AC/DC transformer to test accessories

[e42]

Hi, for easier access I'd like to rig up a separate wiring circuit away from the car to simulate the addition of an electric radiator fan and a few other things. My question is - can I use a mains DC transformer to provide the power or would it be easier to use a spare car battery?

For the transformer, what should the output amp range be?

Thanks

[E-bmw]

How long is a piece of string?

Joking aside.

Anything (apart from a smart charger) that produces 12v will power anything 12v.

So you can use pretty much anything, with the following caveat.

Look at the wattage of the item you want to power, what does it tell you?

12w @ 12v = 1 amp
24w @ 12v = 2 amps etc.

From that & the wattage of what you want to power you can tell if what you have/choose to buy will do what you want it to do.

[e42]

Thanks for the reply, max power would be 120w, 10 amps I guess, hence it may be easier to use a spare battery as the power source for the bench rig

[LordLoveLength]

I’d expect a radiator fan to draw > 10A , especially at start up.
Use a battery.

[hidetheelephants]

Yep, a pair of croc clips big enough to go on the battery terminals, smaller croc clips to go on whatever you're testing and wire to suit is the answer.

[Inbox]

LordLoveLength said:

I d expect a radiator fan to draw > 10A , especially at start up.
Use a battery.

This, I was doing some fault finding on the car and the current draw from a fan was surprisingly high, any sort of ac/dc supply for that would be chunky and expensive.

A car battery is the best thing with the only draw back of going flat and needing to be charged.

[Inbox]

Inbox said:

LordLoveLength said:

I d expect a radiator fan to draw > 10A , especially at start up.
Use a battery.

This, I was doing some fault finding on the car and the current draw from a fan was surprisingly high, any sort of ac/dc supply for that would be chunky and expensive.

A car battery is the best thing with the only draw back of going flat and needing to be charged.

And use some decent wire and connectors so things don't overheat and hot drawing 10A.

[E-bmw]

Not forgetting the fact that if it is an inductive load like a fan the current at start-up will be potentially up to 10 x normal full-load current briefly while it gets up & running.

[xstian]

https://www.amazon.co.uk/Sealey-PP1-Auto-Probe-6-2...

I have something similar the above. They are quite handy, but you will need a car battery. Long leads so you can get to the rear of car. Crocodile clips would do the same, but you haven’t got to worry about shorting out the live end.

[E-bmw]

xstian said:

https://www.amazon.co.uk/Sealey-PP1-Auto-Probe-6-2...

I have something similar the above. They are quite handy, but you will need a car battery. Long leads so you can get to the rear of car. Crocodile clips would do the same, but you haven t got to worry about shorting out the live end.

How does that help the OP?

He wants to power up a fan on-the-bench.

[xstian]

E-bmw said:

xstian said:

https://www.amazon.co.uk/Sealey-PP1-Auto-Probe-6-2...

I have something similar the above. They are quite handy, but you will need a car battery. Long leads so you can get to the rear of car. Crocodile clips would do the same, but you haven t got to worry about shorting out the live end.

How does that help the OP?

He wants to power up a fan on-the-bench.

Well he said, would it be easier just to use a car battery, too which a few replies agreed it might be.

It s just another option.

[hidetheelephants]

E-bmw said:

How does that help the OP?

He wants to power up a fan on-the-bench.

It will do that if he has a car battery to power it with, it functions as a fancy lead with croc clips.

[TwinKam]

xstian said:

E-bmw said:

xstian said:

https://www.amazon.co.uk/Sealey-PP1-Auto-Probe-6-2...

I have something similar the above. They are quite handy, but you will need a car battery. Long leads so you can get to the rear of car. Crocodile clips would do the same, but you haven t got to worry about shorting out the live end.

How does that help the OP?

He wants to power up a fan on-the-bench.

Well he said, would it be easier just to use a car battery, too which a few replies agreed it might be.

It s just another option.

A very good option; I have one wired up to a battery under the bench for testing purposes, exactly as you propose. It gives you a switched pos or neg at the business end (in addition to being a voltage probe). Perhaps ebeemer was not aware of that.

[e42]

Thanks all, all replies appreciated

[e42]

I usually leave the battery disconnected in the car and on a trickle charger, it’s an old analogue car so nothing electronic. Looking at the probe mentioned it has long enough leads to test on the bench and keep the battery in situ in the car, result! Thanks all

[E-bmw]

TwinKam said:

xstian said:

E-bmw said:

xstian said:

https://www.amazon.co.uk/Sealey-PP1-Auto-Probe-6-2...

I have something similar the above. They are quite handy, but you will need a car battery. Long leads so you can get to the rear of car. Crocodile clips would do the same, but you haven t got to worry about shorting out the live end.

How does that help the OP?

He wants to power up a fan on-the-bench.

Well he said, would it be easier just to use a car battery, too which a few replies agreed it might be.

It s just another option.

A very good option; I have one wired up to a battery under the bench for testing purposes, exactly as you propose. It gives you a switched pos or neg at the business end (in addition to being a voltage probe). Perhaps ebeemer was not aware of that.

No, I wasn't, it just looks like a probe tester, having said that, I still don't see any actual real advantage that it brings to the party.

[Richard-D]

The OP might find it worthwhile to find which of his vehicles has the most tired battery, replace it and use the old one for testing. A battery that is a bit tired for car use can be absolutely fine for bench testing for a long time.

As above also, a power probe (or copy) is an extremely useful piece of equipment. You won't find anyone that regularly deals with automotive electrics that doesn't have one.