Making an adjustable electronic load for testing/discharging

rin67630

Solar Addict
Who is tinkering with solar energy frequently needs an adjustable load in order to discharge batteries, put a load on SCCs or BMS, test shunts etc...

With a cheap 600W Step up converter and a 1000W 240V bulb from an old cinema flooder, you can make an adjustable load:

Just wire the output of the step up converter to the 1000W lamp. The input of the buck converter is then your electronic load.

You can e.g.
- by a system voltage of 12 volt continuously adjust the load from ~10W to ~150W, upon changing output voltage
- by a system voltage of 24 volt continuously adjust the load from ~40W to ~150W

If you replace the 1000W bulb by a 100W halogen bulb you will be able to continuously adjust the load from ~1W to 15W, respectively 4W to 15W.
The best is that the output power is independent of the input voltage, so you can exactly dissipate a fixed energy by hour...

Enjoy!

P.S: If you have a 110V bulbs, you can even put almost 4x the max load...
But I live in Europe, so I won't find this kind of bulbs here.
 

MattiFin

Solar Enthusiast
Only chinese aliexpress sellers manage to make 600W out of max 16v 15A input. :p
Construction looks horrible kludge but still that is cheaper than dirt, I'm guessing manufacturer also fiqured out they f*cked it up :poop:

Step-down module and automotive 12 or 24v light bulb might give you more adjustability.

Aliexpress is flooded with much better DC load testers that are not too expensive either.
Some examples (none tested or recommended, do your research)
 

rin67630

Solar Addict
Step-down module and automotive 12 or 24v light bulb might give you more adjustability.
That is what I've done before, but the 1000W AC Bulb is better.
a) a 12/24V car bulb dissipates only 55W, you need many of them.
b) they are bright and were blending me (the 1000W bulb only glows faintly).
c) i did not purchase anything. It's what I had at hand.

P.S. you are right "600W Step up converter" was only a fancy "brand name" I don't care: I need much less...
 

MattiFin

Solar Enthusiast
Did you test your module up to 24v or did it blow up?
I see some jumper selection on the board but documentation is not exactly great.
 

rin67630

Solar Addict
Did you test your module up to 24v or did it blow up?
I see some jumper selection on the board but documentation is not exactly great.
You are right.
Indeed, that specific step-up module has a linear regulator for the current limitation on board, that does not accept more than 16V input.
But I have other step-up modules without this kind of circuitry that will take practically every input voltage.
 

HaldorEE

Photon Sorcerer
Hey guys. You are inspiring me.

Chime in please.


I am going to be aiming this at a single cell capacity tester, but the load portion of what I am doing is able to handle higher voltages at lower current. The MOSFET itself should be good to 600W or so depending on how well it is heat-sinked.
 

HaldorEE

Photon Sorcerer
Wow! A Buck-booster able to get 600W out of 2 or 3V? That kind of beast is surely not easy to find at eBay! ;)
Check my thread, 600W is the MOSFET limit, actually reaching that would take a monster heat sink. I am thinking more like 200 to 300 W max.

I found a 5V, 60A power supply (300W for $25 on Amazon) so that part shouldn't be cost prohibitive. The MOSFET will be operating in the linear range so it will be a CC load, not buck-boost.
 

rin67630

Solar Addict
Check my thread, 600W is the MOSFET limit, actually reaching that would take a monster heat sink. I am thinking more like 200 to 300 W max.

I found a 5V, 60A power supply (300W for $25 on Amazon) so that part shouldn't be cost prohibitive. The MOSFET will be operating in the linear range so it will be a CC load, not buck-boost.
A 5W, 60A switching power supply will never have MOSFETS capable of dissipating 300W in linear mode!

You were ways better off PWM-transfering the power to a powerful resistive load...
Some 12W Car Immersion Heaters or Windscreen Heaters in // could be that load.
 
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HaldorEE

Photon Sorcerer
A 5W, 60A switching power supply will never have MOSFETS capable of dissipating 300W in linear mode!

You were ways better off PWM-transfering the power to a powerful resistive load...
Some 12W Car Immersion Heaters or Windscreen Heaters in // could be that load.
Perhaps you might want to look at the thread I linked.
 
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