[NSRCA-discussion] Internal battery impedance
Emory Schroeter
schroetere at bellsouth.net
Sat Mar 15 10:18:25 AKDT 2008
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
>>>>>>> _______________________________________________
>>>>>>> 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
>>>>>>
>>>>>>
>>>>>>
>>>>>> ------------------------------------------------------------------
>>>>>> ------
>>>>>> Looking for last minute shopping deals? Find them fast with
>>>>>> Yahoo!
>>>>>> Search.
>>>>>>
>>>>>> <http://us.rd.yahoo.com/evt=51734/*http://
>>>>>> tools.search.yahoo.com/newsearch/category.php?
>>>>>> category=shopping>_______________________________________________
>>>>>> NSRCA-discussion mailing list
>>>>>> NSRCA-discussion at lists.nsrca.org
>>>>>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>>>>>
>>>>>>
>>>>>> ------------------------------------------------------------------
>>>>>> ------
>>>>>> Never miss a thing. Make Yahoo your homepage.
>>>>>> <http://us.rd.yahoo.com/evt=51438/*http://www.yahoo.com/r/hs>
>>>>>> ------------------------------------------------------------------
>>>>>> ------
>>>>>>
>>>>>> _______________________________________________
>>>>>> NSRCA-discussion mailing list
>>>>>> 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
>>>>
>>>> _______________________________________________
>>>> NSRCA-discussion mailing list
>>>> 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
>>
>> _______________________________________________
>> NSRCA-discussion mailing list
>> 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
More information about the NSRCA-discussion
mailing list