Paul,
I'm not following you, here. How can you have 4v open circuit applied
to anything? You could measure 4v open circuit across a power supply
or, for that matter, a disconnected battery. But, I thought, the
moment you connect it to something, you no longer have an open circuit.
Unless, of course, the grounds of the two systems aren't connected.
In the latter case, though - if the grounds aren't connected - I don't
see how 4v or 100v would make any difference. There cannot be any
current flowing and thus no voltage being applied.
Peri
------ Original Message ------
From: "Paul Dove via EV" <ev@lists.evdl.org>
To: "Cor van de Water" <cwa...@proxim.com>; "Electric Vehicle Discussion
List" <ev@lists.evdl.org>
Sent: 19-Jun-15 4:10:52 AM
Subject: Re: [EVDL] Bicycle battery
That's what Boeing said but it's interesting that these batteries are
used in many applications and none of them had fires. Open circuit
voltage is what needs to be considered not max charge voltage,
I haven't tried this but I may just to prove a point. If you hold 4
volts on one of these cells indefinitely it will burn. Which is what
they were doing. Also it was a starter battery so they didn't use much
to start the APU and then is held 4 volts on the cells.
Sent from my iPad
On Jun 18, 2015, at 11:47 PM, Cor van de Water via EV
<ev@lists.evdl.org> wrote:
Paul, the 29.6V is not the max charge voltage of the pack. It is the
nominal voltage:
8 x 3.7V (these were Cobalt cells) = 29.6V
So the max 32V on the bus is actually only 4V per cell and that means
that they keep those cells
below max charge voltage of 4.2V
So, it was not possible that the battery was over-charged, unless a
cell shorted and the 32V
was applied to 7 cells in series instead of 8!
Cor van de Water
Chief Scientist
Proxim Wireless
office +1 408 383 7626 Skype: cor_van_de_water
XoIP +31 87 784 1130 private: cvandewater.info
www.proxim.com
This email message (including any attachments) contains confidential
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-----Original Message-----
From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of Paul Dove
via EV
Sent: Thursday, June 18, 2015 8:21 PM
To: Cor van de Water via EV
Subject: Re: [EVDL] Bicycle battery
We already covered how to tell is a cell has internal defects. You
drain the cell to 2.5 volts and then if the cell voltage rises it's
good if it keeps falling don't use it. I did think this up This is
what NASA does. I read it in one of their presentations. I can dig it
up if you like.
As for the Dreamliner I followed that carefully. My favorite chart
that they presented to the FAA said
- the only thing that causes lithium battery fires is overchargeing
- we can find no evidence we are over charging
- therefore the cause of the fire is unknown
One of those statements has to be wrong. And the fire was the
evidence of overcharging.
The open circuit voltage of their battery was 29.6 volts. The system
voltage was 32 volts. They were charging the cells the whole time the
APU was running and wondering why it burned.
As for laptops they were overcharging as well. The paper I read the
designer claimed that leaving a small amount of current flowing or
trickle charge as they call it would not hurt lithium batteries.
Sent from my iPad
On Jun 18, 2015, at 9:59 PM, Cor van de Water via EV
<ev@lists.evdl.org> wrote:
This message has no content.
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