15 AMP adaptor

That is true but have you checked the open circuit voltage? It will be higher if this is not a regulated supply. You should still have a smarter charger if you are planning on using this unattended.

Sicilian Dragon wibbled on Saturday 03 April 2010 13:55

Lead acid car/truck battery?

If so, those are typically charged to around 14.5V give or take, so you need a little higher open circuit voltage to succeed.

How powerful is the "adaptor" (eg wattage, VA or output current rating)?

Is the adapter regulated to 12V, or is that the nominal rating? If the latter, it should work, but I would certainly not leave it connected unattended. You don't want to come back to find the electrolyte merrily boiling away. Use a multimeter to measure the voltage out of the thing open circuit as well as connected to the battery and check it periodically so it doesn't overcharge.

This is more or less true.

But we don't know enough about your 12V 'adapter' or your battery to know how it will behave when used as a charger. If it puts out a high enough voltage when unloaded, if its voltage regulation is too flat (too good), it might be overloaded when you attach it to a lead acid battery. If the battery is of some other type, fireworks may ensue.

You *MUST* be concerned about overcharging. Overcharging can be dangerous and can damage batteries quickly.

A lot depends on the type of battery. But in general a simple power supply is a very different beast from a battery charger and using a power supply as-is to charge a battery will be dangerous and/or expensive.