Power Supply Control Selection

djsfantasi

Joined Apr 11, 2010
9,156
What are you plugging the battery into? There are jacks that will disconnect one source when a second source is plugged in. Think of a headphone jack (use your imagination, because I know this example is for output, but the principle is the same for inputs, such as battery power). Normally sound is heard through speakers. But plugging in headphones cuts off the speakers. I can draw a diagram when I'm on my laptop. In the interim, look at the schematic on this datasheet.
http://www.cui.com/product/resource/mj-3502.pdf
 

#12

Joined Nov 30, 2010
18,224
That is usually done with switches in the connectors. I believe a connector that can switch 1 amp can be found.
In my drawing, a fresh battery will take over when you plug it in because it will have a higher voltage than the tired battery. If you hard wire this with switches in the connectors, it will only make one position disable the other. The other position won't disable the first position, unless somebody here gets really crafty about how to do that. It is not obvious to me without using relays.
 

crutschow

Joined Mar 14, 2008
34,284
Thats what I'm gonna end up doing. I just thought it would be a beat idea if I plugged one battery in and it somehow knew to switch to that one and disconnect from the other
Okay, so whichever battery is connected last is the one that powers the circuit. Suppose the battery that is powering the device is disconnected. I assume you then want it to go back to the other battery to power the circuit?

To do all that would appear to require a logic sequence and memory circuit. This is likely most easily done with a microprocessor.
 

Johann

Joined Nov 27, 2006
190
Thats what I'm gonna end up doing. I just thought it would be a beat idea if I plugged one battery in and it somehow knew to switch to that one and disconnect from the other
With the two diodes, this is exactly what will happen. When battery 1 drains to such an extent that its voltage is a few mili-volts lower than that of battery two, battery two will automatically start supplying your load, etc.
 
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