Laptop Battery use and storage guidelines.

laptop batteries One of my laptop's batteries had died a little while ago and couldn't figure out why, so I've been reading around the subject to try to find out what can be done about it and what I can do to prevent it in future.

First of all, I've learnt that it is possible (for the more technologically ept of us) to replace the Lithium Ion batteries inside of laptop batteries. However I wouldn't recommend this unless you are an expert at wielding a soldering iron.

To avoid this and an expensive new battery I decided to simply buy one cheaply second hand from Ebay, this was not necessarily the best approach however as laptop batteries (which I will refer to as Li-ion batteries from now on) have a definite shelf life which affects the storage capacity of the battery (and therefore how long it keeps your laptop powered). This shelf-life can be be prolonged by various means.

The best guidelines I found was at the excellent Wikipedia , in an article on Li-ion batteries which I found extremely informative and I am now citing here. 

Guidelines for prolonging Li-ion battery life

  • Unlike Ni-Cd batteries, lithium-ion batteries should be charged early and often. However, if they are not used for a longer time, they should be brought to a charge level of around 40%. Lithium-ion batteries should never be "deep-cycled" like Ni-Cd batteries.
  • Li-ion batteries should be kept cool. Ideally they are stored in a refrigerator. Aging will take its toll much faster at high temperatures. The high temperatures found in cars cause lithium-ion batteries to degrade rapidly.
  • Lithium-ion batteries should never be depleted to empty (0%) and then stored.
  • Li-ion batteries should be bought only when needed, because the aging process begins as soon as the battery is manufactured.
  • When using a notebook computer running from fixed line power over extended periods, the battery can be removed and stored in a cool place so that it is not affected by the heat produced by the computer.

snmpd reports ioctl 35123 returned -1

xen chart The updated version of snmpd in Debian Etch doesn't seem to like our customised vif interfaces names that we're using for Xen hosting. I'm seeing the error "ioctl 35123 returned -1" in syslog every 5 minutes. Reverting to the standard "vifx.y" format fixes the problem.

I started using xen guest names for vif interfaces to allow our graphing system (Cacti) to keep track of which interface matched a particular guest. For example a guest called acme would have an interface called acme.eth0 in the xen host instead of a dynamically generated name like vif14.0. This seemed to be working fine with Sarge, but alas not with Etch. I tried some variations like acme-eth0 and acme.0, but nothing seems to get rid of the error except vifx.y.


How to make a CAT 5 cable and presentation point


We rarely have to make our own CAT5 cables, as the amount we use it's cheaper to buy them. However there is the odd occasion, and by then we've forgotten the wiring diagram. So here is a few useful resources for when it has to be done:-