New system

[jlemke]

I have been searching around here looking for the right answers and just have not seem to come up with the correct ones. I have a off grid one room cabin that I use on the weekends year round. Currently have a 200w 12 volt solar setup that charges a 12 volt forklift battery. Pretty simple system that works great for what we need as far as lights, charging, & TV. Can get us through a cloudy weekend with minor monitoring. The plan is to build a little bit bigger cabin (24x24 with loft, looking for plans for that also but that's a different topic) and put in a bigger solar setup that can handle a fridge etc.

I have 4 x 320w (voc 40.1V, imp 9.79A) Renogy panels that I want to be the main setup. I am stuck between keeping it 12 volt or going to 24v. Been looking at Victron but not sure how to size it. Go 24v- panels 2s,2p?? Do I run one bigger controller or go with two smaller controllers and split the array?

Next Lithium sounds great for more discharge and I can afford it but the cabin is not always heated. (central WI). Would lead acid or AGM make more sense for this low used cabin?

I have been researching this for awhile now and am really looking for thoughts. I am fairly knowledgeable and enjoyed setting up the first small system and learning. I want it to be user friendly but also high tech if I need the stats to look back at.

What do you guys have for me. Ask me Questions. Point me towards other forum treads. Looking forward to feedback. Thanks

 

[Bobert]

I have been searching around here looking for the right answers and just have not seem to come up with the correct ones. I have a off grid one room cabin that I use on the weekends year round. Currently have a 200w 12 volt solar setup that charges a 12 volt forklift battery. Pretty simple system that works great for what we need as far as lights, charging, & TV. Can get us through a cloudy weekend with minor monitoring. The plan is to build a little bit bigger cabin (24x24 with loft, looking for plans for that also but that's a different topic) and put in a bigger solar setup that can handle a fridge etc.

I have 4 x 320w (voc 40.1V, imp 9.79A) Renogy panels that I want to be the main setup. I am stuck between keeping it 12 volt or going to 24v. Been looking at Victron but not sure how to size it. Go 24v- panels 2s,2p?? Do I run one bigger controller or go with two smaller controllers and split the array?

Next Lithium sounds great for more discharge and I can afford it but the cabin is not always heated. (central WI). Would lead acid or AGM make more sense for this low used cabin?

I have been researching this for awhile now and am really looking for thoughts. I am fairly knowledgeable and enjoyed setting up the first small system and learning. I want it to be user friendly but also high tech if I need the stats to look back at.

What do you guys have for me. Ask me Questions. Point me towards other forum treads. Looking forward to feedback. Thanks

I am no expert myself but I do have experience with flooded lead acid batteries and cheap lifepo4 batteries in the same application and in cold temperatures. If you have lead acid batteries in a unsupervised location you run the risk of having them discharge and freeze destroying the batteries and surrounding metals if they break open and then thaw. Agm won’t break open under these circumstances but will still need to be thawed in order to be used. If you use lifepo4 without low temperature protection you run the risk of destroying the batteries if you don’t make sure they have an internal temperature of over 26 degrees before you charge them. Flooded lead acid should not be used inside a building because they vent explosive and corrosive gasses during normal use. If you use them in an unheated space their performance will drop exponentially as they get colder. Lifepo4 does much better in the cold until it quits altogether. If it was me I would use lifepo4 and find a means to warm it up if I needed to use it during winter. Agm performs better than fla but a cheap lifepo4 is nearly the same price as agm.

 

[BentleyJ]

I have 4 x 320w (voc 40.1V, imp 9.79A) Renogy panels that I want to be the main setup. I am stuck between keeping it 12 volt or going to 24v. Been looking at Victron but not sure how to size it. Go 24v- panels 2s,2p?? Do I run one bigger controller or go with two smaller controllers and split the array?

Take a look at MPP Solar, Growatt, SunGold or AIMS Inverters. I would recommend you find a good All-In-One Inverter/Charger with built in MPPT solar charge controller that can accept up to 250V. Then you can simply series your 4 panels and have only 2 solar input wires to connect. Generally its better to go with the higher voltage batteries, 24 or 48V because it keeps the DC current lower, smaller wire, fuses or breakers Etc. Much more manageable.

 

[MichaelK]

I would abandon 12V in a heartbeat. The electronics you can buy at 24V are more sophisticated than anything available for 12V. The big difference is the amperage levels you have to deal with. With 1200W of panels, you'd be talking about close to 100A of current flowing. Go to 24V and you halve that to 50A, and just 25A at 48V.

I think the outgassing of lead-acid batteries gets far overblown here on this site. I kept the flooded batteries of my first system in the living room for years with no ill effects.

Magnum, Outback, and Schneider make the highest quality inverters appropriate for cabin/whole house applications.

 

[jlemke]

Take a look at MPP Solar, Growatt, SunGold or AIMS Inverters. I would recommend you find a good All-In-One Inverter/Charger with built in MPPT solar charge controller that can accept up to 250V. Then you can simply series your 4 panels and have only 2 solar input wires to connect. Generally its better to go with the higher voltage batteries, 24 or 48V because it keeps the DC current lower, smaller wire, fuses or breakers Etc. Much more manageable.

I was leaning towards 24 volt. Would it make sense though to go all in series which would give me 160v and less than 10A? Or would 2S2P be a better option at 80v and just under 20A? I have a decent 12volt 3000w pure sine wave invertor now but don't necessarily need to run that one.

 

[Bobert]

I would abandon 12V in a heartbeat. The electronics you can buy at 24V are more sophisticated than anything available for 12V. The big difference is the amperage levels you have to deal with. With 1200W of panels, you'd be talking about close to 100A of current flowing. Go to 24V and you halve that to 50A, and just 25A at 48V.

I think the outgassing of lead-acid batteries gets far overblown here on this site. I kept the flooded batteries of my first system in the living room for years with no ill effects.

Magnum, Outback, and Schneider make the highest quality inverters appropriate for cabin/whole house applications.

This is a bit off topic since fla was never a consideration for this system I only referred to them as they are the real life experience I have. Fla is a inherently dangerous battery it is filled with extremely corrosive acid. I have replaced a lot of clothes and regrown a lot of skin eaten by sulfuric acid that somehow migrated out of the caps. I have seen batteries boiling so rapidly that the acid was drizzling upwards out of the caps even though the battery was being charged at a low rate of charge because of a slightly shorted cell. My cousin had to go to the hospital and an acquaintance of my family was hospitalized because of exploding batteries. I wasn’t there when it happened but if I remember correctly one of my uncles narrowly avoided permanent eye injuries only because he new exactly what to do when a battery exploded in his face. My father almost died because of a structural failure caused by an off gassing/leaking battery. I am not afraid of fla batteries but I respect them and will not charge them in my house unless it is an emergency.

 

[jlemke]

This is a bit off topic since fla was never a consideration for this system I only referred to them as they are the real life experience I have. Fla is a inherently dangerous battery it is filled with extremely corrosive acid. I have replaced a lot of clothes and regrown a lot of skin eaten by sulfuric acid that somehow migrated out of the caps. I have seen batteries boiling so rapidly that the acid was drizzling upwards out of the caps even though the battery was being charged at a low rate of charge because of a slightly shorted cell. My cousin had to go to the hospital and an acquaintance of my family was hospitalized because of exploding batteries. I wasn’t there when it happened but if I remember correctly one of my uncles narrowly avoided permanent eye injuries only because he new exactly what to do when a battery exploded in his face. My father almost died because of a structural failure caused by an off gassing/leaking battery. I am not afraid of fla batteries but I respect them and will not charge them in my house unless it is an emergency.

My current setup with the FLA is in a out shed that is behind my cabin. If I were to go with FLA I would probably keep them out of the cabin and the rest of the components inside. If I went with Lifepo4 everything would be inside the cabin.

 

[Supervstech]

I was leaning towards 24 volt. Would it make sense though to go all in series which would give me 160v and less than 10A? Or would 2S2P be a better option at 80v and just under 20A? I have a decent 12volt 3000w pure sine wave invertor now but don't necessarily need to run that one.

Battery voltage is the important factor, not the PV voltage.

PV voltage is important for wire sizing, just make sure your SCC can handle it.

 

[CamoGreg]

I was leaning towards 24 volt. Would it make sense though to go all in series which would give me 160v and less than 10A? Or would 2S2P be a better option at 80v and just under 20A? I have a decent 12volt 3000w pure sine wave invertor now but don't necessarily need to run that one

24V would allow for easier expansion later if you choose.

I'm a Victron fan but see they're main strong point in mobile applications like boats and RVs where shore power is often available. Power Assist and multiple AC inputs/outputs is great in those applications but it adds costs unnecessarily if not needed.

All 4 in series or 2s2p would work either way. 160V pv input is easily handled by most of the MPP or Growatt AIO. Going with separate SCC, 2s2p would allow for a much cheaper SCC.

 

[12VoltInstalls]

Do I run one bigger controller or go with two smaller controllers and split the array?

Same controller, still split the array

am stuck between keeping it 12 volt or going to 24v.

if you don’t need more than 1500–2000W I’d stay 12V. So many low voltage lighting options - and RV stuff - that’s 12V

bigger solar setup that can handle a fridge

i ran a smaller (5CF) fridge since about a year ago on a 1200W inverter. All spring and summer w/ 400W of panels, didn’t go 800W ‘til winter Dark Months

A newer intermediate sized fridge could run fine on 600-800W with good sun, 1000W+ would be better and your over 1200W

Would lead acid or AGM make more sense for this low used cabin?

Maybe but not necessarily. If you want to stay online and powered (i.e. charging) in below freezing weather that nixes lithium unless they are above 32*F
I use lead acid. Works fine as long as you understand lead battery limits and benefits.

Lithium has a number of pluses and the costs are down quite a lot for them.

I started with lead acid due to budget. As it turned out the ability to charge at -15*F was useful this past winter, too. They’re still going strong several years later. Lead batteries may not be best for you.

FWIW I’ve never seen AGM batteries last as well as flooded lead acid when cycled s lot. More money and less life doesn’t compute for me. If you’re not going to use lithium there’s much better choices than AGM.

It’s hard to argue against lithium batteries- I don’t argue against them but I do know how lead works and I accept those characteristics. In a few situations they’re desirable. So don’t dismiss lithium out of hand and also be aware that lead is an option.
Lead might not be the right option for your situation. If low temp charging is important that’s likely the main reason to use lead acid for a small system. Bigger systems support lithium battery heating overhead less noticeably. People who think you can simply insulate a battery and have it stay 40*F at -20F and 20mph wind don’t live in those environments LOL

 

[Rednecktek]

People who think you can simply insulate a battery and have it stay 40*F at -20F and 20mph wind don’t live in those environments LOL

Don't you just insulate it in an electric blanket powered by a second solar array running FLA batteries for the cold?

 

[12VoltInstalls]

Don't you just insulate it in an electric blanket powered by a second solar array running FLA batteries for the cold?

Absolutely. And it helps if you use a shaggywool bispherium insolence circuit rated for gibbous lunar uptake wattage to help balance the shorter sun days.

 

[jlemke]

All 4 in series or 2s2p would work either way. 160V pv input is easily handled by most of the MPP or Growatt AIO. Going with separate SCC, 2s2p would allow for a much cheaper SCC

Most of the AIO's that I am finding including the Growatt are a max of 145v PV input. Is there something I am missing?

 

[CamoGreg]

Most of the AIO's that I am finding including the Growatt are a max of 145v PV input. Is there something I am missing?

Yes. I am mistaken. I've only paid attention to larger 48V systems that are 250V and up.
24V appears to be more in line with 145V -160v range you mentioned.