[NSRCA-discussion] Internal battery impedance
Keith Hoard
khoard at gmail.com
Sat Mar 15 10:27:09 AKDT 2008
The new FMA 10S LiPo charger is supposed to be able to give you cell
impedance during the charge cycle.
On Sat, Mar 15, 2008 at 1:18 PM, Emory Schroeter <schroetere at bellsouth.net>
wrote:
> It certainly will help you be able to see exactly which cell is going
> bad in a pack. I built one and after it didn't work, I sent it to Ron,
> who was able to undo all the incorrect soldering I had done :-) I have
> yet to actually use the spreadsheet, but I'm sure I will eventually
> get around to it.
>
> Emory
>
>
> On Mar 15, 2008, at 9:40 AM, Ron Van Putte wrote:
>
> > I'd forgotten Earl had the plans.
> >
> > The Lipo Doc is a very simple device that is mostly a rotary switch
> > and a couple of precision resistors. You measure voltage on the
> > cells of a lithium polymer battery in an unloaded condition, with a
> > 10 ohm load and a 1 ohm load. The results are put in a spreadsheet
> > and the internal resistance of each cell is determined.
> >
> > Ron Van Putte
> >
> > On Mar 15, 2008, at 5:25 AM, Earl Haury wrote:
> >
> >> Lance
> >>
> >> I use the "LiPo Doc" built from plans I got from RVP.
> >>
> >> Earl
> >> ----- Original Message -----
> >> From: "Lance Van Nostrand" <patterndude at tx.rr.com>
> >> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> >> Sent: Friday, March 14, 2008 11:23 PM
> >> Subject: [NSRCA-discussion] Internal battery impedance
> >>
> >>
> >>> Earl,
> >>> How do you measure the battery impedance?
> >>> --Lance
> >>>
> >>> ----- Original Message -----
> >>> From: "Earl Haury" <ejhaury at comcast.net>
> >>> To: <chad at f3acanada.org>; "NSRCA Mailing List"
> >>> <nsrca-discussion at lists.nsrca.org>
> >>> Sent: Friday, March 14, 2008 10:10 AM
> >>> Subject: Re: [NSRCA-discussion] Batteries
> >>>
> >>>
> >>>> Chad, you have a point, however it's important to factor in that
> >>>> the 1P
> >>>> packs are also generally higher C rating. My view when considering
> >>>> batteries
> >>>> initially was that higher cell count provided more failure
> >>>> opportunities,
> >>>> both as individual cell failure and connections. I've
> >>>> disassembled a
> >>>> number
> >>>> of "failed", or no longer pattern suitable packs, and measured
> >>>> individual
> >>>> cell characteristics.
> >>>>
> >>>> Generally, the cells in a lower C pack tend demonstrate an
> >>>> increase in
> >>>> impedance, resulting in lower voltage output for a given current
> >>>> draw
> >>>> over
> >>>> their lifespan until no longer "pattern viable". During this time
> >>>> capacity
> >>>> diminishes - but most cells with high impedance will still retain
> >>>> 80+% of
> >>>> their original capacity. Even though these things generate more
> >>>> heat than
> >>>> the higher C packs - they tend to handle abuse (as you've found)
> >>>> partly
> >>>> because of the retained capacity and partly because of "performance
> >>>> limiting" impedance. Post flight imbalance doesn't change too
> >>>> much as
> >>>> these
> >>>> packs age - suggesting a similar "aging" of the individual cells.
> >>>>
> >>>> Conversely, the high C packs demonstrate very low impedance
> >>>> initially and
> >>>> that appears to be retained throughout their life. However, the
> >>>> cell
> >>>> capacity appears to drop pretty early and continue to do so over
> >>>> the pack
> >>>> life. I've measured some of these with an average capacity loss
> >>>> of 40%
> >>>> after
> >>>> 50 flights - that means a 5000 mAh pack is now a 3000 mAh pack.
> >>>> Even
> >>>> worse -
> >>>> there is often a good deal of variance from cell to cell. Their low
> >>>> impedance will provide little warning (as loss of power) until a
> >>>> cell is
> >>>> injured, real easy to do if you try to take 3500 mAh from the now
> >>>> 3000
> >>>> pack.
> >>>> Often one will notice the post flight imbalance increasing as
> >>>> these packs
> >>>> age and it will be greater at higher depths of discharge - a sure
> >>>> sign
> >>>> some
> >>>> cells are getting weak. OTOH - for blazing power the high C packs
> >>>> are the
> >>>> way to go - but there's a price to pay in life, weight, & $$.
> >>>>
> >>>> These observations have led me to surmise that a pack with a high
> >>>> enough
> >>>> C
> >>>> rating to minimize impedance losses (and accompanying heat) and a
> >>>> low
> >>>> enough
> >>>> C rating to allow good capacity retention should provide the best
> >>>> value
> >>>> for
> >>>> pattern. I have no idea just what construction parameters /
> >>>> chemistry
> >>>> defines these characteristics. I chose to try the FlightPower F3A
> >>>> packs
> >>>> because they are mid-C rating and 5350 mAh capacity. So far they
> >>>> provide
> >>>> good power and generate no more heat than the high C packs I've
> >>>> used. I
> >>>> expect that the extra capacity (above 5000) offers a little
> >>>> buffer if
> >>>> there
> >>>> is a capacity decline over their life. I see little balancer
> >>>> activity
> >>>> with
> >>>> these packs regardless of depth of discharge (say 3000 mAh vs
> >>>> 4000 +) so
> >>>> far, time will tell - we're all still learning.
> >>>>
> >>>> Earl
> >>>>
> >>>> Team FlightPower
> >>>>
> >>>>
> >>>> ----- Original Message -----
> >>>> From: "Chad Northeast" <chad at f3acanada.org>
> >>>> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> >>>> Sent: Friday, March 14, 2008 8:22 AM
> >>>> Subject: Re: [NSRCA-discussion] Batteries
> >>>>
> >>>>
> >>>>> I think a huge part of the 5300 Prolites ability to deliver under
> >>>>> extreme abuse (I should know! :) ) is in large part due to a 4p
> >>>>> config
> >>>>> rather than 1p as in the current packs. In a 1p when that cell
> >>>>> gets
> >>>>> weak its over, in a 4p when a cell gets weak the other 3 in the
> >>>>> 4p can
> >>>>> help it along for quite a while before they all get weak.
> >>>>>
> >>>>> I am really convinced that a move to 1p config packs has brought
> >>>>> with it
> >>>>> lower useful cycle life. I feel you need to be a lot more
> >>>>> cautious with
> >>>>> the 1p packs than the 4p's, or they will not last you very long :)
> >>>>>
> >>>>> Chad
> >>>>>
> >>>>> mike mueller wrote:
> >>>>>> Chris Moon and I have bought the new TrueRC 5000 packs. He has
> >>>>>> been
> >>>>>> testing them for the last 2 months. They seem as strong if not
> >>>>>> stronger than his FP 5350 pack. The cost is only $110 a 5S
> >>>>>> pack. I've
> >>>>>> bought 4 packs and I'm hoping that they are as good as initial
> >>>>>> testing
> >>>>>> has shown. I also have 2 brand new TP V2 Extreme 10S 5000
> >>>>>> packs. All
> >>>>>> the packs at the 10S configuration weigh in around 42oz's with
> >>>>>> all the
> >>>>>> connectors.
> >>>>>> The True RC packs have a lower C rating but this may be a good
> >>>>>> thing.
> >>>>>> The higher C ratings seem to come at the cost of lower pack
> >>>>>> life. Look
> >>>>>> at the TP Pro lite's many have exceeded the 200 cycle barrier and
> >>>>>> still have a decent pack. The TP Extreme's V1's were dying in 50
> >>>>>> flights and I have yet to see much better than a hundred
> >>>>>> flights from
> >>>>>> the FP's. From my observation the older TP Prolites deliver
> >>>>>> plenty of
> >>>>>> power for our setups. So I think the TrueRC offerings are going
> >>>>>> to do
> >>>>>> the trick. Dan from True is claiming over 200 cycles on them. I
> >>>>>> hope
> >>>>>> that I can get 100. At the $'s he's getting it will be a huge
> >>>>>> bargain.
> >>>>>> Mike Mueller
> >>>>>>
> >>>>>> The link is www.flightpowerusa.com <http://
> >>>>>> www.flightpowerusa.com/>
> >>>>>>
> >>>>>> I need to buy some packs myself. Anybody know if they will
> >>>>>> be at
> >>>>>> Toledo?
> >>>>>>
> >>>>>> Bob Kane
> >>>>>> getterflash at yahoo.com
> >>>>>>
> >>>>>>
> >>>>>> ----- Original Message ----
> >>>>>> From: Verne Koester <verne at twmi.rr.com>
> >>>>>> To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>
> >>>>>> Sent: Thursday, March 13, 2008 6:58:32 PM
> >>>>>> Subject: Re: [NSRCA-discussion] Batteries
> >>>>>>
> >>>>>> Hi George,
> >>>>>> I'm in the same situation and have decided to go with the
> >>>>>> FlightPower
> >>>>>> 5350's. Even when the 5300's were fresh, I occasionally
> >>>>>> felt like
> >>>>>> I could
> >>>>>> use a little more punch, particularly on humid or windy
> >>>>>> days. I've
> >>>>>> competed
> >>>>>> with a number of guys that had both the TP 5300's and FP
> >>>>>> 5350's
> >>>>>> who would
> >>>>>> switch to the 5350's when they needed the extra power. My
> >>>>>> plan is
> >>>>>> to use the
> >>>>>> FP 5350's and change props for different conditions.
> >>>>>> Nothing is
> >>>>>> free however
> >>>>>> and you'll pick up 2 ounces in the process. I considered
> >>>>>> the 5000
> >>>>>> mah 10S
> >>>>>> packs from both TP and FP but can't afford to gain 4 ounces in
> >>>>>> either of my
> >>>>>> existing planes. The FP 5350's are the best solution for my
> >>>>>> situation. Mine
> >>>>>> just arrived this week and won't be flown until the snow
> >>>>>> melts so
> >>>>>> my
> >>>>>> recommendations come from observations rather than
> >>>>>> experience at
> >>>>>> this point.
> >>>>>> I bought mine directly from FlightPower
> >>>>>> http://www.flightpower.com <http://www.flightpower.com/
> >>>>>>> . Hope
> >>>>>> this helps.
> >>>>>>
> >>>>>> Verne Koester
> >>>>>>
> >>>>>>
> >>>>>> ----- Original Message -----
> >>>>>> From: <glmiller3 at suddenlink.net
> >>>>>> <mailto:glmiller3 at suddenlink.net>>
> >>>>>> To: "NSRCA List" <nsrca-discussion at lists.nsrca.org
> >>>>>> <mailto:nsrca-discussion at lists.nsrca.org>>
> >>>>>> Sent: Thursday, March 13, 2008 12:26 PM
> >>>>>> Subject: [NSRCA-discussion] Batteries
> >>>>>>
> >>>>>>
> >>>>>>> Hi All,
> >>>>>>>
> >>>>>>> I've been flying with Thunder Power Prolite 5300 packs for a
> >>>>>> while now and
> >>>>>>> they are getting very tired. As they poop out, I'm trying to
> >>>>>> decide what
> >>>>>>> to replace them with. From what I've seen, the Flightpower
> >>>>>> "FAI" packs
> >>>>>>> are probably what I'll go with, but if anyone has any other
> >>>>>> suggestions,
> >>>>>>> please sing out. Also, any suggestions as to a source would be
> >>>>>>> appreciated.
> >>>>>>>
> >>>>>>> TIA,
> >>>>>>>
> >>>>>>> George
> >>>>>>> _______________________________________________
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> >>>>>>>
> >>>>>>
> >>>>>>
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--
Keith Hoard
Collierville, TN
khoard at gmail.com
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