Charge controllers in parallel configuration.

[Mike90250]

i sent you a email on your home page. this is kinda to repay you for your time.

no need, posting here keeps me off the streets...

[cyberfast]

I used 8 guage stranded copper wire to connect the pannels together on the trailer. do you think that is enough? also what size should i use running to my house where the battery is. the wire would be 30 feet long?

[Mike90250]

I used 8 guage stranded copper wire to connect the pannels together on the trailer. do you think that is enough? also what size should i use running to my house where the battery is. the wire would be 30 feet long?

10 panels, 100W each. That's 1,000 watts, but you know that already.
Feeding 1,000W into a 12V battery, is 83 amps. That's a lot. Midnight Solar makes a pretty high power controller, the Classic 150, which can handle 93 amps, when fed 110 - 120VDC from the panels.

http://www.midnitesolar.com/images/classicFrontPage/graphs.php

Otherwise, you will need 2 charge controllers to manage the battery charging for 12V, or only use part of the array.
Or, if you move your battery voltage to 24, or 48V, you can easily charge
24V, 100 ah = 2400wh ( 2, 12V, 100 ah batteries in series ) [too small, by just a small amount]
24V, 200 ah = 4800wh ( 4, 6V, 200 ah batteries in series ) [3 jumpers]
48V, 100 ah = 4800wh ( 4, 12V,100 ah batteries in series ) [3 jumpers] **
48V, 200 ah = 9600wh ( 8, 6V, 200 ah batteries in series ) (can take full charge form panels, several cloudy days with out needing to recharge, but also cost's the most.)

** Of the battery options, #3, is very simple, with 4, 12V batteries in series, and it stores enough power to meet your needs (still 1320wh?), and would only need 3 interconnect jumpers, and you could use "big box store" (or 4 of the interstate batteries you got)
I don't like to recommend putting batteries in parallel (see my links in the earlier posts)
1,000W of panel, can generate too much amps at 24V, to give long life to the batteries
1,000W @
24V = 41A
48V = 21A
For batteries, you generally don't want to go much over 13% of the AH rating (if battery is 100AH max charge should be about 13A) That would mean dropping some of the panels out of the array, if you don't go with the 48V, 200 ah = 9600wh. (8, 6V, 200 ah) battery, or you stand a chance of heating the batteries too much from the extra charge current.

So, for practical purposes, 12V is out, as it's just too many amps to manage easily. You would need to plan for a 24 or 48V system, and since you will need to purchase a new inverter, and a MPPT charge controller, to save on copper wire costs, I'd suggest the 9600wh configuration , using 6v, 200ah golf cart batteries. (larger batteries get pretty heavy moving them around)

Now, on to the wire size.
Since you have 18V panels, we'd need 5 of them in series (110V DC open circuit in the mornings)
I'm assuming 48V battery configuration. Setup simulator here Using your panels VOC spec of 21.8V and punching into the string calculator on the classic, for -10F (20 year record low temp for your area), it looks kike we will NOT exceed [132v] the Low Temp Voltage (limit 150V). There is also a simple wire gauge calculator, where I entered 40' of distance from panels to controller (there is wire in the trailer, I'm assuming 10', then the 30' run to the house.) Midnight calculates that only 10Ga wire is needed - giving .08% drop, which is great - no need to go for the expense of #8.

After the wire hits the MPPT Charge controller, it is down-converted to 48V @ 21A, so 6 gauge wire would be fine from the controller output, for the few feet to the batteries.

Wire - stranded or solid, does not really matter, stranded is easier to move/bend, and if you will be moving the trailer around, stranded is MUCH less resistant to breakage from flexing.


Using the Voltage Drop Calculator spreadsheet, and the numbers from above, I get
40' run to controller = 1.5%
5' controller to batteries = 1.8% #6ga OR 1.7% #4 wire
The Classic's DC connector will take up to #4 wire, but #6 would be fine for the batteries. #8 would be too small, and cause voltage drop which would mess up the charge sense.

So, #10 from array, wired 5 panels in series , 2 strings in parallel,
#4 or #6 from controller to batteries.

Hope this helps. Mike

[Sunking]

If you are above 500 panel watts you need to start thinking 24 volt battery.

[cyberfast]

mike thanks that helps allot. i had 2 spool of 1000' of #8 just laying around. here's another ? if i go with to big of a wire does that harm anything? also i have 2 spools of #6 i think there around 500 feet. i have to use my tractor to move them around. one ? if i change to 24 or 48 volt configuration how would i bring the system back to 12 volts? (just cause most inverters and my led system are 12 volts) does a good mppt controller have a 12 output?

[Mike90250]

If you insist on sticking with 12V, you will need to buy 2, expensive charge controllers, if you want to utilize all the panels you have.

Better to go with 48V and just buy 1 controller, and one inverter, and have 4x the storage a 12V system would have.

Larger wire never hurt, as long as it can fit into the terminals. The Classic controller can handle up to #4, I checked it's manual.

[Bala]

if i change to 24 or 48 volt configuration how would i bring the system back to 12 volts?

48 to 12 reducer, a quick google found this web page

http://www.powerstream.com/dcdc.htm

[cyberfast]

Mike i am not insisting on sticking with 12V system. Only reason i keep mentioning 12V is cause my whole led lighting system is 12V sure i can probably wire the in series but the problem with that is then i have to use multiple sets at a time vs one at a time. also i have a few diaphram water pumps i use for circulating water around that are 12 volts. My 12 volt system pulls about 4 amps with everything on. I really think the best set up for my system would be 24v. (just cause i have 10 panel and i can not create 48v without having 12) If use a reducer (like the reply above) to bring it back to 12 volts wouldn't i be losing allot of power?

[Mike90250]

.... (just cause i have 10 panel and i can not create 48v without having 12) If use a reducer (like the reply above) to bring it back to 12 volts wouldn't i be losing allot of power?

1) With the 10 panels you have, you can easily charge a medium size, 48V battery bank, using 1 MPPT charge controller.
48V, 100 ah = 4800wh storage ( 4, 12V, 100 ah batteries in series )
Your array produces 1,000 watts, which, as has been said several times before, is not suitable for a 12V battery bank, it's a rather large array, and will easily boil several batteries.

2) if you wire 5 panels in series, that will produce 110VDC, which after your long wire run to the controller/batteries, is down-converted to 48V for charging. Easy Peasy. I did all the calculations for loss and wire size for you. (Post # 18)

3) the 48V down-converter here http://www.powerstream.com/dc48-12.htm will do a fine and 85% efficient job of down-converteting 48V to 12V, with 12amps output. your 12V stuff works.
I have done this myself, for a commercial art project, where the artist used a large 48V battery bank, to power a large array of 12V led lighting. Commercial wall warts and inverters kept blowing strings of LED's, and I developed a highly efficient (>90%) series of "modules" based on a commercial DC-DC board. He has enough energy storage for several days, can be recharged in a couple of hours with a generator, or solar power array built into the trailer rig. ( several photos and vids exist of it, search for "The Grotto and Garden of Manifest Destiny") Very much like what you are asking for.

[cyberfast]

what do you do to ground your system? example a inverter wants the chaise to be grounded. do you ground it to the house ground or to a separate ground? (a rod staked into the earth ground) also should a ground be connected to the negative side of the battery bank? i know this seems like a silly ? but what is the right way to do this ? i live in a area that has allot of thunderstorms. been hit twice last year with my first small solar system. it didn't hurt the panels but blew out some 12 volt products. i don't want to make the same mistake with my new system. thank you again for your help.

[hillmanie]

Max input voltage

Here I go again - this caught my eye ....
1. What is 'Maximum System voltage' quoted in charge controller specs?
2. I note here the reference to 'Series/parallel' connection - help me here- does it mean that the solar panel voltage goes to the 1st controller Input with the Output of the 1st controller connected to the Input of the 2nd contr. How is the final voltage output connected to the battery?
Trying to figure how to wire the two controllers together........
Many thanks. Hope you can unravel this muddled message.

You need enough solar to recharge your battery in one day, under most conditions. When a battery sits low for 2 days, it begins to sulfate. A sulfated battery is trash. 1,000w of panel will BBQ your single battery, in fact, even 400w is too much for the 1 battery. If you are draining the battery so far with the TV, that it takes 2 days w/400w of panels to recharge, you have likely damaged the battery already.

If you use 12V, you will need to get an 80A charge controller, if you raise your battery system to 24V, []and wire your panels in series/parallel, you could use a 45a controller.

Solar is not at all like a car or truck where you can just throw parts together and come up with a dune buggy. The electronic components have design limits, that you can't just slap parts together and expect it to work reliably, for a long time. Generally, each system needs to be purpose built to match the loads.[/QUOTE]

[James1079]

sorry to hijack I am setting up a new solar system and would like to know where to post my questions I can't find how to start a new thread and in what category thanks

[J.P.M.]

sorry to hijack I am setting up a new solar system and would like to know where to post my questions I can't find how to start a new thread and in what category thanks

See the thread for all new members.

[James1079]

thank you I found where to post a new thread but I'm struggling to do this on the cell phone when I go to eBay to copy a link for the items I purchased I lose my messages when I come back maybe I'll try on the computer thank you JPM