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Old Jun 25, 2001, 03:38 PM
Jesper Reich is offline
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How do you guys do it? Part II

Okay, now I have found out what batteries to use and how to charge them (interesting discussion in part 1), but now I have come across a new problem: How do I discharge 30 cells (36v. 2,4Ah.) at once? All regular discharges can only handle up to about 12 cells...... Can I discharge them using 3 car-headlamps in series? I know that I have to watch the voltage during this kind of discharge, or some of the cells will reverse (oh no! - here I go again...!)

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Old Jun 25, 2001, 05:09 PM
Fitz Walker is offline
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No "R" !!!!!!!
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Moved thread to Modeling Science forum as it seems more appropriate there.

Old Jun 25, 2001, 05:15 PM
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That is exactly correct - use three 12V bulbs in series. Of course, if they are 1 amp bulbs at 12V, then it will take 2 hours to discharge.
The most fun way to discharge is to just go fly...

Old Jun 25, 2001, 09:22 PM
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The Orbit Microlader and Microlader Pro will discharge 30 and 32 cells at 25W and 35W dissipation respectively and taper the current for complete discharge down to 0.9V/cell. There must be other chargers that would discharge this many cells...


Old Jun 26, 2001, 04:18 AM
steve lewin is offline
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There are several chargers that will do that, the top end Schulzes for example. But the real question is WHY do you want to discharge 30 cells other than in the air with them connected to a motor ?

Unless you are doing it to measure the capacity of the cells you're just using up the cells for no purpose. They only have a lifetime of a finite number of charge/discharge cycles. Why use them up just to light bulbs ?

Old Jun 26, 2001, 11:17 AM
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To discharge a 30 cells pack, you can get it done in half an hour....let see..
36 volts(or so), 5 amp(or so) and V=IR, ....R=V/I.....36V/5A=7.2 ohm... and P=IV so 5 amp x 36=180 watt.

Sooo you will need a 6-7 ohm , 250-300 watt resistor to discharge the pack. I would put the resistor in a bucket of water to cool it. Monitor the voltage as it goes. Put the resistor off when the voltage gets to about 25 volts.


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