HELP! Friend in costa rica bought off-grid system, not working, Installer has bailed on him.

Needle27

My friend built a new house in the mountains of costa rica. In the spring he bought a supposedly 1-year old used solar+battery offgrid system from an installer down in the city. The parts are all listed (18 Canadian Solar 350s/ Schneider Electric hybrid inverter (6848), and 24 Trojan flooded batteries) but the system has never worked properly. It shuts off at night with just moderate loads on it, even though system should be big enough for their needs and this not to happen. They would get a beep from the inverter and a low voltage indication. Last week the system shut off abruptly in the afternoon, no beep. Friend went down and smelled burning and saw that one of his batteries had a burn on the wire. The installer has totally abandoned them and they are running their house off a gas generator continuously. Where should he start to trouble shoot this? Any guidance would be a great help. [list says 24 panels below - in reality they have 18]

Thanks!



BATTERY BURN

Photowhit

It might well have been a bad/loose connection.

I would suggest checking the specific gravity of each battery cell. 

The Connection shown is obviously where there was a problem. I suspect just a loose connection. Lots of amps crossing a small area, due to the loose connection creates lots of heat. It appears a stream of melted lead in the photo below the connection.



This may have been the only problem, but may have created others. It may be that this battery can be still used, but the connected wire should be removed and the 'flag' (part of the battery that provides the connection) should be filed flat to ensure a good connection.

If there are no dead cells, you could connect and try to see if the array is charging the batteries. I would suggest someone on site, learn about the maintenance and care of the system.

It is likely, if this battery needs to be replace a robust 48 volt system like this could function off of 23 batteries, it might even help charge up the other batteries with a slight over charge, until this battery can be replaced.

The time to address the problem was when they saw a low battery and before the system shut down, That is when connections, settings and energy use, should have been checked.

Certainly when the system shut down over night for low voltage, it obviously needed attention. At that point if you have an alternate source of energy, like the generator, the system should be taken off line until the problems were addressed.

Trojan batteries are very good and flooded batteries can often survive abuse like this, but they need too be charged NOW, and someone needs too use a hydrometer to check the Specific Gravity of the batteries and figure out what condition they are in, and get them charged, then equalized. If possible before restarting the system. Then the battery capacity should be checked a few times a day, to see that the daily energy use is in the bounds of the batteries.

I would also suggest load shifting too make use of late afternoon sun, when the batteries are, hopefully fully charged and washing, and perhaps water heating can be done with no energy from the battery bank.

Photowhit

Needle27 said:

[list says 24 panels below - in reality they have 18]

18 is still a large 6300 watt array. This is a large array, but off grid it won't do everything in a home without some understanding of how the system works. Things like water heating in Costa Rica, should be done with thermal solar system and not electrically. Air conditioning with an old central air unit, may take most of the electric being generated. I would suggest looking into an energy audit of some type too see if the system is large enough for his energy usage. If he was previously grid connected, he could just look for his energy usage on old bills.

fogeater

That's a nice setup.  The installer failed to double-check the terminal tighteness before leaving or something or someone bump or moved a cable.

If that terminal is salvageable and batts are in 5-7v range dependent on incoming solar just clean and tighten that terminal using a jumper if you need to remove and file flat as he said. Clean and tighten all other dc connection on bb and inverters.

Set an eq charge on cc's for 3-24 hours at 58-60v. Check water levels on all cells, top off with quality distilled h20. Make sure you have like 10 more gallons still on hand and press start eq. Monitor individual batteries with multimeter make sure they're staying in 6-7 volt range. Over 7.5 is to high lower cc setting for safety. Monitor every 1/2 hour whenever it's chargin. 3 hrs is good but you can do more if needed. 6.36v is good battery sitting overnight with no loads. Below 6, keep charging and monitor constantly if you smell sulfur or se smoke shut it all down and test everything.

 Be safe get help if unsure. Just don't leave lead uncharged for to long. Low batteries can be brought up to voltage with nice 30-60amp 6v charger used at shops and such. Good luck and safety first.

mike95490

I'd suggest NOT topping off the cells with distilled.  Make sure the plates are covered and then a bit more.  When charging and getting warm, the fluid will expand, and sometimes overflow the caps.  You permanently loose acid, and get acid all over everything.

Top the cells off after the EQ charge - then you are fine.


And that soldered lug, is exactly why lugs should be properly CRIMPED.  When the connection heats up, solder melts and goes downhill.  Sometimes if cable is under tension, the cable falls out.   Good gas tight  crimps don't need solder.

https://en.wikipedia.org/wiki/Crimp_(electrical)
Crimping is normally performed by first inserting the terminal into the crimp tool. The terminal must be placed into the appropriately sized crimp barrel. The wire is then inserted into the terminal with the end of the wire flush with the exit of the terminal to maximize cross-sectional contact. Finally, the handles of the crimp tool are used to compress and reshape the terminal until it is cold-welded onto the wire.[3]


https://www.passagemaker.com/technical/dont-scrimp-when-it-comes-to-the-crimp
Execute the crimp. The ratcheting mechanism should travel through a full cycle before the crimp is released. Remember, if using a non-ratcheting crimping tool, enough pressure must be applied to break down the oxides that are present on the inside of the connector, and so the serrations can imbed themselves into the wire strands slightly. This area of the crimp must be gas tight. If gas, in the form of air, is present, then corrosion will follow. Alternatively, over crimping will elongate and weaken the wire strands.



https://www.phoenixcontact.com

Gas tightness of crimp connections

 

View lengthways through the crimp

A gas-tight crimp connection is the result of a defined crimping process. The wire strands in one or more conductors and a connector are joined into a largely homogeneous structure with no gaps. This results in a permanent, reliable connection that cannot be detached.

Rezzka

Hi! How did you manage to solve this problem? I came across the same thing in a house I bought a couple of weeks ago.

BB.

Welcome to the forum Rezzka,

Please feel free to start a new discussion (thread) and tell us about your system, your expectations, and what you are seeing happening.

Then we can help debug your system with you.

-Bill "moderator" B.

Franko

It seems to me that the problem was tension. I had often come across a case when too high a voltage in the network ignited the wires due to the poor quality of the material or the high temperature created. You should call a specialist to check the entire system. Otherwise, another time a fire may start at night, and you will not notice how the whole house will be engulfed in flames. When building a house, I even invited building surveyors England to properly use the landscape features. In such a case, caution never hurts since one small mistake can lead to terrible consequences.

BB.

I think "tension" is a version of "Voltage" we use in English--We do talk about "high tension" lines for the high voltage lines used by utilties.

We almost always use "volts and voltage" with lower voltage and DC solar power systems.

From the photo above--I would agree with Photowhit that either or sometimes both) a loose / corroded connection. Created high resistance which overheated the bolted connection. Both "burning" the insulation, and if you look closely, even melting the lead battery post (those "bright silver" vertical pillars are melted lead).

In general, I would not expect any "reasonable" DC voltage to arc from too high of voltage... Probably have to get to 100's of Volts to even begin to risk a voltage caused arc.

However, there is the issue of a current arc. A loose/failing connection starts arcing like an Arc Welder. More or less, 24 VDC systems and higher can sustain arcs very nicely (see "Arc Welder"). ~12 volts is the typical break point between "no sustained arcs" and "sustaining arcs".

Also a problem with solar panel wiring... Here the wiring can be from 100 to 600 VDC (or even higher). Typically, a loose/corroded connection will continue to carry current as a sustained arc. I believe that these series arcs (sometimes called arc faults) are the cause of many solar power system fires in the solar array wiring.

A standard circuit breaker or fuse cannot stop a "series arc" as this is just the average system current (no over current). There are "arc fault" circuit breakers that monitor the "noise" generated by a sustained arc to shutdown in an emergency.

Here is a nice example of 220 VAC vs 220 VDC and how the DC current sustains arc "very well":

https://www.youtube.com/watch?v=Zez2r1RPpWY

This is also an issue in switches, fuses, and circuit breaker design (AC vs DC vs Voltage/Current ratings).

-Bill