I would like some advice from the many professionals in this forum.

BCsolar Registered Users Posts: 2
edited February 2020 in General Solar Power Topics #1


This solar system is mainly for LED lights

•x10 LED light bars 20W, Input voltage:85-265V, 50/60HZ, Efficiency:110-120lm/w

My system includes the following: 

•12V,65Ah, Deep cycle battery (using the lights maybe 3 hours per day.)

•800watt inverter.

•30 amp epever charge controller, with MT50 and temp sensor. 

•60 amp breaker going to the inverter.

•20 amp breaker to the charge controller.

•20 amp breaker located outside acting as a rapid shut down. 

•x1 100 watt renogy panel.

•40ft of 10AWG solar cable to panel.(coming out of 1/2” conduit in photo)

•All 8 AWG cable is 4 feet of jumper cable, properly crimped with ring terminals and heat shrink. 

Is my inverter cable is a little under gunned with a 60amp breaker? I was thinking 6 AWG since it’s over 3 feet? I’ll never be using the full potential of the controller, that’s why I kept the fuses at 20 amps. 

Panel located on roof.

I was going to run 6AWG grounding wire(bare??) from the panel into an already existing ground rod beside my shop. Do I really have to run a separate ground rod 8 feet away? 
Also can I ground my epever controller through an closed unused junction box beside my battery to ground my common ground system? 

I realize none of this is up to code or doesn’t follow any NEC regulations. I just don’t want to burn my shed down. 

Please let me know what info I forgot to mention and any discrepancies you see in the given photos. Thanks


  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    You need a fuse on each + cable from the  battery.  If the charge controller fails, it will often short internally and you need to protect the wire from that happening.

    Battery cables - looks like a clever adaptation of the clamp terminal, using ring terminals .   Are those rings hydraulically clamped on or just a hand squeeze ?
    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

    solar: http://tinyurl.com/LMR-Solar
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  • BCsolar
    BCsolar Registered Users Posts: 2
    Thanks for the quick response!

    20amp fuse located on the positive lead traveling to the charge controller off the battery(approx 3 feet away) in the third photo. 

    60 amp breaker less than 150mm from the battery on the positive lead in the second photo. 

    20 amp breaker located outside coming from the solar panels on the positive lead. Approx 10 feet away from solar panel. 

    The terminal rings are 8 awg copper. See photo. 
    I hand crimped them with crimper pilers. Then covered in heat shrink. 

  • Photowhit
    Photowhit Solar Expert Posts: 6,001 ✭✭✭✭✭
    edited February 2020 #4
    Maybe I'm not reading correctly,  but it looks like you want to run;
    BCsolar said:
    •x10 LED light bars 20W, Input voltage:85-265V, 50/60HZ, Efficiency:110-120lm/w
    l0 x 20w  or 200 watts for LED lights for 3 hours?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,404 admin
    I will type up some observations... Don't get me wrong, I am talking about how we (as engineers) had to design to meet NEC (USA national electric code) and NRTLs (Nationally recognized testing laboratories--such as UL--Underwriters Laboratories).

    It is wonderful to see people ask about safety. And engineers typically make everyone feel bad about asking.  :#

    So, some basic starting information. First, details matter (such as what is the configuration of your solar array). And sizing the components to "play well" together (a 65 AH battery  can, at best supply around 8 amps continuously for a few hours, 8 amps * 12 volts = 96 Watts, and something like 26 amps for a few seconds). An 800 Watt inverter at rated load can draw (continuously):
    • 800 Watts * 1/0.85 AC inverter eff * 1/10.5 DC cutoff voltage = ~90 Amps max load, minimum battery voltage
    So, I would suggest reviewing your power needs and sizing your battery bank, solar array, AC inverter, solar charge controller to support those loads.

    Next, you need to look at how much current each size of wire can carry... You can use NEC charts (and various deratings) which is pretty conservative, or use a Boat type wire chart for maximum (usually less conservative). For example, 8 AWG cable can carry a maximum of:

    40-55 Amps (depending on insulation type, and other factors like ambient temperature, conduit fill, etc.). And any wiring that goes to the solar array should be UV (ultra violet) rated for use in sunlight/weather. Normal wiring (not in conduit) will have the insulation harden and crack overtime.

    For solar power systems, I like to derate the wiring (and breakers) by 80% (or 1/1.25 NEC derating factor). For example, say you use 50 Amp breaker and 8 AWG wire rating, I would suggest a maximum current of:
    • 50 amps * 0.80 = 40 Amps max continuous branch wiring and breaker/fuse current
    Fuses and Breakers tend to be rated for 80% or less load, no trip. >100% load, trip in minutes to hours.

    While it is very easy to mount solar and wiring to plywood/chipboard... You really should mount to something that is not flammable (wiring in metal conduit or raceways), and/or mount on sheetrock or concrete backer board or similar. And have some sort of no flammable floor material (clay/cement/rock tile, etc.) and not "raw" plywood sub floor (we had to assume that any plastics could catch fire and drip--And our computer systems had to have a metal "floor" or small diameter screen to prevent burning plastic from leaving the enclosure.

    Using "real" UL/NRTL rated components and following good installations techniques are important too. Here is a discussion where black market solar panels were installed by a licensed installer on a home GT Solar power system. And the panels caught fire:


    Other issues--Especially when you get more batteries in your battery bank--You want any exposed wiring / electrical equipment to be protected against falling objects and kids with metal things. That typically means batteries in locked/bolted shut battery boxes or in a locked room.

    Also lead acid batteries can vent hydrogen and sulfuric acid mist (and oxygen). Having batteries in a well ventilated room/box with power venting is a good thing. Hydrogen can be explosive at a relatively low percentage. And the sulfuric acid mist can corrode nearby electrical equipment other items nearby. And some folks are very sensitive to the "rotten egg" smell when finish charging.

    Flooded Cell Lead Acid batteries definitely vent hydrogen/et.al, when charging (and equalizing). AGM and sealed Lead Acid Batteries usually do not vent except if overcharged and at end of life (battery needs to be replaced).

    I suggest conservative designs for solar/off grid power systems... You want to design/install them correctly and safely. And only do your normal weekly/monthly maintenance checks. And pretty much assume that anything that can go wrong will go wrong (spouse plugs hair drier into your 800 Watt inverter when the power goes out, etc.). You want to make sure that things "fail gracefully".

    DC power systems look simple, but they are different than AC power systems... For example, 10 Amps @ 120 Watts (1,200 Watt load) is >100 Amps @ 12 VDC battery bus... So most DC wiring is much heavier than its AC wiring equivalent (Watts). Power=Voltage*Current. 1/10the current means 10x the current on your 12 VDC battery bus.

    Also, switches, fuses, circuit breakers need to be rated for DC voltage/current applications. DC current is "more difficult to interrupt" than the same AC current (DC current sustains "electrical arcs" better than AC). Having good/solid crimps/connections on DC wiring, and DC rated breakers/fuses/switches is important. DC "Arc Faults" are a common ignition source for solar power fires.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset