Idiots guide to electrics

kimbowbill said:
if i were you Jess, i would try the "trial and error" method go out in your van, use you power and roughly time it how long you get, for eg, when i went to RH i used my lights, water pump and tv over 4 days on 2 leisures
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This is also useful espec if you have older or second hand batteries and you don't know how much capacity is left in them. When trying it out don't let the leisure battery voltage drop much below 11.8-12v though as deep discharge is not good for the battery. That voltage is about 50% charge or a bit less.
 
Ok Ladies... I know how you feel about electricity...feel much the same way and I have O level physics!


Assuming you have 1 x 12volt car battery (or leisure battery) fully charged:
Rough guide if you have a 300 Watt inverter such as the 'Powering RINV300' which is about £60 from a camping store -
(I would always suggest running the engine when using an inverter so as not to drain the battery just as quick as below)


Computer (monitor and printer) 200w to 400w - 1.5 hours
Electric Blanket 200w - 400w - 1.5 hours
Portable Fan 50w - 200w - 3 hours
Laptop 60w - 95w - 4 hours
Small fridge (14cu. ft) 200w - 300w - 1.5 hours
TV (19") 100w - 160w - 3 hours

Now you see why generators and EHU's are popular....an electric blanket on hookup thats luxury lol...most of us would use a hot water bottle!
 
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Firefox said:
Actually the above Watts law.

Ohms law is the other equation I gave : V= IR or Voltage = current x resistance

Otherwise, all present and correct :lol-053:

For those who have problems with W = VxA, V=W/A, and A= W/V.... think off 6=3x2, 3=6/2 , and 2=6/3

Sometimes putting in example numbers instead of letters helps to see the relationship :cool1:
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:scared:

I'm having problems with both numbers and letters!! I think it's gonna take me some time and some reading to get my head round all this.
 
Thanks to everyone for the suggestions and comments and advice, much appreciated. I think I'm going to have to spend some time going right back to basics, some of the links look useful and I've found a few others too.

I'm not going to be doing any work on the electrics myself, but after blowing my incar 4 way adaptor by plugging a 12v mini fan heater through it, I realised that I am going to need to properly understand the basic principles of electricity so as not to do further damage or trip the elec when hooked up and I need to be careful about using high powered appliances etc.

I'm not going to be wanting luxuries like microwave / hair dryer / straighteners etc but on the other hand, I don't want to have to grope around by torchlight if the leisure battery dies when simply changing the lights from florescent to led would double or triple the length of time the battery will last.

I will eventually be getting my local garage to wire the leisure battery in using this relay switch thing that is apparently what I need. But not until I've decided on the layout and where the battery will be best located. But in the meantime it is like Kimbowbill said, a good way of testing the various different gadgets etc.
 
whitevanwoman said:
:scared:

I'm having problems with both numbers and letters!! I think it's gonna take me some time and some reading to get my head round all this.
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It can be difficult trying to explain the basics in only a few written sentences or posts without causing confusion. Maingates' suggestion of getting hold of one of the books by John Wickersham would be a good idea. The books explain it with diagrams, pictures and real-life examples to make it easier to understand. Plus of course, other chapters in these books cover many other areas such as gas, water systems, accessories and self-build etc.

Look online at Amazon, Ebay etc. Here's an example on Ebay......

Haynes The Motorcaravan Manual by John Wickersham. Motorhomes.. | eBay
 
that's why I need an idiots guide.
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Sorry, there is no idiot's guide to motorhome electrics and nothing makes that plainer than the simple fact that a large proportion of automotive electricians haven't much of a clue about the inner workings of a decent MH system, and an even larger proportion of normal electricians are similarly ignorant - and they do know Ohms law.

If you are serious about wanting to learn a bit more, then I strongly suggest you ignore most of this thread and instead do some research on the internet and be prepared to learn slowly at first and then faster as you pick up some basic stuff --

or do what most RVers do and just hope that nothing breaks down and if it does, call in the experts.

Psssst The 12volt Side of Life (Part 1) might get you started.
 
You don't need to know that much about electricity to wire up a van.

The problem is is knowing exactly which bits you do need to know. That's why a good read round everything will be helpful. The most important things are seperating the 240v and 12v systems, knowing what size of currents are expected and hence how thick to make the various wires, and also providing fuses, RCD's, earths and insulation to protect your various circuits.
 
I have a 100 W inverter which plugs into cig lighter for normal 3 pin house plugs and am trying to figure out the wattage of my new android tablet, I'm guessing it will be under 100w but just wanted to be sure. But I can't work out what numbers to use in the W = V x A equation that Firefox posted earlier (I am really dumb with maths, failed O level 4 times).

On the tablet plug it says Input : 100-240VAC0.3A, Output 9V---2000mA

so would this be right... watts = 240 x 0.3 therefore watts = 72 ? :confused:
 
That's what I would have thought WVW 72 watts.....but I would also need a second opinion.
 
72 watts is correct.

If you have an iPhone or Android phone, there are resistance calculators available which can make life a lot easier.
 
Here's a link to a handy little online auto-calculator that I posted earlier.

Ohm's Law / Watt's Law Calculator

You just enter the two values that you know (in WVWs' example above, the voltage and current) and it will give you the answer, with no maths needed!
 
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whitevanwoman said:
Thanks, just had a look. What is ohms?
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Ohms is the unit of Electrical Resistance in a circuit.

The Resistance very very basically is a measure of how easily a current will flow through a cable, and depends on things such as type of material (eg copper), length and diameter of the cable, temperature etc.

For example, the longer the length of cable, the higher the Resistance.

(I'm tempted to repeat my Motor-Ohms joke, but I won't!)

PS. For the calculation that you needed earlier, you can just ignore the Ohms figure, it was just the Watts that you were looking for.
 
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There's an analogy for resistance that's quite good ...

Imagine the wire is a length of water pipe.

Small pipes will only carry small amounts of water before you have to apply pressure to increase the rate of flow. The reason you have to apply pressure is because there's resistance to flow.

To make it easier for the water to flow, make the pipe bigger. This means there's less resistance.

The same with wires or cables. Make them bigger, and there's less resistance ...
 
whitevanwoman said:
I have a 100 W inverter which plugs into cig lighter for normal 3 pin house plugs and am trying to figure out the wattage of my new android tablet, I'm guessing it will be under 100w but just wanted to be sure. But I can't work out what numbers to use in the W = V x A equation that Firefox posted earlier (I am really dumb with maths, failed O level 4 times).

On the tablet plug it says Input : 100-240VAC0.3A, Output 9V---2000mA

so would this be right... watts = 240 x 0.3 therefore watts = 72 ? :confused:
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Sorry guys but wrong!!!

As it's a universal charger the 0.3A is at 100v, the lower the voltage the higher the current.

therefore it's 30w input and 18w output (9v x 2A) it will dissipate 12w as heat on full load:dance:
 
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