Off-grid solar charge controllers

[joe shepherd]

Can anyone tell me what size wire to run from a 30 amp charge controller, 75-100 feet, to the house?
reason is I want to keep my bat. an controller in the barn. The panels are on the roof of the barn for the most sun.
Thanks, Joe

[conntaxman]

wire size

Can anyone tell me what size wire to run from a 30 amp charge controller, 75-100 feet, to the house?
reason is I want to keep my bat. an controller in the barn. The panels are on the roof of the barn for the most sun.
Thanks, Joe

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Their is a chart I used, and found it on google. I have 100ft. and I used #8 stranded.
John

[Naptown]

Can anyone tell me what size wire to run from a 30 amp charge controller, 75-100 feet, to the house?
reason is I want to keep my bat. an controller in the barn. The panels are on the roof of the barn for the most sun.
Thanks, Joe

If the batteries panels and charge controller are all in and on the barn what will run to the house?

[joe shepherd]

Thanks John,
Does it really matter if its hard wire or stranded?
I'm not using a converter either, so #8 would be the wire for my lights an small fridge?

[joe shepherd]

I want to run the wire from the barn to the house. Its only a small system for a small fridge an maybe a few small things. I'mm gonna add on a little at a time.

[Mike90250]

There is a great link to a spreadsheet caculator in my .sig

it was desigend just for solar PV and batteries.

stranded wire is mre flexible, solid belongs only in condouit so it cannot flex. (if it flexes much, it will break)

[minijason9]

Solar system

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[Sunking]

Well you did not give the voltage or current so I assume 12 volt system running the full 30 amps will require #2 AWG to keep voltage drop to 2% or less.

[paradiseisle]

Suggest a controller for my off grid system, (10) REC 245 watt panels, Thanks

Hi John,
I believe you and I are correct in most cases, unless you are talking about high latitude locations where it is very cool for substantial parts of the year. Then MPPT may be worth the cost. Although I am a bit wary of why an Outback 60 amp MPPT contoller costs twice as much as a Morningstar 60 Amp PWM controller and also that the Outback has two years warranty against the Morningstar's 5 year warranty. Is there something inherently less reliable about MPPT controllers? I would be interested in hearing about people's experience with MPPT controllers.

Jason the moderator has asked me to start a new thread, since this charge controller thing is only slightly related to LiFePo batteries. So I will do that by posting my original piece about the difference between charge controllers and the economics of their use. Derek disagreed with me which is fine because what we should all care about here is not who is right but what is factually correct. Without facts, we can make expensive errors and then people can say, See? I told you solar doesn't work! Gr-r-r!! that gets me mad since I have been living off-grid with all the amenities for decades and never had a power outage or burned out a light bulb, so I know it is superior to grid power.

Suggest a controller for my off grid system, (10) REC 245 watt panels, Thanks Paradise Isle, My cabin is in the Sierra foothills at 3,000 feet, panels at full southern exposure, sun prevailing 6-8 hours daily year round.

[Sunking]

Suggest a controller for my off grid system, (10) REC 245 watt panels

What battery voltage are you running? I assume 48 volts because at 2450 watts no one controller will work. At 48 volts will require a minimum 60 amp Model like Morning Star Tri-Star 60 Amp MPPT model. Bu tI suggest a 80 amp model so you can expand up to 4000 watts input if needed later on. Best is Outback FM80 and the very best is Mignight Solar 150 Classic.

My cabin is in the Sierra foothills at 3,000 feet, panels at full southern exposure, sun prevailing 6-8 hours daily year round.

No exactly, the hours of daylight have little to do with Sun Hours. Winter you are lucky to get 3 hours.

[paradiseisle]

Battery Plan

What battery voltage are you running? I assume 48 volts because at 2450 watts no one controller will work. At 48 volts will require a minimum 60 amp Model like Morning Star Tri-Star 60 Amp MPPT model. Bu tI suggest a 80 amp model so you can expand up to 4000 watts input if needed later on. Best is Outback FM80 and the very best is Mignight Solar 150 Classic.

No exactly, the hours of daylight have little to do with Sun Hours. Winter you are lucky to get 3 hours.

I have yet to develop a battery plan, I was told to purchase enough deep cell 6 volt batteries to hook them together in series to develop a 24 volt system. I have a considerable supply of 6 volt 50 amp hour batteries and can renew them very cost efficient. Is this a bad idea?

[Sunking]

I have yet to develop a battery plan, I was told to purchase enough deep cell 6 volt batteries to hook them together in series to develop a 24 volt system. I have a considerable supply of 6 volt 50 amp hour batteries and can renew them very cost efficient. Is this a bad idea?

Yep it is, sorry.

Here is the deal. With a 80 amp MPPTcharge controller the max panel wattage is roughly

1000 watts @ 12 volts
2000 watts @ 24 volts
4000 watts @ 48 volts

You have 2450 watts.

OK with 2450 watts will produce roughly 50 amps of charge current. The minimum size Flooded Lead Acid battery you can run with 50 amps of charge current is 400 Amp Hours. So for a 6 volt battery you are looking at 8 batteries something like a Trojan LR16RE-B or a Rolls S-530 battery.

Ideal size is a 500 to 550 AH battery which pushes you into the 4 volt batteries so you would need 12 of something like a Rolls 4CS17PS battery.

[paradiseisle]

Yep it is, sorry.

Here is the deal. With a 80 amp MPPTcharge controller the max panel wattage is roughly

1000 watts @ 12 volts
2000 watts @ 24 volts
4000 watts @ 48 volts

You have 2450 watts.

OK with 2450 watts will produce roughly 50 amps of charge current. The minimum size Flooded Lead Acid battery you can run with 50 amps of charge current is 400 Amp Hours. So for a 6 volt battery you are looking at 8 batteries something like a Trojan LR16RE-B or a Rolls S-530 battery.

Ideal size is a 500 to 550 AH battery which pushes you into the 4 volt batteries so you would need 12 of something like a Rolls 4CS17PS battery.

Thank you for the heads up, I will research cost and availability of some of the batteries you suggested.

[paradiseisle]

Planing my Battery plan

I have decided to go with a 24 volt battery plan, my panels are 165 feet away from the controller and inverter and I know there will be a power loss with that long a run. I have yet to decide on a controller but am looking at the Outback Flex max 80 and a MidNight Solar Classic. Checking to see if they are over load or sufficient for what I need. Any info on what gauge wire to use on the 165 foot run would also be very helpful. A friend has 250 feet of 6 gauge he will sell me at a reduced price, but I don't want to buy it if it is not the right size.

[Sunking]

I have decided to go with a 24 volt battery plan, my panels are 165 feet away from the controller

OK then that demands a Midnite Solar Classic 250 unit as it will allow you to run up to 274 Volts Voc panel voltage.