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Old Jan 04, 2002, 02:57 PM
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CGR17500 Lithium-Ion cells...I need some more information

I've bought 3 Qualcomm packs and have already broken them open, soldered on the wires, and shrink-wrapped the pack. I need to know, is the capacity really 830 mAh? Will the saftey circuit likely kick in at all for a plane that draws under 3 amps? How long does the saftey circuit shut down the battery? I would like a charger that brings the capacity up to the rated capacity, I read that a fixed rate charger that shuts off at 70% rated capacity. I'm going to use these in a J3-stick, and I've seen great results of use with them. Please give suggestions.

(I'd also like to see the video of the exploding battery pack, so I have a stronger concept of saftey requirements...)
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Old Jan 04, 2002, 03:55 PM
aka: A.Roger Wilfong
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Novi, Michigan, United States
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The Panasonic spec sheet on these cells lists a maximum draw of 2C (actually, they recommend 1C, but supply discharge curves for 2C). This is about 1.66 amps. Your projected draw of 3 amps is almost twice the recommended and will likely kick in the protection circuit. The protection circuit activates like a circuit breaker - only to reset it, you have to disconnect the load.

I use the 830 packs with out the protection circuit in LiteStik variants and a TigerMoth. The TM (with the stock prop) pulls 1.8 amps static which is over the 2C limit but the actual load is lower in the air.

For charging, you need a charger that is specifically designed for Lithium cells. It needs to be constant current (~900mA) until the battery reaches 8.3v and then be constant voltage until the current decreases to a few milliamperes. Your best bet is get a Qualcomm charger from Hackett and modify it (there have been a couple of threads here {make that in <i>Park Flyers</i>} on making the modifications or you can look here http://www-personal.umich.edu/~aroge.../qbattery1.htm ).
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Old Jan 05, 2002, 12:55 AM
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Well, I already have the parts for the charger I'm using, and it's been used by other club members effectively. I am using it in a J3-cub, and if I encounter problems with it shutting down, I'll just take off the saftey board. (no exploded batteries yet!)
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Old Jan 06, 2002, 12:27 AM
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Well, I've checked the voltage on my packs, and one of three registers any voltage. The one of three registers slightly over 6v, the others are dead. What can I do to restore them? Nothing?
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Old Jan 06, 2002, 12:43 AM
Sweet!
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There is a likelihood that they shut themselves off due to low voltage or overcurrent (less likely). If you search under Qualcomm, you will find volumes of information. Meanwhile, you said that you broke them open. Can you read the voltage on the individual batteries?
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Old Jan 06, 2002, 12:49 AM
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if the packs get too low, the protection circuit will cut them off. this is why people fly their lion packs on a timer. if your cell voltage is too low, you need to use a lion field charger (orbit etc) or a constant low current source to bring it up to an acceptable level (i dunno.. say 3 volts or so? someone that's done it want to give some more details?). CAUTION: you need to use very little current, and constantly monitor the voltage with a multimeter. if you overcharge the packs this way, REALLY bad things (fires etc) could possibly happen. these aren't your daddy's nicad cells. be careful, and wait for someone who HAS charged them this way to give you exact current/voltage advice. you don't want to really experiment with lions.

if you need more current, you could always wire two serial packs in parallel, so you can do about 4 amps...
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Old Jan 06, 2002, 01:09 AM
Sweet!
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Right. You can attempt to bring the cells up with a very low current. Use no more than C/10. The cell should rise in voltage in a few minutes. Get it to at least 2.9 volts (I use 3.0 volts). Note that you should do this with each cell individually, not two in series. If it refuses to come up with low current, toss it.

Good luck,
Q
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Old Jan 06, 2002, 01:26 AM
high-speed freak
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I would be very surprised if you can't revive them, and they're bum cells. I've passed quite a lot of them to aussie slowman, and he said he only found a couple bad cells... if they are bad, oh well, you got unlucky... worth the $2 investment to toss them and buy another pack, rather than screw around with your safety. quacker's advice has the right technical ring to it
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Old Jan 06, 2002, 07:07 AM
aka: A.Roger Wilfong
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One of the 6 packs I've repackaged wouldn't charge initially on the Qualcomm charger - the LED went red and then, after about 30 seconds began flashing. I measured this pack with a multimeter and it read only about 4 volts (each individual cell was around 2 volts). I figured I had nothing to loose so I set the pack in a coffee can in the middle of the floor and hooked it up to my Astro 110D at 0.1 A for about 5 minutes. This brought the terminal voltage up to a little over 6 volts so I hooked the pack up to the Qualcomm charger and it charged normally.

I suspect the sensor circuitry in the charger detects less than ~6 volts as a "bad" battery and gives up.

I don't notice any performance difference between this pack and the 5 others.
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Old Jan 06, 2002, 02:04 PM
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Here's some detail about the charger. It automatically shuts off when the peak voltage is reached, to whatever you set it to. The charger should charge at about 80 mA. That's within the C/10 boundary, the capacity being 830 mAh. What I don't understand is why do I take the packs apart, and charge each cell individually?

I now understand why the saftey circuit shuts off any current to the volt-meter, it's below a certain voltage (Thanks opualuan). So, will the protection circuitry shut-down the charger?! I can remove the circuitry, but I'd rather have a crashing plane than a flying bomb.
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Old Jan 06, 2002, 02:13 PM
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Li-Ion charger



I didn't make the page, it's somebody elses...
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Old Jan 07, 2002, 10:18 AM
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Roger,

I also have a dead pack. One cell reads 3.6v, the other 1.5v

Did you charge the pack through the protection board, or directly to the cells with the Astro charger???

My Supernova can go to 100mah. Sound like a fix.

Chris
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Old Jan 07, 2002, 12:56 PM
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I've put some of my experiences with these cells on:
http://www.flyelectric.ukgateway.net/lithium.htm
3A is too high in my experience; it might handle it for a while but you are unlikely to get sustained life. You can get a good write up of the characteristics here:
http://www.mbi.panasonic.co.jp/oemba...ow/ionedow.htm
Supernova and Astro chargers for Lithiums? Surely not!
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Old Jan 07, 2002, 08:11 PM
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I'm using a lite-stick, so I'm at about 1.5 amp draw, not 3 amps. I was off on my first post by a bit
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