Mailinglist Archive: opensuse (1620 mails)

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Re: [opensuse] UPS : replacing battery with 12 volt Jelly Car Battery
On 11/25/2014 02:43 PM, John Andersen wrote:
Just for you Anton,

You're a sweetheart :-0


I flipped over my 19v laptop (dell 9400) yanked the
battery out, in preparation to measure it, but found it impossible to get
probes into the slots where the contacts are.

Good try :-)


But on the battery it said 11.1Vdc output.

This is the second battery I've had for this laptop, and different
models were available from Dell, which had different voltages, one was
13, as I recall.

I didn't go for the 8-pack for my HP, but the (fully charged) voltage
for the 3500mAh for my phone (OEM was 1800mAh) was just very slightly
over the OEM one. Similar for the battery, replacement and OEM, in my
P&S camera -- but those are both the same physical size.


I suspect the charging voltage on this 11.1v is somewhere around 14v.

So I'm guessing that they need 19 for charging and powering at the
same time.

I've done some googling around and that does seem to be the case.

However it seems to be a design decision to stack the cells that way.
Whether this is because the previous generation -- the days of
"lug-ables" -- of power packs was 19V and they stuck with that, I don't
know.

I'm convinced it is a design decision because the cells in my phone and
in my tablet are stacked to be able to charge of 5V. I have no doubt
that these are the same basic cell technology, Lithium Ion cells with a
maximum charging voltage of 4.2VDC. Its all about how they are stacked.

Four cell in series would amount to 16.8V.
The 8-cell option for my HP laptop would have been 2 parallel strings of
4, that is the 16.8V. 19 minus 16,8 leaves 2.4V for the electronics.
HMMMMM. Maybe its only 'headroom' allowing for losses

The six cell does 12.6V which gives more 'headroom'.

Of course this is all speculation.



When running on battery they may need step-down dc-to-dc regulators inside for
all the peripherals, and god only knows what for the screen.


In my "headless, burnerless firewall under the desk" scenario we're back
to the electronics only.





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