[NSRCA-discussion] Internal battery impedance
Lance Van Nostrand
patterndude at tx.rr.com
Fri Mar 14 20:26:10 AKDT 2008
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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