how much voltage will the vems take?

[Tony C]

How much is the max limit the vems will take?
reason i ask i have been given a 240V/12v transformer,
and when powered up its giving a voltage reading of around 16.6 - 17.8 volts
this too high to power the vems up???

[dnb]

It's probably an unregulated power supply - as soon as you put load on it, the volts will drop to something more sensible.

I have seen 15v peak on my VEMS with no ill effects before now.

[Sprocket]

A 240v to 12v transformer is of no use as the 12v output will be AC. Unless of cource you are infact talking about an inverter which will give a '12v' DC output.

I personaly steer clear of unregulated power supplies as its a bit of an unknown in certain circumstances. In rush is a worry

[dnb]

Doesn't have to be AC.  Some have diode bridges in

[Tony C]

this is defo 12V dc output,
says on the top.
240V AC / 12v DC

[Sprocket]

Doesn't have to be AC.  Some have diode bridges in

Its not exactly a transformer then, its a power supply

[MWfire]

ihmo vems has 18V zener diode for protection.

[rob@vems.co.uk]

Theres a lot of over-voltage protection to handle the transient voltages caused by noise, cranking, alternator variation.
As said earlier if you're testing the voltage across the + and - terminals with no other load than the voltmeter then you're going to see a high value in an unregulated powersupply.
Try putting a 5K resistor across the terminals and measure the voltage across the resistor.

For a solid 12v supply I use a hard disk Power connector from Maplins and plug the VEMS into a spare PC PSU connection.

[DI-Racing]

  or, try an in line fuse,,works for me when dealing with unknown quantities ,,,;-)