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Discussion Starter #1
Does anyone have a DIY design for an automated battery cell tester?

As my other post points out I am looking to build a battery pack for a race car with a large volt and amp draw. It has gotten down to the fact that we need to test cells to confirm advertised specs or discover unknown specs.

Thinking something using an arduino to control the load and log the data. Then I can use a PC to analyze the data from those logs.

The data will then be used to build up the complete race pack.

Specs for the test rig:

0-15 Volt (most cells are 3.2 to 4.2 Volts)
Up to 1500 AMP
Up to 8000 Watts

Max Load tests will run up to 2 minutes.
Lower 1C tests will be run upto an hour.

Would like the cells and test equipment to be water cooled by aluminium plates.

I would like to log: Time, Cell volts, Output AMPs, Cell Temp, Water Inlet temp, Water exit temp (anything else people can think of)

May want monitor more than one cell in a parallel or serial configuration.

Here are a couple that I have been looking at to use as a starting point and maybe scale up.

https://www.instructables.com/id/Arduino-Programmable-Constant-Current-Power-Resist/

https://www.youtube.com/watch?v=acAuW0IVXKw

I know that West Mountain has a tester for up to 2000W.
http://www.westmountainradio.com/product_info.php?products_id=sys2000_watt

Also I know some DC electronic loads like from BK Precision and they can do battery tests also they get up to $10,000.
 

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Discussion Starter #3
Built into iCharger Duo units innit?
The iCharge Duo can only do 40 AMP with external sink. I am looking doing 0-15 V, 1500 AMP and up to 8000 watts.

Looking at driving parallel IGBTs dumping to a heating elements in a water tank with cold water refresh once water gets up to temp. The IGBTs will be on a cooling plate also.

(Honey, I am just heating the pool!!!!)
 

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Hi SpeedRacer93,

keep in mind that IGBTs have a voltage drop (VCE) and are therefore commonly used in circuits with higher voltages. For your purpose some power MOEFETs could be the better choice.
 

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Hi SpeedRacer93,

keep in mind that IGBTs have a voltage drop (VCE) and are therefore commonly used in circuits with higher voltages. For your purpose some power MOEFETs could be the better choice.
Thanks for pointing that out. I need to pull spec sheets on components. I stated IGBTs because of the AMP load with out really looking at all the spec. I am working to meet up with a friend that works with a electronics production firm here locally.

I am the mechanical engineer and project management type.
 

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The BUK954R8-60E seems to be okay if you have enough of them. Here is another power MOSFET:

https://www.mouser.de/datasheet/2/205/DS100209(IXTK-TX600N04T2)-1110259.pdf

I'm also interested in a high power dump load. First trials I made with glow plugs, and for higher voltages (up to 400 volts) I used some 2000 W oil heaters. To test single cells I bought tester from ZKETech, but only up to 200W (5V/40A discharge current).
 

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You may want to take a look at the DC Electronic Load on this page, it can probably adapted to your test rig. It's a nicely done DIY build. https://www.youtube.com/channel/UCDqryeq1kMDSEQwltWqASrA

I did a lot of cell testing using the West Mountain Radio CBA at 1C to profile all of the cells for racing packs. Then balanced distribution of them across the sub packs.

Also did some high amp testing using lengths of bare 12 ga wire submerged in water, and with the CBA recording voltage & time for discharges and recovery. 26 feet of 12 ga was about 60 amps on a single 3.3v cell. Shorten the 12 ga wire to increase amps. The wire took a 744A load from a test 2P4S pack with no problem.

It's a quick and dirty method but provided the data I was looking for.
 

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If you want a good dummy load, go to the dump and pull the element out of an electric clothes dryer.

It will be a metal pan 2' in diameter with ceramic lifting plates that hold a thick coil of nichrome (like a Slinky) in a circle around the pan with two spade terminals on each end of the wire.

A clothes dryer is 240v and maxes at 7200 watts, almost all of which is the element.

That makes the element around 8 ohms (though it probably is lower when cold and higher when hot).

It's designed to have a fan blowing air over it non-stop to cool it obviously, but then it's also designed to sit in a metal box. Not sure just how hot it would get if you gave it 240v.

You could run a gater clip anywhere down the coil like a variac to tap progressively smaller sections of the total resistance, though note that you'd be heating the wire section increasingly hotter. I'd consider hooking the coil up in parallel pairs or tripples (cut and restitch the coil) if you want more heat or lower voltage.

Alternatively, an oven heating coil (3000 watts, 240v) can be pretty much flatlined without damaging it, ditto for stovetop elements (1000-3000 watts), both of which you can get for cheap/free at the dump if you're kind and polite and mention it's for a science project for school. These make great loads and you can safely sink them into a metal can of water (except for where the ends are exposed through the white insulator). They're insulated and designed to be rapidly chilled because that's what putting a cold pot of water on them does anyway.

Water has massive heat capacity, so, a simple tank will take forever to actually boil itself dry and the element can handle full power in open air without fan cooling regardless.
 

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Heating elements (pulled from an oven, washing machine, dryer...) are doubtless a good option to test a whole pack (100+ volts), but you would need a lot of them if you want to test a single cell.

I’ve hooked-up some 300Ah cells in parallel just to equalize them, but with copper rails instead of the thin wires and a sufficient voltage difference the pack should be able to sink some thousands amps.

Another thought: What about large electrodes (e.g. 1 sqm steel plates) instead of heating elements dipped into a (salt-)water tank? At power stations they usually feed them with AC, but for short time currents also DC should work. However one should take care of the hydrogen...
 

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Heating elements (pulled from an oven, washing machine, dryer...) are doubtless a good option to test a whole pack (100+ volts), but you would need a lot of them if you want to test a single cell.
Oven and stovetop elements are insulated (the nichrome is inside, then a white insulator, then a soft iron exterior). Those are tricky to partially use.

Clothes dryer elements are just a bare slinky of nichrome. You can use gator clips to select any resistance along its length.

Another thought: What about large electrodes (e.g. 1 sqm steel plates) instead of heating elements dipped into a (salt-)water tank? At power stations they usually feed them with AC, but for short time currents also DC should work. However one should take care of the hydrogen...
You don't want to use steel and you don't want to use table salt. Table salt will instantly create chlorine gas and rust even stainless steel in moments, turning the water into a thick diarrhea blend of green and brown.

Use stainless plates, and battery acid. TSP in a pinch. Baking soda will work but isn't great.

You'll be splitting H2O into H2 and O2 in a perfectly explosive mixture, but both gasses diffuse almost instantly ("water torches" are safe for use in malls and other enclosed spaces). A fan and an open room would be fine. It just bubbles up to the surface.

There's much better ways to create ghetto resistors.
 
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