Questions about building solar

Discussion in 'Power - Site Power/Batteries/Generators/Solar' started by Watchamakalit, Jun 28, 2020.

  1. Watchamakalit

    Watchamakalit New Member

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    My plans and intentions are for alot of boondocking in the future. I am trying to chase the limitations of our camper and see how far we can extend them. I am well aware water will generally be my barrier, that in mind I am trying to ensure enough power generation and storage to stay indefinatley. I kept my 2yr old well maintained deep cycles off my fishing boat when I sold it. I am aware that a pair of 29 series deepcycles aren't the ideal way to go but batteries being the large expense I am willing to make do with what I have for now with the intentions of upgrading to something lighter and more efficient in the future.

    It will just be me and the wife 90% of the time. We really don't use alot of extra power, maybe charging devices daily and the wife MUST have her fan at night. I am interested in about 100W worth of panel and a charge controller, but I am finding out really fast that I am solar stupid. So I come to the portal looking to peer deep inside and discover the knowledge I need to reach my goal.

    Save me from my ignorance fellow campers.....
     
  2. rabird

    rabird Howdy!

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    what are the questions?
     
  3. Watchamakalit

    Watchamakalit New Member

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    HAHAHAHA I guess I forgot that part. I am unclear on how to size and select a charge controller and panel combination. Is it something that can be mixed and matched? Will I need a disconnect for the times I connect to shore power? I am thinking a breifcase style panel that can be moved to the sun as needed will be my best option as we would normal park in the shade if available. I basically need a crash course in solar systems and how they tend to interact with the existing system. Is it really as easy as connecting a charge controller and panels?
     
  4. Eric Webber

    Eric Webber Active Member

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    I am close to the upper limit on what can be done with Solar in 2020 and still learning

    what do you want to know?
     
  5. Watchamakalit

    Watchamakalit New Member

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    I must have posted while you were....
     
  6. Eric Webber

    Eric Webber Active Member

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    It is.

    Your panels go to the charge controller. They can be any size you want, provided the charge controller can handle the spec. Charge controllers have limits in Amps and Volts rather than watts.

    a PWM charge controller is cheap, and may even come with the suitcase panels. Pwm works but isn’t fantastic. A single suitcase is fine but if you increase to several suitcases, you benefit from moving to an MPPT charge controller.

    charge controller can go to battery or can even go to the fuse combiner in your converter panel.

    you do not have to disable anything while connected to shore

    now, if you also add an inverter, there will be more considerations

    for a starter kit that will still be useful no matter what, that can also be handy in a power failure- get a Renogy suitcase kit.
     
  7. rabird

    rabird Howdy!

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    based on battery size you start with 200 watts of solar min
    based on usage who knows, fridges with a 12v brain add to daily minimum.
    based on days of autonomy who knows, as a minimal power user your 200 ah battery capacity could be days to weeks! No one knows your real demand and time of year can change that as it changes solar production.

    100w solar / 100ah of battery is a starting point that would let most folks extend a weekend for a few days. Others go a week of more on 100ah capacity.
    My concern for what you are suggesting indefinitely is battery care. Weekly 100% FULLY charge means much more solar or some other method to care for batteries. One needs enough batt capacity to last for days of no sun and then enough solar to recharge from 50% to 100% in a day (or gen/utility recharge weekly). Weekly 100% charge for acceptable battery life.

    1-2 hr daily to twice a week generator would be helpful for daily bulk charge and then let the sun top off the batteries, definitely indefinite with regular fuel additions/maintenance.

    12v charges for gadgets or inverter, ability to cut usage if batt is deeply discharged.

    Start with battery care, hydrometer, sulfation, equalization, top charge, 100% FULL regularly, guessing at state of charge, batt monitor, ...

    [ramblings off]
     
  8. Anthony Hitchings

    Anthony Hitchings Well-Known Member

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    there is no right or wrong answer, but try and avoid upgrading when it means discarding something. You already have batteries :)
    so get 2 x 100W panels of identical electrical characteristic, and a decent charge controller. The rest is busy work - wiring, switches, connectors, receptacles, fuses blocks and so forth.

    It helps for one of the panels to be truly portable to follow the sun, the other can be on your roof.

    Roof mounted panels suck when using forested campsites such as Yellowstone and Glacier.

    Thus far our PUP has not been connected to TV for charging, but it can be, all I need to do is add one wire in my electrical cubby in the PUP.

    If you plan to also charge PUP fro TV preferably use an isolating solenoid in the TV wired to a hot-in-run location in the TV. My solenoid is in placed but I jumpered a bypass for now; as I am still looking for an easy hot-in-run wire to tap in to for 3/4A draw.
     
  9. rabird

    rabird Howdy!

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    On my ole S-10, I used an add a fuse inserted in an unused sun roof slot to power a relay. It was hot with ignition so when I turned the ignition off the relay was open. 8 gauge or bigger would be appropriate for the long run to the rear. I used smaller (10) and plastic loom.
     
  10. Brewman

    Brewman Member

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    First thing I would do is make your trailer as energy efficient as you can. Install LED bulbs, ECT..

    Do a power audit and find out your max draw in amps. You can do this in a few ways.

    1. Read the products lable for power requirements.
    2. Install a cheap meter to show you your power draw.

    I personally would install a capacity monitor. Not only will it tell you your battery capacity, it will also show you your amp draw. Even if you don't go solar it will be a great addition to your trailer.

    Items like fridges that cycle can be misleading. The sticker may say for example 12V 3A. At initial turn on it will draw the full 3A or more but will lower as it comes to temp. Also it's not always on so the amp calculation will be based on its cycle time. A meter give you the the option to do a 24 hour test to see what it really draws over time.

    Also remember that during the day with a correct sized system the power you are generating from solar will run your loads as well as charge your battery. (Sunlight condition applies)

    After you determine your total load you need to figure out if you want any backup days of power you want. It could rain for two days so do you want power during this time.

    Now you can size your battery bank, number of panels to charge that bank in 5 hours, and Solar Charge Controller that can handle that amp load.

    Dan
     
  11. SteveP

    SteveP Well-Known Member

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    First, nice truck, I was always a big fan of both the MJ and the XJ.

    Starting with 200 AH of battery is a big plus. Your big draws are gonna be the fans and the furnace. The bunk end fans move a decent amount of air, but they draw pretty high amperage, are a bit noisy, and are not really directional. I like to use the O2cool D cell fans when camped, they are quieter, can be pointed directly at your face and are no drain on the house battery. They do take a lot of batteries but they last a long time.

    If it hasn't been done already, convert your ceiling lights to led, that saves a lot of juice.

    The old rule of thumb was to use 1 watt of solar to 1 AH of battery capacity. That can be done incrementally if budget constricted, 100 watt now, add 100 watt later. The controller is really your primary concern. Do the cost comparison but I don't see any cost benefit to less than a 30 amp controller. I've used Sunpower, Morningstar and Renogy, all PWMs, and would go with either of the latter two, or Victron MPPT, if I did another implementation. The MPPT really has very little benefit in a 100 watt implementation but if combining 2 100 watt panels it allows you to connect them serially, which reduces voltage drop in long wire runs between the panel and the controller.

    Mount the controller as close to the battery as possible and connect it directly to the battery, both positive and negative. You do not want to see any voltage drop between the two if possible.
     
  12. tenttrailer

    tenttrailer Art & Joyce - Columbus, O

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    It's all going to depend on you usage.

    We did the 2 G31 battries and one 80 watt panel for years on our popup and it worked well. But we dont use much battery.

    Our big thing is the high number of day with heavy overcast. So we need to span the overcast days. With the two battries we can go about 4-5 nights in the 20's running the furance at 68 at night. If we get one sunny day every 3 days we are good to go.
     
  13. Eric Webber

    Eric Webber Active Member

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    The 1w to 1ah rule is based on off-grid living, where you want to be full battery as often and quickly as possible. In a PUP, many/most just want to slow the depletion so they get longer before running out - say a week instead of a weekend. At least, that's how I started
     
  14. kennedyma

    kennedyma Member

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    The biggest thing you can do is an energy audit. Figure out what you are going to use and work backwards for there. Otherwise you might over/under build the system.
     
  15. Watchamakalit

    Watchamakalit New Member

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    Ok so i guess I left out some info that is relevant to this discussion.

    1. I have already swapped every light on the camper to led. Including the running and tail lights.
    2. I have a 3 way dometic fridge. I have heard they are power hogs on 12v and had plans that it would just stay on propane most times we don't have shore power.
    3. Our pop up didn't come with the bunk fans. (I believe this was the only factory thing other than the screen room that was missing. Not bad for a 17yr old camper) My wife already got an O2cool fan, so that is taken care of.

    Unless I am missing something I believe our actual power usage should be fairly low overall. I base this on the fact that the only things that will be consuming power would be the water pump, co detector, lights, and whatever we plug in. When we are camping we prefer to leave the distractions of the modern world behind. So no tv, not much device usage other than the occasional forum check or you tube bender. Usually charging phones once daily. I am sure there are things I am missing but feel this is a really good start.

    So I need a usage meter, any recommendations?
     
  16. Watchamakalit

    Watchamakalit New Member

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    Thanks for the compliments on the truck. I have always been a Jeep guy. I have owned several mjs over the years and regreted selling them all. This one will stay as long as possible.
     
  17. Anthony Hitchings

    Anthony Hitchings Well-Known Member

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    u donT NEED a usage meter. Its just a nice to have item. You can do a good power consumption estimate in Excel.
     
  18. SteveP

    SteveP Well-Known Member

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    As a fractional user, only using a small portion of your available battery capacity daily, it is less important. As you add to your power usage, and especially if you start dealing with inverters, it becomes more important. I'm still using the voltage display on my solar controller as my meter. As with any voltage only meter, during the day it displays charging voltage, not true battery voltage, so there is a bit of faith involved relying on knowing the current health of the battery bank.

    I've toyed with the idea of adding a Victron BMV-712 to my system, but they seem to have increased in price about 20% the last few weeks. Probably part of the Covid-19 demand/price increase on anything camping related. There are much cheaper versions available but if you get one make sure that it can count both amps in and amps out of the battery bank and can calculate percentage, or you might as well just stick with a voltage display.

    For fractional use of FLA batteries, a good charging regimen and use of a good battery hydrometer the best starting point.
     
    Last edited: Jun 30, 2020 at 10:06 AM
  19. rabird

    rabird Howdy!

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    go camping, check batt voltage each morning (after furnace has been off some time).
    use 'open-circuit voltage test' as described (other care available also)
    https://www.trojanbattery.com/tech-support/battery-maintenance/

    estimate usage, if your start 100% and later are 70%, ya used 30% of your battery bank capacity.

    the lower a battery's voltage gets and the longer it stays discharged the harder to reverse the chemical reaction back to 100% FULL, repeated undercharge is the slow demise of batteries.
     
  20. bobinfleet

    bobinfleet Well-Known Member

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