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Old 02-09-2014, 02:50 AM   #1
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Got electrical questions? I have answers!

I'm about to start building my skoolie, and I have so many questions on framing, pluming, diesel maintenance, etc. But I have no electrical related questions however. Why? I'm an electrical engineer. I work with low voltage circuitboards, all the way up to 480Vac and 600Vdc lithium battery stacks! I also used to build EVs. While other more knowledgeable people are answering my plumbing and carpentry questions, I'm here to answer your electrical ones. Battery banks, solar, wind power, gennys, 120Vac, DC-DC converters, you name it!
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Old 02-09-2014, 09:04 PM   #2
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Re: Got electrical questions? I have answers!

This is what makes this place so special, everyone is willing to openly share their knowledge with each other.
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Old 02-14-2014, 11:31 PM   #3
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Re: Got electrical questions? I have answers!

I'm getting ready to buy my first bus. I have no idea where to start with electrical, but I do know I want to go with solar panels. Due to budget restraints I will have to start small and add on as I go. How and where do I start?
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Old 02-16-2014, 12:36 AM   #4
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Re: Got electrical questions? I have answers!

I'm trying to make a bus trip worthy in a few weeks. Any advice on how to charge my phone or power a radio? I can figure out the big stuff later, but those seem doable in my timeframe.
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Old 02-16-2014, 03:28 PM   #5
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Re: Got electrical questions? I have answers!

Quote:
Originally Posted by The Painted Lady
I'm getting ready to buy my first bus. I have no idea where to start with electrical, but I do know I want to go with solar panels. Due to budget restraints I will have to start small and add on as I go. How and where do I start?
I'm planning to go all solar as well. Solar power gets expensive really fast. A refrigerator that uses only 60W needs to run all day, and will require 1440w/hrs over the course of a day. Solar panels put out good power about 5 or 6 hours a day on average. You need 1440/5 = 228W of solar just for the fridge. But what if you have a rainy day? You'll need to make extra power to save for the bad days, and to buy enough batteries to store it.

Okay, where to start. First you need to decide on a system voltage. You cannot change later. 12v means it's easier to add on to, but lower voltage means you need thicker wires, and anything over 1000W on 12v is starting to get impractical. Then you need an inverter. There are two types of inverters. Modified sine, and pure sine. Modified sine is always cheaper, and works with most devices. Pure sine works with all devices. If you use modified sine on say, a motor, it will have reduced efficiency, and may not even work at all. It works fine with things like laptops though. Then, get the inverter that is made for your chosen voltage (12, 24, 48,) . You need to decide on a wattage. This is determined by the most power hungry device you will ever use on the system. 2000w is about the most any appliance will ever use, but most are less than 1000w.

Solar: I've found panels as cheap as $120 for a 100w panel on eBay with shipping. They are 12v panels

Batteries: you need deep cycle lead acid batteries. Stay away from anything that says "marine" battery. They will not last as long. Trojan t-105 batteries are widely available, and are good quality. They run about $150 each. They are 6v batteries, so you need two to run 12v. Two will hold 2700w/hrs.

You will need a solar charge controller. This device makes sure the solar panels aren't trying to charge the batteries when they are already full. That will really hurt their lifespan. Standard (PWM) charge controllers are 80% efficient at best. MPPT type charge controllers can get 99% efficient! but they cost so much more it's sometimes just cheaper to buy more panels to offset the efficiency loss.

Once you have all that equipment,

Solar hooks to to charge controller, which hooks up to batteries, which hooks to to the inverter. Power comes in, gets stored, gets converter to 120vac and used.

The most important thing about solar is it's not about how many watts you make, it's about how many you use. It's usually cheaper to get appliances and devices that use less power, than it is to upgrade a solar system to make more.
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Old 02-16-2014, 03:28 PM   #6
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Re: Got electrical questions? I have answers!

Quote:
Originally Posted by The Painted Lady
I'm getting ready to buy my first bus. I have no idea where to start with electrical, but I do know I want to go with solar panels. Due to budget restraints I will have to start small and add on as I go. How and where do I start?
I'm planning to go all solar as well. Solar power gets expensive really fast. A refrigerator that uses only 60W needs to run all day, and will require 1440w/hrs over the course of a day. Solar panels put out good power about 5 or 6 hours a day on average. You need 1440/5 = 228W of solar just for the fridge. But what if you have a rainy day? You'll need to make extra power to save for the bad days, and to buy enough batteries to store it.

Okay, where to start. First you need to decide on a system voltage. You cannot change later. 12v means it's easier to add on to, but lower voltage means you need thicker wires, and anything over 1000W on 12v is starting to get impractical. Then you need an inverter. There are two types of inverters. Modified sine, and pure sine. Modified sine is always cheaper, and works with most devices. Pure sine works with all devices. If you use modified sine on say, a motor, it will have reduced efficiency, and may not even work at all. It works fine with things like laptops though. Then, get the inverter that is made for your chosen voltage (12, 24, 48,) . You need to decide on a wattage. This is determined by the most power hungry device you will ever use on the system. 2000w is about the most any appliance will ever use, but most are less than 1000w.

Solar: I've found panels as cheap as $120 for a 100w panel on eBay with shipping. They are 12v panels

Batteries: you need deep cycle lead acid batteries. Stay away from anything that says "marine" battery. They will not last as long. Trojan t-105 batteries are widely available, and are good quality. They run about $150 each. They are 6v batteries, so you need two to run 12v. Two will hold 2700w/hrs.

You will need a solar charge controller. This device makes sure the solar panels aren't trying to charge the batteries when they are already full. That will really hurt their lifespan. Standard (PWM) charge controllers are 80% efficient at best. MPPT type charge controllers can get 99% efficient! but they cost so much more it's sometimes just cheaper to buy more panels to offset the efficiency loss.

Once you have all that equipment,

Solar hooks to to charge controller, which hooks up to batteries, which hooks to to the inverter. Power comes in, gets stored, gets converter to 120vac and used.

The most important thing about solar is it's not about how many watts you make, it's about how many you use. It's usually cheaper to get appliances and devices that use less power, than it is to upgrade a solar system to make more.
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Old 02-16-2014, 03:33 PM   #7
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Re: Got electrical questions? I have answers!

Quote:
Originally Posted by Nebes
I'm trying to make a bus trip worthy in a few weeks. Any advice on how to charge my phone or power a radio? I can figure out the big stuff later, but those seem doable in my timeframe.
This totally depends on how long you want to run for. If you can get a phone charger and radio that use 12v, you can wire them directly into your busses electrical system without anything else needed. If they run on 120v, you can get a cheap 100W modified sine inverter. If you go to 200W, it should be enough to charge a laptop too.
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Old 02-17-2014, 01:35 AM   #8
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Re: Got electrical questions? I have answers!

Thanks Plasma that helps a lot
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Old 02-24-2014, 08:58 PM   #9
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Re: Got electrical questions? I have answers!

Plasma,

Working on our 1985 International, and before we start building out the interior we think we should plan the electrical system. I'd love to go solar in the method you described, but also to be able to plug in when we pull into someplace with power and 'get gridded.' I imagine some of our appliances won't ever be run when we are on solar, like an AC unit, and for the most part we won't be needing much juice from the solar setup, just laptops and phones and some lights I think. Not sure how this sort of system would look, where the switch from solar to shore power would be in the system, or if I would need a big 240 plug at the input end or if a standard 120 plug would be enough...can you lend some knowledge on what the major components would be of this dual system, or how a typical system would be set up?

Up to this point we've used a big inverter wired to the batteries to supply those phone and laptop needs when rolling down the road, but I guess the upgraded system will be totally separate from the bus's batteries?

Thanks

Leon
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Old 02-25-2014, 01:36 PM   #10
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Re: Got electrical questions? I have answers!

Speaking of solar, let me share a recent revelation of mine.

12v compatible solar panels are expensive. I was able to find a local producer of 300w/36v panels for way cheaper per watt than I've seen on the internet for 12v panels. $300 for 300 watts, local pick up.

The caveat? Instead of a cheap PWM solar charger you'll need a more expensive MPPT charger to take high voltage panels and make them work with a 12/24v battery bank. The upside is that MPPT are more efficient. For me, buying two cheap 300 watt 36v panels offsets the price of the MPPT charger, plus you'll save money using thinner cable from the panels to the charger.

Tracer, a Chinese company, makes some affordable MPPT chargers. I picked up a 4215rn (I think)
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Old 02-25-2014, 05:16 PM   #11
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Re: Got electrical questions? I have answers!

True, but if you're like me and already have all 12v appliances and only a few low-amperage 110vac appliances, a quality built 12v system may make the most sense. By all means, though, up the volts if you can!
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Old 02-25-2014, 10:09 PM   #12
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Re: Got electrical questions? I have answers!

we will be using a donor camper/trailer for our build. It is complete for the most part. I used to pull romex, but was never more than a glorified helper. I want to wire my build first thing. It is about to be summer here in MS, so we will need a/c in order to even be able to be in the bus to work on it. I plan to install the electrical as similar to how it is in the camper as possible. I will probably add a generator with this first build, but will want to expand my power options in the future. I want to be able to add solar in the future, so how do I leave that option open on the front end?
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Old 04-07-2014, 10:50 AM   #13
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Re: Got electrical questions? I have answers!

I have a 2001 Amtran school bus. How do I disconnect the window alarm system? It's been sticking lately and want to eliminate it totally. (it's a parts delivery unit and no longer in service as a student/child carrier)

Thanks!
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Old 04-19-2014, 12:08 AM   #14
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Re: Got electrical questions? I have answers!

Hi garry is my name and I am going to pull my 1994 Mercedes Benz, LS812 33 seater bus out of service this year.Its inside measurements is 7,9"wide and 28 ft of usable floor. I will be converting to a mobile home, I am a carpenter and have a vast experience in all types doing my own tiling furniture and other aspect to the trade have a welder and have put pullout side to my friends caravan .This is what I will be doing to mine as well. what i would like to know is the electrics to it .I don't mind paying for it .Do you design or know someone to design the electrics for me.I am in Australia and will require pumps for water all types and Australia our shore power is 240 volts. will be having solar power and solar heating assisting a 12 volt heater. the stove will be gas and might be the hot water heater...question we want to be self sufficient for about 3 weeks there is heaps of area under the bus for 2 120 gallon fresh water.. basically my other question is that i can have 20 12v or 10 24 volts batteries. the bus is 12 volts separate to the living area . and inverters are they power eaters.will be carrying a 8 kw generator. any help would be appreciated thanks garry owen
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Old 04-25-2014, 11:42 AM   #15
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Re: Got electrical questions? I have answers!

Hi all, I am having a hard time putting together my electrical system. I pretty much know what I want to do I just don't know the right equipment I need to get there. I tried to find the information in discussions already posted but the more I read the more overwhelmed I get. I want to buy the right equipment for the job. If anyone can help I'd greatly appreciate it. I'd be happy to pay someone to help design a system.

* I want to have a solar focused system. I plan on having as many solar panels on the roof as is practical. I'm not sure how much weight, space, and output makes sense.
* I want to avoid having a generator if at all possible
* I will not be out in the woods but I'd like to be able to go a while without having to hook up (with 2 people and conserving I'd like to go 1-2 weeks).
* I was thinking I wanted a 12 volt system but I will do whatever is best. I was going to use 12v appliances as much possible and limit 110v.
* I want to be able to charge a couple phones and a couple tablets, run a tv (2 hrs?), run/charge a mifi internet device, some lights (few hours), coffee maker (twice a day), occasional small microwave (not every day), two roof vent fans, water pump.
* I have a Norcold 2-way refrigerator that I can run off propane if I don't have enough battery/solar.
* cooktop and on demand water heater are propane (I'd like to supplement the with a hot plate to reduce propane consumption if I have the extra solar).
* propane tank is new 30 gallon horizontal dot
* lighting will be 12v led as much as possible.
* I have a wood burning stove for heat but I intend on being in warmer weather most of the time. I might hook up one or two of the original bus heaters that hook to the engine coolant system.
* the bus has two original a/c units, I know I won't be able to use them except when running. We generally do fine in the heat with just windows open. I rarely use my car or house a/c. I will install vent fans in the two emergency roof vents.
* I'd like to have about 10 outlets around the bus but few would be in use at any one time.
* Toilet is porcelain rv petal toilet.

I live in Tampa. Most of my travel will be around Florida with occasional trips across the south to California and to Maryland to visit family. And other random trips to see/do things around the U.S. We will stay in RV parks/camp grounds for a few days here and there but I don't want to be tied to them.


What is the best for my needs?
Inverter
Converter
Charger
Battery bank
Solar panels
Solar controller
Main panel
Wire

What else might I need? Again, I don't know what I'm doing so if my ideas seem unworkable, unreasonable, cost prohibitive, or if there's a better way, I'm all ears.
Thank you very much for any help you can offer.
-Jeremy
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Old 06-12-2014, 04:01 PM   #16
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Re: Got electrical questions? I have answers!

I was realllly excited to find this thread... According to the mechanic who worked on it, our bus (apparently) had its electrical mangled by the previous owner. I completely lack the vocabulary to name the parts - would it be OK to just post a picture?
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Old 06-12-2014, 04:25 PM   #17
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Re: Got electrical questions? I have answers!

Quote:
Originally Posted by pictureLOVE
I was realllly excited to find this thread... According to the mechanic who worked on it, our bus (apparently) had its electrical mangled by the previous owner. I completely lack the vocabulary to name the parts - would it be OK to just post a picture?
Pictures always help
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Old 08-04-2014, 12:53 PM   #18
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Re: Got electrical questions? I have answers!

Helping a friend with the electrical on a Aerotech shuttle bus. I can usually figure out most thing with electrical systems, ie... Wiring, switches, etc... I plan on using a 12 volt dc and 110 volt ac prebuilt panel, 30 amp. I have yet to look at the fuse box for the shuttle, but I'm assuming nothing will work with out the key in the ignition. So any circuit I use (existing lights) I will remove the breaker and disconnect the feed wire then hook into the new system, going through the new panel. Couple if questions. I've been looking at surge protectors which seem really expensive. Is there anything out there that is reasonably priced and resettable? (Under seventy five dollars). Is there any way to make my own with off the shelf breakers? I'm not using gfci breakers but instead gfci outlets. It's the cost issue. Thanks, and this is a great forum.
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Old 08-07-2014, 08:46 PM   #19
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Re: Got electrical questions? I have answers!

Hi,
so I'm trying to figure out how to power my inside electronics by wind. I have searched everywhere, but I have a really rudimentary knowledge of electrical work. I was wondering if you could give me instructions on how to build/buy a turbine and then how to hook it up so I can have outlets inside the bus.

Any help would be awesome!
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Old 10-03-2014, 05:48 PM   #20
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Re: Got electrical questions? I have answers!

Hello, everyone! Sorry I haven't posted answers to any questions in a long time. I have been traveling a lot. Ill see if I can give a decent answer to some questions here.

Quote:
Originally Posted by Noonien
Hi,
so I'm trying to figure out how to power my inside electronics by wind. I have searched everywhere, but I have a really rudimentary knowledge of electrical work. I was wondering if you could give me instructions on how to build/buy a turbine and then how to hook it up so I can have outlets inside the bus.

Any help would be awesome!
The electronics you are powering is the driving factor in your entire design. If you are just powering some 12v lights and maybe a stereo, you wont need much wind power. However, dont expect to be able to power your fridge, your computer, your heater, etc with a small homemade wind turbine. Depending on where you live, I generally discourage wind power. You can buy a 350W wind generator for about the same price as 350W worth the solar panels, but when you really crunch the numbers, the 350W wind generator puts out far less power on average. Only the most windy places really get the generator running at it's max, and you cannot always rely on windy conditions. Solar on the other hand may only generate power during the day, but it is more reliable. In addition, even a moderately sunny day gets it operating near it's peak. Most wind generators practically require gale-force winds to generate their rated power.

Bottom line is unless you plan to stay in particularly windy areas, where the weather is bad (Like the country I was last in: Ireland) The best bang for your buck comes from solar even if you don't live in a particularly sunny area.

As for building a wind generator, it's doable,but not practical to make a very powerful turbine without specialized parts and equipment. For example, a few days ago, I built a wind generator with a friend. We took a scrap ventilation motor, stuck some blades on it, and it made power... but only just enough to run some strong LEDs, and only when the wind blows. People who make seriously powerful wind generators rewind the coils in a car alternator, and machine a rotor with slots for neodymium magnets. In the latter case, you get a useful amount of power, but the cost is almost as much as a new turbine. Building one from scrap parts is usually not practical for making useful power.

If you still want to make a wind-turbine, ill get you looking in the right direction. As i mentioned, modifying a car alternator is one powerful, but expensive route (a stock car alternator will not make useful power). Another common option is using the motors from treadmills (or any other permanent-magnet DC motor which runs at a high voltage). Sometimes, people make the generator entirely from scratch; embedding magnets in a circular sheet of plywood which rotates, and embedding coils in another stationary plywood sheet. The blades of the wind turbine are often made with sections cut from large PVC pipe. I've done that once myself.

Both solar and wind generators require a charge controller to prevent over-charging the batteries. In the case of wind, the charge controller must have a dummy-load (or else the turbines spin too fast without one).
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