power source

[JD]

I'm looking into getting one of these for my van. Does anyone have one (or similar) in theirs, and if so, do you think it would it be a good investment?

http://cgi.ebay.co.uk/3000W-Peak-1500W- ... dZViewItem

I'm after something basic (and easy to install!) that will power TV / DVD, hair dryer for the missus, etc without having to spend a fortune. It has a minimum 1500W, which I know provides plenty of power for what I need and the price seems pretty reasonable.

I just wanted to ask for your input before I go ahead and buy

Cheers, James

[tonytech]

Power inverter 101.....

1. you get nowt for nowt.
If you draw 1500w this is 125 AMPS from your battery. ie about 30mins of use for a 85 amp hour battery. OK your TV
Dvd wont draw this much but the hair dryer is a no no.

2. inverters are not 100% efficient so it will get hot.
Look here http://wiki.80-90.co.uk/index.php/Campi ... efficiency

3. you must have a leisure battery or starter battery connected as a leisure or you wont get your engine started after a nights camping.

T

[Other-Power]

I would take the figures on Wiki with a pinch of salt. The load on the inverter was not measured and was just assumed.

Most inverters efficiency drops of rapidly when the load falls below 30% of there maximum.

[img:592:398]http://spie.org/Images/Graphics/Newsroo ... 2_fig1.jpg[/img]

On a 500watt inverter this would be 150watts or less, worth considering.

Jon

[JD]

I must apologise cos I aint no expert in physics n all that!! I'm quite new to this n trying to learn as I go on

I kind of understand what you're saying Tony. If I was to get an inverter it would be connected to my leisure battery. Okay, I know a hair dryer draws a lot of power, however, would it take too much from 20 minutes usage every now and then?

I was looking at no less than 1500W (peak 3000W) which I initially thought would be enough for general use. If I was to go down that line, would I be better going for something more powerful?

[irish.david]

The problem you'll have with an inverter that size is the sort of cables you'll need to run from the battery to the inverter. The thing to remember with electrical stuff is that power is a product of voltage and current. In other words:

Power = voltage x current

If you take power to be constant (1500W in this case) then when either current or voltage goes down, the other one goes up (this is true for DC but is a bit simplified for AC where power factors come into play. However in AC it can still be used for a rule of thumb).

In this example if you plug a 1500W, 240v hairdryer into your inverter it needs to produce Y amps where

1500 = 240 x Y

1500 / 240 = Y

Y = 6.25 amps

Cause Y is only 6.25 amps you only need a thin bit of cable to carry this and everyone is happy.

However.......

You need to supply your inverter 1500W of power from you battery (assuming it's 100% efficient, which it isn't). Our poor battery can only supply 12v so when we plug that into our equation we get:

1500 = 12 x Y

1500 / 12 = Y

Y = 125 amps

The big, thick, expensive, hard to install, starter type cables would barely cope with a continuous 125 amp draw and a fully charged 63 amp/hour battery would struggle to last for 25 mins and put a huge strain on the battery.

On a kind of related trivia note, this is why the cables that run from pylons are so dangerous. These things carry voltages that go from 11,000 volts upwards. The reason for this is that when you have a stupidly high voltage you can supply the same amount of power with much less current so you don't need cables as big.

As a final thought i'd also be wary of a 1500W inverter off ebay. This size of inverter (if it can even supply 1500W which i doubt given the size of the item) is wayyyy too big for all normal car installations. I have a 600W (50 amp max continuous draw) inverter fitted in my van and i still consider that as overkill.

Dave

[kevtherev]

Well put Dave...so if it heats it's an inverter no no

Agree with dave again.. 600 watt is an ideal...TV DVD X-box. lamps

small lcd tv's only draw around 0.7 to 1 amp..DVD's around 0.5 amp



As for hair drying....get a propex then your lass can enjoy hot air safely piped to 'er 'ead

I have slowly moved away from inverters to 12V electricals

just the TV to do now

["WEAZLECHIN"]

inverters are VERY inefficient. for that price i think i would rather get a 900w generator.

[JD]

Thanks so much Dave. I'm starting to get the hang of it now. I think. Hair driers definitely a no-no. She'll just have to go without, oh well!

Kev you say you've moved to 12v, how have you done this? I've had a look on wiki and seen a little on zig units, but it's all new to me so I got to get my head around it all! Plus they're a tad out of my price range at the mo. Did an inverter work ok for you when you had it?

There seems to be divided opinion when it comes to inverters so I'm going to keep looking into it.

Thanks for the replies peeps, much appreciated

[shepster]

Kev you say you've moved to 12v, how have you done this?

Buy stuff that works off 12V in the first place!

TV DVD etc and wire them up accordingly.

Oh and tell the missus to forget the hairdrier or go and buy a static somewhere.