H.A. wrote:I say you are not looking very hard...
There are dozens of on-line suppliers,
Amazon, Digikey, Newark, et.al. 'Brick & Mortar' suppliers to the professional trade as well as the local Radio Shack.
A socket base general purpose relay for your application could be had for less than 20$
GuitarPhotog wrote:You want a relay with a 120VAC coil and spdt contacts rated at 12VDC 5A. They are available as open frame or enclosed.
Here's a whole assortment from digikey
http://www.digikey.com/product-search/e ... dt%20relay
<Chas>
Hennesseystealth wrote:The issue is you have to have the search terms right. I looked at hundreds of items from dozens of sites, including DigiKey. Nothing was 120v trigger and 12v circuit. Again, if you don't have the name they have the item listed as, your search will be pretty fruitless.
Dale M. wrote:How about a simple diode to prevent reverse current flow....
Dale
kludge wrote:You don't need a 120VAC trigger.
Any old 12VDC coil relay will work.
Put the coil on the output of the Converter but before the contacts of the relay.
The Converter will turn on when AC is applied and give you 12V on the output. The output from the Converter will power the relay coil, the contacts will close connecting the battery, and the battery will charge.
Let me know if you need a picture.
H.A. wrote:kludge wrote:You don't need a 120VAC trigger.
Any old 12VDC coil relay will work.
Put the coil on the output of the Converter but before the contacts of the relay.
The Converter will turn on when AC is applied and give you 12V on the output. The output from the Converter will power the relay coil, the contacts will close connecting the battery, and the battery will charge.
Let me know if you need a picture.
A picture might be nice,
As I envision by your description, What happens when 120vac is removed from the charger ?
Will the battery back feed thru the closed contacts to keep the relay coil energised ?
Further, Many of these 'smart chargers' wont switch on its charging output until it first measures a correct polarity voltage from the battery.
Its a safety feature what prevents its output from becoming energised if for example its output leads are shorted to each other or connected in reverse polarity.
I expect the small constant battery drain previously mentioned is related to this voltage measuring circuit.
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