[NSRCA-discussion] Battery discharge/storage question

Wed May 8 11:22:48 AKDT 2013

FWIW Thunder Power chargers will not top off any battery that is 90% +
charged but that's not thru to other chargers. I always top off my
batteries. No issues here.

Ken

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Scott Pavlock
Sent: Wednesday, May 08, 2013 2:51 PM
To: General pattern discussion
Subject: Re: [NSRCA-discussion] Battery discharge/storage question

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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Sr. Systems Engineer - Infrastructure

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Scott A. McHarg
Sr. Systems Engineer - Infrastructure

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