>> Unlisted wrote in
>> news: snipped-for-privacy@4ax.com:
>>
>> > I have a 12volt regulated power supply that was probably made for
>> > using automotive CB radios in a house. It's rated at 3 amps. Can
>> > this be used to slow charge 12V car batteries? I have a big car
>> > battery charger, which puts out 15 or 60 amps, but I want to
>> > trickle charge a battery in severe cold weather.
>> >
>> > I'm more worried about damaging the power supply than the battery.
>> >
>> >
>>
>> If you can set the supply voltage to 13.6 volts under the supply's
>> full rated load, then yes.
>>
>> The problem is not you needing to worry about the supply. The
>> problem is that you could overcharge the battery and blow it up
>> (lead acid).
>>
>> If you can ensure that you do not exceed the fully charged voltage
>> and stop charging when that is attained.
>>
>> If you can't, you'd better find a way to monitor the battery's
>> temperature, or have some other means to determine full charge state
>> and turn OFF the charge device.
>
>Old car chargers had no cut-off when full, folk just unplugged them after a while.
>You can do that if you don't make a habit of it. If you do it often, use a better cha
>rger. Old unregulated chargers will kill batteries if you leave them on day after day.
I have an old charger, a small 6A model, which only has an over current cutout. No cut-off. I had it connected to my farm tractor last week, when we got a huge snowstorm. The tractor and charger were outdoors, but I had a cover over the charger. However, the plug was laying on the ground, connected to an extension cord. That cord is plugged into a GFI outlet on the barn. After the storm, I unplugged the charger, which had been connected for around 36 hours. However, the GFI had tripped from the cord being buried under the snow.
I soon found that battery was completely dead. (It was only halfway discharged when I applied the charger). The tractor ignition switch and lights were NOT turned on.
So, what drained the battery? It had to be the charger, which drained it after the GFI tripped. I did not think that current is supposed to go backwards on battery chargers, but I assume it did. With the ingition switch and lights turned off, there is nothing to drain the battery. (this is a simple OLD tractor, no radio or heaters or stuff).
I can only assume that the charger has a leaky diode...... I guess thats possible???? I am not quite sure how to check this???? I can only guess to hook my multimeter across the plus and minus clamps, then reverse it and see if there is low resistance both ways????
Or maybe I should just put new diodes in it. 6A rated diodes cant be too costly...