20-500amp programmable, 12volt, dummy load?

[oldway]

I started studying a project that would suit for this application .

It is an electronic load combining resistors with a MOSFET dynamic load, so that 2/3 or more of the power is dissipated in the resistors , and the load is adjustable in a continuous manner without variation of levels .

The resistors are very low cost and made of stainless steel wire (in my case , welding wire 0.8 mm in diameter - acceptable current : 5A)

For your project, load resistance should be chosen for 30A/resistor and switching would be done by automotive- relay of 30A.

The amount of relays and resistors depends on the total current value.

An Hall sensor is used for current measurement and regulation.

In parallel , there must be a MOSFET dynamic load 12V 50A 600W which will be used to fine tuning .

The assembly is cooled by forced ventilation with a fan recovered from an electric heater.

The stainless steel wire is very cheap compared to the Kanthal wire, but its resistance varies with temperature .

But that does not matter because it will be offset by fine tuning of the MOSFET dynamic load.

[TerraHertz]

Basically! I'm looking for a way to easily load test batteries, or battery banks, with a settable 20-500amp load...
Is this a possibility?

... at 12volts ...

Wait, are you talking about battery banks? Isn't it rare (ie never) for many lead-acid batteries to be connected in parallel? I thought this isn't done because the batteries can't be balanced, and also what happens if one goes short circuit.
Battery 'banks' are normally wired in series. Certainly the large banks used for large UPSs (that back up whole buildings) are wired in series, with total output voltage in the 200 to 300VDC region.
So why are you talking about needing to draw load from a 12 volt source?

[oldway]

We always hope that topic starter knows what he is looking for. 

But battery discharge current is Cah/10 or Cah/5.

500A discharge current is thus for a battery of 2500Ah or more.
Such big batteries are used for 48V telecom applications, but I never seen such a 12V battery....Always only 2V cells, never 12V !

[ConKbot]

Basically! I'm looking for a way to easily load test batteries, or battery banks, with a settable 20-500amp load...
Is this a possibility?

... at 12volts ...

Wait, are you talking about battery banks? Isn't it rare (ie never) for many lead-acid batteries to be connected in parallel? I thought this isn't done because the batteries can't be balanced, and also what happens if one goes short circuit.
Battery 'banks' are normally wired in series. Certainly the large banks used for large UPSs (that back up whole buildings) are wired in series, with total output voltage in the 200 to 300VDC region.
So why are you talking about needing to draw load from a 12 volt source?

If youre running flooded batteries (or AGM with a recombination catalyst) that you can do a high voltage (~15+V ?) balance charge regularly, you can keep all the batteries balanced, but your cells better be identical, have the same age and cycle count. 

Paralleling lead acid batteries is asking for one to fail eventually.  Ive seen a vehicle with a bunch of radios and stuff that had an optima yellow top (AGM) added as a deep cycle for the radios.  But a standard flooded main battery.  In not to long one of them failed (I think the optima, not 100% sure) because they charge at different voltages. 

I was doing a  ~300AH battery backup for a sump pump and went with 2 6V FLA cells just because it would be more reliable in the long run than 2 paralleled cells.

[G7PSK]

Get a starter motor and a disc brake drive the brake with the motor the more pressure on the brake the higher the current drawn. A starter motor will easily draw 500 plus amps, use one from a large diesel engine, truck tractor etc.

[mzzj]

Get a starter motor and a disc brake drive the brake with the motor the more pressure on the brake the higher the current drawn. A starter motor will easily draw 500 plus amps, use one from a large diesel engine, truck tractor etc.

Why not something steam powered 

[AmmoJammo]

This was intended for load testing car batteries, or banks of them in parallel...

Was basically wanting to load test batteries like in this video:


OR, load them with a lower load, for an extended period, to monitor the discharge characteristics.

The banks of batteries would consist of 4 or more 100+ah batteries in parallel

I'll be leaving this for now (too many things on the go) but thanks for the ideas.

[turbo!]

Use a carbon pile with the adjustment stem driven by a servo.

Mod the input lead to four wire so you're monitoring at the sense wire.

Monitor the amps and volts. How you coordinate the amps/volts/servo is in microcontroller based setup. 

[hibone]

good luck

http://www.chirio.com/electronic_load.htm