[NSRCA-discussion] Batteries
Earl Haury
ejhaury at comcast.net
Fri Mar 14 07:10:43 AKDT 2008
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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