battery charge current will continue to taper.
This apparent battery charge current taper, could also be that with FIVE STRINGS (!!!) of batteries, that there could be poor current charge current sharing between all of those batteries, and the one or two batteries that are hogging much of the current have gotten to Absorb ... just guessing.
Your thoughts are common ones, at least about using an external PS that feeds an MPPT CC input. Direct rectification for this input is also risky, as there is NO isolation between the genset AC output, and DC side of the system ... this is often risky in its own right, for Safety reasons.
To determine the approximate value of the "softening" resistor, you could look at the Vmp verses Voc curves of the PVs that you are using, and figure out about what is the output impedance is of the String of PVs that you are using, this could possibly guide you. BUT, this will become a bit of a heater.
And so on, GOOD LUCK ! Vic
.....rob,
This is obviously is something that you really want to do.
On this Forum, MidNtie Engineering said that this is not recommended -- a polite way of saying DO NOT DO THIS.
There may not be enough time in a day to discuss this in detail, at least there is not enough time in my days.
I have no horse in this race. You seem to have the answers, so who am I to try to dissuade you from your task.
Vic
Quote from: ClassicCrazy on March 27, 2016, 09:06:41 AM
My thought about building the ideal generator rectifier like you are talking about is that by the time you engineer to put in all the parts and design to consider all the details you will have something like what you see in an inverter charger or the better Iota chargers mentioned above.
I am not an electrical engineer so couldn't begin to design such a device like you want. I watch tear downs of devices on EEV blog on youtube and he explains in detail all the engineering and design details of devices - there is so much to consider. Check out that youtube channel - he can spend 45 minutes just scratching the surface on what thoughts went into some electronic device.
And as mentioned above by vic - no matter how big your generator capacity is , for lead acid batteries once they reach the Absorb setpoint the current is going to taper back. If you want a battery pack you can quickly dump a lot of power into then you should consider getting lithium batteries .
Larry
It is a wonderful thing we all have opinions, and all are different, if all were the same---not everyone would be needed ;D
Having thought and read about this some more...
It seems that the "don't do it" comments are mostly directed towards rectifying mains/line and trying to feed that into a Classic. I would agree that this is a bit more dangerous.
I think that people are extending this to include generators.
Remember, the Classic has a Wind Mode and a Hydro mode. I really don't see a lot of difference between wind/hydro and a gas generator.
(Ok, maybe some variances based on the characteristics of the output - whether it is "raw" or coming through an inverter.)
I haven't seen anyone saying I can't hook a hydro generator to the Classic.
I wish the Hydro mode was a bit better explained in the manual. I did watch the video, but it sure would be good to have a bit more detail than that.
For anyone else watching this thread, I quote boB in one of his posts: http://kb1uas.com/mnsforum/index.php?topic=917.msg6112#msg6112
So, maybe our discussion should really focus on how a gas generator is different from a hydro generator. Let's assume a constant flow rate for now.
If we can't come up with any real differences..... then the conclusion should be obvious....
Let's say that I want to connect my hydro generator to my Classic.
My hydro generator puts out AC RMS 120V.
I can full wave rectify this and end up with a lot of ripple.
I can filter this and end up with "less" ripple.
Does anyone know how the Classic responds to this ripple?
Does the rectified waveform need to be smoothed out? If so, how much?
Is there a spec for acceptable ripple at the input of the Classic?
Read, carefully, the following;
Quote from: Halfcrazy on March 27, 2016, 09:58:03 AM
... That said I have a set up just like this, 120vac generator rectified and filtered slightly with capacitance fed through a resistor and then fed to a classic. I use Hydro mode with a low voltage limit of like 145 and current limit set to 40 amps. The Resistor acts as a shock absorber. I use 2 ohms and it seems ok.
Of course tech support will tell you this is "Unsupported" and will "Void your warranty"
I can agree with them on both parts as it can be a large consumption of time to walk some one through making it work and then they have the liability if the Classic blows up. So long story short, yes it can be done, Yes it is slightly tricky and YES it can blow up the classic if not done right
Since HalfCrazy (Ryan) is Sales Manager at Midnite Solar you can take his advice with complete confidence.
He has been "stress testing" Classics for years now. ;D ;D
Just saying...
Tom
Yes, I read the post.
It validates the whole process.
But in the post from HalfCrazy:
That said I have a set up just like this, 120vac generator rectified and filtered slightly with capacitance
The term: "filtered slightly" is not very specific.
Interpretations of this could lead to a ripple well over a hundred volts, or maybe only a few volts.
If probably matters....
Quote from: cabinrob on March 28, 2016, 03:59:52 PM
The term: "filtered slightly" is not very specific.
Interpretations of this could lead to a ripple well over a hundred volts, or maybe only a few volts.
If probably matters....
I think his point is that is NOT necessary to have a pure DC voltage on the input.
I will tag him on this see if he is online to get you a more precise answer.
Tom
Quote from: cabinrob on March 28, 2016, 02:32:40 PM
Let's say that I want to connect my hydro generator to my Classic.
My hydro generator puts out AC RMS 120V.
I can full wave rectify this and end up with a lot of ripple.
I can filter this and end up with "less" ripple.
Does anyone know how the Classic responds to this ripple?
Does the rectified waveform need to be smoothed out? If so, how much?
Is there a spec for acceptable ripple at the input of the Classic?
The Classic really wont care much about the ripple. If it is real bad you may get a RFR of #9 witch is reverse current is greater than 9 amps and if so you need to add a little filter capacitance
Quote from: TomW on March 28, 2016, 03:06:26 PM
Since HalfCrazy (Ryan) is Sales Manager at Midnite Solar you can take his advice with complete confidence.
He has been "stress testing" Classics for years now. ;D ;D
Just saying...
Tom
Remind me tomorrow to post my first attempt at charging with a classic from my 120vac generator :) there was smoke and fire yes!
Quote from: cabinrob on March 28, 2016, 03:59:52 PM
Yes, I read the post.
It validates the whole process.
But in the post from HalfCrazy:
That said I have a set up just like this, 120vac generator rectified and filtered slightly with capacitance
The term: "filtered slightly" is not very specific.
Interpretations of this could lead to a ripple well over a hundred volts, or maybe only a few volts.
If probably matters....
Honestly the filter caps really dont seem to effect the classic so to speak. Again I think like you do so when I had the reason to do this I did it. Of course it helps I get free classics ::)
I cant' wait to hear about your smoke/fire experience.
Life is to short to make all of the mistakes yourself.... :-)
I would have thought that a lot of ripple would have driven the Classic a bit nuts. Your comment about reverse current on the input side sort of substantiates this.
I'm guessing that there is a "reasonable" (ha ha, there is another one of those precise engineering terms) amount of filtering/capacitance in the front stage of the CC.
Is there a register where one can observe the reverse current?
This would be a good way to tune how much capacitance to add to the generator.... I mean to the hydro generator.... ;-)
I'm thinking that I may put a temporary shunt on the input side and hook that up to a storage scope. That should take a bit of the mystery out of the setup.
Generators and hydro plants react differently to loads, and the controller will get into a battle - the weaker device will fry.
120VAC ends up being close to 180V P-P, close to the limits, but not likely to exceed - As long as you have some loading, if you let it go open circuit, you may hit 200V as the caps charge up. Maybe you can use a variac or a 2:1 step down transformer to
get the voltage down lower, the higher the voltage is, the higher losses in the controller. Lower DC = cheaper filter caps too.
What size resistor ? Well you want it to pass a lot of power, but still have enough effect to allow the charge controller to be able to regulate. Maybe a water heater element (in a tank of water) will be a decent ballast resistor, 120V 1Kw
You are going to have to play "Limbo" with it and see how low can you go. The resistor will not be small or cheap, it will have to have a good size heat sink.
Also, modern gensets are pretty scant on their cooling, I've got a 3.3Kw peak, rated for 3Kw cont, but can only pull 2.5kw at 100% duty and still have to give it a 5 min cool down before shutdown. Charging batteries is a pretty stout load for a genset, and it won't like it.
Quote from: cabinrob on March 28, 2016, 10:13:14 PM
I cant' wait to hear about your smoke/fire experience.
Life is to short to make all of the mistakes yourself.... :-)
I would have thought that a lot of ripple would have driven the Classic a bit nuts. Your comment about reverse current on the input side sort of substantiates this.
I'm guessing that there is a "reasonable" (ha ha, there is another one of those precise engineering terms) amount of filtering/capacitance in the front stage of the CC.
Is there a register where one can observe the reverse current?
This would be a good way to tune how much capacitance to add to the generator.... I mean to the hydro generator.... ;-)
I'm thinking that I may put a temporary shunt on the input side and hook that up to a storage scope. That should take a bit of the mystery out of the setup.
No reverse current can not be monitored on the Classic by the user, The reverse current makes sense if you think about ripple. As the peak hits the classics caps go high. When the spike goes low the power goes back out of the caps. I would start with NO filter caps and see if its an issue. I would also put resistance in series and set the current limit to a very low setting on the start
Quote from: mike90045 on March 29, 2016, 02:44:35 AM
Generators and hydro plants react differently to loads, and the controller will get into a battle - the weaker device will fry.
>>Agreed that a generator is a bit different - in that as load increases, so does engine power.
120VAC ends up being close to 180V P-P, close to the limits, but not likely to exceed - As long as you have some loading, if you let it go open circuit, you may hit 200V as the caps charge up. Maybe you can use a variac or a 2:1 step down transformer to
get the voltage down lower, the higher the voltage is, the higher losses in the controller. Lower DC = cheaper filter caps too.
>> Not sure I see this. 120VAC RMS is (120 x 1.414) 170V P-P Unless the generator voltage is very unregulated, I don't see how I can get to 200v ??? Lower DC may mean cheaper caps, but variacs are even more expensive.
>>Even if there were a few cycles that did get to a high voltage, putting a resistor across the caps would solve this. I would do this anyway as a safety thing - to bleed away any charge so that there aren't surprises after things are shut down.
What size resistor ? Well you want it to pass a lot of power, but still have enough effect to allow the charge controller to be able to regulate. Maybe a water heater element (in a tank of water) will be a decent ballast resistor, 120V 1Kw
You are going to have to play "Limbo" with it and see how low can you go. The resistor will not be small or cheap, it will have to have a good size heat sink.
Also, modern gensets are pretty scant on their cooling, I've got a 3.3Kw peak, rated for 3Kw cont, but can only pull 2.5kw at 100% duty and still have to give it a 5 min cool down before shutdown. Charging batteries is a pretty stout load for a genset, and it won't like it.
>> I guess I'm still not getting this.
>> Let's work backwards.
>> My Classic 200 is rated for an output of 79A at 14.4V, or 1140W
>> Let's assume 100% efficiencies for now. So, the maximum load on my generator would be 1140W, or about 9.5A at 120 VRMS. I should be able to run my 2500W generator all day at this load.
>> If we go with using the Hydro Manual MPP mode and set the Minimum Voltage to say, 110V, why do I need any resistor at all?
>> My interpretation is that in Manual mode, the Classic will not sweep the input. It won't draw any power if the input voltage is below 110V.
>> I start my generator. My filter caps start charging. When they get to 110V, the Classic wakes up and starts drawing power.
>>The Classic by it's own design will current limit it's output to 79A. The generator will never have to push more than 10A. (Let's ignore inrush currents for now.)
>> What am I missing ???
Quote from: cabinrob on March 29, 2016, 09:32:04 AM......>> What am I missing ???
Let's just hope you are real lucky.
If you don't know how RMS and a bridge rectifier works, and think that setting the controller to 110V min will solve things, you are going to have an expensive surprise. Just a few little spikes from the generator and you are over 200VDC quickly.
The controller is expecting to be able to vary the loading on the Input (PV or Hydro) and have the input respond in a predicted way. A generator with 2 or 3x the output capability of the controller will not respond as expected, and you are likely to cook something.
>Even if there were a few cycles that did get to a high voltage, putting a resistor across the caps would solve this
That is a lesson I learned in high school, on the classroom budget. V x A = Watts.
So, anyway, fire it up and tell all us naysayers how it worked.
Quote from: mike90045 on March 29, 2016, 06:42:20 PM
Quote from: cabinrob on March 29, 2016, 09:32:04 AM......>> What am I missing ???
Let's just hope you are real lucky.
>> I was really really trying to avoid luck by discussing this on the forum. Luck should have nothing to do with the solution.
If you don't know how RMS and a bridge rectifier works, and think that setting the controller to 110V min will solve things, you are going to have an expensive surprise. Just a few little spikes from the generator and you are over 200VDC quickly.
>> I'm thinking I may understand rectifiers and RMS. I guess that a safety check would be to put my diodes and capacitors on the generator output and then check voltages. This can be done without the Classic connected. This should show me the worst case (highest voltage) scenario.
The controller is expecting to be able to vary the loading on the Input (PV or Hydro) and have the input respond in a predicted way. A generator with 2 or 3x the output capability of the controller will not respond as expected, and you are likely to cook something.
>>So obviously I don't understand how Manual MPP works. From what I could tell - in that mode, the Classic doesn't try to match the source. It just takes power when the input voltage goes above a minimum value. I thought there were no sweeps of the input.
>>If anyone can point me to any documentation on how Manual MPP works - that would solve a lot of speculation.
>Even if there were a few cycles that did get to a high voltage, putting a resistor across the caps would solve this
That is a lesson I learned in high school, on the classroom budget. V x A = Watts.
>>Sorry, but I don't understand that answer.
So, anyway, fire it up and tell all us naysayers how it worked.
>> Yes, I do hope to experiment with this. Hopefully, somewhere, somehow I will get some real technical info on the operation/characteristics of the Classic. Just my take, but there seems to be way to much speculation and too little data.
>> Yes, I'm going to get flamed for my attitude - hopefully it won't end up with the Classic doing the same...... :-)
Posted by: cabinrob
« on: Today at 07:20:50 PM »
>> Yes, I'm going to get flamed for my attitude - hopefully it won't end up with the Classic doing the same...... :-)
I don't think you need to be flamed, (MAYBE) the information is there to do what you need but not enough information that will flame a CC if you not sure of what your doing. That's just a thought on my behalf as I have seen to many try placing blame for what they thought was said, usually a mind set. I don't believe anyone here wants you to flame a classic. From what I've seen here is if you have the basic knowledge to perform the task than the technical information will be given. JMHO
Walt
So guys I'm dying to know how it turned out? Did it work? I'm trying to pull 240 volts off of a Prius high voltage battery through the MidNite to keep my 48v house batteries at float through the night. So I ended up here looking for answers. I'm searching for in depth descriptions of how the different modes actually function. Started a thread about it elsewhere
there are some people, i mean only some, when you tell them "don't do it" or "it can't be done" , they take this as a challenge and spend a lot of time thinking or even trying to do it.
and then, after a while you hear nothing more about it. ( they are either too embarrassed to talk about their misadventure or trying to do something else that can't be done)
Then again... Some do it and it works just fine !
I think you just REALLY have to know what you're doing to make it work good.
Plus a wee bit of luck.