conversion chart for classic 200

[Westbranch]

eaj, there are other factors to consider, wrt the daily amount of input you will get, and that is the time of year and your location.

High latitude = shorter days and colder temps.

Will you get a full 2 hours of input on Dec 21?
(I note you will have the array a godly distance from the house just to get full sun)

Do you get -40* temps?

hth

[eajonesyk2]

Hi hth,

The property is located in a high desert area but heavily forested (mostly ponderosa pines) at about 5200 ft ele. While we get sunny days a vast majority of the year winters are quite cold and snowy at times. Snow levels average about 4 feet a year and some of that snow stays on the ground from about December through March. I have owned the property since 2008 and the coldest temp I have seen was -12 f. Usual low winter temps are in the teens with the coldest temps early am (5:00 to 7:00 am). Daytime winter temps average in the 20s and 30s

Reason for array being located a 100 ft distance from house is because of trees. Some are mine and some on neighboring property. Cutting them down is not a likely option:). The answer to your question about 2 hours of sun on Dec. 21 is I don't know. I don't live on the property right now. Most of my trips down there occur between May and October. I will be making a trip down there this Dec to check out the potential locations of the array.

I am not to worried about the sun that late in the winter because my power requirements will be much lower in the winter. Power requirements will be highest in the summer which will be when I have more sun then I know what to do with.

Spring and Fall should be fine too. I was just down there on Labor Day and the 100ft location was still getting sun from around 10:00 to 5:00. The current panel on my roof was only getting sun from about noon to 3:00 and the sun was not to far from going behind the southern tree line. By the end of October I expect the panel on the roof to be shaded by tree line except for a small clearing where driveway is, maybe an hour of clear sun at best. By Dec 21 panel on roof may have no direct sun at all.

[Westbranch]

I took pics at 15 minute intervals at each solstice and equinox, should have used a tripod so they would have melded together to 'watch ' the shadows move. .  Very interesting.  Picked up a couple of faint shadows I had not 'seen' previously.  Those faint ones can make significant drops in output , especially if in series.
Will do it again this year as some trees are now gone

[Vic]

  Remember, these numbers are at full power.  The cable losses will be much lower at more typical power levels but the efficiency gains in the controller will persist at the more typical power levels.

--vtMaps

However,  when the CC is in a voltage-regulating mode,  the load on the PV is lighter,  and  the string V rises,  with some CCs,  this Vin rise  can cause more heat loss in the CC,  than when it is in Bulk or when in EQ prior to achieving the target V.  It is conceivalbe that under this situation,  that added losses in the CC due to increased Vin could be higher than the wire loss increase twix Absorb and Bulk.  This appears to be some exponential relationship of Vin -- it is not linear with the change in Vin.

While I have never used ALunimum wire for power distribution,  it might be worth considering a somewhat larger guage AL wire for this run -- taking proper precautions with terminal compatibility,  and use of NoALox or similar compounds.

Will look at the pricing of 8 GA THHN Building Wire,  BUT,  last 10 AWG THHN Stranded that I bought was US$ 105/500 ft....

EDIT;  8 GA  at HD is $188.  for a full 500 ft spool.
Thanks eaj for the added info about your location .. end edit
 
Note eaj,  if you could add a signature line in your profile,  it would help all of us to make better guesses, Your location,  etc are  important items. Thanks,  Vic

[Vic]

...  AND, eaj,    Do realize that you could well  be planning on NOT running these PV conductors in conduit,  such that THHN wire prices may not really apply.   Just going on how I'd probably do the job.
YMMV,  Vic

[eajonesyk2]

Vic, I will work on a signature line.

I was planning on using wire that is suitable for direct burial (not planning on running conduit). I was basing wire cost on prices found at solar-electric.com. Actually I completely goofed my estimated wire cost. I was thinking I would need 200ft of wire but disregarded the fact that the wire is two conductor wire so I will only need 100ft. The 10 awg wire I am looking at is 1.20 a foot so $120 for the run. The 8 awg is 2.26 a foot or $226 for the run. So I would only be saving about $100 bucks going with the 10 awg.

So I guess I can stick with the four panels after all and run the 8 awg wire. This would give me about a 3% voltage drop but more efficiency in the controller? 6 awg is definitely not in my budget so 8 awg is as good as it will get. I could squeak by with a 3%v-drop for now, especially if the controller is running a little more efficiently. Running two strings of panels would require 2 awg wire to keep the v-drop under 2% and I am pretty sure that will never be in my budget

I will purchase the Classic 200 either way in case I want to add two more panels at a later date.  Hopefully I can increase my battery system voltage to a 48 volt bank down the road and then maybe add two more panels in series at that time, if needed.

[Vic]

Hi ea ..

Thanks for doing the signature,  it should save you quite a bit of time answering questions.

Do you already own the Deka Gel batts?
Gells are fragile batteries.  They must be charged very carefully.  The Absorb voltage setting has a tight tolerance,  and MUST be temperature compensated on every charge source.   Usually,  the maximum charge current must be limited to about 5% of 20 Hr capacity.  Please carefully read and follow the recommendations of the mfg.

You may know these things and more about sealed batteries.  Usually a good Battery Monitor is recommended,  as there is no way to directly measure the SG  or SOC in an active Off-Grid system.

If you do not yet have these batteries,  you may want to think some more about the batt purchase.  YES,  I do have an attitude.
Good Luck,   Vic

[vtmaps]

However,  when the CC is in a voltage-regulating mode,  the load on the PV is lighter,  and  the string V rises,  with some CCs,  this Vin rise  can cause more heat loss in the CC,  than when it is in Bulk or when in EQ prior to achieving the target V. 

I think that is one more argument in favor of using the lower voltage array configuration.  If the Vin is going to rise on a 12 volt system, I would think that it is better to start rising from 56 volts than from 112 volts.

It is conceivalbe that under this situation,  that added losses in the CC due to increased Vin could be higher than the wire loss increase twix Absorb and Bulk.  This appears to be some exponential relationship of Vin -- it is not linear with the change in Vin.

When the CC is in voltage regulating mode, the current is decreasing while Vin is rising.  Both of those will reduce the cable loss.  What that will do to the controller is unknown for the classic.  On the outback the answer to the question depends where on the power curve you are.  The outback hits its peak efficiency at about 300 watts.  If you are producing 600 watts when voltage regulation begins, the rise in Vin will make the outback less efficient, but the reduction of power being drawn from the panels will make the outback more efficient.

--vtMaps

[Vic]

vt,

YES,  this is what I am saying,  indirectly.

This string V is high,  especially on a 12 V system.

Yes,  was saying that the lower input current does cause less cable loss,  BUT probably even more loss in the CC (due to Vin rise),  than cable loss.  This may seem somewhat moot,  (as by definition,  at this point,  the unused power is unneeded) --  if the power is not needed,   then system losses must not matter -- but the tehrmal impact is negative.

AND,  my exprience with the MX-60  with almost identical string V as the proposed system by eaj,  is that the only time that the internal fan in the MX runs,  is under quite light CC loading -- usually in Float,  delivering a few hundred watts,  but  since Vin has risen to 120-ish Vin,  the CC needs to rid itself of more heat than when delivering 2KW,  causing Vin to be dragged considerably lower.

Know that this seems like Angels and Pins.

YES,  believe that if there is a reasonable way to run a more moderate Vin,  especially on a 12 V system,  it should be done.

IMHO,  I would strongly consider running the PV conductors in PVC conduit,  allowing the use of,  perhaps,  AL cable,  which could be quite a lot less expensive.  AL  is harder to pull,  and would probably require some extra splicing giblets to make transitions from PV/CC leads to AL,  etc ...  This could still reduce the cost of increased wire size to support lower Vin with increased currents.

However,   the higher voltage Classics may well be more well-behaved at high Vin than the venerable MX and other CCs.  One might guess that this is the case,  but dunno.

Final thing is the ambient temps in the place where the CC is located.  Cooler temps are better,  especially with high string V.  The power rooms,  here have priority for A/C,  but would guess that with the proposed system of eaj,  there is NO power budget for A/C.

Final thought,  all CCs,  and other power electronics make some acoustic  noises.  It is a very good idea to try to locate these items away from living areas if at all possible.   Vic

[eajonesyk2]

Vic, yes I already have the gel batts. I bought a small used pv system from a guy who had used the system for a prototype portable charging station he was trying to build. He ended up giving up on it and I bought the components. I like the idea of the gel batts for various reasons but now understand the charging limitations. When it is time to replace the batteries I will definitely purchase wet cells golf cart type. Since my budget is not expected to loosen up for a while, I have to work with what I got for now.

Regarding cc operating temps. During a majority of the year the local ambient temps are somewhat cool so that should help the cc maintain reasonable operating temps. During July, August and early September when the ambient temps will be warmer the panels will also be warmer and that should cause the panels to operating at a lower voltage, which should cause a little bit less heat stress on the cc. Does that sound right?

I will price out some other wire options including al and running conduit but if my v-drop calcs were right I would need to 2/0 copper or 4/0 al wire to run two strings of two panels each at 200ft of total wire length. I just can't see how these increased wire costs could possibly be justified with increased cc efficiency and reduced wire losses. Maybe on a much larger array this could be the case but not on 600 to 900 watt system. I will be happy to hear I am wrong?

This post is getting a little long and I thought that I would post a new post with some of the recommendations I have received so far and see if I can get some feedback on costs per watt. Thanks all for the help.

[eajonesyk2]

I will post my request for estimated costs per watt feedback over at the naws forum since the subject isn't mainly related to the midnite controller. thanks again for all the help here.

[Westbranch]

Maybe on a much larger array this could be the case but not on 600 to 900 watt system. I will be happy to hear I am wrong?

eaj, I am seeing a disconnect in you statement above and your sig line.
If you are planning this install to be a permanent home you are investing in the future by putting in wiring that will NOT have to be replaced or dug up or ??  You may not need it right now but you save yourself a lot of work and double expenditures...
for example what if you just want to add 50% more panels, what are the implications to losses by having smaller wire?
One sure thing is that loads grow over time... thus so may your PV
your choice..

[Vic]

Hi ea.

Great on the batteries.  I do like that they appear to GC2 sized 6V batts.

It is easy for folks like to snipe at others' systems.  We all do run what we got FBOW.

You will probably do fine with the batts.  IIRC  this makes two strings @24 V.  Just try to keep strings balanced by  using good,  well made batt cables of equal lengths.  A Clamp-On DC  Ammeter can help by allowing easy measurement of individual string currents.

Much of what I mentioned about reduced efficeincy of CCs relates to the prior generation(s) of CCs.  The HV Classics have been tailored for more efficient operation at higher Vin,  so they would have to be better at the high Vin operation.

There are losses in every system.  The only thing,  is that the losses accumulate every day,  and accumulate over time.  But,  PV is getting less expensive,  and if one has enough PV,  and if losses do not over-stress components,  then,  ignorance in my case IS bliss!  Although, from an investment standpoint,  additional Cu  pays off every day of operation,  to the point of diminishing returns etc.

If you find a use for almost every watt available from PV,  then this rise in Vin will not be a problem,  as the PVs will almost always be heavily loaded.  Mileage WILL Vary.   Vic

[eajonesyk2]

Hi westbranch,

Sorry for any conflicting ideas i have thrown out there regarding the system usage. This will be my permanent home upon retirement or possibly layoff. I have been lucky to have a caretaker staying at the property since the winter of 2009/2010. The cabin was broken in to twice before that. Besides security he has provided me with the awareness of what is necessary to survive down there. Up until Labor Day weekend he had zero watts of ac power available to him, except when I visited solo and he was able to stay during my visit. He has made do with alkaline batteries for the lantern, radio and nature provided refrigeration during the winter. He doesn't even use propane. He seems perfectly content and is happy to have a warm place to stay (wood stove for cooking and heating rooms and water). I desire a little bit more of the creature comforts the rest of us are used to. But I have no expectations of living like I do know with the only power concerns being the price of the electric bill each month.

Anyhow I installed a single 64 watt panel on the roof of the cabin Labor Day weekend and hooked it up through a simple shunt type controller and in to a 12 volt marine/rv deep cycle battery. I supplied him with a 150 watt Samlex pure sine inverter so he can run the CFL bulb in the cabin now and charge a nicad battery pack for the lantern. I also suggested he buy some rechargeable AA batteries for the radio which he can charge through the inverter as well. I won't be back down there until October to see how it is working for him but I haven't heard of any problems yet.

Moral of the story. I expect to live just fine with 1kwh or less a day so any future upgrades to the planned pv system will be very limited. I will take in to consideration the maintenance and life expectancy of wire I put in the ground so maybe conduit will work it's way in to my system after all, we'll have to see.

Thanks for your input. Also check out my planned systems over at the naws forum to be posted later today, I would really like to get the cost per watt nailed down.

[eajonesyk2]

Thought I might as well throw these potential pv systems up here too since you guys helped give me the basis for arriving at these numbers. They all include the Classic 200 CC as well. Let me know if these useable watt expectations and costs sound reasonable. Also posted at naws, thanks.

Proposed System 1. Estimated watts coming out of controller 407 watts/component cost $836=$2.05 per useable watt.
Calculated useable watts as follows: Name plate panel watts 580x.77=446watts Wire loss 446x.97=433 watts CC efficiency 433x.94=407watts
4 dmsolar 145 watt panels wired in series.
100ft of two-conductor 8awg wire ($226 plus shipping)
Midnite Classic 200 charge controller ($610)



Proposed System 2. Estimated watts coming out of controller 510 watts/component cost $1050= $2.06 per usable watt
Useable watts calculated as follows: Name plate panel watts 870x.77=584 Wire loss 584x.97=567watts CC efficiency 567x.90=510 watts
6 dmsolar 145 watt panels wired in series. ($320)
100ft of two-conductor 10 awg wire ($120 plus shipping)
Midnite Classic 200 charge controller ($610)



Proposed System 3 Estimated watts coming out of controller 420 watts/component cost $1260= $3.00 per useable watt
Useable watts calculated as follows: Name plate watts 580x.77=446 watts Wire loss 446x.97=433 watts CC efficiency 433x.97=420 watts
4 dmsolar 145 watt panels wired in two strings of two panels
200ft of 2 awg welding cable ($600 plus shipping)
pvc 1 1/4 inch conduit 100ft ($50)
Midnite classic 200 charge controller ($610)