New Project

AbnormalSpring
AbnormalSpring Registered Users Posts: 8
Hi I am new here I have done research into what I need but still have some questions.

Here is my project. I am turning my aluminum truck camper into a miniature rv for living. I want to run a portable climate control system, small 19 inch tv, mini fridge, and a lamp.

My battery bank will be 8 6v exide gc-125 golf cart batteries wired in series. That is about all I have figured out so far. I have found out with the research that I have done that batteries are the most explained part and when I look at charge controllers you cant really find much on them and I don't know what kind of inverter I need either. I want 1 or 2 solar panels the space i have to mount them on is 54 inch's wide and 96 inch's long.

I want to start buying all the things I need so that I can have them purchased and start installing everything by march.

Any feedback, help, suggestions, or links to articles for extra research would be greatly appreciated. I am also only wanting to spend 2k on solar parts but no more the 3k dollars.

Thanks in advance

Notes: tv will only be on for 1 hour or less a day same with the lamp. I have chosen 8 batteries because i want to run the ac/heat for 6 hours a day constant while I am sleeping. They only thing that will be running constant is the mini fridge.

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: New Project

    i think some explanation of what you have in mind for climate control is in order here. you will need to determine what your draws are for each load with the time over a 24hr period. that can be done with a kil-a-watt meter and list these out so that others can get a better picture of what you are doing.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: New Project

    Hi "Adnormal", welcome to the forum!
    Now to your project.
    Very First thing to do is calculate what your daily power usage will be. If it's going to work as you wish, you must start here, how many KWH will be consumed each day. guesses can throw you way off course.
    Next, knowing your daily power requirements, pick a battery pack that will supply that power, and make it big enough to supply a couple or more days without sun. How many days is your choice.
    Only after you know all the above, go after the solar panel wattage that will be needed to fully recharge the batteries in ONE day, even with your normal loads still running!
    Once all that is done, then you can look for a charge controller that will handle the power required.
    To do otherwise will be putting the mule before the horses cart and lead to disappointment with a system that cost a lot of money and doesn't do the job.
    Oh, and three other very important things you must do when going off grid solar:
    1) Conserve electricity.
    2) Conserve electricity.
    And finally,
    3) Conserve electricity.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New Project

    First off, do not buy anything until you have a complete system plan. Especially not the batteries. They will go bad over time whether used or not, so there's no sense letting them sit around and sulphate while you're putting the rest of the system together.

    Well this is a bit of a conundrum.

    Eight 6 Volt batteries in series is 48 Volts, so if you go that route you automatically limit your choices for inverter as 48 Volt units tend to come in only one size: large. On the other hand if you want to run some sort of A/C / heater, 'large' is definitely going to be on the menu.

    If you wired it for 12 Volts you have the advantage of being able to recharge from the vehicle if necessary. But it is unlikely that will work for big power demands, and having all those batteries in parallel would also present problems.

    A bit about system Voltages: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power

    There you see the real need to determine power usage beforehand.

    Another thing: you want "1 or 2 solar panels". Chances are that will not be enough to provide full recharging for the size battery bank your proposing. Even at the largest Wattage (and they just get bigger as the Watts go up) you would not make it: two 315 Watt panels is 630 Watts and that's about enough for 400 Amp hours @ 12 Volts.

    Then there's the budget of 2-3 thousand. Pretty easy to blow that on solar stuff. For example you might get panels @ $1 per Watt and need $500 worth of charge controller to handle them. There's $1,000 gone right there. Large battery bank? Say goodbye to another thousand. Then what have you got left?

    So in order to make this viable at all it is critical to have accurate usage numbers. And I'm going to suggest that money would be better spent on a good inverter-generator rather than on a lot of or even any solar.
  • AbnormalSpring
    AbnormalSpring Registered Users Posts: 8
    Re: New Project

    I only plan on 3 day fishing trips at the river and believe I have sized my battery's right.

    Batterys
    6V
    135 minutes @ 75 amps
    226 A.H. @ 20 hour rate

    Potable climate control
    Power and Performance:
    Air Discharge:Front
    Capability:Heat/cool
    Cooling Amperage:10.08
    Cooling BTU:12000
    Cooling Wattage:1200
    Heating Amperage:10.08
    Heating BTU:12000
    Heating Wattage:1200
    Maximum Air Flow (CFM):4
    Rated Amps (Receptacle):15
    Voltage:110/120V
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New Project

    Okay you're looking at running a 1200 Watt load. That is not small by any means. What's more is the issue of duty cycle; exactly how long it will be on/off, which is going to vary by thermostat. This makes the Watt hour consumption a bit unpredictable.

    Here's what it looks like at 1/3 duty cycle: 8 * 1200 = 9.6 kW hours per day, not including other loads.

    Now take the 226 Amp hour batteries @ 48 Volts and run them down 50% (the maximum): 5.4 kW hours per day, not including system losses.

    See the problem? It is highly unlikely that this will work without some serious generator supplementing.
  • AbnormalSpring
    AbnormalSpring Registered Users Posts: 8
    Re: New Project

    Hmm Well back to the drawing bored.

    Could you give me a sugestion on what size battery bank i would need just to run the a/c for 8 hours?

    Because I was obviously way off.
  • AbnormalSpring
    AbnormalSpring Registered Users Posts: 8
    Re: New Project

    The batterys I talked about earlier plus this stuff is what I had in mind initaly.

    Solarland 100-watt Solar Panel
    Blue Sky SB2000E, 12v 25a MPPT Controller w/display
    Blue Sky Wall mount box for SB2000E
    Universal RV Mount-Z Flush Mount Feet
    Midnite MNBCM - Battery Capacity Meter
    4 Star Solar MC4 10 AWG 30' Cable
    Sunlight Resistant Tray Cable (10/2 per foot)
    MC4 Unlocking Tool

    I was looking at around 1200$ for this stuff plus the 900$ for the batterys.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New Project

    Leaving out the cycling issues (which will include a start-up surge) you're trying to supply 9.6 kW hours just for the A/C. But then it gets worse: inverter conversion efficiency at 90% (if it's a good one) puts the number up to 10.7 kW hours and running that inverter for 8 hours will consume another 160 to 240 Watt hours (depending on which inverter) so you have a need for 11-12 kW hours!

    What's that on 48 Volts? 12,000 / 48 = 250 Amp hours used. To keep the discharge around 25% (makes for longer battery life and easier recharging) you'd need a whopping 1,000 Amp hour 48 Volt battery bank.

    Oh and to recharge that entirely from solar would take a huge array too: 6kW and two MPPT controllers to handle it.

    This is in fact much larger than most off-grid systems, despite any claims to the contrary you may have heard.

    So, how much will you really need that A/C for? Could you use something a bit less power-demanding? Could propane be figured in for heating instead of electric? Having to store electric in batteries for heating anything is not very economical, although you may have heard different on that too (familiar statement that electric heat is "100% efficient", which it isn't).
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: New Project

    Sorry to be bursting your balloon "Abnormal", but Cariboocoot is telling it like it is. He's not kidding you, not pulling your leg. You are looking at a HUGE and very expensive system.
    Get yourself a good generator and use propane for heat.
  • AbnormalSpring
    AbnormalSpring Registered Users Posts: 8
    Re: New Project

    Ok Ok no a/c. I dont have it in my house i dont need it in my truck I guess. So i was looking around my bedroom and saw the fan i use to keep it cool. So why would it not work for my truck camper also.

    fan
    Motor:120v 60hz 1.0A
    total current 10A

    I just went and looked at my brothers mini fridge and it states
    120 Volts @ 60Hz, and 0.75A

    would the inital size battery bank i proposed support that with what watt solar pannel if somebody can direct me to the math that would be great so I could just come back later and ask questions about inverters and charge controllers.

    And i thought this would be easy "FACEPALM"
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New Project
    Ok Ok no a/c. I dont have it in my house i dont need it in my truck I guess. So i was looking around my bedroom and saw the fan i use to keep it cool. So why would it not work for my truck camper also.

    fan
    Motor:120v 60hz 1.0A
    total current 10A

    I just went and looked at my brothers mini fridge and it states
    120 Volts @ 60Hz, and 0.75A

    Okay, do not take the numbers on the equipment as being accurate. Invest $30 in a Kill-A-Watt meter and actually measure what you want to use, preferably under typical conditions. You'd be amazed how much that will differ from trying to calculate by supplied Amperage or Wattage figures. Sometimes it's higher, sometimes it's lower.

    For example that mini 'frige is rated as (120 * 0.75) 90 Watts. If its duty cycle is 1/3 of the time (again this will vary as it is thermostatically controlled) it would run up 720 Watt hours in a day. Here's a thread with a lot of refrigerator tests in it: http://forum.solar-electric.com/showthread.php?12272-Just-how-bad-a-small-frige-is
    would the inital size battery bank i proposed support that with what watt solar pannel if somebody can direct me to the math that would be great so I could just come back later and ask questions about inverters and charge controllers.

    And i thought this would be easy "FACEPALM"

    Nah, it's never easy. It's just always expensive. :p

    As before your 226 Amp hours @ 48 Volts is good for a maximum of 5.4 kW hours DC: 50% of the Amp hour capacity * nominal system Voltage - doesn't include losses or conversion factor or inverter consumption. If you limit the discharge to 25% for longer life and include the other factors you get a good 2kW hours AC per day.

    Now here's the good news: if you did have a properly size solar array on that and could use at least some of the power during the day you'd be even better off as an array that could recharge those panels quickly would also be able to contribute to loads as the batteries charge up (less power from panels needed to charge as batteries come up = more power from panels available for load demands).

    Even so for full charging you'd have an array around 1400 Watts (based on 10% peak charge current potential and 77% array + MPPT controller efficiency). This is roughly 2X the size of my cabin system, as it is about the same Amp hours but twice the Voltage. Now some more good news: with my 700 Watt array & 232 Amp hour batteries I manage to run a full size refrigerator plus everything else I need there, sneaking more than 2.4 kW hours out of it by being able to use some loads when the batteries are full and the panels still producing.

    With some hard numbers on your consumption (and a bit of adjusting thereof) it should be possible to put together a system that will work for you. Maybe it won't be all the bells and whistles, but it will be better than nowt.
  • AbnormalSpring
    AbnormalSpring Registered Users Posts: 8
    Re: New Project

    Ok I am back thanks to some more googling and earlier help here.

    I will be using about 920 amp hours if I leave the mini fridge and fan on for 24 hours so in three days i would use 2760 AH. The battery bank I came up with was told it would have 2kW hours AC per day.
    So that would be sufficient for my 3 day outings. This is the largest solar panel I can find that will fit the space I have avalible for one http://www.solartown.com/store/product/trina-240w-solar-panel-tsm-240-pa0508/#null;

    So here is were I am at now will that solar panel fully recharge my battery bank in the 4 days it has to charge with 4.5 peak hours sunlight?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New Project
    Ok I am back thanks to some more googling and earlier help here.

    I will be using about 920 amp hours if I leave the mini fridge and fan on for 24 hours so in three days i would use 2760 AH.

    Uh, 920 Amp hours or 920 Watt hours per day? There's quite a difference between the two.
    This is the largest solar panel I can find that will fit the space I have avalible for one http://www.solartown.com/store/product/trina-240w-solar-panel-tsm-240-pa0508/#null;

    So here is were I am at now will that solar panel fully recharge my battery bank in the 4 days it has to charge with 4.5 peak hours sunlight?

    Okay the Trina 240W is a 30 Vmp panel. That means in order to get the maximum power out of it you must use it with an MPPT type controller. A single panel will work for a 12 Volt system, but the Vmp is too low for either 24 or 48. In order to meet the charging requirements on a 48 Volt system you would need three of these in series.

    That would bring the array to 720 Watts and a peak current of about 11 to 12 Amps on a 48 Volt system. That would be sufficient for around 100 Amp hours @ 48 Volts.

    Depressing, isn't it?
  • AbnormalSpring
    AbnormalSpring Registered Users Posts: 8
    Re: New Project

    watt hours. How would i wire 8 6v battery's so that they would be 12 volts? 4 12v banks wired parallel?

    yes very depressing seems the more i try the further away i get.

    "crying" I just want to run a fan and mini fridge for 3 days why does it have to be so hard "tears"
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New Project
    watt hours. How would i wire 8 6v battery's so that they would be 12 volts?

    Four parallel strings of two in series. This is where current sharing problems can arise. Furthermore it doesn't actually change the amount of power available or the size of the array needed to recharge it, it merely alters the Volts to Amps ratio on things.
    "crying" I just want to run a fan and mini fridge for 3 days why does it have to be so hard "tears"

    It's no accident that we have an emoticon for that: :cry:

    The problem is that refrigeration uses a lot of power, no matter what.
    As for the fan ... a couple of years back it was so hot I had to run a fan overnight at the cabin. There wasn't enough stored power available in the system, so I ran it off a cheap inverter and old 12 Volt battery which I recharged during the day through a battery charger from the main system when its batteries were full. A bit 'Rube Goldberg' but it worked.
  • AbnormalSpring
    AbnormalSpring Registered Users Posts: 8
    Re: New Project

    Ok if you were do my solar what would you do to just run a fan and cell phone charger? both for just overnight hours.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: New Project

    Well a fan can be quite a range of Watts. A small one or one on low might be 35 Watts, which overnight can be 350 Watt hours just for that. Adds up fast, doesn't it?

    So we can fall back on the "build around the cheapest batteries" method. This is usually the GC2 golf cart batteries @ 220 Amp hours 6 Volts. Two in series for 12 Volts. That would bring you around 500 to 600 Watt hours AC all in storage. If you use a good sine wave inverter with low power requirements (Morningstar's 300 Watt 12 Volt unit uses 6 Watts running) it should meet the needs.

    To recharge those batteries your minimal array size would be 5% peak current (no loads drawing at the same time) or 11 to 12 Amps @ 17.5 Volts (Vmp for 12 Volt systems using a PWM type controller) gets you 210 Watts of array. You'll have to adjust to meet the available panels, but two 130 Watt panels would give you 260 Watts and about 14 Amps or 6% peak charge current.

    Also ask yourself what will happen if you run out of power? How much of a tragedy would it be? If you can bring a small generator along it's no problem to recharge no matter what. In fact one system I dealt with recently the guy was going to use an ice maker to provide cooling; make ice while the sun shines and keep it in the coolers instead of running a refrigerator.
  • Coach Dad
    Coach Dad Solar Expert Posts: 154 ✭✭
    Re: New Project
    Ok if you were do my solar what would you do to just run a fan and cell phone charger? both for just overnight hours.
    Why don't you go for the big battery bank, and use a quiet generator/inverter to recharge them while you are out fishing?
  • zoneblue
    zoneblue Solar Expert Posts: 1,220 ✭✭✭✭
    Re: New Project

    Usually for RE systems starting by looking at your loads is right thing to do. However for a mobile system, you are charging source constrained. Therefore looking at what capacity you have, then working out what that will run is also maybe appropriate.

    Charging sources:

    1. for pv, roof space limitation: 200W solar max, not gona go far. Ok for cell phone, and laptop charger/efficient tv, led lighting etc.

    2. vehicle alternator: maybe 25-40 amps for couple hours. when i did the numbers, relying on this for our motorhome the real issue there was the vehicle just didnt run for long enough periods. You can get bigger alternators, up to 100 amps or so, but that may not suit the batterys/ may not fit etc. Still doesnt solve the problem if the vehicle sits still for any period. Fine if your alwasy on the move, then it will add some useful power into the mix, with the right aux charging setup, could help.

    3. what remains... generator. Well that all depends on your routine, who you will disturb etc etc.

    ps. Coach dads idea will maybe work good if you drive far to the fishn spot, stay a couple days, then drive far home. Good luck, theres no holy grail with solar.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • SteveA
    SteveA Registered Users Posts: 24 ✭✭
    Re: New Project

    This comes back to why do you want to use solar? Is it because you don't want to listen to a generator? If so that's a good reason, but as you've seen it's not practical for your application. If you don't mind listening to the generator (the honda EU2000i is really quiet) stop there and just run the gnereator.

    If you don't mind the generator for some of the time (day) add some batteries and run the generator to charge them when needed. You can over size the batteries to provide you with enough Ah to go all three days then charge when you get home by plugging in a charger. Run a generator if you use more power (AC) or stay longer.

    If the AC is running you won't even hear the generator.

    Going solar is a noble idea but in most cases it just doesn't make sense or payoff. For one gallon of gas in a honda EU2000i you can run your whole rig for a day.