Acquired Falling apart off-grid system, need advice

[Artklein]

Completely new to the forum and looking for some advice. This is a lot, so up front: I am very grateful to anyone who takes the time to read and offer me some insight.

I recently acquired an off-grid property that I purchased for many reasons except the house. The property was not well maintained by the previous owner, and the decently large solar system needs some immediate attention. It is very remote, and the few electricians that I can find are booked all through to mid January. I would like to at least keep the power on while I work on other things. I know basic electrical theory, but have little practical experience (I am a software reverse engineer). I am working through the DIY solar channel videos, but am starting late because I did not initially set out to buy an off-grid property. I have an immediate problem that there is a corroded positive battery cable in the large battery bank that I'm unsure how to safely replace, but also I can't evaluate the design choices of the previous owner to know if there are any more lurking issues.

The system:

• 48x 180 Watt 44 Volt, Suntech solar panels (These)
• 4x Flex Max 80 Solar charge Controllers, connected each to 4 parallel connected series strings of 3 panels
• 48x 6 Volt 225 ah golf-cart batteries, wired in 3 parallel blocks of 4 parallel connected series strings of 4 batteries for a 24 volt battery bank configuration
• Xantrex 4000 Watt SW4024 Inverter w/ Trace DC Disconnect and AC Circuit Breaker

Main immediate problem: The battery interconnect cables are fairly corroded in some spots, and at one of the points parallel connecting a series string (the positive to positive connection) is completely corroded off. See my horrible (I apologize, it looks like a child made it) diagram. I am surprised the system is even working, but according to the inverter meter the battery voltage is between 24 and 27 volts (depending on the day/weather), and I've noticed no issues except some occasional light flickering in the house. I don't understand enough electrical theory to understand what this is doing to the system (I assume nothing good) and thus how immediate of a problem it is, or how to safely replace it. I don't want to be touching things when I know theres a lot of current flowing. Do I need to turn off the system at the DC Disconnect (and therefore power down the solar charger controllers and inverter) before I try and replace the battery interconnect, or can I replace it in place? Please forgive my ignorance, but I haven't found any info about this situation specifically.

Secondarily, I'm trying to evaluate if other aspects of the system are sound such as the manner the solar charge controllers are connected to the battery bank. 2 of the chargers are connected to one block of 16 batteries - splitting it, while the other 2 are connected to a whole 16 block each. Does this create uneven charge conditions and is there a better way to connect it?

Any other thoughts or advice for how to maintain this system or things to watch out for would be appreciated as I am 100% new, but have an unusual situation of inheriting a system rather than building one. And a falling apart system at that: When I first looked at the battery bank, almost all of the batteries had the bare metal exposed because they had not been watered in so long.

Thank you thank you for any insight you might bring.

 

[SparkyJJO]

They're just sitting outdoors (under a roof of some sort) and that's it? I'd want to enclose that area to try to keep critters out (such as birds, look at those feathers!).

For a starting point, personally, I'd disconnect the badly corroded connections first (some of those are glaringly green), clean them up, and reconnect them, and fix the broken connection. As it stands, you're missing 3/4 of the capacity in block 1 due to the broken wire, and effectively only have SCC 3 and SCC 4 doing any charging.

Remember all your batteries are in "blocks" of 24V banks in parallel, so they are all interconnected. Your charge controllers may look like they are specific to particular blocks (or pairs of blocks) but really, they all share the entire bank together ultimately. They shouldn't be unevenly charging things too badly once all the wires and connections are solid again.

 

[dougbert]

and insulate your wrenches before working on that sea of battery connectors

terrible access to those further away batteries

 

[12VoltInstalls]

I’ve heard of big small-battery banks but I’ve never seen that many commodity batteries installed in person. Wow! Cool.

Anyways- once you make everything clean on those batteries, check the water(acid) levels, wire-brush and clean all the terminals, and have any new cables installed spray all the battery terminals with a good coat of fluidfilm. That is nasty stuff and I hate it but it does an excellent job protecting batt terminals from corrosion.
There’s dielectric grease and fun-colored stuff at the auto parts store but fluid film is easy, works well, and doesn’t harden up to a rubbery goo.

 

[DThames]

Do you know how to maintain the electrolyte in the batteries. Since they appear negelected, I would expect maintenance is needed.

 

[12VoltInstalls]

Do you know how to maintain the electrolyte in the batteries. Since they appear negelected, I would expect maintenance is needed.

Distilled water from the grocery store. But you should evaluate the electrolyte before diluting it
Deka Temperature Correcting Battery Hydrometer (00231) https://a.co/d/2v3r4Je

You can buy battery acid by the 5-gallon at a parts store. You pick it up and go home and use it within a day so you don’t have anything to show Homeland Security agents when they show up the next day. ?

 

[Mattb4]

Do not just replace the corroded wires. Likely some of the batteries are bad and will need to be left out of the bank. SG checks will need to be done.

 

[John Frum]

I don't see the Trace inverter.
Is it a discrete inverter or inverter/charger?
I don't see a shunt, is there a shunt?

Do you have an ICE generator?

 

[John Frum]

Can you give us a rough idea of your location?
State level is probably sufficient.

I'm guessing Hawaii.

 

[John Frum]

48 batteries * 6.3 nominal volts * 250 amp hours * .5 depth of discharge = 37800 watt hours

The system doesn't appear to make it easy to take a single bank offline for maintenance.

 

[saggys]

Way too many parallel strings of batteries.

 

[RCinFLA]

I have seen a lot worse.

Looks like a long run from batteries to inverter. It appears the two battery lines are going through separate conduits at far end view of battery array. It is better to have pos and neg lines taped together for a long run to reduce their series inductance. This reduces voltage ringing at the inverter input.

First thing is read up on menus for the SW4024 inverter and get familiar with its setting. Copy down what is presently setup.

Big reason for this is on this older inverter all settings are lost when you remove battery power. It powers up with default factory settings. So be prepared to have to reconfigure settings if you remove battery power.

Start by cleaning up battery cables. Get a wire brush and a big box of baking soda. Mix some baking soda with a little water into a paste. It will neutralize any acid on outside surfaces and connectors. Clean and dry off all terminals. Brush off all the green copper oxide. You might have to replace some really bad connectors. I use a wire wheel on an electric drill to clean off lugs, but you will likely remove any tin plating down to raw copper. This is okay but raw copper will corrode again from any acid leakage which will happen over time.

Check each battery voltage. Get a hydrometer to measure specific gravity of electrolyte. If batteries are older than 5 years they are likely getting close to old age and may need replacing. Alway wear old clothes when working on battery as you will get acid burn holes in your clothes. Use appropriate eye protection. Rubber gloves are also good to use.

Golf cart batteries are usually about 225 AH size.

Get a DC clamp on DC amp meter to allow quick checking of current sharing between paralleled battery arrays.

 

[RCinFLA]

Here is manual. Covers both SW4048 and SW4024 models.

 

[RCinFLA]

Setup menus for SW inverter.

Have to simultaneously hit green and red buttons to get into setup menus.

 

[saggys]

I had 5 parallel strings of L16'S for the last 5 years and even with meticulous maintenance I am down to 2 parallel strings now. That is with better than a C10 charge rate. I am now migrating to a 48 volt system single string.

I am not saying it can't be done, just that there are more effective and efficient ways to do it.

 

[Artklein]

Thank you everyone who took the time to respond!

They're just sitting outdoors (under a roof of some sort) and that's it? I'd want to enclose that area to try to keep critters out (such as birds, look at those feathers!).

For a starting point, personally, I'd disconnect the badly corroded connections first (some of those are glaringly green), clean them up, and reconnect them, and fix the broken connection. As it stands, you're missing 3/4 of the capacity in block 1 due to the broken wire, and effectively only have SCC 3 and SCC 4 doing any charging.

Remember all your batteries are in "blocks" of 24V banks in parallel, so they are all interconnected. Your charge controllers may look like they are specific to particular blocks (or pairs of blocks) but really, they all share the entire bank together ultimately. They shouldn't be unevenly charging things too badly once all the wires and connections are solid again.

Yes - they're just sitting on the ground. Yes, those are feathers. That makes sense about the charging, thank you

Do not just replace the corroded wires. Likely some of the batteries are bad and will need to be left out of the bank. SG checks will need to be done.

Can you elaborate on that a little. Let's say I find some bad batteries from the SG tests, you're saying I should leave them out and rewire/reconfigure the bank without them?

I don't see the Trace inverter.
Is it a discrete inverter or inverter/charger?
I don't see a shunt, is there a shunt?

Do you have an ICE generator?

- I believe it is an inverter/charger (there are charging menu items at least)
- There is not a shunt as far as I can tell.
- I don't know what an ICE generator is.

As for the cobwebs you'll notice, I knocked this off immediately. This picture is how I encountered the equipment, covered in cobwebs like everything else.

Can you give us a rough idea of your location?
State level is probably sufficient.

I'm guessing Hawaii.

You guessed correctly

I have seen a lot worse.

Looks like a long run from batteries to inverter. It appears the two battery lines are going through separate conduits at far end view of battery array. It is better to have pos and neg lines taped together for a long run to reduce their series inductance. This reduces voltage ringing at the inverter input.

First thing is read up on menus for the SW4024 inverter and get familiar with its setting. Copy down what is presently setup.

Big reason for this is on this older inverter all settings are lost when you remove battery power. It powers up with default factory settings. So be prepared to have to reconfigure settings if you remove battery power.

Start by cleaning up battery cables. Get a wire brush and a big box of baking soda. Mix some baking soda with a little water into a paste. It will neutralize any acid on outside surfaces and connectors. Clean and dry off all terminals. Bush off all the green copper oxide. You might have to replace some really bad connectors. I use a wire wheel on an electric drill to clean off lugs, but you will likely remove any tin plating down to raw copper. This is okay but raw copper will corrode again from any acid leakage which will happen over time.

Check each battery voltage. Get a hydrometer to measure specific gravity of electrolyte. If batteries are older than 5 years they are likely getting close to old age and may need replacing. Alway wear old clothes when working on battery as you will get acid burn holes in your clothes. Use appropriate eye protection. Rubber gloves are also good to use.

Golf cart batteries are usually about 225 AH size.

Get a DC clamp on DC amp meter to allow quick checking of current sharing between paralleled battery arrays.
View attachment 124949

Thank you very much for this. Especially the info about the inverter settings. Does that apply to the SCCs as well (I think they are powered from the battery bank).

My big question at the end of this is to what extent I need to only replace:

• only the single bad connection
• Any bad batteries that I find
• the entire battery bank

I'm sure I can find some guidance on how to test the batteries on YouTube or Google, but insofar as judging if one is "too bad" to stay in the bank vis-a-vis the others

 

[Rednecktek]

ICE= Internal Cumbustion Engine, AKA gas generator.

First thing I would do is do a SG test of the batteries and just pull any that are toast. No sense bringing the rest of the batteries down by strapping them to dead ones.

Next thing I would recommend is doing the math on how many rackmount LFP's it would take to replace those lead acids and start saving up. Even if you're living on limited capacity it's better than mixing & matching old, new, and different chemistry batteries together.

Next step would be to build a solid little insulated shed to house the new batteries. Then just dump all the lead batteries and convert to LFP all at once.

Critters and humidity are a thing so having a shed for all the batteries that's critter and weathrr resistant is going to go a long ways towards longevity.

But that's just me and I work for a living so I can't imagine trying to do everything at once, especially with Island Pricing.

Unless of course ALL the batteries are borked at which point you're in trouble.

 

[Mattb4]

...

Can you elaborate on that a little. Let's say I find some bad batteries from the SG tests, you're saying I should leave them out and rewire/reconfigure the bank without them?
...

Yes. Having a bad battery in the bank drags everything down. And if you do have some that already are out of the bank due to a corroded out connection you would not want to hook them back in. Depending on what you find you might need to remove a marginal battery also so that when wired back up you still have the right voltage for the bank.

ETA: BTW, do not replace any bad batteries with a new one. If you need more capacity than the remaining old bank provides you will need to replace the entire bank.

 

[Skypower]

Are you going to be completely off grid, grid supported or grid tied( buy & sell power). This is an older system and if it had been up and running it could have been “grandfathered” to previous agreements. However, the meter has been pulled and judging from the cobwebs it’s been a while. Hawaii codes probably have changed and that system may need to be inspected/upgraded before the utility will connect, even for just grid support. You may need to figure out what you want to do and perhaps stealth fully poke around for info from other locals before you talk to any Bureaucracy. Real good chance the batteries are only good for the lead content, probably sulfated from sitting at a low state of charge.

 

[Artklein]

Are you going to be completely off grid, grid supported or grid tied( buy & sell power). This is an older system and if it had been up and running it could have been “grandfathered” to previous agreements. However, the meter has been pulled and judging from the cobwebs it’s been a while. Hawaii codes probably have changed and that system may need to be inspected/upgraded before the utility will connect, even for just grid support. You may need to figure out what you want to do and perhaps stealth fully poke around for info from other locals before you talk to any Bureaucracy. Real good chance the batteries are only good for the lead content, probably sulfated from sitting at a low state of charge.

I could bring in grid-power, but it would likely cost as much or more than fixing this system, at least insofar as I understand what all might need to be done at the moment. The property never had grid power, and would need a lot of poles installed to get it to the premises. While I hadn't been intending to maintain an off-grid solar system, I would like to revive the current system if possible as it seems a lot of it is still functioning (the panels, SCC's, inverter, etc). I live there on and off as I fix things and haven't noticed any issues, even using it quite heavily (dish washer, clothes washer, laptop, lights, etc).