Tare Losses, Cut-in Power Level

[2flit]

Hi There,
I am measuuring 380ma parisitic draw with the array breaker off. This is a huge winter time loss on a small system, heck, I can almost run two littlite's on that much power!

I would like to know what the nightime tare losses are and how this thing knows when to stop being a load?
In my system.... what is the aproximate array wattage at which the controler will cut-in? 
In real world conditions for our system there is often ridiculously little power comming in >> In these conditions (ie 20 array watts for 8 hours, dark the rest) At some point the night time tare losses result in net loss from having the Classic turned on...... At what point would this occure?  Express this in watt-hours/ day input to the controler.

Thanks!

I have a very early version Classic200 with three 200W Sanyo's connected in series. Array is Tree mounted but still suffers heavy shadding in the maritime pacific nortwet.  24VDC Battery with 5amps and 123vpm on the array, 160' #6 cu 1-way array run

[boB]

I am measuuring 380ma parisitic draw with the array breaker off. This is a huge winter time loss on a small system, heck, I can almost run two littlite's on that much power!

Yes, you're right !   LED lights for sure !

384 miliAmps at 25V is ~almost~ 10 watts and I have never seen the idle tare loss (Classic off) that high.
BTW, what are you using to measure this current with ?   Are you using say, A Fluke meter ?

Does the display say "Resting" when that input breaker is off ?  The reason I ask is that if the Classic
is running and you turn off the input breaker, it may still be running for a minute before it
turns itself off.  When it is not resting and the switching circuitry is running, it will draw more power.  That draw
at lower power output will be reduced fairly soon in software so will at least be upgradeable.


If it i indeed  is drawing Resting current this high, give me or Ryan an email or phone call or message and we will see what we can do.

Right now, it shouldn't draw more than around 5 Watts or so when Resting.  On the high side, I have heard 5.5 Watts
and around 4.25 to 4.5 and 1/2 Watts on the low side.

I realize that even 5 Watts is higher than it should be and we are reducing that.  Some of that will be done with just
Software and even more with hardware for future units.  Not too long from now, while the Classic is in Wind mode and
waiting for wind, if the cut in voltage is fairly high, the Classic will draw a bit much power just sitting there for a
minute until it turns off.  This can and will be reduced by about 1/3 with a software only fix fairly soon.

Right now, if the Classic is not producing at least around 15 Watts, that is when it should turn off.
This rule may be made better soon too since the Classic's current sense circuitry is fairly accurate.


boB

[niel]

shuts off at 15w? arbitrary figure or how did you arrive at that? curiously, mine is still going as it's outputting .4a on mppt float. not complaining mind you.

[Vic]

Hi Niel,

I am not a designer of this kind of stuff,  but my guess is that the power to run the converter vs power produced must corss over at about this point,  and the exact value probably depends upon the system voltage and PV voltage.   BUT,  whatta I know ?!

73,  Vic

[boB]

Nahhh....   15 watts is arbitrary, but this value will be changed to  match tare losses at the operating voltage.

If the controller is holding the battery at Absorb, Float or EQ Voltage, it will stay running no matter what the
power output is because that's what it is supposed to do in that case.    In MPPT, (current) mode, that's when
you want it to turn off when there is not net positive output current.

Night time tare loss (Resting) is a totally different story, but should strive to be as low as technically possible.
There's a lot of stuff in the Classic and that doesn't help things, but it can be made a couple Watts or so better.
I'd be happy with, say, 3 Watts or maybe 3.5 Watts.

boB

[niel]

sounds good boB. let us know when you've made that improvement and then i'll have to learn how to do the software upgrade.

speaking of software upgrades, you just came out with one, but i thought it not imperative for me to do the upgrade at this time. for the next upgrade to take hold should the current upgrade be done or will it just be ok to go straight to the next upgrade? i have to ask for once i got behind on windows upgrades and those it turned out didn't take all at once (i think i had like 20+ updates to download all at once and it was on another lesser used pc i have if you're wondering) and i had to load each upgrade singly until up to date.

[Halfcrazy]

Niel
You can skip any software upgrades you like and when you do one it will bring you up to current. This will not add to the time at all it is still about the same amount of data. We promise to never be like windows

[Vic]

Hi boB,

Thanks for the clarification ...  too much assuming on my part.  My comments mostly based on watching the MX-60 do something very similar (latest 5.11 FW) -- late in the day with fading sun the MX would do its wake-up  charge at 20 or 15 watts for a bit,  then go back to sleep for a bit.  My assumption was that it must have been programmed to sleep at poweer levels @/below 15-ish watts,  as it was a net zero production,  else why not just keep on charging down to about nil charge (?).

All assumptions on my part.  Altho the net gain on a system like mine,  where each of the two inverters consume 20 Wh,  it makes no real difference on the net charge.   For a petite system,  the small net gain of charging to the bitter end of evening sun might be more important ...  again whatta I know ?

73,   Vic

[2flit]

Bob,
Yes I was using a Fluke 87 for that 385ma tare loss with the PV breaker off.  I would say that even 3 watts quiescent losses are  too high in a small off-grid system in the wintertime pacific northwest >> (compared to the competition anyway).  The Tri-Star published  is 1.3 watts and the FM60/80 published is under 1 watt. Blue-sky is even lower from my measurements.
If we are seeing even a 5 watt quiescent draw (instead of the 10watts measured) then that 5 watts amounts to 10 amp-hrs/day! (12v system).  That is a stupendously huge load for the little guy with a small off-grid system. In our climate it would take a minimum of a 120 watt module to keep up with this thing in winter sunlight conditions in the Northwest!  (allowing for a 1.6hr average day and .8% charge efficiency, but it is actually worse than this since the controller during the 6 or less hours of low light conditions is robbing more than 5watts while sweeping and tracking).  It is fairly clear that this is not the best choice MPPT for small systems with minimal wintertime input. For the normal size systems that rack up 20 watt standby losses on their Inverters like it was duck soup..... well heck, another 5-10 watts may not even matter.  I am a bit tongue in cheek here but we are learning to treat tare loss like they almost didn't matter.

[boB]

2flit,   was that 385mA at 12 Volts battery or 24V ??

Also, I know the PV breaker was off, but was the Classic "Resting"  ??

I'm not sure if it was 5 watts (12V) or 10 Watts (24V)

I would agree that the Classic is not the best for real SMALL systems (< 300 Watts or so)

I would be happy to have its tare losses as low as 3 Watts, but hopefully we can
get it down lower than that eventually.  It's not real easy, but possible.

boB

[SteveK]

2flit, I'm one of those little guys at ~1KW in a not so perfect location. I also see a higher tare loss but not quite as high as yours (5.5W). Initially I had thought of a contactor to time the on/off of the Classic. Then after I scratched my head a bit and looked in the mirror I decided I really had no business using such a large (and full featured) controller with my lowish inputs. I had lost touch with my intentions for owning the Classic. If I intended to stay low input I should've stayed with what I had.

Having said that I had always intended larger inputs for the Classic, be it wind, hydro or more solar. With that being the case the 3W or so tare boB spoke of would be minimal. So for now here in the better weather it matters very little but winter is right around the corner.

Speaking from my own personal observations, the Classic becomes par with my other cc at 170W input levels and gathers more across the day than the other lower power cc...

[niel]

i just thought i'd bring this up again to ask about what you guys may have gotten it down to? i still haven't updated my software as of yet and did download the latest to the pc, but i just haven't gotten around to trying it yet. i guess i've got cold feet here as i'm a believer in that guy murphy.

[boB]

i just thought i'd bring this up again to ask about what you guys may have gotten it down to? i still haven't updated my software as of yet and did download the latest to the pc, but i just haven't gotten around to trying it yet. i guess i've got cold feet here as i'm a believer in that guy murphy.

I think that the lowest we are going to see is about  3 Watts.    Some of getting down to that level
is software, but I don't have that part quite done yet.   We might get down to just under 4 watts
by software alone.

Hope you had a good thanksgiving !
boB

[niel]

yes, i was told by ryan in a pm that you guys made some inroads into this area.

my holiday was good and i hope it was good for you and everybody else here too.

[Willyarnold]

Hi.  I posted this over at wind-sun.com and was told to repost the question over here.  This seemed to be the appropriate thread, even though it too is over 2 years old.

Thanks in advance for your response,


Willy

-----

Originally Posted by halfcrazy 

"The idle draw is important to us and I can assure you we will work to bring that way down. Possibly even having a super sleep mode based on sunset and sunrise where we turn almost everything off."

Sorry to dig up an old thread, but 2 years later has there been any progress on this issue? It is very important to me.

Thanks,


Willy