[NSRCA-discussion] Battery discharge/storage question

[Peter Vogel]

You have to remember that the chemistry of these batteries is extremely
unstable at full charge (and full discharge for that matter) and it's an
"unnatural state" for the battery.  At full charge (4.2v/cell) the
chemistry is aching to let electrons out and if it cannot it will start to
degrade fairly rapidly.  1 week is the LONGEST I would leave it at full
charge, and even that's a bit long.  Electric cars show "full charge" at
80% of max charge and "empty" at 20% charge for precisely that reason.

Peter+


On Wed, May 8, 2013 at 11:05 AM, Scott McHarg <scmcharg at gmail.com> wrote:

> I got scolded not too long ago for even suggesting it by a ThunderPower
> rep.  I wanted to top off because after a week, one of my packs had dropped
> down to like 94% (yes it was an older pack and had a little over 180 cycles
> on it).  I was told that topping off "could" cause damage to the packs
> immediately regardless of age.  It was a fairly stern warning.  Honestly, I
> didn't ask more because I was already hanging my head from the scolding.  I
> just said "Yes sir, sir".  :)
>
>
> On Wed, May 8, 2013 at 1:00 PM, Atwood, Mark <atwoodm at paragon-inc.com>wrote:
>
>> Okay, I'll bite. Why don't you want to top off the charge? I know a lot
>> of people who insist on doing this even if they just flew the day before.
>>
>> Sent from my average intelligence  phone
>>
>>
>> On May 8, 2013, at 1:44 PM, "Scott McHarg" <scmcharg at gmail.com<mailto:
>> scmcharg at gmail.com>> wrote:
>>
>> I haven't seen any issues with a battery left a full charge for a week
>> but I wouldn't recommend longer at full charge.  Just make sure that you DO
>> NOT top off the charge prior to flying.  I have started doing what Keith
>> does as well which eliminates all concerns.  The worst part is having to
>> wait at the field while you bring that battery back up to 50%.  Last one
>> out has to lock the gates.
>>
>>
>> On Wed, May 8, 2013 at 11:23 AM, Keith Hoard <klhoard at hotmail.com<mailto:
>> klhoard at hotmail.com>> wrote:
>> I take my batts to the field at 50% and leave the field at 50% charge. If
>> I can't do that, then I discharge when I get home. My batts seem to last a
>> long time.
>>
>> The (dis)charger is supposed to get hot, that is where the energy from
>> the battery is going - into the heat sink. That's Ok, my PL 8 gets hot too.
>>
>> The PL8 can only discharge 100 watts by itself, but can do much higher if
>> it is using "regenerative" discharge - dumping your LiPo's charge back into
>> a lead acid battery. I don't know if the 10X has that capability or not.
>>  Otherwise I'd just keep using the low discharge rate, or plan your flying
>> day to end with a storage charge.
>>
>> Wow, that was a lot of typing to do on a phone!!
>>
>> Sent from my iPhone
>>
>> On May 8, 2013, at 11:15, "Bob Kane" <getterflash at yahoo.com<mailto:
>> getterflash at yahoo.com>> wrote:
>>
>> I have had to abort a couple of planned flying sessions so far this
>> spring due to weather.  I have read that lipos should not be left at full
>> charge for any significant length of time. So what is a significant length
>> of time?
>>
>> Hours?  Days? Weeks?
>>
>> My Turnigy 10XS charger has a discharge/storage mode, but the maximum
>> discharge current is 1 amp. It takes a couple of hours to bring a 10S pack
>> down to storage level, and the charger gets pretty warm(!) during the
>> discharge.  Up to now I have only worried about discharging the pack for
>> long term storage.
>>
>> If leaving the cells fully charged for more than a day or so is bad, I am
>> considering building a dedicated discharger, there are some pretty simple
>> yet effective designs on RCU.
>>
>> Bob Kane
>> getterflash at yahoo.com<mailto:getterflash at yahoo.com>
>> _______________________________________________
>> NSRCA-discussion mailing list
>> NSRCA-discussion at lists.nsrca.org<mailto:NSRCA-discussion at lists.nsrca.org>
>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>
>> _______________________________________________
>> NSRCA-discussion mailing list
>> NSRCA-discussion at lists.nsrca.org<mailto:NSRCA-discussion at lists.nsrca.org>
>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>
>>
>>
>> --
>> Scott A. McHarg
>> Sr. Systems Engineer - Infrastructure
>> _______________________________________________
>> NSRCA-discussion mailing list
>> NSRCA-discussion at lists.nsrca.org<mailto:NSRCA-discussion at lists.nsrca.org>
>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>> _______________________________________________
>> NSRCA-discussion mailing list
>> NSRCA-discussion at lists.nsrca.org
>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>
>
>
>
> --
> *Scott A. McHarg*
> Sr. Systems Engineer - Infrastructure
>
> _______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>



-- 
Director, Fixed Wing Flight Training
Santa Clara County Model Aircraft Skypark
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20130508/0fd14bd5/attachment.html>