[NSRCA-discussion] Battery discharge/storage question

Wed May 8 11:25:21 AKDT 2013

That's why they give you load agents, operations agents and a FMC Keith.

On Wed, May 8, 2013 at 2:17 PM, Keith Hoard <klhoard at hotmail.com> wrote:

> Van Putte told me there would be no math.
>
> Sent from my iPhone
>
> On May 8, 2013, at 13:46, "Dave Harmon" <k6xyz at sbcglobal.net> wrote:
>
> ** **
>
> At the end of every flying session, I leave the field with the batteries
> in whatever state of charge that they have.****
>
> I don’t do a storage charge at the field.****
>
> I do the storage charge at home.****
>
> ** **
>
> If I am going to fly the next day or in a few days….less than a week, I do
> not discharge the already charged batteries….but I DO top them off at the
> field the next time out.****
>
> Today’s chargers usually go into the balance mode immediately when
> charging a previously charged battery so I don’t believe there is a problem
> topping off a previously charged battery.****
>
> ** **
>
> Before I leave for the field, I charge all batteries that are discharged
> or in storage charge.****
>
> If I have several flying sessions in a week or so I will NOT put any
> discharged batteries in storage charge….****
>
> Then I charge them just before I leave home on the next day I go flying.**
> **
>
> If I know I am not going to fly for several days then I DO put discharged
> batteries in storage charge….AND discharge charged batteries low enough to
> put into storage charge.****
>
> ** **
>
> ** **
>
> If I need to discharge any batteries I do it with a 17 ohm 100w Dale
> resistor.****
>
> I made a 12” heavy zip cord lead with alligator clips on one end and a
> matching connector for the battery on the other end.****
>
> I use a Fluke DVM across the resistor to monitor the voltage and I
> discharge down to about 35 volts.****
>
> Then I immediately do a storage charge.****
>
> I might not have to take them down to 35 volts but the battery must be
> below the storage charge voltage to get the charger into the storage mode.
> ****
>
> ** **
>
> If you do the math….the discharge on a fully charged battery is about 2.4A
> and the resistor is running within its wattage range.****
>
> ** **
>
> *Dave Harmon*
>
> *NSRCA 586*
>
> *K6XYZ[at]sbcglobal[dot]net*
>
> *Sperry, Ok.*
>
> ** **
>
> *From:* nsrca-discussion-bounces at lists.nsrca.org [
> mailto:nsrca-discussion-bounces at lists.nsrca.org<nsrca-discussion-bounces at lists.nsrca.org>]
> *On Behalf Of *Scott McHarg
> *Sent:* Wednesday, May 08, 2013 1:06 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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