I found a 15 AMP adaptor that converts 220 V AC from mains into 12 DC current at a shop. My question is will this adaptor be able to charge a
140 AH 12 V battery? The shopkeeper doesn't know anything about it. I'm not concerned about over charging or anything like that just will it charge it? My understanding is that the voltage from a charger should be slightly higher than 12 V if it is to be able to charge a battery of 12 V??
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wrote:

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.
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wibbled on Saturday 03 April 2010 13:55

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)?
--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.
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Sicilian Dragon wrote:

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.
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Sicilian Dragon wrote:

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.
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Paul Hovnanian snipped-for-privacy@hovnanian.com
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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.
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Brian Gregory. (In the UK)
snipped-for-privacy@bgdsv.co.uk