Discharge Lipo battery pack  
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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> Discharge Lipo battery pack
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Discharge Lipo battery pack - 12/23/2007 9:51:58 PM   
avaughan61


 

Posts: 3
Joined: 7/20/2005
From: Westmont, IL, USA
Status: offline 		I quite new to the battery systems in electric planes. Its been quite a while since I've been flying and I'm quite worried about my Lithium polymer battery. Its a 11.1 (3 cell) Li-po battery with a 10-12C discharge of 1550 mah.

I was wondering if anyone had any ideas on how to discharge this pack. I was told that the lithium batteries could go "bad" if the ions where not moving on a regular basis. This is one reason I want to discharge the pack. I was wondering how i could manually discharge my battery (safely) without necessarily attaching it to my rc motor. On Google some people had suggested using a light bulb as a resistor and discharging it that way. Of course I didn't want the voltage (or current) to spike and the pack to overheat. I was unsure of what type of bulb or wire to use in that type of setup to safely discharge the pack. If any one has ideas it would surely help.
       Post #: 1

RE: Discharge Lipo battery pack - 12/23/2007 10:20:40 PM   
k8svrick


 

Posts: 125
Joined: 3/21/2007
From: Columbus, OH, USA
Status: offline 		You do not need to routinely cycle your lithium batteries. That should take care of all the other questions you posted on the discharge subject.

You will get several hundred cycles out of a good quality battery. Depending on the quality of the pack and the depth of each discharge, that could be higher; say, 500-700 cycles. A cycle is defined as a discharge followed by a recharge, regardless of the depth (how far down) of the discharge.

Assuming you have a charger that is designed to charge these types of batteries, let's talk about charging for a minute. You're only going to be able to charge most lithium battery packs th the 1C rate. The C rating of your pack is 1550 mah (1.5 ampere hours) So, the 1C charge rate is 1.5 amps or 1500 ma. I just left off the 50 ma to make the math easier. Unless you're using a lithium-manganese battery, this is what you're limited to as far as charge rate is concerned. Charging at rates higher then 1C for Lithium-polymer (aka lipo) batteries can, and has resulted in damaged and/or destroyed packs. They aren't intended to be charged at higher rates than 1C, typically.

Always follow the battery maker's operating ninstructions, as not all batteries are created equal.

Good luck and have fun.

It's disappointing that there is so much bad information out here on the web.

_____________________________

Rick - Columbus, OH
www.ricktressler.com

(in reply to avaughan61)
       Post #: 2

RE: Discharge Lipo battery pack - 12/23/2007 10:28:38 PM   
guver


 

Posts: 9100
Joined: 3/7/2003
From: LaGrange, OH, USA
Status: online 		Hi welcome to RCU. It isn't necessary to discharge it, but if you want to store it for a long time then dischargeing to 3.8 volt/cell is a good storage voltage (11.1-11.7 is good)

You can probably use an automotive tail light bulb (12 volt) and a dvm to monitor the voltage. OR you can just fly the thing for about half the normal time. If you fly once a week then there's no point.

< Message edited by guver -- 12/24/2007 12:58:47 AM >

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(in reply to avaughan61)
       Post #: 3

RE: Discharge Lipo battery pack - 12/23/2007 10:57:05 PM   
avaughan61


 

Posts: 3
Joined: 7/20/2005
From: Westmont, IL, USA
Status: offline 		Well according to k8svrick then i guess i don't need to discharge the battery.

The reason I was asking was because I wanted to put the battery in storage for a long while. Is this still the case?

(in reply to guver)
       Post #: 4

RE: Discharge Lipo battery pack - 12/23/2007 11:09:27 PM   
guver


 

Posts: 9100
Joined: 3/7/2003
From: LaGrange, OH, USA
Status: online 		Yes, if you are going to store it then discharge it to 11.5 resting volts.

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       Post #: 5

RE: Discharge Lipo battery pack - 12/24/2007 12:56:39 AM   
avaughan61


 

Posts: 3
Joined: 7/20/2005
From: Westmont, IL, USA
Status: offline 		my battery is only a 11.1 V battery. Are you saying that keeping it charged would be healthy for the battery or do I need to take some course of action to store my battery for a significant period of time.

(in reply to guver)
       Post #: 6

RE: Discharge Lipo battery pack - 12/24/2007 12:59:37 AM   
guver


 

Posts: 9100
Joined: 3/7/2003
From: LaGrange, OH, USA
Status: online 		Store the battery at 11.5 volts for a long time. That is a partial charge.

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       Post #: 7

RE: Discharge Lipo battery pack - 12/24/2007 3:13:56 AM   
exeter_acres



Posts: 6125
Joined: 9/22/2004
From: Johns Creek, GA, USA
Status: online 		Your pack is 11.1 NOMINAL....
at full charge it should be around 12.6v

_____________________________

Extreme Flight RC tech support
IMAC members, Thanks for voting!

(in reply to guver)
       Post #: 8

RE: Discharge Lipo battery pack - 12/24/2007 3:43:45 AM   
safeTwire


 

Posts: 183
Joined: 3/3/2003
From: Rye Brook, NY, USA
Status: offline 		For storing your battery, make certain that the battery does not drop below 3.8 to 3.9 volts per cell. (As recommended by Thunder Power)

IMO you cant shelf a Lipo and forget about it. Every now and then, test it and charge if necessary.

(in reply to exeter_acres)
       Post #: 9

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