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R/C Related Electronics DIY DIY R/C Electronics for tinkerers and the budget minded


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Old 10-11-2015, 11:39 PM   #1 (permalink)
TT
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Join Date: Nov 2006
Location: Kansas City & Nakhon Sawan Thailand
Default 'Dumb' discharger

Bear with me...my electronics knowledge is 'junior high' at best...

I plan on building some modular load banks to discharge lipos with. I plan on building modules that I can use in parallel depending on how much load I need.

For each module my plan is to use 5 8Ohm 100W resistors in parallel. My math tells me this will pull 15.75A on a 25.2V battery for 396.9W of dissipation. Is that right?

My current charger (Hyperion 720i Duo) does not handle regenerative discharge so until I buy a charger that does I need something to ramp-up the current to the load bank. Would a properly-sized motor controller work for this?

I plan to use a wattmeter and lipo low voltage alarm to keep an eye on things.

Any help here would be great!
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Old 10-29-2015, 06:35 PM   #2 (permalink)
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Yep - that works out the way I calculate it.

I would set the size of the resistor "stack" to limit the current to 1C or 2C max.
I assume the 15A current draw is for a 6S 5000mAh pack at 3C. I wouldn't go that high.

And, the 100W resistors may be marginal.
I would look for 150W or 200W resistors

By "motor controller", do you mean an Electronic Speed Controller (ECS)?
No, most likely not.
The typical ECS is a micro processor that switches on/off/on a set of 3 transistors and those are connected to a brushless motor.
The transistors are either fully on or fully off.

You need a big variable resistor ("pot" or potentiometer) to "dial up" the resistance you need.
They used to be used with DC motor speed controllers.

Last edited by ticedoff8; 10-30-2015 at 11:26 AM..
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