Need some power at the cabin

[Fordtrucksforever]

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.

[Fordtrucksforever]

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?)

[nwdiver]

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 will 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.

[Fordtrucksforever]

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?

[Fordtrucksforever]

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.

[nwdiver]

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.

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...

[Mike90250]

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

[Ampster]

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.

[Mike90250]

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

[PNW_Steve]

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.

[MichaelK!]

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

https://ressupply.com/

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.

[Fordtrucksforever]

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>

[Mike90250]

There were some hard back volumes of manufacturing companies information books. They were light green and huge. Cant remember the name of them tho. I spent weeks making phone calls all ovr the country,but running into dead ends. Finally found some old timer guy in retirement years that gave me the lowdown. I added some water to them, then charged overnight with a dc welder, per his advice. For something that had been left outside neglected for 20 plus years, came right back to life and worked great. But too much time passed and they are gone.

Thanks again for your help.

Edison cells are seldom "gone" unless they rust away. New electrolyte and they are good as new. The electrolyte is ALKALINE - KoH Potassium Hydroxide very much like lye, which could be used in a pinch.

[Fordtrucksforever]

WOW! Thanks so much for all the info. I have been getting a headache every time trying to run the numbers. Reading all of the stickys just made it worse. I know its not that difficult, after working with it. You broke down the basics really simple enough. I do have a new charge controller that was within my budget, and works for whatever battery combination. Currently for the minor needs at hand, one of the inverters in question is what will be used. I am still in the dark on so much. But have some basic understanding to know whats within my limitations. I will likely stay with the 24 volt bank until the load demands are exceeded. Then pay the big bucks and get a 48 volt inverter and more panels.

The roof on by cabin is facing just a little south of due west and steep enough in pitch to take advantage of sunlight until it sets. I want one set of panels there and another set on front of cabin facing south. My cabin is deep under the trees, so trying to make best use of available sunlight when shows itself. Watching where the sun shines during the day, this seems to be a possible plan.

The reasoning for those batteries is simple enough. They cost almost nothing. Actually, these four cost $30 a piece. For the life I can get out of them, then sell back for scrap at $25 a piece, makes my net cost negligible over the next few years. What really gets me, is I had, tho many years ago, several electric forklifts for the taking. These were very old and powered by Edison cells. I wanted to keep the batteries around, just in case of a use might arise. I was not familiar with them at the time. No internet back then either.

There were some hard back volumes of manufacturing companies information books. They were light green and huge. Cant remember the name of them tho. They are called Thomas Register. I spent weeks making phone calls all over the country,but running into dead ends. Finally found some old timer guy in retirement years that gave me the lowdown. I added some water to them, then charged overnight with a dc welder, per his advice. For something that had been left outside neglected for 20 plus years, came right back to life and worked great. But too much time passed and they are gone.

Thanks again for your help.

[MichaelK!]

I did a bit of research into your 12HX540 batteries, and what I'm seeing is that they appear to have specifications similar to Trojan's SAGM12-135 battery. That might give you a guide as to how much power you can expect out of them and how they should be charged. They have an 8 hour capacity of 123AH, so their 20hr capacity is about 140? That's why I mentioned the Trojan comparison. If you want to charge them at about 20% of C, that would mean 140AH X 0.2= 28amps. Now you just plug in that number into a formula to see the solar needed.
28amps X 50V X 1.25 effeciency conversion ~1800 Watts. That's triple the amount your panels are using now. Keep in mind these numbers are a guestimate, because you are using the batteries for an application they are not meant for. If you want to adher to the standard admonishment of never depleting your batteries more than 50%, that gives you about 3.4kwh of power.
140ah X 48V X 0.5capacity =3360watthours. I'd say that's enough for a lights, a TV/computer, and a small 15-17 cuft refrigerator. my guess though is that these batteries will not last long, being used in a way they are not designed for.

Later in time, you can upgrade your system with more capable electronics, better inverter, better batteries. If you went with 24V instead of 48, your numbers would be exactly half. You could raise the 24V capacity by having two parallel strings of 2 batteries. The charging voltage would go down, but the amps would need to be doubled, so the watts is the same. Cobbling together components now is going to be a problem for future expansion. I'd say try to zero in on either a 24 or a 48V system. All the major companies make components to match those voltages. If you go with 36V, you are pretty much limited to using Outback equipment. Outback makes high quality equipment, but it would be your only choice for 36V. If you want to power nothing bigger than a frig, you can get by with 24V, but serious power needs 48V.

Keep in mind these numbers are estimates for what's best for batteries other than what you've actually got. You really won't know until you get it up and running, and trash at set. For sure you can get by with much less solar if you are limiting yourself to just lights and a TV. The frig however raises electrical demands an order of magnatude.