[NSRCA-discussion] Internal battery impedance
Earl Haury
ejhaury at comcast.net
Sat Mar 15 02:26:11 AKDT 2008
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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