Grounding

lwilli01lwilli01 Registered Users Posts: 12
What's the proper way to ground a "portable" generator - this is a DIY that I put together with:

2-50watt panels
1 30amp controller
1 3000watt inverter
1 108ah battery

Second question:
on the back of my panels (that you have to hard wire) there is not a way to tell which post is postive and which is negative - any ideas?:confused:

I'm also considering selling the 2 panels I have and replacing with one large panel - thoughts on that? (one with mc connectors)

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Grounding

    Welcome to the forum.
    lwilli01 wrote: »
    What's the proper way to ground a "portable" generator - this is a DIY that I put together with:

    2-50watt panels
    1 30amp controller
    1 3000watt inverter
    1 108ah battery

    Okay, grounding can be tricky. First of all, it's probably safe to assume that your inverter is an MSW type. This means you shouldn't make the typical neutral-ground bond anywhere on the AC side. The second issue is how the generator is connected. Does this inverter have a built-in charger? Probably not. So is the gen running a battery charger or taking over AC loads or both? If its AC is going to the loads at any time, its output should be entirely isolated from the inverter via transfer switch so there's no chance of them being connected together. The generator itself probably has "floating neutral" (no ground bond) and can safely be used as such. Depending on the exact model, it may have a ground lug on it which is supposed to be connected to Earth ground for safety reasons. Meanwhile, even an MSW inverter will expect a case/(-) terminal ground to Earth.

    A few more details about the equipment and we can give you a more detailed response.
    Second question:
    on the back of my panels (that you have to hard wire) there is not a way to tell which post is postive and which is negative - any ideas?:confused:

    Digital Volt meters are your friend. Connect the (+) lead to one panel terminal and the (-) lead to the other. A positive Voltage reading means you've got the +/- right. A negative reading means it's the other way around. They don't need to be in full sun for this either.
    I'm also considering selling the 2 panels I have and replacing with one large panel - thoughts on that? (one with mc connectors)

    The #1 question is: what are you trying to do with this equipment? If you have a plan for what your trying to supply power to run it's a lot easier to determine what equipment you need to run it. The two 50 Watt panels might just be enough to recharge that 108 Amp hour battery - possibly put out 5 Amps. Therefor the 30 Amp controller is very large. You could only expect about 600 Watt hours max out of the battery. I'd also suggest the 3 kW inverter is oversized for the rest of the equipment.
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Grounding

    Don't ground the inverter, as 'Coot suggests. Your inverter is way too big given the size of your battery and PV. 3000 watts at 12 vdc is ~ 250 amps. Your 108 ah battery would go to nearly zero volts if loaded any where near that. Additionally, it will run very inefficiently, perhaps only ~ 50% net/net.

    Second, you 100 watts of panels, on a perfect day might put out ~ 5 amps, so your controller is also pretty big, leading to more loses, depending on what kind/brand it is. Consider a simple Morningstar PWM 10-15 amps controller,, under $100.

    100 watts of panel, either 2 50's or 1 100 is sort of academic. For your situation, I would consider just keeping what I have bought and paid for. On the other hand, I have seen riduculous prices paid for single small panels on E-bay. (If you are interested in selling them you might PM me an tell me what they are).

    Ideally, your panels should charge your batteries at between 5-13% of ah capacity, or ~ 5-13 amps.

    Back to the original question, I don't think I would ground anything, except perhaps the panel frames and the negative side of the battery if you are concerned about lighting.

    Tony
  • mike95490mike95490 Solar Expert Posts: 7,225 ✭✭✭✭
    Re: Grounding

    If it's really portable, on wheels or a cart, I'd not bother grounding anything. Nobody grounds the automotive jump start power packs, or the internal 120Vac outlets in some cars nowdays.
    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
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators Posts: 26,666 admin
    Re: Grounding

    Why do you think you want grounding?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • lwilli01lwilli01 Registered Users Posts: 12
    Re: Grounding

    I set this up to act as a portable generator and to experiment with solar power.
    I bought a large inverter thinking I didn't want to be trapped into a small unit if I wanted to add additional batteries or panels. Same thinking when I bought the charge controller.

    Thanks on the volt meter tip - I'll do that today.

    Here's another question: My step-son has done the same thing but with completely different equipment. The question is two fold: when connecting multiple panels I know we need to do the daisy chain. However, one of his panels (2 we have to hard wire) has the MC Connectors. Can he combine these on the charge controller or should he combine them in a combiner box?

    1 panel is 230 watts the other 2 are 90 watt panels

    THANKS GUYS!
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Grounding

    Wire panels in series, + to - (like a flashlight) and you will double the voltage of the series.
    Wire the panels in parallel + to +, - to - will keep the voltage the same, but double the current.

    Remember, a conventional controller (PWM type) will only accept input voltage of it's rating (IE 12/24/48vdc) while most MPPT controllers can take a higher panel voltage (24/48 vdc) and down convert it to 12 vdc for example.

    It is important that the Panel voltages (if you are using PWM controller) are ~ the same, with in a couple of percent, Typically ~ 17.5 vdc for a "12 volt" panel.

    Tony
  • lwilli01lwilli01 Registered Users Posts: 12
    Re: Grounding

    We've wired them in parallel and the voltage of each panel is 12
    However, the larger panel because of the MC connectors is directly connected to the charge controller and the other two (parallel) are connected the the controller. Does this create a problem.

    I realize the appropriate way would be that all three are in parallel with a single connection to the charge controller. But, due to the fact that one has MC connectors and the other two don't .... we were'nt sure what to do.
  • icarusicarus Solar Expert Posts: 5,090 ✭✭✭✭
    Re: Grounding

    What many folks do is buy one set of MC connectors and cut them apart, such that you have bare ends to wire as you wish.

    tony
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