Date: Wed, 01 Feb 2006 09:02:34 +0800
From: Raymond <[EMAIL PROTECTED]>
Subject: Re: [LIB] battery check
At 04:59 PM 30/01/2006 -0800, you wrote:
Date: Tue, 31 Jan 2006 00:57:08 GMT
From: "carval" <[EMAIL PROTECTED]>
Subject: Re: [LIB] battery check
Hi
I have two batteries I would like to check
with a ohm meter.
The Libertto battery has 6-8 contacts,
which ones do I use to test for voltage?
tia
Hi Carval,
Just a not-so-quick word of warning - Lithium batteries ARE in theory more
dangerous than your run-of-the-mill NiCAD and NiMH batteries - I know a guy
who set his car on fire and I've heard of a Solar Car team burn their
building down, in both cases by mis-handling the charging of LiIon and
LiPoly batteries (having said THAT, I've burnt myself several times on
NiCAD batteries whilst I've never once received an injury from LiIon and
LiPoly despite having used the latter significantly more nowadays). If
you're not putting any charge into the battery things are somewhat safer
but still, if you're unfamiliar with them, I suggest 2 things - first, do a
google for LiIon or LiPoly safety and do a bit of reading and secondly, get
yourself a dry powder extinguisher (it's the most effective household
extinguisher to use against lithium and electrical fires - you should be
using something like a Metelex extinguisher but they're generally only
available to industries) and/or a fire blanket (actually, you should have
one within a few seconds dash of you whenever you work with electronics
anyway). At any rate the usual disclaimers apply - all advice provided in
good faith, no responsibility taken for
injury/damage/death/insults-to-your-so-and-so/etc. :-)
Now for the info you actually asked for! An ohmmeter won't do you any good
- you need a voltmeter (or a multimeter on the 20V DC range). Do NOT
connect an ohmmeter or ammeter (or pretty much any other meter that isn't a
voltmeter or battery meter) directly across a battery unless you really
know what you're doing - there's a good chance you'll blow up your meter
and at worst you'll put a direct short across the battery and cause a fire.
Just checking - I'm sure you knew the difference, I'm just accounting for
the small (but potentially not insignificant) chance that you didn't ;-D
If you look at the Libretto service manual (available on David Chien's site
I believe), Appendix C has pin assignments which include the battery
connector (C.12 PJ510). According to it, the terminals you want are pins 1
and 10 (the outermost 2) - so if you use a DMM with auto polarity, just
connect the probes across the outer 2 terminals (you don't need to worry
about which way around they go). For reference, it's hard to do any damage
(at least not to the device under test) by connecting a voltmeter across it
(about the only exception is if you use a cheap voltmeter with a relatively
low resistance and you're careless with your anti-static precautions and
the circuit you're testing has high impedance drivers in which case you
might cause some spiking of lines and/or static discharge problems) so for
batteries you could just test lines at random and see where you get the max
voltage.
Now for the bad news ... testing a battery under open circuit (no load)
conditions often doesn't tell you much about its condition (apart from it
being completely gone if it's reading too low). You really need to load it
up (and often for a little while) before testing it, that's something you
need to be very careful of if you're not doing it in-circuit. If you're
brave, you could disassemble the Libretto's motherboard, plug it into the
battery then monitor the terminal voltage as you power it up but I think
that may be a little outside the scope of what you may be willing to do! ;-P
Good luck!
- Raymond
P.S. As for handling posts that you regard as abusive, here's a tip that
you probably already know ... if you can, read the posts for 'interest', if
you can't, just ignore the posts ... this is the Internet, people are free
to post what they want and you are free to read what you want and people on
the sidelines will take their sides accordingly. Whatever you do, don't let
it upset you! :-)
---
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