-------------------------------------------------- From: "Michael Watterson" Sent: Monday, June 21, 2010 12:30 PM To: "Microcontroller discussion list - Public." Subject: Re: [EE] proprietary power supply for HP/Compaq nx7300 - what = isthefunction of cetral pin? > Oli Glaser wrote: >> >> It doesn't sound too unlikely to me - if by adding a bit of component = >> cost >> they can make sure people have to use their power supply then I think = >> most >> would go for it. The situation with laptop batteries is similar - I had = >> to >> hack one a while back as it had a lifespan set by the on board chip which >> had expired, but the cells were still okay. Why make a battery that live= s = >> a >> long time and has easily replaceable cells when you can do otherwise and >> charge people half the cost of a new laptop for replacements? :-) >> >> On a side note, whilst hacking the battery, I made use of this app note = >> from >> microchip on SMBus etc - quite useful: >> >> http://www.microchip.com/stellent/idcplg?IdcService=3DSS_GET_PAGE&nodeId= =3D1824&appnote=3Den011076 >> >> >> > The battery issue is for safety. Read up on failure modes of LiIon > battery packs. It certainly doesn't stop cheap replacements. > The PSU issue is likely to use same connector on different ratings of > PSUs. It certainly doesn't stop cheap replacements. Yes, I'm aware of the safety issue with LiIon cells, but I wasn't getting a= t = that - there is still some attempt to keep people buying their batteries, = there's plenty of reading on it out there. Whilst "smart" batteries that = control charge and monitor temperature are obviously a good an necessary = thing, there is also the fact that many batteries have a set life span = dictated by the firmware, and the cells are not easily replaceable (surely = providing some form of plug in replacement cells would not be unsafe?). I'm = sure they would say something like "we can't guarantee performance past a = certain date" with the set lifespan, but it's reasonably obvious that there = is some attempt to make it difficult to use anything but their stuff. When = you can but a set of replacement cells for =A310, charging =A3200 for a = replacement battery seems a bit over the top, considering the contents. If the PSU issue is like the Dell ones mentioned that use some form of IDin= g = on an eeprom connected to the middle pin, it would certainly make cheap = replacements more difficult. = -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist