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Author Topic: How to control very very really very high currents with arduino?  (Read 2212 times)
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And sometimes they do burst into flames
At 30,000 feet over the Atlantic...

Well that was a well engineered Li-ion battery, not LiPo...  LiPo is more like plastique IMO.
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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?

I am with you, discharge at rates of 100 amp is very very really very high currents, plus LiPo and LiIon fires are very very really very dangerous.


This guy got lucky. Another guy had his house burn to the ground.

stackexchange

before u build discharge circuit, u MUST build protection circuit;-

1. over current protection.
2. over temperature protection.
3. under voltage protection.
4. over voltage protection.
...

after protection circuit in place, now is time for current sink.

few ways you could do.
1. use High-Current Operational Amplifiers, 100A one is very very really very pricy and if you could get it( u are lucky).
2. use JFET current sink.



change Q1 and Q2 for support high current, and put Q2 on heatsink. connect Vin to output of Arduino DAC.

TI App note



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if I were you, I would buy  pro made HIGH RATE DISCHARGE TESTER instead of build one.




make sure HIGH RATE DISCHARGE TESTER type match with battery type. HIGH RATE DISCHARGE TESTER most case has RS232 interface. via TTL/RS232 adaptor to Arduino. Set, Ready, Go.
« Last Edit: March 19, 2013, 05:37:11 pm by sonnyyu » Logged

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Discharging a 24V battery at 100 amps means 2.4 KW has to be dissapated somewhere.
If the aim of the project is to maintain a constant current whilst the battery is discharging, then the OP needs
a dynamically variable load rated at 2.4 KW.
Thats not something you make very easily.


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For loads, get 24 100W, or for the heck of it, get 6 400W LEDs . . . when energy get converted to light, it would generate less heat compared to pure resistive loads. Well, you have to figure out how to wire them correctly.

Just a thought.

Or build 24 of this and PWM it to adjust current:

« Last Edit: March 20, 2013, 10:50:17 am by mjkzz » Logged

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But 100W LEDs take 32V.... Think it through!!
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For loads, get 24 100W, or for the heck of it, get 6 400W LEDs . . . when energy get converted to light, it would generate less heat compared to pure resistive loads. Well, you have to figure out how to wire them correctly.

Just a thought.

Maybe if you shoot it straight up and into space.  If you dump it into a room all that energy is going to be heat anyway when it is absorbed by the walls.  
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But 100W LEDs take 32V.... Think it through!!

OK, I think I am taking some information for granted, so let me explain and share this knowledge with others as well.

A 100W led consists normally 100 1W led, assembled into one unit.

These 100 1W leds are normally arranged in 10 rows of colunm of 10 1W led in series so the wiring inside the assembly is much simpler. This make the voltage required to be, like you said, 32V

However, manufacturers can make the internal wiring according to your specification. I was lucky that I bought two leftover of custom ordered 100W leds that are wired as two 5x10 blocks with 5 in series, making the voltage required to be around 16V

Of course there are limitations on how the wiring goes -- it would be a mess to have 11 3x3 blocks.

Having said above, the 32V 100W is probably the norm on the market, but 16V ones do exist, maybe require some luck to get them.

For OP's purpose, maybe 240 10W led is easier to acquire and build, also need lower spec'ed MOSFET to drive them, heat sink for 10W leds is probably off the shelf stock item and maybe use liquid to improve it further.

The key point I am making here is to convert energy into light instead of heat like a pure resistive load.
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If the LEDs are pointed at some PV panels you could reclaim some of the wasted electricity!

More constructively you could in theory use a very high current adjustable boost converter to
drain one battery into another (or a bank of others), thus recharging some batteries from the one
under test, recycling most of the energy and thus producing a lot less heat.

Finding a 100A inductor would be interesting.
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few things might worth to clear;-

1. 100 amps at 24V is not big deal. The car starter draw normally between 60-150 amps but some general motor starters can pull up to 250 amps. However  LiPo and LiIon battery discharge 100 amps IS.

2. Power v.s. Energy, for 30c battery discharge at 100 amps, will be only last 2 mins.
Energy=2400/30=80Wh. same Energy rate as my desk lamp.

3. Measurement method, it is pulse, i.e. on for few ms( to be long enough for Arduino read  battery voltage), then off for x ms and allow Q2 and R1 cool as well as keep battery cool. 1st pulse is 100 amps, 2nd  is 1 amp, 3rd is 99 amps, 2 amps, 98 amps...

4. Resistor current over load, working with pulse, Resistor current over load rate could be 10-20 time high then constant current rating.


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