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Old Apr 05, 2009, 06:06 PM
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Phoenix, Arizona
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How should I store my lipo?

I have a cx2 battery and the charger that came with it. I know your supposed to discharge batteries to 3.6 volts for storage. Should I plug my lipo battery monitor into it http://www.helidirect.com/deluxe-16s...tor-p-7198.hdx and run the helicopter until it is at 3.6 volts or 3.7 just to be sure that I dont go under 3.7?

I also think I might have over discharged the original battery that came with it. When I try to charge it some times the charger flashes the green and red light meaning charge error. Other times it does not say charge error. When check the voltage of it with the monitor I check my other battery with it says 4.2 volts.
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Old Apr 05, 2009, 06:11 PM
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No, not 3.6 volts per cell - storage voltage is 3.8 volts per cell. Temperature is important - cooler is better. Many store them in a refrigerator - not the freezer.

Bill
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Old Apr 05, 2009, 06:35 PM
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I had a 3s 25c 2500 mah kept in a Walmart $26 aluminum clad COSMETIC case since DEC 2008 and it still delivered full power for 10 min starting @ 12.58V when I ran it two days ago
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Old Apr 05, 2009, 07:15 PM
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The best way to store lipo is to store them like when you bought them. Cool dry place and half charged.
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Old Apr 05, 2009, 08:50 PM
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http://www.rcgroups.com/forums/showt...hlight=storage
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Old Apr 05, 2009, 10:17 PM
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How should I discharge them to 3.8 volts? Should I put it in the helicopter with the monitor and go until it is 3.8 volts? Im afraid Ill go to 3.7 by accident.

The original battery (I have 2) that came with it seems to have been overdischarged. But the charger sometimes says charge error and sometimes just charges it. As I explained above. The monitor says 1 cell at 4.28 volts and the other at 4.25. Is the battery still good?
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Old Apr 06, 2009, 01:35 AM
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There is a difference between rest voltage, and the voltage under load (e.g. when Your helicopter is running).

Do not stick with precise value for storage voltage. Just store Your lipos right as it is if discharged after flight - but make sure that is is not overdischarged. Any value between 3.6V and up to 3.9V or even 4.0V will be OK.

It means, that if the battery voltage runs down to 3.1V in flight (it means under load), it is probably flat empty but still OK. After power down, the voltage should rise up to 3.6V or more, which is OK for storage.
(Note that as better pack is used, as less the voltage will rise. Old and tired pack may run down to 3.0V and still jump to 3.7 or 3.8V, but new perfect pack may hardly reach 3.6V even if You stop using it at 3.3V - it is the reason why the end of flight voltage is simply NOT certain)

IF it remain below 3.6V at any cell, the flight was too long and the battery was discharged way too deep - such use will degrade battery and decrease its usable life much. In such case, the way of storage has no significant effect on its (reduced)service life.
Occasionally, if such overdischarge will happen, charge the battery as soon as possible. To store that pack, just stop the charge after approximately 1/3 or even less of time, which ordinary charge should take using Your charger - it should leave the pack charged to approximately 50 percent, which is the most recommended 50% charge level for storage.

As for voltage above 4.20V any cell - IF the monitor is not simply reading it wrong (it is possible because such simple voltage monitors are ofter far from accurate), that voltage is above given maximum voltage per cell for lipos in general. If Your charger really overcharges Your packs, You may save money by buying better charger.
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Old Apr 06, 2009, 05:53 AM
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Quote:
Originally Posted by lazer155
How should I discharge them to 3.8 volts? Should I put it in the helicopter with the monitor and go until it is 3.8 volts? Im afraid Ill go to 3.7 by accident.
Why are you afraid when the maximum low voltage you can safely go is 3.0v per cell. Dont worry about going 3.7v instead of 3.8v per cell.
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Old Apr 06, 2009, 06:45 AM
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You can use a #1156 tail light bulb (from Auto Parts store) and solder some leads to it. Use a D/C voltmeter to check the resting voltage. 3.6 to 3.85 volts per cell is OK. I try to get it to 3.7 to 3.8 volts per cell for storage.

Challenger413
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Old Apr 06, 2009, 06:55 AM
Southern Pride
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Haralson County GA. USA
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Quote:
Originally Posted by freechip
Why are you afraid when the maximum low voltage you can safely go is 3.0v per cell. Don't worry about going 3.7v instead of 3.8v per cell.
That depends.

With many of the newer very good 30C plus discharge rate LiPoly if you go to 3.0 per cell it has better be at their max. discharge rate. My experience shows that a good 40C will deliver more than 90% of its' capacity down to 3.2 per cell at 20C or greater.

With LiPolys the rules are always changing.Five years ago we used 2.7V per cell,soft cutoff and flew till LiPolys were really empty at a 5C average discharge rate. We used 100% of the rated capacity and used LiPolys rated at 8 or 10C and they were the best available.Try using 2.7 per cell and 100% today and you will pay the price. . Only accurate gage is mAh put back in.
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Old Apr 06, 2009, 09:13 AM
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the monitor says it has an accuracy of 0.02=-. So to be safe I should discharge the battery into the range of 3.7-3.9 possibly 4.
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Old Apr 06, 2009, 10:06 AM
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Haralson County GA. USA
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Quote:
Originally Posted by lazer155
the monitor says it has an accuracy of 0.02=-. So to be safe I should discharge the battery into the range of 3.7-3.9 possibly 4.
Ther is no exact safe discharge to voltage under load. It will vary depending on the quality of the cells,the past useage of the cells,the load on the cells at the time LVC is reached ,etc..

A given battery discharged at 10amps. to 3.7 volts will have a different open(resting) voltage than the same battery discharged at 5 amps. or 20 amps.

In general terms the better the battery (higher real C rate) the greater percentage of real capacity will be delivered at higher discharge rates to a LVC of between 3.2 and 3.7.
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Old Apr 06, 2009, 07:06 PM
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well if I discharge until the battery is at 4.0 volts under load then continually unplug and check the battery. Then replug it in after letting it come to a no load voltage and checking the voltage with my monitor. If the voltage has dropped into the 3.2-3.7 range I will call it ready for storage. This way I the battery will be at 3.2-3.7 volts without a load for sure. If its not I will just plug it back in for a little while then unplug it and check the voltage again. Sorry if the way Im explaing this is confusing, I cant think of a good way to explain this method.
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Old Apr 07, 2009, 07:32 PM
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Ok I discharged the battery but one cell is at 3.8 and the other is at 4 volts. How do I get the cells to be at the same level?
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Last edited by lazer155; Apr 07, 2009 at 08:17 PM.
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Old Apr 07, 2009, 07:36 PM
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Haralson County GA. USA
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Did you discharge through the power leads or the balancing leads?
You should have used the mai power leads.
Now you will have to do each cell , the other two one at a time.
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