I am trying to power a 12 V 8 W cordless phone using a 5 V 1 A wall adapter.
I am using a step up DC/DC boost converter MT3608 for boosting output from 5 V to 12 V.
Theoretically it works – when I connect adapter to boost convertor input and setting potentiometer to 12 V by measuring output through multimeter – it shows 12 V.
But as soon as I connect the cordless the voltage drops to 2-3 V and cordless does not power on. So its not working on load.
I also have a 7.4 V li-ion cells which powers on the cordless fine – using the boost convertor.
My question is the DC coming from adapter different than DC coming from battery?
Also I noticed that the adapter indicator light is constant when charging a basic (non smartphone) phone battery but it pulsates when connected to step up convertor and cordless powered on. This made me more confused.
Please help me understand this behavior of adapter and what's wrong in what I am trying to do?
Best Answer
No it doesn't. In theory 5 V x 1 A = 5 W maximum from your PSU. Your phone needs 8 W and you'll lose another 1 or 2 W in the voltage booster. It doesn't work in theory and, as you've found, it doesn't work in practice.
That's the open-circuit or unloaded voltage.
Yes. The battery has a much higher current limit.
Why the confusion? Check the manual for the adaptor and you'll probably find that it's indicating over-current fault.