240v to 12v 20A transformer

[Nick_H]

Anyone know where I could buy a 240v to 12v transformer that will provide 20A output at 12-14v?

The only ones I could find look like they're designed to be built into appliances or attached to a wall, whereas i'm just looking for something standalone in it's own relatively robust body/housing that I can plug into a household socket.

The application is to run a high capacity 12v airpump directly off the mains (generator), as I can't find a 2-stage 240v air pump that inflates at high volume then switches to high pressure. The 12v pump I already have states max 20A.

Is there any reason I can't use a 20A battery charger?

 

[pvb]

If you Google for led power supply 250w, you should find loads at around £25.

 

[BabaYaga]

Is there any reason I can't use a 20A battery charger?

If using a charger I think you would have to make sure it has a 'supply mode', so that it can work without being connected to a battery. Like for instance the CTEK MXS25.

 

[Nick_H]

Thanks both, whilst neither option was exactly what I wanted, they led me to what I was looking for. It seems the term I should have been googling is "13.8v power supply" rather than "240v to 12v transformer". I've now found and ordered something (hopefully) suitable.

http://www2.ripmax.net/Item.aspx?ItemID=O-IP2000&Category=O0170

 

[Chalker]

You also need to be careful regarding AC from a transformer rather than the DC that you will get from the 13.8v power supply that you have now identified. The pump will almost certainly need DC.

 

[Nick_H]

Yes, transformer was the wrong search term. As you say I needed something to convert ac-dc, as well as reduce voltage

 

[savageseadog]

Yes, transformer was the wrong search term. As you say I needed something to convert ac-dc, as well as reduce voltage

Power supply.

 

[dmjburrows]

Basic question if I could please- why 13.8v rather than 12v? I have the same issue, want to run a 12v 180w pressure washer from the mains rather than car occasionally.

 

[Chalker]

It's generally seen as the voltage of a lead acid battery on charge.

 

[William_H]

Basic question if I could please- why 13.8v rather than 12v? I have the same issue, want to run a 12v 180w pressure washer from the mains rather than car occasionally.

As said 13.8 volts is typical of DC voltage in any "12v" vehicle when engine is running. Hence most equipment is designed for 13.8 volts (or even 14v). A 13.8 volt power supply means you can use it as a battery charger as well as having the battery float across the load. It will work well as a battery charger but will have that characteristic of declining charge current as battery voltage rises. (just like your old alternator system) A proper battery charger will overcome this with boost voltage to charge more quickly. olewill