100,000+ amps through my charge controller?

CALLD
CALLD Solar Expert Posts: 230 ✭✭
in Off Grid Solar & Battery Systems #1
Ok, apologies for the catchy title, but the issue of a lighting strike must have come up so many times on this forum before it may possibly be overlooked out of boredom!

Anyway - the dilemma:

There is not much anyone can do to prevent lightning from hitting if it wants to. The only thing to do is try to control the path of discharge. Unfortunately my panels are pretty much the most conductive thing on my roof, and the cabling to the charge controller is the most conductive thing running vertically between the panels and the ground. The roof is metallic, although coated in insulating paint. As far as I know the solar cells are insulated from the aluminum frame of the module & so is the cabling - however lighting is unlikely to care about the 3 inch gap between the junction box and the frame after tearing through several miles of open air to get to them!

I have a choice:

1) Do nothing and rely on the fact that the panels are insulated from the metallic roof by a wooden frame and hopefully offer a less attractive path to ground than several nearby structures that happen to be 10 to 20 feet higher.

2) Ground them and give the lightning a very attractive target to hit, potentially burning the modules with the shear heat and light intensity of the plasma channel...

Any suggestions?
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Comments

  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    #2
    Re: 100,000+ amps through my charge controller?

    Surge Protection Device ( aka, SPD ) Midnite Solar has them as do others.

    http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=23&productCatName=Surge%20Protection%20Devices
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  • Ks Solar
    Ks Solar Solar Expert Posts: 47 ✭✭
    #3
    Re: 100,000+ amps through my charge controller?

    Draining any static that may build up via a good ground would be my choice. I had a small fiberglass multi band vertical antenna hit. It had only one 8 ft ground rod. It was only 20 ft up. It exploded and also the mosfets in my homebrew charge controller. My poor lab was never the same. She use to sleep in the garage the antenna was mounted to. Then I took a hit to a tv antenna hooked to the house, only 15 ft. up. No ground rod. Insurance claim this time :( lots of stuff fried in the house.

    Now I have a 50 ft. tower. I have two 14 ft. ground rods welded to the base of the tower. And a Ufer ground welded to all the rebar and tower as well. 10 yrs. no more hits. I think letting any static build up attracts lightening .. I also don't run any wire antennas. Wind across a wire will build up a large charge. You could probably charge your batteries with it I suppose.. joking
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  • Mountain Don
    Mountain Don Solar Expert Posts: 494 ✭✭✭
    #4
    Re: 100,000+ amps through my charge controller?

    Install an air terminal (lightning rod) system on the roof, chimney, all highpoints, etc. These are connected together with approx 7/16" dia. braided wire connected to at least two grounding rods or plates in the earth. These grounds are separate from the electrical system grounds.

    This is what was recommended to us after we were struck. Draining static build up is one theory that I believe in. The ground wire path between earth and the air terminals promotes the 'leakage' of charged particles from the earth to the sky thus preventing lightning strikes from occurring locally. A key element is to achieve good solid grounding to the earth. That can be the most difficult part.



    And make sure the nearby taller structures have air terminals and proper earthing as well.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
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  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    #5
    Re: 100,000+ amps through my charge controller?

    Theres nothing you can do about a direct hit. First buy quality gear. For instance midnite controllers are ETL tested to withstand 3000V. Second, if your PV frames are not grounded correctly you are just asking for trouble. Negative side grounding is also considered an industry standard, and required by law in most jurisdictions once your array voltage exceeds a certain threshold. SPDs are a no brainer. Read the good grounding and lightening howtos on the shop side of the NAWS site.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #6
    Re: 100,000+ amps through my charge controller?

    Lightening can indeed have a mind of it's own, a mind we can't always understand. Several Summers ago a neighbour of mine had a strange incident. About 50 feet from his 3 story house, and surrounded by 40 foot spruce trees, several less than 20 feet away, sits his baby barn containing a ride-on lawn mower.
    I saw the flash, I heard the huge thundering roar, I saw the smoke, I heard and saw the fire trucks.
    For some unknown reason, lightening decided to ignore the house, ignore the circle of trees and find it's way down between all these things to hit his little baby barn. It was 8X12 feet, all of 7 feet high at the peak and had no electrical connections. Figure that one out, I can't!
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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #7
    Re: 100,000+ amps through my charge controller?

    I would tend to agree with the statement that lighting has a mind of it's own. One of the most famous photographs of Cape Town shows a spectacular thunderstorm over Table Mountain, but for the less romantically inclined one of the most striking things is the fact that a lot of the lighting completely ignores the 4000ft mountain (with the 4x 2" steel cables running from top to bottom for the cable car!), and prefer to hit the city beneath...!

    https://vpblogs.files.wordpress.com/2008/06/lightningcpt.jpg

    I am in the process of grounding my panels, and installing an 8' aluminum lightning rod on the roof where it cannot cast shadows. Hoping for the best!

    Not sure how and where I would put a surge protection device as I would want any hit to completely bypass all my equipment, not easy to figure out...
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #8
    Re: 100,000+ amps through my charge controller?

    "Distract" the lightning with an easier target (a grounded "flagpole", Franklin Rods, whatever) and load your gear up with SPD's There is the "Rolling Sphere" model of protection from the lightning rod, that is well modeled and reliable. Avoid ESA type systems, as they merely purport to prevent lightning, and are not a robust enough ground to absorb a bolt.

    And there is the Solar Guppy model, who lives in lightning city (Florida) who places an "attractive" ground on nothing, and lets the neighbors take the hit! I believe he also disconnects everything with air gaps (pull out 600V "knife switches") when a storm is active.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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