Re: [EVDL] NMC cells ran below 2.5 vots n left

[Robert Bruninga via EV]

The key thing to remember, due to this high impedance, is that any attempt
to charge them in series will end up with almost ALL the voltage across
the single cell with the highest internal resistance and then it gets all
the energy and ... Big problem!
Bob


-Original Message-
From: EV  On Behalf Of Haudy Kazemi via EV
Sent: Tuesday, March 19, 2019 10:57 AM
To: Electric Vehicle Discussion List 
Cc: Haudy Kazemi 
Subject: Re: [EVDL] NMC cells ran below 2.5 vots n left

Here is an article has some info on restoring LiPo cells. Batteries tend
to exhibit increased internal resistance as voltages fall. The article
empasizes that restoration doesn't mean the cells will be like new. They
may have lost capacity and may have increased self discharge rates, but
may also be useable again.

Do the charging in a fire safe area.

In short, charge the cells very slowly (suggested 1/20 to 1/10 C rate) and
monitor them continuously for bloating or heat buildup, at least until
they get back into normal voltage ranges.

At normal voltages, a standard lithium charger should work, just keep the
C rates low while charge levels come back up.

Once charged, you'll be able to assess damage by doing capacity and
discharge rate checks. This data is useful for identifying acceptable
future charging C rates as cell characteristics may have changed from
their original values.

https://www.electricrcaircraftguy.com/2014/10/restoring-over-discharged-Li
Pos.html


On Tue, Mar 19, 2019, 02:28 ken via EV  wrote:

>  I bought a pack or lihium ion of cells and they arived pretty much
dead.
> like 0 or .25 each cell.
>
> I used 306b nicad setting to bring them up to  3.00,  then swtiched to
> lipo to charge to 3.70 .
>
> someone told me that charging theses cells could be dangerous, because
> the dendrits could lead dangerous overheating. theses battery i think
> where used for like a bus or something. theses are from
>
>
> https://www.techdirectclub.com/johnson-controls-24-cells-solar-battery
> -90-vdc-total-2-5-kwh/
>
> theses cells can do 10c so i'm rather concrned.  I wish I knew that
> manufacuter or specs or more about the cells property.
>
>
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> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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> Please discuss EV drag racing at NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>
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Re: [EVDL] NMC cells ran below 2.5 vots n left

[Haudy Kazemi via EV]

Here is an article has some info on restoring LiPo cells. Batteries tend to
exhibit increased internal resistance as voltages fall. The article
empasizes that restoration doesn't mean the cells will be like new. They
may have lost capacity and may have increased self discharge rates, but may
also be useable again.

Do the charging in a fire safe area.

In short, charge the cells very slowly (suggested 1/20 to 1/10 C rate) and
monitor them continuously for bloating or heat buildup, at least until they
get back into normal voltage ranges.

At normal voltages, a standard lithium charger should work, just keep the C
rates low while charge levels come back up.

Once charged, you'll be able to assess damage by doing capacity and
discharge rate checks. This data is useful for identifying acceptable
future charging C rates as cell characteristics may have changed from their
original values.

https://www.electricrcaircraftguy.com/2014/10/restoring-over-discharged-LiPos.html


On Tue, Mar 19, 2019, 02:28 ken via EV  wrote:

>  I bought a pack or lihium ion of cells and they arived pretty much dead.
> like 0 or .25 each cell.
>
> I used 306b nicad setting to bring them up to  3.00,  then swtiched to
> lipo to charge to 3.70 .
>
> someone told me that charging theses cells could be dangerous, because the
> dendrits could lead dangerous overheating. theses battery i think where
> used for like a bus or something. theses are from
>
>
> https://www.techdirectclub.com/johnson-controls-24-cells-solar-battery-90-vdc-total-2-5-kwh/
>
> theses cells can do 10c so i'm rather concrned.  I wish I knew that
> manufacuter or specs or more about the cells property.
>
>
> ___
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> Please discuss EV drag racing at NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>
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Re: [EVDL] NMC cells ran below 2.5 vots n left

[paul dove via EV]

NMC charge up to 4.2 Volts

Sent from my iPhone

> On Mar 19, 2019, at 2:28 AM, ken via EV  wrote:
> 
> I bought a pack or lihium ion of cells and they arived pretty much dead. 
> like 0 or .25 each cell.
> 
> I used 306b nicad setting to bring them up to  3.00,  then swtiched to
> lipo to charge to 3.70 .
> 
> someone told me that charging theses cells could be dangerous, because the
> dendrits could lead dangerous overheating. theses battery i think where
> used for like a bus or something. theses are from
> 
> https://www.techdirectclub.com/johnson-controls-24-cells-solar-battery-90-vdc-total-2-5-kwh/
> 
> theses cells can do 10c so i'm rather concrned.  I wish I knew that
> manufacuter or specs or more about the cells property.
> 
> 
> ___
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
> 

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[EVDL] NMC cells ran below 2.5 vots n left

[ken via EV]

 I bought a pack or lihium ion of cells and they arived pretty much dead. 
like 0 or .25 each cell.

I used 306b nicad setting to bring them up to  3.00,  then swtiched to
lipo to charge to 3.70 .

someone told me that charging theses cells could be dangerous, because the
dendrits could lead dangerous overheating. theses battery i think where
used for like a bus or something. theses are from

https://www.techdirectclub.com/johnson-controls-24-cells-solar-battery-90-vdc-total-2-5-kwh/

theses cells can do 10c so i'm rather concrned.  I wish I knew that
manufacuter or specs or more about the cells property.


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