Need some power at the cabin

Those big heavy banks of individual cells are no longer in my possession. I knew they would last for 100 years with little maintenance. Unfortunately the forklifts were hauled off and scrapped without my knowledge. So they really are gone....<Insert very sad emoji here>

Here's a company I've purchased from in the past. They basicly sell everything. I bought both my Schneider inverters from them.

Check out their Conext inverters. They make both 24 and 48V models. These are serious inverters designed to be hard-wired to a whole-house electric panel. I have a 4000W unit running my workshop. I also have a XM6848 inverter for the cabin. It has enough ummph to run my 240V well pump.

The Edison cells caught my attention. They sound fantastic. Unfortunately, to replace my 24volt 400a/h FLA bank, that cost a bit over $1000, would cost me $8000+.

Not terribly cost effective. If I win the lottery I will definitely be looking closer at the Edison cells.

Edison cells have 2 drawbacks (just 2)
1) low charge efficiency, only 70% compared to higher for any other battery.
2) the electrolyte gets slowly poisoned by Co2 in the atmosphere, and has to be drained and replaced about every 10 years

I can think of a couple more:
They have a self discharge rate of 1% per day
They produce a lot of hydrogen.

The 1% self discharge is only meaningful for un-attended systems. If you are charging daily it's a non issue

Hydrogen production is not a bad thing, but it is a byproduct of the low recharge efficiency as water is electrolized into gas

The are Freeze Proof at any state of charge, except in ultra severe environments, where humans are not likely to live for very long

I had considered them because they're ~indestructible.... but then I remembered the time-value of money. Instead of paying $15k for 20kWh of batteries that last forever I can buy 40kWh of premium PbSO4 batteries for $5k that will 'only' last 8 years only use ~50% and invest the $10k difference. In 8 years when the batteries die I'll have ~$20k and can spend another ~$5k on more batteries...

I picked up 4 more panels and ready to install everything. So far that is 2) 300 watt panels and 4) 280 watt panels. Series in three sets and parallel them. That should give me 48 volts at 860 watts. Then set up the 4 12 volt battery bank series parallel for 24 volts. That keeps me well under the max for the 30 amp control charger. This allows me to use for the time, a 24 volt dual conversion online UPS for inverter. Output is 670 watts. I also have two pole breakers for everything. This should get me thru this winter and reduce reliance on generators for lighting and very small load conveniences. I am only working out there two or three days a week.

Is there anything I should be aware of or concerned about when wiring everything together? Just want to keep from burning my cabin down to the ground. So far everything I have found on this site has been straight forward and reliable. I havent seen that on many forums. I would like to thank everyone for their advice and help.

So for the last couple of months everything has been working great. The 30 amp mppt control charger has been working as advertised. It is well built but like most things is third world. I have learned a lot watching display how it charges the battery bank. Originally I had the four 280 watt panels put up. But the very first night back to civilization I found some much needed materials to finish the roof, so two of the panels came back down. Even with just two remaining panels in use, I have not even been able to drain the 24 volt battery bank below 25.2 volts. Using lights working late into the night, there is little drop in voltage. Running a squirrel cage fan to remove sanding dust, a Rigid orbital sander to prepare the floors for a finish, laptop to post here, and all the led lights to look like a normal house after dark has been working great. The old UPS has given no trouble as a temporary inverter. It does seem to consume some power tho. Try not to leave it running unless needed.

I need to fabricate some mounts to hang all six of the panels permanently on roof now. Also have a 48 volt inverter on the way. A couple of questions tho.

Can I mix the panels in series? I have two 300 watt and four 280 watt panels. Instead of wiring each pair in series then parallel to controller....Is it feasible to connect two of the 280 watts in series with one of the 300 watt x 2 and parallel them at a higher voltage? The control charger is good to 160 voc from panels, and within the recommended range for 48 volt battery bank.

This would give me ~37 from each panel times 3 at less than 120 volts output. But keep well below the max 30 amp rating at roughly 16A.

I have a lot of shade that cant be altered without cutting 100 year old oaks down. So none of the panels usually get complete sunlight thru much of the day. As summer approaches this will definitely improve.

Does this sound doable?

As long as the current though the panels is roughly the same (<10%) you shouldn't lose much performance mixing them... just make sure you're not exceeding the open circuit voltage of your Charge controller. You might be better off with 3 strings in parallel depending on your shading situation... might take some experimenting. If 1 panel is shaded the voltage of that string may dip enough that the other two panels will no longer be able to push any current so you lose 50% of your production. With 3 parallel strings you would only lose 33% with 1 panel shaded.

Its been a while since everything went together at my cabin. With every ones help here, i cant complain about any of it. Originally I chose retired storage batteries for my bank. Four monster agm's that weight 104 pound a piece. They were replaced at some big company with UPS. These are changed out every 5 years regardless. I bought them at $60 a piece. When they finally go bad, I sell them back for scrap at $25 a piece. So out of pocket is very minor.

Currently these batteries check out at less than 2% sulfating. Same as when I picked them up a few years ago. I am sticking with them, now that my learning curve is not so steep. They are now 7 years and no signs of failing at all.

I found out real quick something I dont think some have realized. Or maybe I am still clueless. If I dont put a high load on the batteries, voltage will almost never drop. So at night I have very minimum amount of usage. In the morning only a short time to top them off.

During the day I can use them like anywhere else. Just so long as I dont pull over a few hundred watts during peak hours. They dont drop. The bank never falls below 50.2 volts anytime after the sun goes down. I figured out by doubling my battery bank, night time usage could become moderate. Instead of a high load shared between only four batteries, that is cut in half by doubling. Still with enough panels I already have to keep them full all the time.

As my cabin nears completion, the battery bank will finally get doubled. Most minor amp draw usage will be all solar. Everything else from the grid.

Another thing I see with the batteries. All four of them will charge full at different voltages. Doesnt matter if I charge separately of as a bank. When they are full that is where they stop. Each battery has its own voltage and doesnt affect the others. Open voltage may be high as 13.1-2, but after stabilizing for a day they all fall around 12.4-8. All four are different, but very close to each other.

Again thanks for your continued help with my learning experience. I am in the dark about most of it, but the lights are still on.«--(See what I did there?)

I had one of these storage batteries die today. It is only charging to 10.9 volts. My 48 volt bank never dropped below 50.6 volts thru the night. Today I saw it at 48.9 volts. Two of the batteries are fine and still showing right at 12.8 volts, the other one at 12.6 volts. These older ones were really good when I picked them up a couple of years ago. Last year I picked up the two others. They had been sitting for a while. They were down to 12.4 volts at the time. I charged them up but still would not stay above 12.6 volts. This bad one is one of these.

The older batteries still check less than 2% sulfating and charge up and hold at 12.8 volts. The one bad battery must have a bad cell. Even with the lower voltage it still doesnt drop way down like I would have thought after loading very much. Just my total voltage is down that amount. I guess its time to swap it out with another one. This time I am going thru the whole pallet full of them and find another one that checks out like the first two.

Been a while since I had any problems with the solar array. All this time I had been using AGM data storage batteries. Rated at 123 amp hours. The first set of four finally bit the dust approaching 9 years old. So for the $240 worth of batteries, they lasted nearly four years of my use, averaging $60 a year in cost. Not bad overall. I replaced 3 of them with new surplus of the same size and type. Today they are still at 100% and holding strong. The fourth battery was new in 2014. It died last September.

A dead cell is my diagnosis. The nominal 12.8 volts just dropped to 11.9. I nursed it along from last September until two weeks ago. Except for lower voltage readings it still held out functional. Last month I picked up some telecom suitcase batteries, These are bigger and heavier at 131 pounds and 180 amp hours. I like the size and convenience of them, but informed they may not perform as well as I am hoping. They are cheaper than those data storage batteries. But if these dont carry the weight for very long, I can cash out and recoup 1/2 my investment,

Another option I have considered is those large, like huge single cell batteries for forklifts. These only produce 2 volts each. Right now the cost by scrap weight and actual weight to move around is a big hinderance. I would need 24 of them. But think they would more than satisfy and expand my needs for a long time. These must weigh 150 pounds each.

I can purchase a 36 volt set of them for really cheap, considering, but would not do so much good since everything is setup at 48 volts. Or finding 6 additional cells. So holding off on this until I am in a more permanent position to move on something like this.

The sealed suitcase telecom batteries may be a step backwards. I was told they have a tendency of drying out without much chance of servicing. They are supposed to have about a 12 year life expectancy. So still have some time to confirm if they will work well enough for a few more years of service. They do not charge up as high like the new replacement data storage batteries. I have not yet tried to drain them down to see how long they will last at night.

Last summer I added a chest freezer to the cabin, giving me a fridge of sorts. Set up on a timer to run during peak hours. It stays on for about 3 hours and is adjusted close to the warmest setting. It will just keep 6 one gallon jugs of water frozen in the bottom. For rest of the day, everything stays cold, just like the ice chest I used to deal with coming down here. So for off-grid I am getting by when out at the cabin.

I was considering doubling my solar array. But unsure about my plans. The shop should be finished in a few months. I want to add the second array on the shop roof. Another set of batteries and a matching 30 amp charge controller. Then parallel both systems together. I dont think there is any problem doing this with the charge controller I am using. The shop is about 20 feet away from cabin. My equipment needs three phase to operate. So that will come from the grid with some type of converter or I have a 50KWA diesel generator that will work for this.

Just concerned if having the two separate systems like I am considering is a good idea. Then to parallel them together. This gives me twice the battery at the cabin, which is mainly what I am wanting. Then having lights in the shop and power for smaller things. This also keeps me with power if something takes a dump.

I finally made it happen and met up with the local poco. Sometime next month I will be tied to the grid. All of the power lines will be buried and totally out of sight. No overhead poles anywhere on my property. So now I can stretch out a bit. Dont need to fire up the big 50kva diesel generator when using the welder anymore.

Last week I went ahead and picked up 10 more solar panels. Currently I have 4 panels mounted on the south roof and two panels facing west side. Overall they have been very useful. Now I am replacing the older 280 watt panels with 315's. Then the other 4 will tie in with the two 300 watt panels on the south roof section.

So a total of 12 panels pushing about 3750 watts. My charge controller is only rated at 30 amps. I will be way over with the new panels. So considering upping to a 60 amp control charger or running a parallel system with another 30 amp control charger. The price is negligible between the two choices. My expense will be increasing the inverter size. Still working on options for that.

I am not totally sure how to wire up the strings to be most beneficial. It does not seem to matter so much one way or another from what I understand. I was thinking 4 strings of three panels wired in series then all paralleled together. This would get me about 1250 watts at 135 volts give or take. This falls well within both parameters using either one 60 amp CC or two 30 amp CC.

The two 48 volt battery banks consists of 4 180ah telecoms and a bank of 4 123ah data storage. These are AGM batteries. I had considered installing a separate system on the roof of shop using the existing 30 amp CC and panels. Then only parallel the battery banks together to make use of them at either location. The shop is right next to cabin, so no long distance wire pulls involved.

If someone has anything to offer would gladly appreciate your advice and suggestions. Thanks