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Oct 04, 2018, 01:55 PM
Did I make the A Main?
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How to make a battery discharger


Having a battery discharger can be very useful in creating battery discharge graphs if you have a charger that exports discharge data. You can also use a discharger to quickly get your packs into storage mode.

I will be discussing how I made a 30A discharger using mostly random materials around my house.

*** CAUTION ***
There are no safety features with this discharger, you must monitor the voltage yourself, preferably by connecting your charger in parallel and manually disconnect the bulb discharger when you hit your target voltage reading.


First I ordered some "12v 10w halogen bulbs" off eBay, I think I paid around $15 to get about 40 bulbs shipped:






Then used some scrap plastic and drilled some holes to get all the bulbs lined up in a grid pattern:



Then I used some scrap lamp wiring to route all my connections:



I tinned several wires to use as my wiring "bridge":



Here is my first row of lights soldered up to the bridge:



I just repeated this process by soldering each bridge together in parallel, note that the polarity on the bulbs don't matter, just make sure to keep each bridge consistent with the polarity on respective sides:



I repurposed an desktop power supply box to enclose my grid and soldered up some deans connectors in parallel with the existing cooling fan to get this:



I used a power analyzer to check my current draw and saw that I was pulling 36A with 27 bulbs + cooling fan:



My goal was to get as close to 30A as possible so I started disconnecting 1 bulb at a time until I got just under 30A, it actually came out to 24 bulbs to get a 29.8A draw:




The other 0.2A draw is what I use on my charger to get a combined total of 30A for my discharge graphs using the data exported from from the charger:


More info here on how I was able to connect my charger to my PC to export data:
Thunder AC6 Software Demo (7 min 56 sec)


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Last edited by bill_delong; Sep 15, 2019 at 05:49 PM.
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