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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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