Today's Message Index:
----------------------
1. 09:29 AM - Re: How do you figure C-Rating of a battery? (Robert L. Nuckolls, III)
2. 10:17 AM - Re: How do you figure C-Rating of a battery? (Christopher Cee Stone)
3. 09:05 PM - Fw: Re: Re: Alternator/Strobe whine (Rick Beebe)
Message 1
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| Subject: | Re: How do you figure C-Rating of a battery? |
At 02:22 PM 9/11/2020, you wrote:
>
>Hi Group I'm a bit confused how to figure C-rating of a battery.
>Here's my dilemma, here's a 5,000mA battery that say's it's good for
>10C continuous and 15C burst:
>https://hobbyking.com/en_us/turnigy-sub-c-1-2v-5000mah-high-power-series-nimh-single-cell.html?queryID=3ed79812e155e159b8e96c63dba8378a&objectID=41335&indexName=hbk_live_magento_en_us_products
>Initial thoughts is just multiply 5 times 10 or 15. Then I read a
>review and the battery never made it to 5amp capacity and the
>capacity goes down the more amps you draw from it. Here's the
>review:
>https://lygte-info.dk/review/batteries2012/Turnigy%20Sub-C%205000mAh%20(Gray)%20UK.html
>If I wanted to know what the continuous C rating is for this
>battery, would you take the unrealistic too high 5aH capacity rating
>from the Mfg times 10? Take the ~3.5 20 amp discharge capacity
>rating from the review times 10? Or??
>Now for another hard question, how would you figure out burst amp
>rating? Thx. Ron P.
One generally doesn't 'figure' any of that stuff.
I'm pleasantly surprised when bench tests echo
the nameplate ratings on any consumer production
cell. Incorporation of any particular
device into a project requires good DATA.
Brands like A123, Samsung, Panasonic, Enersys,
et. als. will publish data sheets with realistic
performance metrics.
Here are some sample engineering data sheets
on products offered by reputable manufacturers.
https://tinyurl.com/y425k3x6
Note that they offer detailed information, particularly
discharge data that allows the system integrator
to incorporate the device with confidence.
No way in this universe are these cells
capable of 6000 mAH . . .
https://tinyurl.com/yyf64qe6
Another example of 'blue smoke' merchandising
https://tinyurl.com/y2j9dkoh
Note the 12v, 2A power input jack . . . 200
watts? Gimme a break. Now, I've used numerous
examples of these amplifiers over the past 20
years . . . and they're quite capable of the
2-3 watts per channel called out in the spec
sheets for the integrated circuits from which
they are built.
Attached are data plots on some 18650 cells
marketed as '5500 mAH' devices with '10A
pulse capability'.
I was considering these cells for modifying
a 20+ year old Makita drill from MiMh to
Lithium. Tests on the drill demonstrated
peak loads on the order of 10A.
Based on some 'marketing' assertions I purchased
some cells for consideration. The cells clearly
tested at MUCH less capacity and sagged by 25%
voltage under just a 5 Amps load. Clearly
incapable of practical service at 10A.
Note the difference in stored energy for having
been charged to 3.7 versus 4.2 Volts. If you
charged these cells in a charger optimized
for LiFePO4, you would achieve about 1/2 the
chemical capacity of the cell.
Sorry Ron, the short answer is, "Lacking
engineering performance data on the proposed
device, you're searching around in a coal
mine for a black cat with no flashlight."
I'm not implying that ALL marketing hype is
suspect . . . I've purchased many products that met
their nameplate performance ratings quite
well. But lacking hard data from the manufacturer
or your own measurements, then it's a bit of
a crap shoot.
If you have exemplar cells you're considering
for the task, mail them to me and I'll suck
out their precious bodily fluids to MEASURE
from what stuff they are made.
By the way, the performance benchmark "Ampere-Hour"
is useful only when comparing one device with
a competing device. It has no definition in the
science of energy measurement. The scientific
description for energy will be in units
like Watt-Hours, Joules, Ergs, etc.
Definition of an Erg: "The energy required to lift
a postage stamp to a height equal to its thickness"
== Robert A. Heinlein, "Rocket Ship Galileo" 1947 =
Bob . . .
Message 2
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| Subject: | Re: How do you figure C-Rating of a battery? |
Regarding 18650 cells... etc.
I purchased a few samples from different suppliers with ratings up to 4500
mAh. The ones rated at 4500 mah felt lighter in weight than the similar
cells rated at 3000 mAh. A friend designs medical x-ray machines so I
asked if he would x-ray one of the light weight cells and one "normal"
cell. Unfortunately I don't have an image to share. A description will
suffice. The light weight cell housed a much smaller cell. Hmmm!
Simerly I was replacing the output transistor in a regulated bench power
supply. I recall it was a 2N3055. I found a "deal" on Ebay. Five for
$5... Upon receipt I noticed the marking on the case didn't appear quite
right. It was labeled STM... lightly scratching the marking it readily
came off. Hmmm. Using a Dremel tool with a cut-off wheel I removed the
top of the case. Voila! A tiny junction with .002" bond wires! That
someone can make a living going to the trouble of
counterfeiting transistors!
Caveat Emptor
Chris Stone
On Sat, Sep 12, 2020 at 9:36 AM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 02:22 PM 9/11/2020, you wrote:
>
> rparigor@hotmail.com>
>
> Hi Group I'm a bit confused how to figure C-rating of a battery. Here's my
> dilemma, here's a 5,000mA battery that say's it's good for 10C continuous
> and 15C burst:
> https://hobbyking.com/en_us/turnigy-sub-c-1-2v-5000mah-high-power-series-nimh-single-cell.html?queryID=3ed79812e155e159b8e96c63dba8378a&objectID=41335&indexName=hbk_live_magento_en_us_products
> Initial thoughts is just multiply 5 times 10 or 15. Then I read a review
> and the battery never made it to 5amp capacity and the capacity goes down
> the more amps you draw from it. Here's the review:
> https://lygte-info.dk/review/batteries2012/Turnigy%20Sub-C%205000mAh%20(Gray)%20UK.html
> If I wanted to know what the continuous C rating is for this battery,
> would you take the unrealistic too high 5aH capacity rating from the Mfg
> times 10? Take the ~3.5 20 amp discharge capacity rating from the review
> times 10? Or??
> Now for another hard question, how would you figure out burst amp rating?
> Thx. Ron P.
>
>
> One generally doesn't 'figure' any of that stuff.
>
> I'm pleasantly surprised when bench tests echo
> the nameplate ratings on any consumer production
> cell. Incorporation of any particular
> device into a project requires good DATA.
> Brands like A123, Samsung, Panasonic, Enersys,
> et. als. will publish data sheets with realistic
> performance metrics.
>
> Here are some sample engineering data sheets
> on products offered by reputable manufacturers.
>
> https://tinyurl.com/y425k3x6
>
> Note that they offer detailed information, particularly
> discharge data that allows the system integrator
> to incorporate the device with confidence.
>
> No way in this universe are these cells
> capable of 6000 mAH . . .
>
> https://tinyurl.com/yyf64qe6
>
> Another example of 'blue smoke' merchandising
>
> https://tinyurl.com/y2j9dkoh
>
> Note the 12v, 2A power input jack . . . 200
> watts? Gimme a break. Now, I've used numerous
> examples of these amplifiers over the past 20
> years . . . and they're quite capable of the
> 2-3 watts per channel called out in the spec
> sheets for the integrated circuits from which
> they are built.
>
> Attached are data plots on some 18650 cells
> marketed as '5500 mAH' devices with '10A
> pulse capability'.
>
> I was considering these cells for modifying
> a 20+ year old Makita drill from MiMh to
> Lithium. Tests on the drill demonstrated
> peak loads on the order of 10A.
>
> Based on some 'marketing' assertions I purchased
> some cells for consideration. The cells clearly
> tested at MUCH less capacity and sagged by 25%
> voltage under just a 5 Amps load. Clearly
> incapable of practical service at 10A.
>
> Note the difference in stored energy for having
> been charged to 3.7 versus 4.2 Volts. If you
> charged these cells in a charger optimized
> for LiFePO4, you would achieve about 1/2 the
> chemical capacity of the cell.
>
> Sorry Ron, the short answer is, "Lacking
> engineering performance data on the proposed
> device, you're searching around in a coal
> mine for a black cat with no flashlight."
>
> I'm not implying that ALL marketing hype is
> suspect . . . I've purchased many products that met
> their nameplate performance ratings quite
> well. But lacking hard data from the manufacturer
> or your own measurements, then it's a bit of
> a crap shoot.
>
> If you have exemplar cells you're considering
> for the task, mail them to me and I'll suck
> out their precious bodily fluids to MEASURE
> from what stuff they are made.
>
> By the way, the performance benchmark "Ampere-Hour"
> is useful only when comparing one device with
> a competing device. It has no definition in the
> science of energy measurement. The scientific
> description for energy will be in units
> like Watt-Hours, Joules, Ergs, etc.
>
> Definition of an Erg: "The energy required to lift
> a postage stamp to a height equal to its thickness"
> == Robert A. Heinlein, "Rocket Ship Galileo" 1947 =
>
> Bob . . .
>
Message 3
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| Subject: | Re: Alternator/Strobe whine |
So it is alternator whine. It's present when the strobes are off. When
they're on, it does warble a bit. There is a bit of strobe noise with
both alternators off and just the battery on but it's not obnoxious at
all. There's no noise at when running on the backup alternator.
--Rick
-------- Forwarded Message --------
Subject: Re: AeroElectric-List: Re: Alternator/Strobe whine
From: Rick Beebe <rick@beebe.org>
I'll be back at the plane on Saturday and I will do some controlled
tests. The noise pitch is definitely in sync with the strobes. When I
turn the main alternator off the noise goes away completely. My memory
is that it also goes away when I turn the strobes off (main alternator
on), but I'm not sure if there's a residual whine.
--Rick
On 9/8/2020 4:41 PM, Robert L. Nuckolls, III wrote:
> Alternator, strobe or both?
>
> Alternator whine is almost always a ground loop issue.
> Pitch of whine will go up and down with engine rpm.
> It often gets louder when alternator loads are highest
> like right after starting engine (recharging battery)
> and all loads turned on.
>
> Strobe whine pitches up and down in synchronization
> with flashes from the strobes and is generally of
> constant volume.
>
> Which one(s) disappear when appliance is OFF.
> Alternator, strobe or both?
>
>
> Bob . . .
>
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