In a NAWS thread on a problem with snow stuck on panels, it was suggested that changing to Legacy P&O from solar may help. The poster was getting about 100w from the array even when snow covered. As my objective is basically to just offset Classic tare and self-discharge, even 100w would help a lot. I'll be at the cabin sometime in the next 10 days or so, and can change the mode if that will help, but want to get the settings right as I won't be back there until late March at the earliest, late May latest.
Last winter panels got covered about the same time as the sun is low enough that a treed hill to the south shades them (mid-Dec). Snow accumulated deeply enough that when the shading stopped (mid-Jan) it didn't melt off. Because of ice conditions, it was mid-Feb by the time I got there, by which point batteries were in dire straits.
Logs for 12v array show Vin of ~60-74v and High Temp of 0 about 1/2 the time and up to 10 otherwise. High Power is small (eg. 0.019kW) but not zero. Daily kWh is consistently zero. 48v arrays had comparable numbers. Does this suggest there may be a few hundred watts available by changing settings? If so, what settings for sweep depth and interval would likely be best?
Hi estragon,
Missed that Discussion on the wind-sun Forum.
What was the stated-reason that Legacy P&O would be a benefit?
Personally, would not even consider diddling with sweep depth/interval, as this is experimental, and one would need to be there to monitor/modify.
So you are saying the there was some evidence that there was a maximum 19 Watts available, at the peak?? IIRC, it requires a bit more that 10 watts just to run the Converter inside the Classic, and, if there was 000.00 kWh produced on many/most/all days, think that this tells quite a bit.
Some, in the Far North (as you probably know), mount one, or more PVs at 90 degrees elevation -- vertical, to shed the maximum amount of snow/water and perhaps run a PWM CC, or connect a fairly small PV directly to the battery.
If you could get this battery bank fully-charged (and perhaps EQed), and disconnect all electronics, you might be able to weather three or four months, if the battery is COLD. Self-discharge is quite low on Flooded batteries, when cold.
I know nothing of this from personal experience.
Good Luck, Vic
The thread is
http://forum.solar-electric.com/discussion/351516/12v-panel-to-keep-48v-bank-floating#latest
I think the poster (mike95490) also posts here so may be able to elaborate on what he did.
The arrays are at the maximum angle the racks allow, 65deg IIRC. At some point I may re-do the roof under the arrays, and might add some 6x6 sleepers under the back legs to get a bit more tilt.
In the NAWS thread options such as a couple of small 12v panels to a PWM controller and 12v-48v boost controller etc. are being discussed, and the P&O thing came up. As I'm going to be there soon, I figured maybe I could get a better grasp on that here.
Yes, grasping at straws to improve the harvest, the Legacy solar mode seems to be reliable, I have seen the other modes freak out the controller in varied clouds.
And I too, earlier this week, had frozen panels, under clouds, producing nearly nothing, the weather warmed and the snow came off last night. But it was still cloudy today.
But I've not had a situation where the controller ran down the batteries in 3 months. Seems like some harvest should offset the controller consumption.
Also suggested pull one controller out, and jumper the entire snow array to a single controller. Technically, it would be overpaneled, but if the array is barely producing anything there is no overload. And if the sun returns, the controller should limit itself to safe limits, and unloaded batteries would charge quickly.
Mike,
Here, on very cloudy days, midday, if is not uncommon to see 5% solar production, or less. This is with PVs aimed true South, and elevated at Lat +15 degrees.
So, even with no snow and no ice, clouds can reduce PV production to almost meaningless levels.
Regarding 'estragon's concern, seems to me that an MPPT CC is not a good fit as a Wintertime CC to try to keep batts topped off, due to the amount of input power required to run the Converter, IMO.
Seems to me, that estragon's PV production is generally so little, that there is not even enough PV power to run the Converter, so the CC would Rest, but still consume some Tare.
This part of CA is cold enough for me.
FWIW, Vic
Mike, Vic , I am wondering about the settings for the CL, in the power consumption(?) section, where you set back lighting, etc, if all the options to limit use of power are in play there should be less than 3A 3 Watts IIRC from what boB said a while back.... no?
Quote from: Westbranch on January 04, 2017, 11:53:28 PM
Mike, Vic , I am wondering about the settings for the CL, in the power consumption(?) section, where you set back lighting, etc, if all the options to limit use of power are in play there should be less that 3A IIRC from what boB said a while back.... no?
Oh, I hope it is not 3A. IIRC it was 3Watts
Quote from: estragon on January 04, 2017, 02:29:20 PM
... Logs for 12v array show Vin of ~60-74v and High Temp of 0 about 1/2 the time and up to 10 otherwise. High Power is small (eg. 0.019kW) but not zero. Daily kWh is consistently zero. 48v arrays had comparable numbers. Does this suggest there may be a few hundred watts available by changing settings? ...
Just to try to reiterate, the above means to me, that the peak power in this Log was nineteen watts!! But, there was absolutely NO POWER PRODUCED for the day. Why could this be? Well, IMO, probably the Classic detects some PV voltage, wakes up, tries to make some power from the input PV voltage, but the Classic sees that it takes more power to run its Buck Converter, than the power produced, so goes back to Resting, and on, and on ... and on.
Just not enough PV power available to make any power, above what it costs the Classic to run its power-producing electronics, IMO.
If the Classic in this scenario is a later production unit, then the Tare Loss might be reduced a bit by turning OFF the Arc Fault detector, but, again IMO, seems that irrespective of the Classic Tare, there seems to be just too little PV power to make any power, probably on many days, at least for days that are similar to the one noted by estragon from that Log data.
IMO, perhaps a PWM CC with low Tare, would seem to be a better fit for this situation. Whatta I know! Vic
OOOps.. :-[ you're so right John...
Oh, I hope it is not 3A. IIRC it was 3Watts
I'm kind of leaning towards PWM for winter as a longer term solution, either on an A/B switch to existing arrays, or to a couple of new panels that I could put where sun will definitely hit at least for an hour or two.
In the meantime, I'll be at the cabin next week. Not sure how long I'll be there, or if there will be any sun, but might try the Legacy mode as a temporary thing. Any hints on what settings to use? Any downside aside from maybe not producing as much as possible?
A PWM is not a bad thing to have around. Might be worth the investment. My understanding is you would gain another useful tool with it as well, in that if you were to drain your batteries too low and the classic would not charge them, a PWM like the Brat still would. If you are fully off grid, without another source of charging you could get your system back up and running easily.
if you go with a pwm to your existing arrays then be sure the input voltage to the pwm will not be exceeded. be aware the voltage is apt to be higher during the cold snaps and must be calculated into it. if you present arrays will be shaded due to ice and snow then go with a separate near vertical array.