Lipos overcharged?!..kinda weird?!

[Ralph Matile]

This message from "Ralph Matile" <r.matile@comcast.net> brought to you by EFLIGHT!

Lipo guys,

I have some older 3 cell kokams that I charged last 7-10 days ago, it
was raining so I couldn't fly until today.

I charged with an Astro 109.

I check voltage and balance before I charge packs.
I check voltage after I charge packs.

I check the voltage before I fly and when I did the first pack I tested
was at 13.4...high...right?? (all cells were in balance at 4.45-4.46V.)
Now I thought that somehow, maybe I screwed up...not knowing how.
I then checked another identical pack....same thing..high voltage.

The only thing that was a little unusual was that it may have been kind
of cold in the garage....(maybe 30 degrees F) when I charged
them......(I know that's not real cold considering you east coasters!)

I mentally note the cutoff voltage when the charge is over, and I think
I would have noticed a high ending voltage...especially on 2 packs?

I tested the VM, and with other packs it seems ok...

So I guess some questions I have, is it possible to finish a charge,
test the pack and have a 12.6V state....come back a week later and have
them test at 13.4???....one pack a fluke...but 2 packs.....I'm
mystified?

I've been known for breaking laws of physics before...so if that's it
don't be afraid to tell me....

And if I did overcharge....are they ok....no puffing is evident.

Thanks

Ralph Matile



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[Rick Page]

This message from Rick Page <rick-page@shaw.ca> brought to you by EFLIGHT!

>The only thing that was a little unusual was that it may have been kind of
cold
>in the garage....(maybe 30 degrees F) when I charged them
Charging below freezing (or even close) is not recommended. I have heard
that you should charge to both lower and higher voltages below freezing.
I think the difference is that if you want power, you need to charge to
higher voltages below freezing to get a useful amount of current out when
the batteries are used below freezing. This undoubtedly causes damage to the
batteries though.
The recommendation to charge to lower voltages below freezing I think is
for safety since you can't be sure how the chemistry in the different
batteries will respond.

Contractors put their chargers under heat lamps to use them in freezing
temperatures. If the batteries are used right away, they stay warm as well.

Rick.



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[Ralph Matile]

This message from "Ralph Matile" <r.matile@comcast.net> brought to you by EFLIGHT!

Rick,
The more I think about it...I think really the garage was 35 to 40....I
live in east bay San Francisco area.....doesn't get that cold usually.

I'm going to use the batts, watch them closely on the next several
charges and report back if anything weird happens.

Doesn't resistance go up as temps go down..and would that affect
charging with the Astro 109, and the point of cutoff.......just
wondering?

Ralph Matile



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[Al Eastman]

This message from "Al Eastman" <astroflyer@rushcomm.ca> brought to you by EFLIGHT!

> The only thing that was a little unusual was that it may have been kind
> of cold in the garage....(maybe 30 degrees F) when I charged
> them......(I know that's not real cold considering you east coasters!)

Ralph...not sue exactly why but my FMA cellpro chargers have a 4.10 volt per
cell cutoff when the temperature when charging is below 55 degrees F to
prevent cell damage. I seem to remember some discussion about the voltage
rising after a charge at cold temperatures.

the other day after driving home from an indoor, my packs were cold and I
saw this first hand. The charger triggered into the cold charge mode and cut
off at 4.10. the next morning when they were up to normal room temperature
I plugged in the charger again and the packs continued charging to the usual
4.2 volts per cell.

cheers
Papa Sharptooth

Bouncing about the living room, my then three year old grandson declared
himself "a kangaroo".
"If you're a Kangaroo, what is Grampie", I ask.
His reply: "you a dinosaur"





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[Shell Shrader]

This message from Shell Shrader <shell@shellware.com> brought to you by EFLIGHT!

It would be really cool if there was a version of the Blinky available that by use of a pin or dip you could switch it in to a "safe storage" discharge mode that'd automatically take any cells connected to it down to a voltage that is suitable for long-term storage.
Looking over all my existing equipment, I can't find an easy way to perform what I think should be a useful task. My Triton knows of no such voltage nor does any of my "static" dischargers.


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[Ralph Matile]

This message from "Ralph Matile" <r.matile@comcast.net> brought to you by EFLIGHT!

Harp,
You're probably right...but isn't it a bit strange that both packs are
doing the same thing and that all the cells are in balance!?!??
Ralph Matile




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[Sid Kauffman]

This message from Sid Kauffman <sid@slkelectronics.com> brought to you by EFLIGHT!

At 04:40 PM 2/17/2007 -0500, Shell wrote:
>> It would be really cool if there was a version of the Blinky available
that by use of a pin or dip
>> you could switch it in to a "safe storage" discharge mode that'd
automatically take any cells
>> connected to it down to a voltage that is suitable for long-term storage.
>> Looking over all my existing equipment, I can't find an easy way to
perform what I think should
>> be a useful task. My Triton knows of no such voltage nor does any of
my "static" dischargers.

The Computer Battery Analyzer will do it and is a great tool for 100 bucks.
An M1 cell charger will do it, as will the Dapter. Most chargers with
discharge capabilities are slow enough that you could watch the discharge
and simply disconnect when you get to around 3.7 volts per cell. You can
also use a wind-up kitchen timer and do a little math. What you want is
about half empty (or half full if you're an optimist).

Sid




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[Rick Page]

This message from Rick Page <rick-page@shaw.ca> brought to you by EFLIGHT!

>isn't it a bit strange that both packs are doing the same thing
I'm always suspicious of the voltmeter in these situations. What voltage
does the AF109 say? Don't let it charge because it might detect 4 cells.

Rick.


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[Ralph Matile]

This message from "Ralph Matile" <r.matile@comcast.net> brought to you by EFLIGHT!

The Astro read it correctly....it was slightly different than the
VM..can't remember up or down....
I'll be watching these packs closely.....Now I think they are
ok.....I'll let you guys know otherwise if anything happens.

Ralph Matile



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[Shell Shrader]

This message from Shell Shrader <shell@shellware.com> brought to you by EFLIGHT!

>The Triton can discharge to away cut off voltage you want to if you use the
>NiCad setting. In the NiCad discharge you set the discharge current and the
>cut off voltage.
I'll have to check out the nicad discharge settings. If it's variable like you descibe (it's been a number of years since I've even used the nicad setting) then it's exactly what I'm looking for.
Thanks,
Shell






From: Paul Hinz
Sent: Sat 2/17/2007 10:18 PM
To: eflight@ezonemag.com
Subject: RE: [EFLT] AF Blinky Enhancement


This message from "Paul Hinz" <phinz@excel.net> brought to you by EFLIGHT!



-----Original Message-----
From: owner-eflight@ezonemag.com [mailto:owner-eflight@ezonemag.com] On
Behalf Of Shell Shrader
Sent: Saturday, February 17, 2007 3:41 PM
To: eflight@ezonemag.com
Subject: [EFLT] AF Blinky Enhancement

This message from Shell Shrader <shell@shellware.com> brought to you by
EFLIGHT!

It would be really cool if there was a version of the Blinky available that
by use of a pin or dip you could switch it in to a "safe storage" discharge
mode that'd automatically take any cells connected to it down to a voltage
that is suitable for long-term storage.
Looking over all my existing equipment, I can't find an easy way to perform
what I think should be a useful task. My Triton knows of no such voltage
nor does any of my "static" dischargers.


The Triton can discharge to away cut off voltage you want to if you use the
Nicad setting. In the Nicad discharge you set the discharge current and the
cut off voltage.

Paul



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[Peter Bech]

This message from Peter Bech <peterb@home.informi.com> brought to you by EFLIGHT!

Kokam LiPo charging should stop at 4.21 volt pr cell. The voltages mentioned
sounds wring in my ears.

Please be aware, that the balancer must be able to outbalance the cell
differences faster than the charger can fill up the cells and increase the
differences.

For small cells, a balancing current of 100mA might be sufficient, but for big
packs you might need up to 1A balancing current.

And with high balancing current, the highest quality balancer connectios are
needed to ensure, the cell voltage reading is not false due to a high
balancing current over a bad connector which, according to Ohms law will
result in, that cell voltage is actually higher than what the balancer
measures, an then the balancer will pump us this cell instead of leaning it.


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[Doug Ingraham]

This message from Doug Ingraham <dpi@rapidnet.com> brought to you by EFLIGHT!

On Sat, 17 Feb 2007, Ralph Matile wrote:

> I have some older 3 cell kokams that I charged last 7-10 days ago, it
> was raining so I couldn't fly until today.
>
> I charged with an Astro 109.
>
> I check voltage and balance before I charge packs.
> I check voltage after I charge packs.
>
> I check the voltage before I fly and when I did the first pack I tested
> was at 13.4...high...right?? (all cells were in balance at 4.45-4.46V.)
> Now I thought that somehow, maybe I screwed up...not knowing how.
> I then checked another identical pack....same thing..high voltage.
>
> The only thing that was a little unusual was that it may have been kind
> of cold in the garage....(maybe 30 degrees F) when I charged
> them......(I know that's not real cold considering you east coasters!)
>
> I mentally note the cutoff voltage when the charge is over, and I think
> I would have noticed a high ending voltage...especially on 2 packs?
>
> I tested the VM, and with other packs it seems ok...

Until I got to this line I was convinced that your Volt Meter is reading
incorrectly. I would still check that first. A low battery in the DVM
can cause the internal reference to be low which makes all readings the
meter takes read high. For the cells to actually be that high doesn't
make any sense. They should be puffed. Try using the 109 as a DVM.
Turn the current to zero and plug in the pack. I suspect that you will
see more normal numbers.



Doug Ingraham
Rapid City, SD USA



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[Doug Ingraham]

This message from Doug Ingraham <dpi@rapidnet.com> brought to you by EFLIGHT!

On Sun, 18 Feb 2007, Peter Bech wrote:

> This message from Peter Bech <peterb@home.informi.com> brought to you by EFLIGHT!
>
> Kokam LiPo charging should stop at 4.21 volt pr cell. The voltages mentioned
> sounds wring in my ears.
>
> Please be aware, that the balancer must be able to outbalance the cell
> differences faster than the charger can fill up the cells and increase the
> differences.
>
> For small cells, a balancing current of 100mA might be sufficient, but for big
> packs you might need up to 1A balancing current.
>
> And with high balancing current, the highest quality balancer connectios are
> needed to ensure, the cell voltage reading is not false due to a high
> balancing current over a bad connector which, according to Ohms law will
> result in, that cell voltage is actually higher than what the balancer
> measures, an then the balancer will pump us this cell instead of leaning it.

If the cells are pretty closely balanced to start you dont need much at
all to bring them back into balance. A few hundred ma is more than
adequate even for 10AH cells. If the cells are massively out of balance
you have a different problem to solve and the balancer would have to be
able to handle the full charge current in the worst case. But if it is
that badly out of balance you need to ask why and probably never use that
pack again because it is broken and will cause you problems you dont want
to face.

I haven't seen any balancing harnesses that I would put more than a couple
of hundred ma of current across. It is one of the reasons that the Astro
Blinky turns off the balancing current while it measures the cell voltage.
Thats why it blinks every couple of seconds. To stop the current flow
over the wiring harness and to allow the cell voltages to jump up to
unloaded so it can get an accurate reading.


Doug Ingraham
Rapid City, SD USA



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[Doug Ingraham]

This message from Doug Ingraham <dpi@rapidnet.com> brought to you by EFLIGHT!

On Sat, 17 Feb 2007, Shell Shrader wrote:

> It would be really cool if there was a version of the Blinky available
> that by use of a pin or dip you could switch it in to a "safe storage"
> discharge mode that'd automatically take any cells connected to it down
> to a voltage that is suitable for long-term storage. Looking over all my
> existing equipment, I can't find an easy way to perform what I think
> should be a useful task. My Triton knows of no such voltage nor does
> any of my "static" dischargers.

I've thought about making a blinky that would discharge to 3.5V-3.7V per
cell for storage purposes. The problem as I see it is that it would take
many hours and this would mean that it might be forgotten and left on the
pack for days or weeks. Now the Blinky doesnt draw much current when the
dischargers are turned off but it does still pull some current. If you
forget to take it off it will eventually run down the pack and ruin the
cells. The CPU on the blinky draws about 0.000013 amps but the divider
resistors draw quite a bit more than this so it depends on how many cells
are hooked up what the actual current draw of the device is. For an extra
few dollars in parts and a little more software I could probably get the
idle current down to 0.000003 amps but its hardly worth it for the way the
product is currently used.


Doug Ingraham
Rapid City, SD USA



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