12V INVERTER

[HERTS P&D]

I have a 12v inverter which is rated at 300w constant load, what amp of wire will I need for it to be wired to the van battery? approx. 1 metre away.

Andy

 

[RF Lighting]

300 divided by 12 equals....

 

[pukka]

25

 

[HERTS P&D]

It's easy when you know the calculation!

Andy

 

[bernardgreen]

Output 300 watts will require an input greater than 300 watts.

300 watts out of an 80% efficient invertor will require

300 times ( 100 divided by 80 ) = 375 watts input

which will be 31.25 amps

 

[HERTS P&D]

I've just looked at the inverter again and it says 600w peak and 300w continuous use.

So does that mean I need 50amp wiring or more?

Andy

 

[ban-all-sheds]

Before you invest any time or money in wiring it up, what is the output waveform of the inverter, and what do you want to power with it?

 

[HERTS P&D]

Hi BAN, the inverter says 330w continuous use and 600w peak. It does say pure power on the top of the inverter, I have already wired it up with 27amp wiring and fitted a 25amp fuse to the wiring and a 20amp fuse to the inverter.

I will use it to power a 2 x 60watt tubular heaters to stop my jetter from freezing. At the moment it is on 24hrs with no side effects or fuse blowing. My van comes with an extra auxiliary battery, but I have also wired in another battery, so there is plenty power to my inverter.

Andy

 

[JohnW2]

I will use it to power a 2 x 60watt tubular heaters to stop my jetter from freezing. At the moment it is on 24hrs with no side effects or fuse blowing. My van comes with an extra auxiliary battery, but I have also wired in another battery, so there is plenty power to my inverter.

120W load at 80% efficiency will only draw about 12.5A from your battery, so cable requirements would be fairly modest (for that load). If it's 'on' continuously (24/7), that amounts to about 300 Ah fromthe battery per day - so you'd need very hefty batteries if you were to leave it very long without the engine running or otherwise charging the bateery(ies). Are the heaters perhaps thermostatically controlled, such that they are not actually 'on' all the time they are powered? If so, the Ah requirement might obvioulsy be far less.

Kind Regards, John

 

[HERTS P&D]

Hi John, my van comes with 2 batteries, one for starting and one for everything else (but I have also added another one) even if I completely flatten the aux. battery the van will always start.

The aux batteries are 590ah & 740ah, also the van is driven every day.

The heater is the one below:

http://www.ebay.co.uk/itm/Thermotub...arden_Hearing_Cooling_Air&hash=item4d0859be4b

But saying that I could also fit a frost stat to the wiring.


Andy

 

[ericmark]

Likely 44/0.012 auto wire would be ample. Or around 6mm but you should always fuse so with 6mm for example a 30A fuse will insure the wire will not over heat the fuse will blow first.

However even with 4 x 160Ah batteries and two 80A alternators on the engine I would never dream of that sort of load.

What comes out has got to be replaced and 10A is a heavy drain when the engine is not running.

An Eberspacher heater or similar is more what you should be looking at.

 

[ericmark]

With 4 x 160 Ah on a narrow boat it was OK just removed some concrete ballast but with a van that's a lot of weight to lug up and down dale.

 

[DetlefSchmitz]

Strikes me that a suitable 1.2 Ohm resistor would be cheaper than an inverter plus a retail heater.

 

[ban-all-sheds]

If you want electric heating, surely there must be 12v products available, which would avoid the expense and losses of an inverter?

 

[HERTS P&D]

I was quoted over £1000 to fit an Eberspacher to my van, I only need the heat in freezing weather 2 months a year.

So far I have only spent £50 on 2 heaters and wiring. (I bought the inverter many years ago) Also the alternator on my van is 150A

Andy