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Thread: Would like some help hashing out an electrical system.

  1. #1
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    Default Would like some help hashing out an electrical system.

    So my build with my van is moving ahead and I am starting to have to seriously look at electricity for my van. I'm on a bit of a tight budget and looking for an economical setup for just myself.

    I'm looking to run a 12V fridge, lights, propane alarm, water pump, and charge my cell phone. With my budget being what it is, I'll skip an inverter for now and charge my laptop where I can and use it sparingly, as most of the things I need up front are 12V.

    I'm going to have to start with a very basic system and add onto my system as funds allow. Since I am going to be doing most of my 'camping' dry I have decided to move in the direction of solar first giving priority to all my 12V needs first.

    Here is what I am thinking for a basic setup to start
    100 Watt solar panel array
    20 amp solar charge controller
    12V 200ah battery bank

    And then of course I'd need some 8 ga wire, 30 amp fuse(s), a battery shutoff, and I think I'll need a 4 or 6 circuit distribution panel.

    Later down the line I'll probably add a 3rd 12V 100Ah battery, a 1,000-1,500 Watt pure sine inverter, a 20 amp converter/battery charger, and an automatic transfer switch.

    Do I have everything about right?

  2. #2
    The heart of such a system is the Auxiliary/house batteries.

    Have you made a choice as to flooded batteries or more expensive AGM batteries?

    Flooded batteries should not be mounted in the cabin unless they are in sealed boxes vented to the exterior, as they will offgass when being charged.

    Consider mounting batteries under the floor with pre-made battery or custom made trays.

    Of course the batteries should be able to be charged by the alternator, and the engine battery should be isolated from house loads with the engine off, so a method of isolation is required. There are many many threads here on methods of doing this. I'd prefer the Simple/dumb Solenoid for automatic switching like this 45$ unit:
    http://www.texasindustrialelectric.com/pdf/SAS_4202.pdf

    Maximizing alternator recharging requires thick cabling between alternator and isolator/solenoid/contacter and isolator to batteries. Do not think a 100 amp alternator can ever feed 100 amps into the batteries. It will produce just enough amps to raise and then keep the voltages in the mid 14's if you are lucky. This might be as low as 12 amps despite the batteries being in the 50% range and able to accept 50+ amps. Idle speed alternator amperage can be truly pathetic depending on the vehicle. Most people will vastly overestimate their alternator's contribution to battery recharging.

    Solar is great but might not really be too cost effective for you if you are balking at a 50$ 400 watt inverter for your laptop.

    Speaking of the laptop, goto Amazon electronics, type in you laptop's brand and model number and add 'car adapter'

    There will likely be a product in the sub 30$ category that will silently step up your Van's 12 volt system to the Laptop's ~19.5 volt System silently and much more efficiently than using an inverter to power the Laptop. It will plug directly into a ciggy plug receptacle.

    Look at the power brick on your laptop. Multiply the output amps times the output volts and this will give you the maximum output watts of the power brick. If this number is under 60, you can get a universal laptop car adapter for under 10$. I spent 31 dollars delivered for the one powering this laptop right now. It is capable of providing 90 watts.

    Expect a 12v fridge to use about 25 amp hours a day. Most agree a 60 watt panel is needed in a sunny environment to replace what the fridge will use.

    I use a regular Automatic battery charger as my 12 volt Converter. It works pretty good as long as the fridge is also running on 120 volts. If the fridge is not on 120 volts during battery charging, the voltage skyrockets after the compressor shuts off, and the charger goes into fault mode and shuts off. If the batteries are fully charged this does not occur and it works very well as a RV type converter..

    I'd say to start by figuring out where you are mounting the batteries, and how you will route the cabling/wiring to allow alternator recharging. Also figure out where you are going to mount the interior electronics like the Fuse panel/ Ciggy plug outlets/ inverter/ Solar charge controller.

    It is also better to have the batteries be the same age and make. Adding another battery down the road is not a great idea. Having too much battery for the solar is not ideal for the batteries either, and 300 amp hours of battery is probably more than you need for what you have listed.

    A cell phone charger uses very little electricity.

    Really to keep the batteries happy via solar, they should be recharged at 5 to 13% of the battery capacity, so 300 a/h of battery should get 15 amps from the solar. That is around 260 watts of solar panel, Midday.

    Most devices have no issues with cheaper MSW inverters. What you expect to need to power that requires Pure Sine wave at 1500 watts?

  3. #3
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    I would like to go with a AGM batteries for my system as I don't see the point on skimping on really good batteries. Like you said, this also eliminates out gassing issues.

    My laptop requires 90W, I can't seem to find a 12V product designed for it. So I suppose that's out of the question?

    A 50 dollar inverter is out of the question, but because It's too small, the reason I wanted a larger inverter is to eventually add a few more things to my system. I was under the impression I need a pure sine inverter for a few applications but perhaps I overshot the wattage and could do with a smaller one. I'm looking at adding a small microwave and charging a few tool batteries down the line once I get the pure basics sorted.

    The batteries and electronics will be mounted around the passenger side wheel well in the back. I'll be building a box to cover this wheel well and housing my batteries and electronics in a linear fashion, the distribution panel will face towards my sliding door.

    You make a good point and I think if I scale back a little I can do more on my budget. How about if I ran some cable from my battery bank, punched a hole in the floor and ran the cable under my van in a conduit to my alternator? What kind of gauge cable would I need? Then I'd just need that isolator and a 100 amp fuse, right?

    At the same time I could scale back to a smaller solar system and go with a 50W panel and 20 amp solar charger to offset my fridge.

    Then I could go with a 1,000 watt pure sine inverter.

    For the battery charger how does that work? Do you have a two way fridge wired to both 12V and 120V that automatically switches or what? And then you just plug the battery charger into a power plug? I like this idea and would like some more info.

  4. #4
    I just typed a long response, and it f'ing disappeared.

    Here's the short version.

    My fridge does automatically choose 120v AC when available. I keep it, and a battery charger plugged into the power strip. The inverter is located right above the power strip. When I need to, I unplug an accessory from the power strip and plug it into the inverter. Simple and effective. My Automatic charger also will turn on automatically but only on the 2 amp setting, not the 12 or 25. It does not like having larger loads( 1.5 amps +) cycling on and off when charging the batteries, but is okay with such loads when the batteries are full and are being 'floated' by the charger. So it would not like a DC only Fridge, and a RV type converter would work better.

    My house batteries are located under the floor behind the driver's seat. 12 foot 2 awg cables are used. I would not go thinner than 2 awg for your proposed location. Thinner will work, just will slow down recharging, possibly significantly.

    Post the make and model of your laptop and I'll shop for a car adapter for you. They really save a lot of battery power versus using an inverter.

    Microwaves can consume upwards of 120 amps from the battery bank. This is really hard on the battery banks and will significantly shorten their longevity. Some report better longevity of the microwave on PSW versus MSW. Some also run the engine while using the microwave. This only slightly offsets the battery draw, depending on the engine rpm and alternator capability at said rpm. I urge you to use propane for cooking duties. This necessitates a roof vent preferable with exhaust fan.

    Some portable power tools chargers will self destruct on MSW inverters. Some will not. I do not have a list. Most of these will not draw more than 100 watts, so you might save money by having a small PSW inverter, and a larger MSW inverter for the bigger stuff.
    Last edited by wrcsixeight; 03-21-2011 at 08:45 PM.

  5. #5
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    One thing I should note is I don't want to do any hardcore wire splicing, crimping, soldering, etc. I am having a fiasco of a time installing my new stereo and speakers and decided to just hire it out seeing as how I have blown so much money on supplies and done damage to my van.

    Ideally I'd like as much of a plug and play system as possible. I can do a bunch of things myself, but wiring just isn't my thing, especially dealing with so much current.

    I have a Lenovo T400s. The microwave I am looking at is 600w. I cook once or twice a week and just heat my dinner up usually. Since I will be living in the van full time for a few years I'd like to go this route.

    So any 2 way fridge I can wire to a 12V distribution panel and plug into a power strip from my inverter and it will switch back and forth automatically when it detects shore power? And the battery charger I just plug into the 120V power strip and when I have access to shore power just plug it into an outlet?

  6. #6
    Here is just one of the Car adapters I found for a lenovo T400.

    [ame="http://www.amazon.com/Adapter-Fits-Lenovo-R400-Hiport/dp/B003WH9LPS/ref=sr_1_14?ie=UTF8&s=electronics&qid=1300748553&s r=1-14"]http://www.amazon.com/Adapter-Fits-Lenovo-R400-Hiport/dp/B003WH9LPS/ref=sr_1_14?ie=UTF8&s=electronics&qid=1300748553&s r=1-14[/ame]

    Here's one for super cheap:
    [ame="http://www.amazon.com/Adapter-Charger-ThinkPad-63666au-TABLET/dp/B003F43B9A/ref=sr_1_11?ie=UTF8&s=electronics&qid=1300748553&s r=1-11"]http://www.amazon.com/Adapter-Charger-ThinkPad-63666au-TABLET/dp/B003F43B9A/ref=sr_1_11?ie=UTF8&s=electronics&qid=1300748553&s r=1-11[/ame]

    Are you planning on a chest style 12v fridge, or a front loader?

    A front loader is pretty much designed to be in a cabinet that promotes ventilation over the compressor.

    I Do not know if the chest style fridges like ARB and Engel switch automatically to 120 volts when available.

    I think this is a good charger for a 200+ AH battery bank.
    [ame="http://www.amazon.com/Vector-VEC1093-Smart-Battery-Charger/dp/B00009RB0T/ref=sr_1_cc_1?ie=UTF8&qid=1300749159&sr=1-1-catcorr"]http://www.amazon.com/Vector-VEC1093-Smart-Battery-Charger/dp/B00009RB0T/ref=sr_1_cc_1?ie=UTF8&qid=1300749159&sr=1-1-catcorr[/ame]

    Some fridges can be found here:
    http://www.defender.com/category.jsp...1|406&id=10789

    Since these 12 v compressor fridges are $$$$, some elect to power a 100$ dorm style fridge with an inverter 24/7 instead. I believe this option is much less efficient, and will use significantly more battery power than a 12 volt fridge.

    If you cannot find someone reasonable in your area for the electrical install, I'm in North County, and need work.

  7. #7
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    Quote Originally Posted by Basement Yeti View Post

    You make a good point and I think if I scale back a little I can do more on my budget. How about if I ran some cable from my battery bank, punched a hole in the floor and ran the cable under my van in a conduit to my alternator? What kind of gauge cable would I need? Then I'd just need that isolator and a 100 amp fuse, right?

    At the same time I could scale back to a smaller solar system and go with a 50W panel and 20 amp solar charger to offset my fridge.
    I think wrcsixeight already mentioned that you'd want to run an isolator for that. I'd go with 8 gauge personally, make sure it's fused and isolated.

    If it's a solenoid isolator you can wire it up to only trigger when the key in the in run position. Just tap a key-on power circuit and run it to on of the trigger posts, then ground the other.

    If you don't want a solenoid isolator you can use a diode isolator, it'll cost a little more and loose a little power to inefficiency but it'll keep the house and charging batteries completely separate. For your budget I'd stick with the solenoid type.


    Personally I wouldn't trust solar to power a fridge, I'd look around and pick up a used generator.

  8. #8
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    Hrmm....a few thoughts.

    For me, the point of a cheap aux battery is that I know ahead of time that I will be draining it below 50% and thus shortening its useful life. Since I know I'm going to abuse it and plan to replace it every couple of years, I don't spend a lot on a high quality aux battery. (I do spend money for a high quality engine start battery however, that's mission critical.)

    Putting the battery in the rear brings up the spectre of voltage drop. If your alternator is putting out 14.4v but only 13.4v is getting to the battery, then your nice expensive AGM will not be getting a full charge and you'll be doing a thing called "deficit charging" - which will shorten the battery's life.

    Wire size is not only about the amperage, it's also about getting the voltage from Point A to Point B with the least amount of drop. This becomes more important the lower the voltage you start out with, and 14.4v ain't all that much voltage.

    Diode type isolators generally have -at least- a .5v drop to begin with, and then add whatever additional voltage drop due to insufficiently sized wire. There are a few diode type isolators that are designed to not have that problem - you probably won't find one at the local auto parts store. Solenoid isolators are the good stuff.

    With a 100w flat mounted solar panel, your power budget will be roughly:

    100w x 5 hours of good sun = 500 watt*hours / 12v = 41.5 amp*hours

    It's actually worse than that, since most of the time the panel will be hot and only putting out about 80%, so:

    80w x 5h = 400wh / 12v = 33.3ah

    But actually, your charge controller won't be putting out 12v, it'll usually be putting out more like 15v or 16v (unless you spend extra for an MPPT charge controller - I wouldn't) so:

    80w x 5h = 400wh / 16v = 25ah

    Is what you can realistically expect to harvest on average.

    But...the battery isn't 100% efficient either, nor is the charge controller, so figure you'll only get 25ah * .8 (80% efficiency) = 20ah actually stored in the battery.

    Okay, so you can replenish 20ah per day into the battery. If your fridge actually does consume 25ah/day as mentioned in a previous post - then your 100w panel won't keep up. Deficit charging again, and shortening battery life.

    (I have no idea how much the fridge will draw. On another thread someone posted actual usage figures for their fridge, but since I don't have one of those fridges, I never looked at them.)


    The other thing to consider is battery capacity vs. solar harvest. With a 20ah/day harvest, you could take a 40ah battery down to 50% and recharge it in one day. If you use any battery capacity larger than that - then you can't recharge it in one day.

    If you had a 100ah battery, and you drain it 25ah/day, then it'll last 2 days before it'll hit 50% and need recharging, but will take more than two days to recharge.

    That's fine if you only use it on weekends - you can leave it sit in the sun all week to recharge, and then drain it on the weekends. It's not fine however for long-term daily use - because once again, you'll be into deficit and reducing the life of that nice expensive battery.


    For portable solar systems - RV, boat, whatever - it basically comes down to "how many watts of solar do you have (or can fit)?" That dictates your average harvest. Your average harvest dictates how much battery capacity you need to store that harvest.

    Half of that battery capacity is your daily power budget if your only source of power is the solar.
    Last edited by dwh; 03-22-2011 at 03:03 AM. Reason: typo gremlins
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  9. #9
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    Great info guys, thanks.

    Quote Originally Posted by wrcsixeight View Post
    Here is just one of the Car adapters I found for a lenovo T400.

    http://www.amazon.com/Adapter-Fits-L...748553&sr=1-14

    Here's one for super cheap:
    http://www.amazon.com/Adapter-Charge...748553&sr=1-11

    Are you planning on a chest style 12v fridge, or a front loader?

    A front loader is pretty much designed to be in a cabinet that promotes ventilation over the compressor.

    I Do not know if the chest style fridges like ARB and Engel switch automatically to 120 volts when available.

    I think this is a good charger for a 200+ AH battery bank.
    http://www.amazon.com/Vector-VEC1093...sr=1-1-catcorr

    Some fridges can be found here:
    http://www.defender.com/category.jsp...1|406&id=10789

    Since these 12 v compressor fridges are $$$$, some elect to power a 100$ dorm style fridge with an inverter 24/7 instead. I believe this option is much less efficient, and will use significantly more battery power than a 12 volt fridge.

    If you cannot find someone reasonable in your area for the electrical install, I'm in North County, and need work.
    I would prefer going with a front loading fridge to free up counter space. Thanks for finding those chargers for me, I will definitely grab one. Where is North County in regards to where I am?

    I learned something valuable today and it's that some things on this van are best left to professionals who know what they are doing. Messing with high voltage stuff like this can cause some serious damage and I will definitely be looking for help installing it.

    Quote Originally Posted by 2500ak View Post
    I think wrcsixeight already mentioned that you'd want to run an isolator for that. I'd go with 8 gauge personally, make sure it's fused and isolated.

    If it's a solenoid isolator you can wire it up to only trigger when the key in the in run position. Just tap a key-on power circuit and run it to on of the trigger posts, then ground the other.

    If you don't want a solenoid isolator you can use a diode isolator, it'll cost a little more and loose a little power to inefficiency but it'll keep the house and charging batteries completely separate. For your budget I'd stick with the solenoid type.


    Personally I wouldn't trust solar to power a fridge, I'd look around and pick up a used generator.
    I am just looking at solar as a way to trickle some power into my system between drives.

    Quote Originally Posted by dwh View Post
    Hrmm....a few thoughts.

    For me, the point of a cheap aux battery is that I know ahead of time that I will be draining it below 50% and thus shortening its useful life. Since I know I'm going to abuse it and plan to replace it every couple of years, I don't spend a lot on a high quality aux battery. (I do spend money for a high quality engine start battery however, that's mission critical.)

    Putting the battery in the rear brings up the spectre of voltage drop. If your alternator is putting out 14.4v but only 13.4v is getting to the battery, then your nice expensive AGM will not be getting a full charge and you'll be doing a thing called "deficit charging" - which will shorten the battery's life.

    Wire size is not only about the amperage, it's also about getting the voltage from Point A to Point B with the least amount of drop. This becomes more important the lower the voltage you start out with, and 14.4v ain't all that much voltage.

    Diode type isolators generally have -at least- a .5v drop to begin with, and then add whatever additional voltage drop due to insufficiently sized wire. There are a few diode type isolators that are designed to not have that problem - you probably won't find one at the local auto parts store. Solenoid isolators are the good stuff.

    With a 100w flat mounted solar panel, your power budget will be roughly:

    100w x 5 hours of good sun = 500 watt*hours / 12v = 41.5 amp*hours

    It's actually worse than that, since most of the time the panel will be hot and only putting out about 80%, so:

    80w x 5h = 400wh / 12v = 33.3ah

    But actually, your charge controller won't be putting out 12v, it'll usually be putting out more like 15v or 16v (unless you spend extra for an MPPT charge controller - I wouldn't) so:

    80w x 5h = 400wh / 16v = 25ah

    Is what you can realistically expect to harvest on average.

    But...the battery isn't 100% efficient either, nor is the charge controller, so figure you'll only get 25ah * .8 (80% efficiency) = 20ah actually stored in the battery.

    Okay, so you can replenish 20ah per day into the battery. If your fridge actually does consume 25ah/day as mentioned in a previous post - then your 100w panel won't keep up. Deficit charging again, and shortening battery life.

    (I have no idea how much the fridge will draw. On another thread someone posted actual usage figures for their fridge, but since I don't have one of those fridges, I never looked at them.)


    The other thing to consider is battery capacity vs. solar harvest. With a 20ah/day harvest, you could take a 40ah battery down to 50% and recharge it in one day. If you use any battery capacity larger than that - then you can't recharge it in one day.

    If you had a 100ah battery, and you drain it 25ah/day, then it'll last 2 days before it'll hit 50% and need recharging, but will take more than two days to recharge.

    That's fine if you only use it on weekends - you can leave it sit in the sun all week to recharge, and then drain it on the weekends. It's not fine however for long-term daily use - because once again, you'll be into deficit and reducing the life of that nice expensive battery.


    For portable solar systems - RV, boat, whatever - it basically comes down to "how many watts of solar do you have (or can fit)?" That dictates your average harvest. Your average harvest dictates how much battery capacity you need to store that harvest.

    Half of that battery capacity is your daily power budget if your only source of power is the solar.
    Well since I will be living in my van an AGM battery bank will be a good investment in my mind. Plus it eliminates the need for venting and stuff.

    With my idea for placement of electronics my battery bank will only be about 6 feet or so from the alternator. I can change my layout and move my the batteries a couple feet closer if need be, let's say 3 or 4 feet.

    If I went with a good solenoid isolator, moved my batteries a bit closer, and went with the proper gauge wire would this help to alleviate some of this problem?

    If I combine my alternators charging capacities with a solar panel and charger plus a battery bank that will last me for more than just a day or two wouldn't this help?

    So if I had a 200ah battery bank my maximum capacity would about 50ah a day with the alternator and a solar panel charging the system?

  10. #10
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    Quote Originally Posted by Basement Yeti View Post
    Well since I will be living in my van an AGM battery bank will be a good investment in my mind. Plus it eliminates the need for venting and stuff.
    Sure, and if the battery is going to be inside the cabin, then AGMs are nice since they don't vent hydrogen into the living space when they are being charged. (Unless you overcharge them and pop the seal...)


    With my idea for placement of electronics my battery bank will only be about 6 feet or so from the alternator. I can change my layout and move my the batteries a couple feet closer if need be, let's say 3 or 4 feet.
    Or just use big enough wire to keep the voltage drop to a minimum and you can put the batteries wherever you want.


    If I went with a good solenoid isolator, moved my batteries a bit closer, and went with the proper gauge wire would this help to alleviate some of this problem?
    Each of those steps would alleviate one possible cause of voltage drop. If you use adequately sized wire, then there's no need to move the batteries.


    If I combine my alternators charging capacities with a solar panel and charger plus a battery bank that will last me for more than just a day or two wouldn't this help?

    So if I had a 200ah battery bank my maximum capacity would about 50ah a day with the alternator and a solar panel charging the system?
    That depends on how much you drive. If you drive a few hours a day, you probably don't need the solar in the first place.

    Personally, when I find a spot I like, I'll stay there for days - so I have a small generator that I can use to recharge the battery every 3-4 days if I'm not driving much.
    ...
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    Current: 76 E-250, bubble-top, self-contained|couple of old Yamaha enduros
    Previous wheelers: 41 Willys|78 FJ40|78 Bronco|84 Bronco|74 Ramcharger|78 Ramcharger|79 D150 PowerWagon|77 D100|79 D400 dually, converted to 4WD, utility bed, 10' Lance|75 Westy|69 Scout, RHD|bunch of others|bunch of bikes|couple of boats|couple of motorhomes|blah blah|so what|not my idea|just doin' what I'm told|wank wank|this space for rent|candy is dandy|but liquor is quicker

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