Laptop ACDC adapter modification

Thread Starter

BusManJamie

Joined Dec 9, 2020
9
Hi all, I have a 18-32v DC appliance for a battery powered vehicle I want to test at home.

I've found an 18-20c AC/DC laptop adapter and have adapted and soldered. I have taken the inside wire of the cable to be positive, the outside wire core to be return.

Is this safe, and correct?
20210120_153154.jpg
Cheers,

Jamie20210120_153219.jpg
 

Thread Starter

BusManJamie

Joined Dec 9, 2020
9
There is no indication on the case. Test it with a multimeter. Or an LED with a 1/2W 2k resistor...
Hi, thanks for responding.

Other than that, which I can work out, is this safe to plug into mains once that's determined? It's not going to destroy anything it touches?:eek:
 

djsfantasi

Joined Apr 11, 2010
7,558
It's not going to destroy anything it touches?
That’s a pretty broad statement... The only answer is that “it depends”. If the case touches you, nothing is going to happen. If the power output isn’t connected to a complete circuit (e.g., one wire is disconnected. Nothing is going to happen. If it’s connected in a circuit, maybe something will happen.
  • If the circuit is only rated for a lower voltsge (e.g., 2 volts), the circuit will be destroyed
  • If the output is shorted together, the power may stop. The device may have short-circuit protection and recover. Or it might not.
  • If the output is connected in reverse polarity, the circuit may be damaged
So it depends on what you mean by touch and what it is touching.
 

Thread Starter

BusManJamie

Joined Dec 9, 2020
9
That’s a pretty broad statement... The only answer is that “it depends”. If the case touches you, nothing is going to happen. If the power output isn’t connected to a complete circuit (e.g., one wire is disconnected. Nothing is going to happen. If it’s connected in a circuit, maybe something will happen.
  • If the circuit is only rated for a lower voltsge (e.g., 2 volts), the circuit will be destroyed
  • If the output is shorted together, the power may stop. The device may have short-circuit protection and recover. Or it might not.
  • If the output is connected in reverse polarity, the circuit may be damaged
So it depends on what you mean by touch and what it is touching.

Hey,

I more mean the concept of using that laptop charger to power DC. Since it provides 18-20v, and the unit I want it to power is 18-32v, the voltage should be fine. I've just never messed with AC converters before.

Cheers
 

djsfantasi

Joined Apr 11, 2010
7,558
Hey,

I more mean the concept of using that laptop charger to power DC. Since it provides 18-20v, and the unit I want it to power is 18-32v, the voltage should be fine. I've just never messed with AC converters before.

Cheers
It looks fine. It will probably work. It may or may not work. Depends now on correct polarity and the current required by the unit. If it needs more than 3.79A, you’ll likely have issues.
 

Thread Starter

BusManJamie

Joined Dec 9, 2020
9
It looks fine. It will probably work. It may or may not work. Depends now on correct polarity and the current required by the unit. If it needs more than 3.79A, you’ll likely have issues.
Great. I'm off to immediately get a multimeter right away, which I will have absolutely no idea how to use haha.
 

Dodgy Geezer

Joined Nov 30, 2009
146
I more mean the concept of using that laptop charger to power DC. Since it provides 18-20v, and the unit I want it to power is 18-32v, the voltage should be fine. I've just never messed with AC converters before.

There are initially three things to consider for connecting power to DC circuits.

1 - have you got the polarity right? Use a multi-meter to check this - cheap ones can cost less than a cup of coffee.
2 - is the electricity supplied at the right pressure (voltage)? If not it will either do nothing (too low) or blow things (too much)
3 - is there enough electricity? This is Amps. If your component requires more amps than the supply can provide, the supply will probably close down.

So it would be useful to see any labels on your battery-powered vehicle as well as on the laptop supply...
 
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