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gcrank1
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# Posted: 6 Sep 2021 11:18pm - Edited by: gcrank1
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We went to the cabin for the L.D. weekend, all went as normal until yesterday morning.
Everything was working, that is, the light I turned on worked, nothing to flag a fail....
But as is my O.C. normal once I made it outside (into a nice, bright morning with the array well in sun, oriented s-se) I took the 90' hike to the toolshed/powerhouse and the scc dig readout was BLANK. The inverter was running fine off the bat-bank, no low-voltage alarm or shutdown. Hmmm
A quick check with the dig-voltmeter showed the bats at 13+v, not depleted, so this must have just happened?
I disconnected the array and checked the array output, 36v (2s/3p), Ok, input to mppt scc same.
So, I figure disconnect the bats and read each; ie, start at the beginning.....
That is how I found the neg. con. at one battery, the one that goes to the scc was loose. Surprisingly loose. These are a screw lug fitting that I know I originally tightened well. Ive heard that there is a minute vibration in connections.
Retorqued it and the others and all is well again. Less than 1/2 hr spent trouble shooting. Waayyy better than saying,"hey hon, the solar elec aint working, guess I have to call the service guy to come figure it out".
And he'd maybe say I need a new scc + service call today and another to install it when it comes in?
Truth: When you 'build' a solar elec system You Are The Power Company
Moral: before winter/once a year while conditions are decent it might well be worth while to check All Connections, especially those out in the weather.
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Steve_S
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# Posted: 7 Sep 2021 06:40am
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Blessed are the Serrated Lock Washers. Loose connections are the bane of systems. With Lead Posts on FLA batteries, should be doing an annual corrosion & cleaning check on the terminals, I always check them when I do a Gravity Test on my FLA Bank. One of those extra 5 minute tasks added to the maintenance process. I saw 1st hand what a loose connection at a battery terminal can do. You are fortunate nothing nasty happened, loose connections can get extremely HOT resulting in very bad things.
Let me just say, I had plenty of respect for the amount of energy stored in my Lead Batteries and was always aware of the potential BUT holy crap, after installing all the Lithium Iron Phosphate I had an eye-opening experience with the amount of stored energy. Here's the GOBSMACKER: 40 Cells capable of dumping @ 5C (1400A per cell X 40 Cells for 56,000A Burst Rate Dump) I saw 2/0 vapourize in a flash - so safety dad mode kicked in - covered / blocked off terminals and more. Oopsie potentials identified and addressed.
Never Ever understimate the amount of juice lurking inside batteries and I also have to say it because I am guilty of it, DON'T GET COCKY With them, they have no forgiveness for stupid. I paid a price for it and luckily not permanently injured (but I have a scar as a reminder). hint, never let plates get exposed in FLA, bad things DO happen. (see respect the batteries part). I am actually surprised bad things don't happen more often, or maybe they just don't make the news unless it's a "Tesla PowerWall" or some other Target Brand the press likes to attack.
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ICC
Member
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# Posted: 7 Sep 2021 08:33am
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I have a set of wrenches that are almost completely covered in thick PVC tape except for the one end that is intended to be used on the nut or bolt head.
... You haven't seen a "fail" until you have been struck by lightning. 
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Steve_S
Member
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# Posted: 7 Sep 2021 09:02am
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hahaha, I accidentally did discover Man Made Lightning.... lucky I survived it.
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paulz
Member
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# Posted: 7 Sep 2021 09:07am
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Many years ago, before I learned the proper way to R&R car batteries, I shorted the positive terminal to ground with a wrench. Blew the case open, but fortunately spared my young dumb ass from injury. Tough way to learn a lesson but it sure worked.
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Brettny
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# Posted: 7 Sep 2021 02:38pm
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I have worked on many piece of equipment and hardly ever have had a loose battery connection. Usualy they corrode and cant make contact. Are you sure it was tight?
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hueyjazz
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# Posted: 8 Sep 2021 10:14am - Edited by: hueyjazz
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I was a facility manager for industrial operation for the last 40 year. I had electricians on my staff. There's mandatory training for arc flash with myself included as being the guy ultimately responsible.
One year I got in a trainer that's was once part of company that worked with transmission lines. Part of his training were pictures of people that got vaporized. Never hired him again but I will admit it left a lasting impression.
When working on high voltage equipment we had to wear special clothes, gloves, and maybe helmet with insulated tools that increased with protection with the increase of hazard.
An arc flash explosion will vaporize cotton clothing in a second. It's vaporized molten metal in a plasma atmosphere. If I have to work on live equipment I do protect myself with proper gear and tools.
Electricity can be very unforgiving without a second chance. Even 110 volts can be quite dangerous if a metal tool gets drop in a panel. I know a lot of you don't have insulated tools. At least wrap them in electrical tape but treat them as they are not.
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paulz
Member
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# Posted: 8 Sep 2021 11:22am
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Quoting: Brettny I have worked on many piece of equipment and hardly ever have had a loose battery connection. Usualy they corrode and cant make contact. Are you sure it was tight?
Hasn't happened much to me either but I'm going to check the nuts on the 4 FLA bank on the shop solar today..
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gcrank1
Member
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# Posted: 8 Sep 2021 11:41am
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These 'lugs' are the typical elec service box ground-lugs, an alum square with a hole and big setscrew for the wire and a hole in the base that I have bolted into the top of the battery.
The bat con was Tight.
The setscrew holding the multi-strand 4ga wire was not even what I call snug. Whatda? I never just 'barely tighten' that kind of con like that, no need, I would fully tighten as I go.
The bat-bank is outside of the toolshed/powerhouse (FLA) and unsecured.
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gcrank1
Member
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# Posted: 8 Sep 2021 09:06pm
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When I was a young teen, way back in the '60's, car batteries still had the exposed lead cell connectors on the top. One cold winter day my dad had to take the big, old car battery out (might have been a 6v, dont know) and carry it through the house and down to the basement to put by the wood/coal furnace to warm up (it was my job every morning to reload that stove from embers and 'keep the home fires burning').
As he started down the stairs I saw sparks, his metal belt buckle crossed the cons....and welded his buckle to them. He didnt drop the battery! By the time he tore the buckle off the bat he had branded the back side of it onto his belly.
He dispensed some wisdom during this.....
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NorthRick
Member
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# Posted: 9 Sep 2021 01:27pm
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I have a couple of tools with bits missing. A reminder to the power of electricity and how fast things can happen.
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