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### Topic: How to control very very really very high currents with arduino? (Read 7323 times)previous topic - next topic

#### juanfsepulveda

##### Mar 19, 2013, 04:04 pm
Hello,

I'm working in a discharger of LiPo batteries that must discharge at rates of 100 amp, with batteries of 12 and 24 volt. I've seen some tutorials of "high power control with arduino" but the high power is only 5 or 10 A, and they recommend some FET and/or MOSFET for that currents. My question is: Is it possible to manage 100A currents with those diagrams? and what mosfet or transistor do you recommend for this job?

#### retrolefty

#1
##### Mar 19, 2013, 04:12 pm
Depends on what you mean by 'manage'. If you just need to be able to measure the current I think there might be hall effect current sensors that can measure that range of currents and give you a simple DC measurement voltage proportional to the current flow. If you mean to turn on and off or regulate the actual current flow then that is another matter all together. One could use very high current rated relay contacts if just switching on or off that level of current, although the size of relay would probably be pretty massive. There are some IGBT high current transistors rated at that kind of current, and of course one could parallel several high current/power MOSFETS to get that kind of current control. Pretty demanding application, I would look around and see what other people and firms have used to perform that task first I think.

Lefty

#### majenko

#2
##### Mar 19, 2013, 04:21 pm
MOSFETs with many hundreds of amps constant drain current are pretty common.

A quick search on Farnell turned up loads with currents up to about 480 amps.

Quote

MOSFET, N CH, 30V, 190A, TO220
Transistor Polarity: N Channel
Continuous Drain Current Id: 260A
Drain Source Voltage Vds: 30V
On Resistance Rds(on): 1.6mohm
Rds(on) Test Voltage Vgs: 10V
Threshold Voltage Vgs Typ: 1.9V
Power Dissipation Pd: 230W
Operating Temperature Min: -55°C
Operating Temperature Max: 175°C
Transistor Case Style: TO-220AB
No. of Pins: 3
SVHC: No SVHC (19-Dec-2012)
Cont Current Id @ 100°C: 190A
Cont Current Id @ 25°C: 260A
Current Id Max: 260A
Operating Temperature Range: -55°C to +175°C
Package / Case: TO-220AB
Termination Type: Through Hole
Transistor Type: Power MOSFET
Voltage Vds Typ: 30V
Voltage Vgs Max: 1.9V
Voltage Vgs Rds on Measurement: 10V

Of course, you'll be wanting some very very fat PCB traces, and a rather large heatsink to dissipate the heat...  Maybe you could boil a kettle with it

#### Grumpy_Mike

#3
##### Mar 19, 2013, 08:03 pm
Quote
I'm working in a discharger of LiPo batteries that must discharge at rates of 100 amp

So is this an incendiary device then. What is to stop the battery bursting into flames?

#### majenko

#4
##### Mar 19, 2013, 08:07 pm

Quote
I'm working in a discharger of LiPo batteries that must discharge at rates of 100 amp

So is this an incendiary device then. What is to stop the battery bursting into flames?

Maybe they're 100Ah batteries, and he wants to discharge them at 1C - A resistor the size of a small cow would do the job...

#### retrolefty

#5
##### Mar 19, 2013, 08:09 pm

Quote
I'm working in a discharger of LiPo batteries that must discharge at rates of 100 amp

So is this an incendiary device then. What is to stop the battery bursting into flames?

There are special Li-Po packs that are designed to supply that kind of current discharge (for a short time of course) used in high performance R/C electric motor powered craft.

Lefty

#### mixania

#6
##### Mar 19, 2013, 08:22 pm
Using a relay:
https://www.sparkfun.com/products/100

#### juanfsepulveda

#7
##### Mar 19, 2013, 08:29 pm

Quote
I'm working in a discharger of LiPo batteries that must discharge at rates of 100 amp

So is this an incendiary device then. What is to stop the battery bursting into flames?

There are special Li-Po packs that are designed to supply that kind of current discharge (for a short time of course) used in high performance R/C electric motor powered craft.

Lefty

Exactly, this are batteries for an Unmanned Aerial Vehicle, with 8000mAh. And according to the datasheet, the battery can supply 30C, so if my maths are not wrong, the battery can supply 240A (in theory) but 100A is not a problem for this bateries

#### lokidude

#8
##### Mar 19, 2013, 08:30 pm
Perhaps use something like this \$50 ESC

http://hobbyking.com/hobbyking/store/__24566__HobbyKing_120A_ESC_4A_UBEC.html

Hook it up to a brushless motor with a big paddle fan for a load. ( mount it to something very solid :-) )

It basically takes a servo input to control the motor speed so using the servo library you should be able to do a nice variable load controlled by the arduino.

If you need more amps, just get a bigger ESC

#### fungus

#9
##### Mar 19, 2013, 08:34 pm

Using a relay:
https://www.sparkfun.com/products/100

Maybe you missed it but that page says "The contacts are rated up to 5A"...

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

#### juanfsepulveda

#10
##### Mar 19, 2013, 08:45 pm

Depends on what you mean by 'manage'. If you just need to be able to measure the current I think there might be hall effect current sensors that can measure that range of currents and give you a simple DC measurement voltage proportional to the current flow. If you mean to turn on and off or regulate the actual current flow then that is another matter all together. One could use very high current rated relay contacts if just switching on or off that level of current, although the size of relay would probably be pretty massive. There are some IGBT high current transistors rated at that kind of current, and of course one could parallel several high current/power MOSFETS to get that kind of current control. Pretty demanding application, I would look around and see what other people and firms have used to perform that task first I think.

Lefty

My work is to get a steady current flow from the battery of diferent currents until 100A, to see the behaviour of the voltage trough the discharge of the battery. So I'll use feedback to the arduino to regulate the current flow. So, the FET or MOSFET or Relay or wathever is the key to controll the exact current flow that I need using PWM and arduino. I hope this explication will be useful to understand the idea :-) and thanks for your answer

#### fungus

#11
##### Mar 19, 2013, 08:57 pm
Put a few of these in parallel until you get the right resistance:

http://www.ebay.com/itm/250911322119

Then all you need is a big MOSFET to switch it.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

#### dc42

#12
##### Mar 19, 2013, 09:09 pm
Alternatively, a few of those in parallel but each with its own mosfet to switch it. Then you can vary the load by turning more or fewer mosfets. And you can use smaller mosfets.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

#### MarkT

#13
##### Mar 19, 2013, 10:10 pm

Quote
I'm working in a discharger of LiPo batteries that must discharge at rates of 100 amp

So is this an incendiary device then. What is to stop the battery bursting into flames?

100A is not particularly large for many LiPo packs.  A 30C pack of 3Ah is rated to discharge 90A continuously
(well upto 2 minutes of course!).   And sometimes they do burst into flames, but usually after over-discharge
and then overcharging.  They certainly want cooling in use at these levels.

That 1.6mOhm MOSFET is getting there, but even that will dissipate 16W at 100A, needing forced air cooling.
Several in parallel will be much more like it.  [and a good beefy MOSFET driver for them]

IGBTs would be a farce, given saturation voltages are several volts, so perhaps 400W or more dissipation!

Of course if you need a dummy load as well, thats going to have to take kW levels of dissipation anyway...
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### majenko

#14
##### Mar 19, 2013, 10:18 pm

And sometimes they do burst into flames

At 30,000 feet over the Atlantic...

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