solar newbee needs help

wvwoodsman

Re: solar newbee needs help

Thanks BB , you seem to understand what i need. I only bought that controller cause we wanted to add wind power down the line. Will it work or should i send it back and get another ? Thanks

icarus

Re: solar newbee needs help

Personally, I would do a whole lot of research on the limits of small scale wind, (here and else where). The reality of small scale wind is that in most cases, if you have enough wind to be truly useful,, ~ 12 mph average, all day, every day over the course of a year, you paradoxically have too much wind and the hard ware doesn't stand up to the stress.

Small scale wind is large live loads, in a hostile environment and hardware life span can be very short, and repairs difficult, especially when it is windy!. Most people suggest going with more PV and unless they are hobbiests scrap the idea of wind.

So, I would go with sending your CC back, and get a good Pv Charge controller, Ideally an MPPT unit. (Avoid BZ controllers like the plague!)

Tony

mike95490

Re: solar newbee needs help

wvwoodsman wrote: »

Mike, if you read back some , Carriboocoot told me that solar panels don't have a "Dump load" . Is this right or not ?

True, but you bought a Dump Load controller, so for it to be able to do anything, it must have a Load to dump excess power to.
I did not see anywhere where it performs PWM charge control, or any sort of multi-stage charge, just a simple threshold, and above that, it turns on the LOAD to prevent the batteries from overcharging.

Until you find out from the Mfg of the controller, I would assume it needs a LOAD, and does not perform PWM regualtion or 3 state charge control.

( note, I see it is wired for "disconnect" control with solar, and does not need a load ) So you could do the same thing, with a volt meter and a knife switch, and disconnect the panels when the battery is 90% full. May as well locate a good battery vendor, as I dont think this will contribute to long battery life. (improper charging) About the 2nd set of batteries, you may decide to get a better controller.

BB.

Re: solar newbee needs help

You could keep the dump controller and even use it as a dump controller for your solar array, but it is far from ideal.

Look at pwm and mppt charge controllers and understand how they work and what functions you may want.

I will have to go into the details later as I am not on a computer right now.

What will help is defining your loads, battery bank, inverter and such.

Then we can start picking out the hardware to meet your needs.

The other way is to say "I have $2,000 to spend, what should I buy for the best bang for the buck with the solar panels I currently own?"

Also a perfectly good question to ask/answer.

But I to would put wind way down the list for now. I an not a fan of small wind if you have access to good sun.

-Bill

dwh

Re: solar newbee needs help

wvwoodsman wrote: »

I have 12 solar panels. Each has 36 cells each at .5 volts x 36 = 18 volts. When i check voltage with my meter in the sun , i produce from 18 to 20 volts and 3.5 amps. The 36 cells are soldered in series , for higher voltage not amperage.

Okay, that's the Voltage Open Circuit (Voc). With a Voc of 18v, then the voltage under load (Vmp or Voltage Max Power) should be up around 15v, which is what you need to properly charge a "12v nominal" battery.


So, if you rig a 12v system, then you'll need to wire those 12 panels in parallel, since wiring them in series will give you too high a voltage. As you seem to already know, wired in parallel, the voltage stays the same, but the amperage adds, so 12 x 3.5a = 42a. So you need a charge controller which can charge a "12v" battery bank on the output side and can handle at least 42a on the input side.


If you rig a "24v" system, then you'd need to wire 2 panels in series to get a 36v "series string" and then parallel the 6 strings. In that case, you'll need a charge controller that can charge a 24v system and can accept at least 21a on the input side.


There are alternatives. For instance, if you had an MPPT type charge controller, it could handle higher input voltage and then down-convert the voltage to what is needed by the battery. Without an MPPT type charge controller, you don't want to rig your solar panels so that their voltage is too much higher than the battery voltage, since too much voltage difference between the solar array and the battery will be inefficient for charging the battery.

By using an MPPT controller, you could rig say, 4 panels in a 72v series string, and then parallel those three strings. The higher voltage would allow you to use thinner wire between the solar array and charge controller and save a few bucks on copper, as well as getting a few more watts through the wire for the charge controller to feed to the battery.

wvwoodsman

Re: solar newbee needs help

Ok ,lets say i scrap the charge controller. I have $2000 to spend , what should i buy for the best bang for the buck with the solar panels i already own. Thanks

BB.

Re: solar newbee needs help

If you where not going to run a electric refrigerator, short wiring runs from panels to charge controller, 12 volt battery bank (1,200 watts maximum DC/AC loads)... on 16x Vmp=18 volt 70 watt panels:

• One or Two x TriStar 60 amp 12, 24, 48 volt PWM solar charge controller $185.00 (you are close to Imax for one 60 amp PWM controller, you could use a pair of TS 45 amp controllers)
• 16x ~7.5 amp fuse block/combiner box (1 series fuse per solar panel)
• Morningstar SureSine, 300 Watt Sine Wave Inverter 115VAC $272.11
• One x Inexpensive ~1,200 watt MSW inverter for power tools
• ~570 AH @ 12 Volt Battery Bank using something like:
  • (450 AH bank) 2x Trojan T105-RE 6 Volt, 225 AH Deep Cycle Battery Price: $154.50 x 2
  • (650 AH bank) 2x Trojan L16RE-A 325 AH Deep Cycle Battery price: $297.00 x 2
• One x AC Battery charger like Power Max 12 Volts, 45 Amp $124.50
• One x Honda eu2000i (1,600 watt) or equivalent genset ~$920

The above should be a very reliable, simple to maintain, low cost system with enough storage for a day or two of solar power (depending on your loads).

Use a propane fridge and a the Honda genset for charging / AC power during bad weather.

Use the Honda, or a large/inexpensive genset for large power tools when needed.

This is one way of configuring...

Personally, with that many solar panels/large array... I would look at the TS MPPT 60 amp controller and configure the array to 4 panels in series x 4 panel strings in parallel... That would reduce you do a 4 circuit combiner box (fuse/breaker) and reduce the solar array cable copper requirements by 1/4th:

• One x Morningstar TriStar 60 amp MPPT solar charge controller Price: $545.00
• One x Midnite Solar MNPV6 Solar Array Combiner Price: $87.20

Of course, there is wiring, fuses/breakers, mounts, and other misc. parts.

If you want to run a refrigerator, then you are probably looking at a 24 volt battery bank and a 1,500-1,800 watt TSW inverter. But a used propane RV refigerator might be good enough for now.

I am concerned about the solar panels you currently have... The MPPT controller and 4x4 panel configuration would address marginal Vmp voltage issues (if there are any). Also, depending on how your panels are constructed (glass, plastic, wood) there can be a fire hazard... I would suggest mounting them over a non-flammable area.

-Bill

By the way, pretty much everyone are volunteers here--We are not connected with NAWS. The above is just an example configuration and you will need to perform your own due diligence/research to ensure you have a system that will meet your needs.

dwh

Re: solar newbee needs help

Um...Bill? I think you figured that based on 16 panels when he said he had 12.

BB.

Re: solar newbee needs help

I based it on his first post:

wvwoodsman wrote: »

We built 16 / 18volt/ 3.5amp/ 75watt panels

But I certainly may have missed a change-up in the middle of the thread...

-Bill

dwh

Re: solar newbee needs help

Aw well...I caught the 12, but missed the 16 in the OP...

BB.

Re: solar newbee needs help

I can't win...

-Bill

Edit: Maybe I can :roll: (at least on rare occasions;)).

Edit: Or we can just edit history

wvwoodsman

Re: solar newbee needs help

Well i have 12 done, we may keep the other 4 for replacements. So Bill, can i use the same components with 12 panels ? Thanks

BB.

Re: solar newbee needs help

One Charge Controller will be fine... You can back down on the Battery bank by 25% and the estimated production results by 25%.

Or just go ahead and install them... If they are going to last 5-10+ years, then you don't need really to save the as spares. If they are only going to last less than a year, a few spares is not really going to help in the long term.

-Bill

wvwoodsman

Re: solar newbee needs help

Thanks alot Bill, I will use all 16 panels as you said. Since i will buy the parts from your site, is it possible to send me a wiring diagram on how to wire the system ?

BB.

Re: solar newbee needs help

Wv,

I will try something this evening.

By the way, we are all volunteers here except for windsun and Rick.

None of the rest of us are involved with naws other than as possibly customers.

Us four moderators are here, mostly, for spam control.

Sincerely,
-Bill

BB.

Re: solar newbee needs help

WV,

Regarding the panels, two wiring methods:

A) Vmp~17.5 volt panels charging 12 volt battery bank with PWM controller

[FONT=Fixedsys]parallel solar ~7.5a fuse/breaker

+==[panel]=====o^o======+=== to + PWM charge controller
|                       |
+==[panel]=====o^o======+
[/FONT][FONT=Fixedsys]|                       |
+==[panel]=====o^o======+
[/FONT][FONT=Fixedsys]|                       |
+==[panel]=====o^o======+
[/FONT][FONT=Fixedsys]|                       |
+==[panel]=====o^o======+
|  repeat for 16x total
+=========================== to - charge controller[/FONT]

• 16x 3.5 amps = 56 amps Imp
• 16x 3.5 amps * 1.25 NEC safety factor = 70 amp minimum wiring

For a 15' one way wire run using a generic voltage drop calculator at 17.5 volt battery bank and 56 amps with maximum/minimum of 3% / 1% voltage drop (0.53 / 0.17 volt drop):

• 15' @ 56 amps with 2 awg copper cable = 0.32 volt drop
• 15' @ 56 amps with 3/0 awg copper cable = 0.13 volt drop

Next, MPPT type charge controller with 4 panels in series:

Do the same thing with Vmp=4x17.5v=70 volts and Imp=3.7 amps:

[FONT=Fixedsys]parallel solar ~7.5a fuse/breaker

+==[pnl]=[pnl]=[pnl]=[pnl]==o^o==+=== to + MPPT controller
|                                |
[/FONT][FONT=Fixedsys]+==[pnl]=[pnl]=[pnl]=[pnl]==o^o==+[/FONT]
[FONT=Fixedsys]|                                |
[/FONT][FONT=Fixedsys]+==[pnl]=[pnl]=[pnl]=[pnl]==o^o==+[/FONT]
[FONT=Fixedsys]|                                |
[/FONT][FONT=Fixedsys]+==[pnl]=[pnl]=[pnl]=[pnl]==o^o==+[/FONT]
[FONT=Fixedsys]|
+==================================== to - charge controller[/FONT]

• 4x 3.5 amps = 16 amps Imp
• 4x 3.5 amps * 1.25 NEC safety factor = 20 amp minimum wiring

For a 15' one way wire run using a generic voltage drop calculator at 70 volt battery bank and 16 amps with maximum/minimum of 3% / 1% voltage drop (2.1 / 0.7 volt drop):

• 15' @ 56 amps with 14 awg copper cable = 1.5 volt drop
• 15' @ 56 amps with 10 awg copper cable = 0.7 volt drop

By the way, did you install bypass diodes across every 12 solar cells to protect cells against damage if they are shaded?

Is this what you were looking for?

-Bill

wvwoodsman

Re: solar newbee needs help

Hi Bill,

As you suggested , i want to use the Morning star 60 amp mppt controller, the midnite mnpv67 combinder box and a Samlex america pst-1505-24a pure sine inverter. My question is, if i run the system 24 volts , can i start with 8 panels , till i get the others done ? Also with the 24 volt system are my only concerns , wiring the battery bank for 24 volts and the inverter needs to be 24 volts ? Does this sound right to you ? Thanks, WVW

BB.

Re: solar newbee needs help

wvwoodsman wrote: »

As you suggested , i want to use the Morning star 60 amp mppt controller,

Check. Very nice MPPT controller.

the midnite mnpv67 combiner box

I don't know what a "67" model combiner is--But I am not in the business.

One warning, circuit breakers can be used as on/off switches. Touch Safe Fuse Holders cannot (they will arc).

and a Samlex america pst-1505-24a pure sine inverter.

Looks like it has an On/Off switch... Always a nice thing.

Remember that inverters have relatively large no load current (~0.8 amps in this case)... That is 24 watts.

Turning it on only when you need it vs getting an inverter that has "Search Mode" (inverter turns on every second or so and looks for >6 watt load, turns "on" when AC load is found.

And/or finding a smaller inverter to power smaller loads.

A major downfall for small solar PV systems (wasted power, less than most efficient conversion/loads).

My question is, if i run the system 24 volts , can i start with 8 panels , till i get the others done ? Also with the 24 volt system are my only concerns , wiring the battery bank for 24 volts and the inverter needs to be 24 volts ? Does this sound right to you ? Thanks, WVW

Yes, the battery bank needs to match the inverter input voltage.

What size battery bank (AH/Voltage) did you decide on? Flooded cell or AGM?

-Bill

wvwoodsman

Re: solar newbee needs help

Hi Bill,

Im sorry that was my mistake on the combinder box , it was mnpv6. The batteries my friend can get , US SERIES L16 wet cell 415 AH. As far as the panels go , can i start with 2 sets of 4 , wired like you said for 24 volts until i finish the other panels ? Thanks, WVW

BB.

Re: solar newbee needs help

wvwoodsman wrote: »

Im sorry that was my mistake on the combiner box , it was mnpv6.

I have no direct knowledge--but they should be fine.

The batteries my friend can get , US SERIES L16 wet cell 415 AH. As far as the panels go , can i start with 2 sets of 4 , wired like you said for 24 volts until i finish the other panels ? Thanks, WVW

We aim around 5-13% rate of charge for flooded cell and assume 0.77 panel+charger derating (real life numbers):

• 425 AH * 29 volts charging * 1/0.77 derating * 0.13 rate of charge = 2,080 watts maximum useful (cost effective)
• 425 AH * 29 volts charging * 1/0.77 derating * 0.05 rate of charge =800 Watt recommended minimum array

As long as the Vmp of the array is around 35v<Vmp<100v -- The controller will work fine charging your 24 volt bank.

8x~65 watt panels = 520 Watt Array

On the small side, you might need to use AC / Backup genset once a week or so to help get the batteries > 90% state of charge.

-Bill

wvwoodsman

Re: solar newbee needs help

Bill, Earlier in this blog you talk about wiring my panels together 4 panels in series = 72v x 4 sets of panel in parallel . This way i could use the Midnite MNPV6 combinder box. My question is how many breakers do i need and what size ?

Thanks , WVW

BB.

Re: solar newbee needs help

Realizing that this are DYI panels... You can pick a fuse/breaker that is ~1.56 to 2x full sun/clear day Isc (your panel's short circuit current). Assuming that your wire gauge from the panel supports that wire gauge (i.e., 14 AWG wire, 15 amp maximum fuse/breaker).

You can place the panels in full sun on a hot day, and short the two power leads together and make sure nothing overheats... A properly constructed solar panel should sit short circuited to itself "forever" without any problems.

-Bill

bsolar

Re: solar newbee needs help

something that may need to be considered (making home panels myself 150W) is that panels that are 'factory' or listed are constructed to handle larger voltages and to be series'ed together .. depending on your strategy of cell choice and tabbing wire that may not be the best approach .. im not an expert i want to emphasize that .. but 'weany' tab wire on 'half' cells i dont think is going to work out to well on these serious professional type systems and setups that are being recommended to you ... my personal strategy is more panels .. i can pump them out for under 200$ so theyre going all parallel into 12V .. to me it like 'oh waaahh' im getting alittle voltage drop and its not ideal .. so what is my response .. i can drop 4 more panels on easily and it will overcome it ... the main thing is make sure the supply side to the inverter has huge wire and where you tie all your panels together (im using a box inside my garage and put 2 marine buss bars with 12 contacts each) and the wire going to charge has got to be a serious gauge .. just thoughts ..your panels may be great and fine hooking up like a professionally made setup .. i kinda doubt it .. but maybe .. like i said im not the expert here and just about at the same stage you are ...
.. i have the coleman controller to .. i also have individual 20A switches so i can cut off each panel to get the voltage i want depending on the bank state of charge .. on the coleman my plan is to use 2 12V hot water heating elements (600W each) and rig them into a secondary hot water heater as a diversion load on the panels ..
... just my thought, not trying to contradict anyone or act like i know what im talking about .. your panel construction though i think could possibly be an issue before you invest in all this hardware to try to make it a professional grade system .. make more panels and tie them together heheh .. thats the trick to making the system cheap imo .. get enough of the so-so panels hooked in parallel and i guarantee theres going to be enough potential on the bank to charge it .. its all a matter of controlling it .. hence my switch approach on each panel .. all manual .. the coleman is a backup in case i fall asleep or something so the batts dont boil into goo ..
.. also, im using a 2500 watt true sine inverter .. it will run a full size skill saw, drill press, refrig ect no problem .. i wouldnt want less, in fact i plan on getting a second and tieing 1 inverter to each leg on my panel box so i can divvy up things .. i have 8 golfcart batts, everything wired in 4/0 , 12 150W panels made of 36 6X6 cells.. it works, so far im satisfied