[TriEmbed] TriEmbed Digest, Vol 94, Issue 5

Chip McClelland chip at mcclellands.org
Sat Mar 6 10:54:13 CST 2021


Michael,

Wow, thank you for the very comprehensive response.  I will do some testing
based on your clear instructions.  That said, I think your advice on
recycling or donating the batteries may be the way to go.  At $9 in bulk,
it may not make much sense to retest and redeploy a 2-year old battery.

Thanks,

Chip


____________________________________
Chip McClelland
chip at mcclellands.org
919-624-5562

On March 5, 2021 at 4:46:29 PM, triembed-request at triembed.org (
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Today's Topics:

1. Single Cell LiPO Battery Health (Chip McClelland)
2. Re: Electrical Contacts for free Lid (Michael Monaghan)
3. Re: Single Cell LiPO Battery Health (Rick)


----------------------------------------------------------------------

Message: 1
Date: Fri, 5 Mar 2021 10:15:30 -0800
From: Chip McClelland <chip at mcclellands.org>
To: triembed at triembed.org
Subject: [TriEmbed] Single Cell LiPO Battery Health
Message-ID:
<CABQO2+nVTKQc9yH=qN=+LA+P2E5BMxa9C8_neWVAguiudsPuxw at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

I am currently upgrading my existing Electron-based counters with newer
Boron-based ones. As I do, I will rework / recycle as much as I can from
the older units to reduce waste. These units have been operating on solar
power for anywhere from 1 to 4 years.

How can I tell if it is time to replace a Single Cell LiPo Battery?

Here is the battery I currently use: https://www.adafruit.com/product/2011

I thought it would be straight forward to test the internal resistance of
the batteries (at a consistent charge / temp) as the resistance goes up as
the battery ages. However, I am struggling to find a battery tester /
charger that will measure a single LiPO cell?s internal resistance.

I have tried both of these:

- Tenergy:
https://power.tenergy.com/tenergy-5-in-1-intelligent-cell-meter-capacity-checker-battery-balancer-battery-discharger-internal-resistance-tester-esc-servo-ppm-tester/

- HTRC:
https://www.amazon.com/HTRC-Charger-Battery-Balance-Discharger/dp/B07MWSW3TP/ref=sr_1_4?dchild=1&m=A193SNVHREJU7H&marketplaceID=ATVPDKIKX0DER&qid=1614968073&s=merchant-items&sr=1-4


Any suggestions?


Thanks,


Chip

____________________________________
Chip McClelland
chip at mcclellands.org
919-624-5562
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Message: 2
Date: Fri, 5 Mar 2021 14:07:30 -0500
From: Michael Monaghan <mike at chipworks.net>
To: Triangle Embedded Computing Discussion <triembed at triembed.org>
Subject: Re: [TriEmbed] Electrical Contacts for free Lid
Message-ID:
<CAGToJna5gKYLdQy2FUB0+5bK9ZjuKrgtSG3VNB2hL_RrVF9LCg at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Glen, those look like nice high current connectors. I'll have to file
those for another project.

I'm looking for something more like you might find on a laptop battery. A
fixed set of contacts on the wall of the hamper and some sort of spring
like (but not really spring containing) contacts to attach to the lid.
Think bent metal connector. I just realized, I can picture the device, but
have no noun for it. I think I need to find a connectors guide.

Thanks Glen!

On Fri, Mar 5, 2021 at 11:49 AM Glen Smith <mrglenasmith at gmail.com> wrote:

> Anderson Powerpole connectors would work pretty well in this situation,
if
> I understand what you are describing. As long as the two parts have a
good
> registration, Andersons will make positive contact and stay in place.
They
> may be a little expensive, but having them in your arsenal of connectors
is
> pretty valuable.
>
> On Fri, Mar 5, 2021, 11:16 AM Michael Monaghan via TriEmbed <
> triembed at triembed.org> wrote:
>
>> Hey everyone,
>>
>> I'm working on my "learning project" and hoping someone has chased a
>> similar issue. I'm looking for reliable electrical contact in a high
>> vibration environment. Need 4 contacts. Cost and spacing of contact are
>> blocking issues right now.
>>
>> Design notes:
>>
>> - For a pet feeder with vibrator in the base to encourage kibbles to
>> fall into dispensing scoop.
>> - Lid is detachable, reversible, and wiggles in seated position until
>> locked. Increased pin spacing to avoid cross connection. Pin order could
>> resolve cross connection concerns. Contacts on front and rear of base
>> for reversed lid.
>> - Lid vs hopper wall is roughly 90 degree angle.
>> - Some sort of pressure on contact to avoid loss of contact during
>> dispensing (vibration). Reading of sensor is only done once per cycle
>> while vibrator is off.
>> - Target device is 3.3v rangefinder with 3.3v, gnd, SLA, SLC
>> connections.
>> - Contact on hopper should be flat against side to avoid abuse,
>> accumulation during refill.
>> - Finding $12 per contact solutions. Would like sub dollar per
>> contact.
>>
>> I recall contacts in the lid of an older washing machine. The lid had a
>> pair of copper pads and the base had two copper fingers those pads would
>> land on. When installed, the fingers would bend slightly to ensure good
>> contact.
>>
>> Thanks in advance.
>>
>> Mike
>>
>>
>> _______________________________________________
>> Triangle, NC Embedded Computing mailing list
>>
>> To post message: TriEmbed at triembed.org
>> List info:
>> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
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>>
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Message: 3
Date: Fri, 5 Mar 2021 16:46:12 -0500
From: Rick <nm3g at triad.rr.com>
To: triembed at triembed.org
Subject: Re: [TriEmbed] Single Cell LiPO Battery Health
Message-ID: <eec4c210-b9ad-a00c-9168-807c214d83b8 at triad.rr.com>
Content-Type: text/plain; charset="utf-8"; Format="flowed"

Hi Chip,

I've done similar work in the past in the automotive and industrial
lead-acid battery world and can share a few points.

First, if you plan on measuring relative changes to internal resistance,
you need to have baseline measurements on cells built at the same time,
and preferably within the same batch. Otherwise you are guessing. Not
that guessing is bad, but you can cause yourself (and others) needless
headache and expense if you decide a cell is prematurely aged out when
it's built to different specifications, at a different temperature than
your reference, or how you were holding the test leads (trust me,
experience here!).

Second, measuring internal resistance is simply a measurement of cell
voltage during a constant current drain event. We typically used a
two-second test period between 1000-1500 amps for lead-acid batteries
(even U1 lawn mower batteries passed over 1000 amps in this test). I
used PWM-controlled silicon switches and measured voltage and current
every 100 mS during the discharge using an isolation amplifier for
voltage measurement and a current transducer for the current
measurement. I was using a Motorola 56DSP80x series processor with dual
ADCs (two 8-channel muxed ADCs ... but kept things simple and didn't
change the mux channel). I also tossed the first measurement and then
averaged the next 7-8 measurements and then passed the data along to the
front-end processor (data warehouse, system controller, and decision
maker) PC.

[Sidebar ... on multiplexed ADCs, the ADC input capacitor MAY still hold
a charge from the previous measurement ... thus you read and discard the
first measurement to ensure the subsequent measurements are honest and
true.]

There were (and may still be) devices that claim to measure internal
resistance, but at a very low current (Midtronics Biddle, et all; I'm
talking to you!). Their results were inconsistent and did not relate to
battery capability or life ... and really were not based on any battery
chemistry science.


You do NOT want to draw excessive current from your Lithium-chemistry
batteries ... in your case I would use approximately 0.1C (10% of rated
AH capacity) for no more than 1-2 seconds while monitoring battery
temperature. Measure the open-circuit voltage (no load cell voltage) and
then apply the load. With the automotive batteries, our typical
open-circuit voltage was 12.5 to 13.5 volts, depending on when the last
charge cycle occurred, and no less than 10 volts under load. With these
parameters defined, we were able to show the constant-current voltage
over the test period and observe the change (slope) of the battery (cell
in your case) voltage. Obviously the shallower the slope, the better the
battery performed.

You can produce a direct internal resistance measurement from this test,
however you MUST use Kelvin connections at the cell terminals ...
keeping the voltage measurement leads adjacent to, but not sharing the
current-carrying leads beyond the cell for maximum accuracy and
repeatability. You absolutely need to specify the internal resistance as
x Ohms @ y amps test current for this measurement to be meaningful.


You can compare new vs old cells to get an approximate idea on cell
aging (i.e. internal resistance) ... and you can use this method to more
closely match internal resistance in series-string connected cells. You
really can't determine remaining cell life, as you have no idea whether
active material shedding, internal current-carrying structure changes,
or terminal connection resistance changes have created the difference.

With the cost of Lithium-chemistry cells being at the commodity level,
it is probably more prudent to recycle your used cells, or offer them to
someone willing to risk cell failure for the advantage of low cost (i.e.
FREE) cells. While there are those that are building huge battery banks
from "broken" 18650 cell based battery packs, they are gambling on
individual cell life, as physical age as well as cell/battery treatment
is generally unknown. I certainly wouldn't base any mission-critical
project on a hacked battery built this way.


This may be way more information than you need ... and it may not answer
your question, but I've seen questions like this come up from time to
time and now that the NDA is expired, I can talk about some of my work.


I hope this helps.


Regards,


Rick



On 3/5/2021 1:15 PM, Chip McClelland via TriEmbed wrote:
>
> I am currently upgrading my existing Electron-based counters with
> newer Boron-based ones. As I do, I will rework / recycle as much as I
> can from the older units to reduce waste. These units have been
> operating on solar power for anywhere from 1 to 4 years.
>
> How can I tell if it is time to replace a Single Cell LiPo Battery?
>
> Here is the battery I currently use:
> https://www.adafruit.com/product/2011
> <https://www.adafruit.com/product/2011>
>
> I thought it would be straight forward to test the internal resistance
> of the batteries (at a consistent charge / temp) as the resistance
> goes up as the battery ages.? However, I am struggling to find a
> battery tester / charger that will measure a single LiPO cell?s
> internal resistance.
>
> I have tried both of these:
>
> - Tenergy:
>
https://power.tenergy.com/tenergy-5-in-1-intelligent-cell-meter-capacity-checker-battery-balancer-battery-discharger-internal-resistance-tester-esc-servo-ppm-tester/
> <
https://power.tenergy.com/tenergy-5-in-1-intelligent-cell-meter-capacity-checker-battery-balancer-battery-discharger-internal-resistance-tester-esc-servo-ppm-tester/>

>
> - HTRC:
>
https://www.amazon.com/HTRC-Charger-Battery-Balance-Discharger/dp/B07MWSW3TP/ref=sr_1_4?dchild=1&m=A193SNVHREJU7H&marketplaceID=ATVPDKIKX0DER&qid=1614968073&s=merchant-items&sr=1-4
> <
https://www.amazon.com/HTRC-Charger-Battery-Balance-Discharger/dp/B07MWSW3TP/ref=sr_1_4?dchild=1&m=A193SNVHREJU7H&marketplaceID=ATVPDKIKX0DER&qid=1614968073&s=merchant-items&sr=1-4>

>
>
> Any suggestions?
>
>
> Thanks,
>
>
> Chip
>
> ____________________________________
>
> Chip McClelland
> chip at mcclellands.org <mailto:chip at mcclellands.org>
> 919-624-5562
>
> _______________________________________________
> Triangle, NC Embedded Computing mailing list
>
> To post message: TriEmbed at triembed.org
> List info: http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
> TriEmbed web site: http://TriEmbed.org
> To unsubscribe, click link and send a blank message: mailto:
unsubscribe-TriEmbed at bitser.net?subject=unsubscribe
>
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