Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!ll-xn!ames!amdahl!nsc!gates From: gates@nsc.nsc.com (Tim Gates) Newsgroups: comp.sys.ibm.pc Subject: Re: Overcharging NiCad batteries? Keywords: NiCad rechargeable batteries, laptops, foreign power Message-ID: <6625@nsc.nsc.com> Date: 27 Sep 88 20:03:25 GMT References: <3008@dalcs.UUCP> Reply-To: gates@nsc.UUCP (Tim Gates) Organization: National Semiconductor, Sunnyvale, CA. (Mesa Group) Lines: 27 NiCad batteries have something called Memory. This is when the battery is partially discharged then recharged many times. The battery then begins to act as if it can only store a small amount of energy (the normal discharge amount). The storage capacity of the battery can be restored by FULLY discharging the battery, then fully charging it. This should be repeated 3 or more times. Each time you will increase the storage capacity of the battery. To fully discharge the battery, just leave the computer turned on until it is dead, then connect a low value (2 to 5 Ohms) resistor across the battery terminals for several hours. I suggest that a high wattage resistor be used (3 times the expected power dissapation). If you are concerned about data integrity when the battery is low, use only the resistor to discharge the battery. This will take longer. Allow 3 hours for each amp/hour of capacity for which the battery is rated. If you are interested in other NiCad battery problems and their solutions, send me mail. If there is enough interest, I will post. -- Tim Gates National Semiconductor {amdahl|decwrl|hplabs|nscpdc|pyramid|sun|voder}!nsc!gates "Where the men are men, and the computers run scared."