I need a large 12V load...

[Will Prowse]

Trying to find some 1000W resistors for 12V test loads, but having a tough time! Speciality resistors are not cheap..

I also purchased an 800W 12V car defroster, and it only pulled 300W:


I want to create a 300-600A load. Purely resistive.

I could buy a 10kW inverter, and then hook up a ton of light bulbs. But obviously that's not purely resistive.

There has to be an easier way!

Some 12V batteries claim they can pull 300A for 5 seconds. Others 200A for 20 seconds etc. just need a large simple load for these tests.

What would you guys do?

 

[SparkyJJO]

Go find a bunch of old electric water heaters and steal the elements? Not sure how many you'd need though.

 

[Will Prowse]

Found some!!!

1000 Watt Dump Load Resistor

1000 Watt dump load resistor available in 12 volts. Heavy duty vented standoffs for air flow. Perfect divert dump load for wind turbines and solar panels.

windandsolar.com

And ordered 10

not bad!! Cheaper than an inverter and I can test 10kW!

 

[zcskywire2]

https://www.mouser.com/ProductDetail/Vishay-Huntington/AVE030020ER120KE?qs=sGAEpiMZZMtlubZbdhIBICIaCW2DaBDBj2UgYoLy%2FQU%3D

4x @ 18.5$ USD
+ Used TE Ev200 from battery hookup

Something like $100 total

Edit, 2S2P on the resistors so you keep the 0.12ohms

 

[Will Prowse]

https://www.mouser.com/ProductDetail/Vishay-Huntington/AVE030020ER120KE?qs=sGAEpiMZZMtlubZbdhIBICIaCW2DaBDBj2UgYoLy%2FQU%3D

4x @ 18.5$ USD
+ Used TE Ev200 from battery hookup

Something like $100 total

Oh very nice!!

 

[zcskywire2]

If you have solid DC programmable load already you could use a resistor array to boost it as well. Make the load bank operate higher to its maximum current but under the wattage limit. We do that often at my office because loads will be 120V/480A max with only 3kW of dissipation max

 

[Browse]

You may want to rig up some small fans for cooling the resistors.

 

[bolhuijo]

One of my favorite sites for overstock electronic stuff is MPJA. They have a selection of big power resistors. Ludicrously cheap. https://www.mpja.com/1-Ohm-120W-Power-Resistor/productinfo/17785+RS/

 

[Warpspeed]

There are commercial "metal grid" resistance elements, older ones are cast iron, more modern ones stainless steel.
These individual cast iron elements can be bolted in series to create any resistance needed for VERY high power.

Used as industrial test loads both dc and ac for many purposes. Probably pretty expensive purchased new, but if you check out machinery graveyards its often possible to pick through piles of old crap and find something that can be stripped down and rebuilt.
These are ideal, because you can tap off along a long series string of these things to get the resistance or current you require for a particular test load.

This is something I very quickly found on the internet, but these cast iron resistors are pretty typical of what is out there in junk yards.
https://www.widap.com/en/products/cast-iron-resistors/
https://www.widap.com/wp-content/uploads/artikel_doc150_31.pdf

Usually found rusty and with many broken elements, they can be easily dismantled and rebuilt a bit smaller, and will be pretty cheap as there is no demand for them.

 

[BarracudaBob]

One of my favorite sites for overstock electronic stuff is MPJA. They have a selection of big power resistors. Ludicrously cheap. https://www.mpja.com/1-Ohm-120W-Power-Resistor/productinfo/17785+RS/

I drive past MPJA every day

 

[BarracudaBob]

2 500W 12V water heater elements. They need to be water cooled

Amazon.com

 

[Warpspeed]

Just be careful with commercial wire wound resistors.
If you read the specifications, its normal to rate them for 250 degrees surface temperature rise.
That is bloody hot. They will smoke and smell at full ratings.

The exception are the "gold" metal clad resistors that can be bolted onto a heatsink, available up to 500 watts.
But the heat sink needs to be pretty large for reliable continuous running.
https://www.ebay.com.au/itm/2255246...uroeBjvg90ZS5EdapMIHgxWfQ=|tkp:Bk9SR47mlqSTZA

 

[BarracudaBob]

Just be careful with commercial wire wound resistors.
If you read the specifications, its normal to rate them for 250 degrees surface temperature rise.
That is bloody hot. They will smoke and smell at full ratings.

The exception are the "gold" metal clad resistors that can be bolted onto a heatsink, available up to 500 watts.
But the heat sink needs to be pretty large for reliable continuous running.
https://www.ebay.com.au/itm/225524671595?itmmeta=01J2D45PC21551HNH3FG8N9KZR&hash=item348251646b:g:MxUAAOSwtJ9kJClZ&itmprp=enc:AQAJAAAA0Aj2W5BpxVtXN95M4oBSyLnJ4i8HXh8gtLdoaOBChYbdTe0GL6tLmM5lmhoiJ9U3KabogJ9Cb52UYiidChma2WF3qpPug7EzyZZ8XCBhYuX7YXBLlr4e3CKnkZiOXqaoscJEtV+z27h6WBytXAJWcwrbpXK9OubsO97kT71aYDKS7p9ErdOCf6tyVp+AvhpO9ytKJ04BTpqPKugKGt58WSfiaC6XVLeFtM8VB5BzGAKVc7dZzaTywj2vJ5jH0suroeBjvg90ZS5EdapMIHgxWfQ=|tkp:Bk9SR47mlqSTZA

one issue with putting anything in parallel is that 5-10% difference in values will cause a one to burn much hotter and even fail. All of your big RF dummy loads are oil or water cooled. Their start up resistance will be lower than their hot values. Same goes for lightbulbs.

 

[BarracudaBob]

.

 

[Brucey]

2 500W 12V water heater elements. They need to be water cooled

Amazon.com

I believe some of the hardcore amp testers over on avs use buckets of water and heater elements when pushing them right to their limits. Obviously can't be used for significant time but a few seconds at full power or beyond is doable.

 

[Mkgough]

A DC fridge/freezer?? My IceCo is pure DC

 

[BarracudaBob]

I believe some of the hardcore amp testers over on avs use buckets of water and heater elements when pushing them right to their limits. Obviously can't be used for significant time but a few seconds at full power or beyond is doable.

I like the electric oil radiator through an inverter. That shouldn't have to much reactance. You may be able to PWM the AC load to select your desired load.

 

[Quattrohead]

Car headlight bulbs, you can shine them on your panels for free electricity !!!!

 

[BarracudaBob]

Car headlight bulbs, you can shine them on your panels for free electricity !!!!

Perpetual solar generator with free heat. Nicolas Léonard Sadi Carnot would be pissed

 

[DIYrich]

https://www.harborfreight.com/1000-amp-dc-61224v-carbon-pile-battery-and-system-load-tester-58933.html

 

[Hedges]

Traditionally carbon pile battery testers. Compress to vary resistance.

Amazon.com

Amazon.com

 

[k490]

Also those 100 amp battery load testers for $20-30 not sure how long you can run them for. I remember most Auto parts stores used them back in the 90's to load test an alternator.

 

[Warpspeed]

I want to create a 300-600A load. Purely resistive.

I suppose it depends on what you are tying to do.

Six hundred amps for a few seconds to quickly pass/fail a preowned battery you might be looking to purchase is one thing.

Six hundred amps for an hour or more to do a proper full load sustained discharge amp hour test is going to generate a LOT of continuous heat and requires a fairly stable resistance.
Something really cheap and light duty, just ain't going to cut it.

 

[Brucey]

I believe some of the hardcore amp testers over on avs use buckets of water and heater elements when pushing them right to their limits. Obviously can't be used for significant time but a few seconds at full power or beyond is doable.

Found it:

Measuring Amplifiers

www.avsforum.com

 

[Brucey]

Found some!!!

1000 Watt Dump Load Resistor

1000 Watt dump load resistor available in 12 volts. Heavy duty vented standoffs for air flow. Perfect divert dump load for wind turbines and solar panels.

windandsolar.com

And ordered 10

not bad!! Cheaper than an inverter and I can test 10kW!

Maybe you can use the heat output from these to create some kind of kiln or cooking box - ultimate inverter torture test. Everything comes out as molten slag.