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CamperWill's avatar
CamperWill
Explorer
May 31, 2016

Dry camping electrical questions

Hey all, so we've been camping for quite a while now and are starting to transition to no hook-up camping and have a couple of questions. We are looking to add an inverter and solar charging and could use some pointers for how to wire it all in.

The inverter (12v > 120v) we are looking to add is 1000W which is more then enough for the light loads we will be pulling through it. Now I'm familiar with both 120v and 12v wiring but I've never mixed the two. Am I right in thinking that the inverter can be wired into a spare 120v breaker with a lockout and we can just flip it on when dry camping as well as turning on the inverter itself? I'm guessing the stock power converter may decide to start charging the battery since a 120v input will be detected so what's the best way to deal with this?

As for solar charging, based on my calculations a 100W panel should be enough for our needs. Any tips on wiring this in? Any recommended kits? We have a couple hundred to spend on this.
  • grizzzman's avatar
    grizzzman
    Explorer
    Jun 06, 2016
    rjxj wrote:
    I agree that it may depend on the panel. I have pwm and 4 130 watt panels. If there is some shade on a panel it isn't killed completely.


    It also depends on the type of shade. A power line across the panel about 10ish feet away dropped 3 amps. During this test I was seeing 8.95 amps without the shade.
  • azrving's avatar
    azrving
    Explorer
    Jun 06, 2016
    I agree that it may depend on the panel. I have pwm and 4 130 watt panels. If there is some shade on a panel it isn't killed completely.
  • grizzzman's avatar
    grizzzman
    Explorer
    Jun 05, 2016
    MrWizard wrote:
    Shade disabling a panel depends entirely on that panel and the number and placement of the by pass diodes
    Each cell is approximately 0.5v
    36 cells equal 18v
    Loose two cells you still have 17v if all cells have by pass diodes
    If the file are limited number around a string cells
    Shade on one cell can block power from several cells
    It has nothing to do with pwm , once voltage is low mppt won't do anything with it either


    I agree. I preformed a short circuit test on one of my 160 watt panels I'm getting ready to install. 9.41 amps. Covered one cell....amps dropped to .4...... So... Hmmmm perhaps I should try it on different cells to see the effects in output.
  • Naio's avatar
    Naio
    Explorer II
    Jun 05, 2016
    Thanks very much, smkettner and MrWizard, for the clarifications.
  • wbwood's avatar
    wbwood
    Explorer
    Jun 05, 2016
    You could also go with a 100 watt solar suitcase. More portable and has the legs... we have one.. But we also just ordered this http://www.renogy.com/renogy-200-watt-12-volt-monocrystalline-solar-rv-kit/. It is more expensive than the 200 watt kit you mentioned, but the charge controller is better, has twice as much cabling and etc. We don't plan to mount it right now and plan to just used it as a portable set up. But we may eventually end up mounting it at some time. I want to check this out and see how well it does. If it does more than what we need, then I may sell the suitcase panel. If not, then I may link in the suitcase panel and have a total of 300 watts....still do not have an inverter and have no need for one right now. Every thing we need to use while camping is 12 volt or propane. Or it can be plugged into a 12 volt source via the little 12v 150w inverter(s) we have. We have two brand new group 31 batteries with a total of 210amp hours...
  • MrWizard's avatar
    MrWizard
    Moderator
    Jun 05, 2016
    Shade disabling a panel depends entirely on that panel and the number and placement of the by pass diodes
    Each cell is approximately 0.5v
    36 cells equal 18v
    Loose two cells you still have 17v if all cells have by pass diodes
    If the file are limited number around a string cells
    Shade on one cell can block power from several cells
    It has nothing to do with pwm , once voltage is low mppt won't do anything with it either
  • time2roll's avatar
    time2roll
    Nomad
    Jun 05, 2016
    Naio wrote:
    on a PWM controller, Any shade disables charging on a single panel.
    With MPPT It will depend on the panel. if its has enough bypass diodes it can lose voltage and still charge a bit. so maybe :h
    Is that right? I knew about the bypass diodes, but I had no idea they didn't work on pwm.
    Generally with PWM you will have 12v panels in parallel. Even a single cell shaded will reduce voltage below battery voltage and the panel drops out.

    Bypass diodes are more effective in higher voltage panels or multiple 12v in series with MPPT. If a small section is shaded you may lose 10 volts but the rest continue to work because the total was 30+ volts when all is in the sun.

    Yes there were some 12v panels with a diode across every cell but still does not take much to get below battery voltage.
  • wbwood's avatar
    wbwood
    Explorer
    Jun 05, 2016
    CamperWill wrote:
    2oldman wrote:
    Education will save you: 12v side of life

    What are you planning on the 120v side of the inverter?

    Thanks, I have already reviewed that page. The inverter would be used for laptop charging as well as for a 600W microwave for a minute or so a day.

    behengold wrote:
    Do you know how many amp hours a day are you consuming?

    Best guesstimate has been 25-30Ah.

    smkettner wrote:
    Without a specific need I would cut the inverter by 1/2 and double the solar.
    If $200 is the budget you may need to choose one or the other.

    The $200 budget is just for solar.


    I would look at other ways of doing whatever you are doing in the microwave for a minute a day. Perhaps on the stove? In the oven? That will help reduce a lot of what you are needing it for....
  • Naio's avatar
    Naio
    Explorer II
    Jun 05, 2016
    on a PWM controller, Any shade disables charging on a single panel.
    With MPPT It will depend on the panel. if its has enough bypass diodes it can lose voltage and still charge a bit. so maybe :h


    Is that right? I knew about the bypass diodes, but I had no idea they didn't work on pwm.
  • Almot's avatar
    Almot
    Explorer III
    Jun 01, 2016
    For portable panel you can get this outdoor controller.

    Can be mounted on the panel. Not sure if it allows setpoints adjustment via netport like other small Morningstar units, but the casing and connections are weather-proof. It does have (optional) temp sensor. 10A model is good up to 140-150W.

    I recall that popular "suitcases" by Renogy are using non-weatherproof controllers mounted underside the panel, the only protection from rain being the panel itself.

    With small PWM controller the cable length from controller to battery is not important as long as you're getting 14.6-14.8V at the battery. Panel generates 18-19V but PWM will cut the excess off anyway.

    Some portable users here chose to install controller in cargo bay.

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