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Old 04-18-2019, 06:08 PM
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I am going to upgrade my solar and just wanted to throw it up here before I install it. I want to make sure I've got it right. Any input?

I have 10 232AH 6v golf cart batteries @12vdc. I have 6 315 watt panels, Outback 80 CC, using Midnight Solar Combiner box. Is this too much power for this system?
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Old 04-19-2019, 06:33 AM
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10 - 6v batteries that you are going to wire as 12vDC would mean that you will have 5 pairs of batteries wired in series than all pairs wired in parallel. In series volts are additive therefore each pair of 6v 232ah batteries would make one 12v 232ah battery equivalent. In parallel the amps are additive so you have 1,160ah total in your battery bank.

Typically you want a minimum charge amperage of 10%, though more is better. So for your battery bank that would be about 100 amps. Your 6-315watt panels for a total watts of 1890 divided by 12 v = 157.5 amps, More than sufficient to keep the batteries charged depending on your load requirements.

I don't know the specs for your charge controller or your intended loading so I can't say anything about whether it is sufficient for your needs. Don't forget the size of wire needed for the various hookups you are planning. At 12vDC you are looking at some large cable to handle the amps.
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Old 04-19-2019, 09:08 AM
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I could be wrong, but I believe you might want to wire your array to a 24 volt nominal output, that would reduce your pv array wire size to the controller.


your array size is not too large for your batteries
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Old 04-19-2019, 09:29 AM
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I'll just chime in and say that for the past 2 1/2 years I've had a 1:5 ratio of panel wattage to battery-bank wattage, and it's worked very well. Specifically: I have four 12 volt 160 watt monocrystalline panels (a total of 640 watts), and I have a 3200 watt battery bank. And, my panel tilt isn't optimal for any season; if it were, presumably my system would work even better because I'd be getting more wattage out of the panels.
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Old 04-19-2019, 09:32 AM
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Quote:
Originally Posted by solar1 View Post
I could be wrong, but I believe you might want to wire your array to a 24 volt nominal output, that would reduce your pv array wire size to the controller.
While we don't know the exact details of his panels since each panel is rated at 315 watts they probably produce about 40v.

The Outback 80 amp Flexmax is rated for 1250 watts of panels maximum when hooked to a 12v battery bank so he has to much power for 1 controller on a 12v system. Some controllers clip the excess power, others burn out. I'm not sure what the Flexmax will do but either way he won't get full output from those 6 panels.

That's one of the real problems with running a 12v system. When using more than 1000 watts in panels you're much better off running a 24 or 48v battery bank and inverter.

And by running a 48v system he can use 8 of those batteries running a single string of batteries which is much better than the 5 strings of batteries he's planning to use.
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Old 04-20-2019, 12:16 AM
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Yes, A 24 or 48 volt system would be much better.
Have you already purchased your inverter?
Another possible option is to split your PV array into two separate arrays and add another Outback 80, but that would add cost. Better to put the money into a larger inverter if not already purchased.

I'm running a 2000 watt array to a 24 volt battery bank thru one Outback flex 80 with no problems. While not the best layout, It's been running continuously for over 9 years.
The charge controller/array breaker tripped only once when it had an exceptionally high output one winter day (reflected off snow/low temp added extra output my guess) but it was a slightly undersized breaker (70 amp trip).
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Old 04-20-2019, 09:29 AM
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Yep - looks like too much panel for 1 outback 80 charge controller running at 12V.

My system has the same charge controller set up for 48V. I have 8 batteries (6V 370AH Deka's) run in a string in series. 8 SolarWorld 280 mono panels. Still room for more panels with this configuration.
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Old 04-20-2019, 03:11 PM
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Thanks so much for all the input. In order to make this work, I think I have figured it out. Here are my thoughts. Since my interior lights, fridge, water pump are 12vdc I will make battery bank 48vdc. Use my current Outback 80. Use my current 1200 watt system and a 48vdc to 12vdc converter. Then all I have to buy would be the 48vdc/12vdc converter and 48vdc inverter for my 110ac needs. That saves me trouble and money. What say you?
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Old 04-20-2019, 03:24 PM
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Now that we know you have several 12 volt load such as the fridge, I see why you were going for the 12 volt system.

It's a tough call at this point.
I like the idea of 12 volt system for the fridge as such; not being dependent on the inverter is good, but the cost and use of the 48 to 12 volt converter is somewhat inefficient (power loss thru conversion). You might be close to the point with your size system to use dive in with both feet and go with a 120 vac fridge since you are planning on an inverter anyway.


Just a thought to ponder...a smaller indepentant 12 system for your 12 volt loads and the larger 48 volt system for the larger 120 vac loads.

The 12 volt could be considerened as your "backup" system to the 48volt inverter system.


I personally feel I'm on borrowed time with my system, as my Trace 4024 (old style) inverter has been running for 8 years+ without a hiccup......but, it cant run forever.

When it quits, I have a spare inverter to install, but then what. Maybe a separate 12 volt (without inverter) system as backup is a good idea for me also.
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Old 04-20-2019, 03:40 PM
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Quote:
Originally Posted by solar1 View Post
Now that we know you have several 12 volt load such as the fridge, I see why you were going for the 12 volt system.

It's a tough call at this point.
I like the idea of 12 volt system for the fridge as such; not being dependent on the inverter is good, but the cost and use of the 48 to 12 volt converter is somewhat inefficient (power loss thru conversion). You might be close to the point with your size system to use dive in with both feet and go with a 120 vac fridge since you are planning on an inverter anyway.


Just a thought to ponder...a smaller indepentant 12 system for your 12 volt loads and the larger 48 volt system for the larger 120 vac loads.

The 12 volt could be considerened as your "backup" system to the 48volt inverter system.


I personally feel I'm on borrowed time with my system, as my Trace 4024 (old style) inverter has been running for 8 years+ without a hiccup......but, it cant run forever.

When it quits, I have a spare inverter to install, but then what. Maybe a separate 12 volt (without inverter) system as backup is a good idea for me also.
Since my 12vdc load is so small, I will use this to power that. https://www.walmart.com/ip/DC-48V-St...verter&veh=sem

My power use @ 110ac is less than 500 watts and all I use is Satellite, TV, and HugesNet. Even if we watch TV until midnight, we still have plenty of power.
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Old 04-21-2019, 08:14 AM
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I see. I had figured your 12 volt DC loads to be greater as you mentioned the fridge, pump and lights.

As long as your total simultaneous DC loads are less than the capacity of that 48-12 converter, it appears it may work fine, even considering the conversion loss. Since you do have a fair amount of PV wattage, those losses may not really be an issue.

I might however make a suggestion; The converter you noted looks somewhat Chinese made. The price is low enough that you may consider buying two. You could place the spare in an faraday cage. The nature of these types of import electronics have a questionable reliability. That way you will be ready if one fails.


Added Note: I just took a closer look at the converter you linked from Walmart....the specs note that the unit is non-isolated.

Sometimes non-isolated units have a metal enclosure that is electrically common to one terminal of the input/output. In researching a few cheap import items (solar PV charge controllers) I found that they incorporated a POSITIVE + grounded metal case. This could potentially cause some issues if you are not aware of it. You may want to check this with a meter if you do purchase this unit.

Last edited by solar1; 04-21-2019 at 08:52 AM.. Reason: Added Note
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Old 04-21-2019, 09:56 PM
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Tough call on creating a mix of 2 systems as opposed to switching over to a whole new system. I would suggest keeping what has been working and adding on with the new system over time.

The price of panels has come down so much in the last 5 years that it is easy to overcome some efficiency loss throughout the system by getting extra panels... as long as your inverter/charge controller can handle it.

The biggest loads in our house are the refrig, freezer, and the water pump. Each of these are daily draws that add up. Everything else is either intermittent/optional use or a pretty low load in comparison. If you are happy with your 12v appliances, I'd find a way to keep using them. It can be expensive to start from scratch and pick up new energy efficient 110AC appliances.
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Old 04-22-2019, 09:42 AM
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Fepony - I am far from an expert being newer to solar, but I'm wondering why you don't just go all 110V? I did a lot of research and came to the conclusion that that was the way to go, particularly now that you can get really efficient fridges. And I also went 48V - (8) 6V sealed batteries. So far (after 1 yr) everything is working incredibly well!
A little re-wiring now and getting a new $500 fridge will save you a lot of money/time/trouble down the road, I would think.....
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Old 04-22-2019, 03:17 PM
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Quote:
Originally Posted by hoodoo View Post
Fepony - I am far from an expert being newer to solar, but I'm wondering why you don't just go all 110V? I did a lot of research and came to the conclusion that that was the way to go, particularly now that you can get really efficient fridges. And I also went 48V - (8) 6V sealed batteries. So far (after 1 yr) everything is working incredibly well!
A little re-wiring now and getting a new $500 fridge will save you a lot of money/time/trouble down the road, I would think.....
I agree with going with one 120vac system, as I did years ago.
The point I was making is that since fepony has already invested and wired for 12 volt DC in a small off grid system, he could keep that as a redundant system. Not much to fail with a passive 12 volt dc system other than his planned 48 to 12 converter and the PV charge controller which he needs either way.

Life is much easier with a single system for sure, but there is more expensive components to fail. the 12 volt could serve as a backup since he appears to be off grid.
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Old 06-17-2019, 04:39 PM
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I'd upgrade to 24 volts. Theoretically you should only need to swap fuses and the inverter. Most off grid DC appliances are dual voltage (12/24), you can use a voltage buck for your cheap road appliances if you use them. I'm not sure, it might be possible to use some of coffee pots etc. Eventually I will feel the pull to 48 volts but its siren song disturbs me, I don't feel like frying myself on a charging battery bank that can reach 60 volts. 24 is still touch safe and more common when it comes to components. I highly recommend a inverter/charger. You can pick up older trace inverters for under 500, even pure sine. Quality units if they ever fail, have them repaired. Magnum is a good second in quality. I have an exceltech MX unit I need to get rid of thats 12 volts, the power quality is better than the power grid, fit for medical equipment. Unfortunately not a inverter/charger.
I'm team midnite so I can't say much on charge controller. My house i bought came with an off grid solar system I am upgrading. It uses a flex controller. I am not a fan. The midnite can do more, is easier to navigate and has more features. If you do decide to join me on team midnite (TM!) I recommend the 200 over the 150. The slightly higher amperage of the 150 isn't as useful as the extra voltage ceiling on the 200, especially for wind or hydro. I run about 100 volts.
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