1. NiMH batteries never were subject to any sort of memory effect; the chemistry doesn't do that. But they are harder to charge properly than a NiCd. Now that dual chemistry or even triple chem chargers are commonplace, people forget that-- all the newer chargers have a recent chip in them that figures out from the charge curve what the chemistry is and watches for the little negative delta that signals "full up." Not charging to that point wastes capacity and makes you think the cell can't hold a full charge. Going just slightly beyond shortens cell life a little. Going more than slightly beyond shortens cell life a lot. 2. NiCD batteries never had a memory effect either! Read the literature he says he's one. Yes, NiCd's wear out, yes, their discharge curve gets steeper as they age, but memory effect? Want to know where that whole thing came from? NASA. Satellites. Batteries charged by a mil-spec charging circuit that cost millions to develop and build, that routinely allowed a set of satellite batteries to discharge to EXACTLY the same point EVERY time, and then charged them back up to EXACTLY the same point again. And guess what? Those batteries DID develop a memory effect. So how many of you have a multi-million dollar charging circuit? On the other hand how many of you have spent a $30-40-50 or $90 on a fancy charge-discharge battery conditioner? I have one, only because I couldn't seem to buy a multichemistry versatile charger without that feature. But I have never used it. I have never purposely discharged a NiCd battery except in normal use. What happens to a cell in a multi-cell battery when you put a heavy enough load on the stack to discharge it in an hour or two, or 15 minutes like some of them do? Well, since all cells in all batteries have perfectly uniform internal resistance, all the cells discharge to the same voltage, and sit there pretty, waiting for you to charge them back up so they can lead fulfilled lives again. Right? I think what can happen is that some cells discharge a lot sooner than others, since in the real world the internal R is lower for some cells than others. Since you are now pulling current *backwards* through at least one cell in the stack, odd are good that some day one of the cells is going to reverse on you, and become a highly inefficient inverted battery, one that's unlikely to ever take an appreciable charge again. This is a real-world problem for discharge devices that don't have both a timer and a voltage monitor, and some ever sense temperature too. So why does every peddler of LiOn and NiMH batteries tout their resistance to the dreaded "memory effect"? Because those technologies are newer, and you need something to differentiate the new from the old. Makes a great selling point, and the myth of the memory effect having something to do with real life and the way normal people use batteries is something that has been repeated so often, it's become indistinguishable from reality. References: (Which I urge you to read!) http://www.hippy.freeserve.co.uk/nicdmyth.htm http://en.wikipedia.org/wiki/Memory_effect http://www.repairfaq.org/ELE/F_NiCd_Memory.html http://www.sheldonbrown.com/marty_sla-nicad.html#memory which quotes the GE tech notes and from which I quote: "To the well informed, however, 'memory' is a term applied to a specific phenomenon encountered very infrequently in field applications. Specifically, the term 'memory' came from an aerospace nickel-cadmium application in which the cells were repeatedly discharged to 25% of available capacity (plus or minus 1%) by exacting computer control, then recharged to 100% capacity WITHOUT OVERCHARGE [emphasis in the original]. This long term, repetitive cycle regime, with no provisions for overcharge, resulted in a loss of capacity beyond the 25% discharge point. Hence the birth of a "memory" phenomenon, whereby nickel-cadmium batteries purportedly lose capacity if repeatedly discharged to a specific level of capacity. "The 'memory' phenomenon observed in this original aerospace application was eliminated by simply reprogramming the computer to allow for overcharging. [Note that no mention is made of adding an intentional *discharge* to clear the problem - RLM] In fact, 'memory' is always a completely reversible condition; even in those rare cases where 'memory' cannot be avoided, it can easily be erased. Unfortunately, the idea of memory-related loss of capacity has been with us since. Realistically, however, ' memory' cannot exist if any one of the following conditions holds: 1. Batteries achieve full overcharge. 2. Discharge is not exactly the same each cycle - plus or minus 2-3% 3. Discharge is to less than 1.0 volt per cell. "Remember, the existence of any ONE of these conditions eliminates the possibility of 'memory'. GE has not verified true 'memory' in any field application with the single exception of the satellite application noted above. Lack of empirical evidence notwithstanding, 'memory' is still blamed regularly for poor battery performance that is caused by a number of simple, correctable application problems." End of quote ... Basically memory (loss of capacity) due to discharge is a myth. Reduction of your NiCads / NiMH capacity due to overcharging (heating) and, cell reversal in voltage depressed battery packs kill your batteries. http://www.resrchintl.com/memory_effects.html Very good, well written, good hints for using your batteries effectively. http://www.saftbatteries.com/110-MS_Telecom/20-40-20_technical.asp#aa Here's a battery maker saying No Memory Effect in currently produced product. http://shop.store.yahoo.com/greenbatteries-store/nibafa.html which says, in part: If you use NiCd batteries you should be aware that most of the problems experienced by NiCd battery users are not due to a "memory effect" but are due to overcharging or improper storage. Overcharging is usually caused by poorly designed first generation battery chargers. These chargers continue to deliver current to the batteries even after the batteries are full charged. Regards, -Tom At 09:30 PM 10/21/2004 -0400, you wrote: [Sex] Dietrich is some something that never existed before and may never exist again. That's a woman. --Josef von Sternberg --... ...-- -.. . -. ----. --.- --.- -... tpeters(a)nospam.mixcom.com (remove "nospam") N9QQB (amateur radio) "HEY YOU" (loud shouting) WEB ADDRESS http//www.mixweb.com/tpeters 43? 7' 17.2" N by 88? 6' 28.9" W, Elevation 815', Grid Square EN53wc WAN/LAN/Telcom Analyst, Tech Writer, MCP, Cisco Certified CCNA