From ???@0x00000F24 Mon Aug 07 13:44:24 2000 Path: pitt.edu!newsflash.concordia.ca!sunqbc.risq.qc.ca!newsfeeds.belnet.be!news.belnet.be!newsfeed00.sul.t-online.de!newsfeed01.sul.t-online.de!t-online.de!fu-berlin.de!nntp.infostrada.it!i2unix!not-for-mail From: "Bansuri" Newsgroups: sci.electronics.design Subject: Re: Shelf Live of NiMH and Nicad batteries -Question rephrased Date: Tue, 1 Aug 2000 06:18:10 +0200 Organization: IUnet Lines: 86 Message-ID: <8m5jml$3kc$1@serv1.iunet.it> References: <8m1h3q$2fp5$1@otis.netspace.net.au> <39856F3D.278BDEBD@hotmail.com> NNTP-Posting-Host: 192.106.185.112 X-Trace: serv1.iunet.it 965104149 3724 192.106.185.112 (1 Aug 2000 04:29:09 GMT) X-Complaints-To: newsmaster@iunet.it NNTP-Posting-Date: 1 Aug 2000 04:29:09 GMT X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 Xref: pitt.edu sci.electronics.design:199710 Status: N If Nicads are in continuous use and well maintained, I found a life of maybe 3-4 yrs. I bought a nimh replacement with 1.5x the capacity, but even with optimal care it made it only two yrs. Now everything has Li-ion here I had 3 batteries, one of which was hardly used, but all declined after 2.5 yrs. rapidly. For storage I discharge the batteries to 20% capacity. After 20 yrs. a modern make would be not working any more, but maybe the older ones were fabricated without special means to shorten lifetime! regards Ban "&retired0" <&retired0@hotmail.com> schrieb im Newsbeitrag news:39856F3D.278BDEBD@hotmail.com... > It's extremely variable. > I've bought a lot of old (some 20 years old) but unused > nicads over the years. > Some of them work great. others are shorted. > Failure modes I've experienced are: > > 1) cell venting.There's a seal in the vent that > deterioriates. > Once that happens, you've got white powder all over the > place and the > cell rapidly deteriorates as the electrolyte goes away. > > 2)cell shorting, or self discharge over a period of days. > > So, if you're buying new cells for a commercial project, buy > the ones with the lowest capacity > and highest temperature rating you can get. The fast charge > and high > capacity cells make compromises. You'll be at a new job > before there's a problem. :-) > > If you're buying old used cells for hobby use that haven't > been charged, measure > the voltage. If it's not zero, > the cell will probably work...unless the seller just charged > them. > If it is zero, the cell may work, but it may be shorted or > leaky. > I've had reasonable luck selecting used cells that have > non-zero terminal voltage. > > It's not what you asked, but how you charge cells can affect > their life. > Think of it as a plating problem. If you interleave > charge/discharge current during > the charge process, you can reduce the formation of > dendrites that eventually pierce > the insulator. It's the same process platers use to get > smooth plating. > > mike > > Joseph Goldburg wrote: > > > > Hi All, > > > > I have rephrased my question in the hope of getting > > a more specific answer. > > > > QUESTION > > > > If a NiMH or Nicad battery is not charged for months ~ 12months > > (or for years), what is the probability the battery will be faulty after > > this > > time (won't charge, dead cell, leaky etc). > > > > In other words what it the "Self Live" specification state by > > > > a) Battery manufactures > > > > b) Experienced users of Nicads and NiMH batteries > > > > Regards > > Joseph > > -- > Big list of WANTS and FORSALES at link below. > Return Address is Bogus. Click below to reply > http://nm7u.tripod.com/startpage/ > Or you can DELETE the & in the "from" address.