# I need a high wattage dummy load

Discussion in 'The Projects Forum' started by bolm, Feb 3, 2014.

1. ### bolm Thread Starter New Member

Feb 3, 2014
4
0
I'm interested in Big dummy load. Has circuit to look at some pls.

2. ### THE_RB AAC Fanatic!

Feb 11, 2008
5,435
1,305
I didn't use a circuit. I'll go have a look at it.

The heatsinks have 16 large NPN power transistors (equiv 2N3055) driven as darlington pairs by 16 smaller NPN transistors. Then the 16 emitters are tied to ground through 16 emitter resistors, each is 1 ohm 5W.

That whole array is in parallel; so all collectors, bases and grounds connected together. Then the collector to the red terminal and ground to the black terminal.

To make it conduct there is a pot and a couple of resistors from red to black terminals, making an adjustable voltage. That pot is connected to another NPN base, in "trilington" with the main array so its collector joins their collectors, and its emitter goes to their bases.

The thing is so simple I never bothered drawing a diagram.

It works well for 6v, 12v loads up to about 20v. But I remember grabbing the soldering iron and changing a resistor value on the pot circuit at least once, possibly to test a 24v or 36v high current supply.

3. ### TIP31 New Member

Aug 17, 2013
25
0
Are you looking to make one or buy one?

4. ### tubeguy Well-Known Member

Nov 3, 2012
1,157
197
Welcome to the forum bolm.

You should post what kind of voltage and current you want the dummy load to handle.

5. ### TANDBERGEREN Member

Jan 20, 2014
74
4
Just make it like a standard current limiter from any powersupply.
Then You will have a coarse scale for Your potmeter to determine what load You are to put to test.
And actually, with a wide voltage range too.
Supply the load with a thermoswitch or two to protect Your devices, and you are good to go.

6. ### ronv AAC Fanatic!

Nov 12, 2008
3,224
1,078
What voltage and what current?

7. ### bolm Thread Starter New Member

Feb 3, 2014
4
0
I'm find the power load for test battery 48v 100A

8. ### tubeguy Well-Known Member

Nov 3, 2012
1,157
197
This is heating element wattage.
You might want to use water cooling, so one choice would be a modified electric water heater using multiple heater elements as power resistors.

You could switch these with some high current Mosfets.

Last edited: Feb 6, 2014
9. ### ronv AAC Fanatic!

Nov 12, 2008
3,224
1,078
I'm guessing you are talking about 4 big lead acid batteries in series???

If so most are specified at a constant current discharge rate of either 25 amps or 75 amps. You will need to test each one separately to get good data on their capacity.

Tell us more about your final objective.

bolm likes this.
10. ### bolm Thread Starter New Member

Feb 3, 2014
4
0
That all right. thank you for all

11. ### inwo Well-Known Member

Nov 7, 2013
2,421
315
I may have access to a bunch of these.

This is my private stash.

Half are .5 ohm and half are 1 ohm.

The .5 ohm are the ones bracketed together making the pair .25 ohm.

~ 300 watt each.

• ###### MVC-007F.JPG
File size:
109.4 KB
Views:
103
Last edited: Feb 6, 2014