[NSRCA-discussion] Battery discharge/storage question

Wed May 8 11:23:31 AKDT 2013

I think the problem is that LiPos are VERY sensitive to overcharging. John Grzan, owner of the Revolectrix factory even recommends limiting charging to 4.1V per cell to maximize battery life. 

My guess is that when you "top off" using a less than full quality charger that it may be overcharging by starting off in constant current mode instead of constant voltage mode. 

Sent from my iPhone

On May 8, 2013, at 13:50, "Scott Pavlock" <f3aflyer7 at gmail.com> wrote:

> I have found that when I fly after work around 6, after charging the night before, the pack will lose about 7%. This is enough for the auto lipo setting on my HV85 to only detect 9 cells. I assume I could fix this by going to a custom cutoff voltage, but with current settings it forces me to top off my packs before I fly.
> 
> I wasn't aware that topping off was an issue; I'd like to see some supporting data however.
> 
> Scott
> 
> On May 8, 2013 2:33 PM, "Scott McHarg" <scmcharg at gmail.com> wrote:
>> For what it's worth,  I did just go online to see what others were saying.  I found forums that said it's no problem and others that said don't do it.  Of course, a lot of them that were "for topping off" were talking about charging from storage and not truly topping off.  My comment was only for topping off say, above 90+%.  I'm sure chargers still detect it but I'll take my scolding and just do as he said.  Gaining <5% doesn't seem worth it to me.
>> 
>> 
>> On Wed, May 8, 2013 at 1:29 PM, Jay Marshall <lightfoot at sc.rr.com> wrote:
>>> This is an interesting issue. I’d like to hear more justification for not doing it. Never heard it before or seen anything in the literature.
>>> 
>>>  
>>> 
>>> Jay Marshall
>>> 
>>>  
>>> 
>>> From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Scott McHarg
>>> Sent: Wednesday, May 08, 2013 2:06 PM
>>> To: General pattern discussion
>>> Subject: Re: [NSRCA-discussion] Battery discharge/storage question
>>> 
>>>  
>>> 
>>> 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>
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>>> --
>>> Scott A. McHarg
>>> Sr. Systems Engineer - Infrastructure
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>>> Scott A. McHarg
>>> Sr. Systems Engineer - Infrastructure
>>> 
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>> 
>> 
>> 
>> -- 
>> Scott A. McHarg
>> Sr. Systems Engineer - Infrastructure
>> 
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