Ryobi charger "fries" batteries?

I have one of Ryobi's chargers that takes six of their 18V Li-Ion batteries at once and will charge them all in sequence and then (so it is claimed) "maintain" them ready for use.
However, I have found that many of the batteries that have been left in there are now reported to be dead -- or near enough dead.
Anybody else had any problems with Ryobi batteries or chargers?
I haven't opened up any of the newest 4AH battery packs, but the 2.4AH one I opened up had the same Sanyo cells that just about everybody uses in their battery packs -- even including the RIDGID ones with the lifetime warranty.
Perce
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Percival P. Cassidy wrote:

Charger could malfunction.
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On 12/4/2015 3:02 PM, Percival P. Cassidy wrote:

A lot of chargers are naively (cheaply) designed. (cheap) consumer kit often has no smarts in the charging algorithm; akin to putting a float charger on a car battery (and hoping the natural losses accommodate any long term overcharge tendency).
Even "smart" (integrated) chargers have little more knowledge than that required by the battery chemistry (charge at this rate, until this is observed, then do the following...).
Multicell batteries (a battery is a collection of one or more *cells*) are ven harder to address because most devices employing them only bring out the connections to the endpoints of the series string (and, possibly, a temperature sensor). So, the charger has no way of knowing how individual cells within the battery are sharing the charge; one might be practically flat (low voltage across it) while another is being overcharged (because the charger is trying to develop a particular voltage across the entire *string* of cells and doesn't realize that one is not responding as well as the others).
To effectively charge a battery, you need to observe a lot more than the voltage across the entire pack (and current flowing into it). E.g., batteries in electric vehicles have many points within the pack that are monitored -- so the battery controller can determine that one (or more) cells are failing and take measures to alert the driver to this instead of blindly ruining the other cells in the pack.
(batteries in electric vehicles can be serviced at the cell level so one bad cell doesn't make the entire battery disposable!)
Even laptops, with all their potential "smarts", do a piss-poor job of charging and monitoring battery state. I.e., a laptop can know how long it has been charging the battery, what the battery voltage and current have looked like throughout that charging cycle (i.e. laptop has MEMORY to hold this information) as well as what the *usage* characteristics of the battery were prior to this charging cycle!
"Hmmm... we should have pumped enough charge BACK into the battery pack BY NOW to account for the charge that we monitored being drawn from it, BACK THEN!"
And, of course, consumers play a big roll. Folks want to put their rechargeable devices back on the charger before they should -- "so it's fully charged when I need it!". If the charger wanted to maximize battery life, it would refuse to "top off" the battery if it knew that doing so would hasten the battery's demise.
OTOH, the user would be annoyed if, having placed the device on the charger, came back and retrieved it -- only to discover that it was in the same state of (dis-)charge as when he placed it there!
And, of course, the charger needs to know *which* battery it is dealing with -- which means the battery has to identify itself in some way and/or allow the charger to "leave notes" ("cookies"!) in the battery to help it perform its duties in the FUTURE!
Read, carefully, the care and feeding instructions that the manufacturer provided with your product wrt its batteries. Try to keep track of *how* you use them to see how conformant you are being with those policies.
I have a couple of battery powered devices that I've been designing/refining. One of the things I've done is embed knowledge in the devices of their usage and charging patterns. The batteries aren't (easily) removable so I can more accurately track how they are being used and mis-used. And, can advise the user of problems in his usage patterns that he can then change to maximize useful life, minimize maintenance cost, maximize availability, etc. (i.e., someone may be willing to replace batteries sooner in exchange for them ALWAYS being "fully charged")
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wrote:

If the battery packs for power tools, laptop computers and other stuff were made PROPERLY, the cells could easily be removed and a bad cell (or all of them) could be replaced the same way you change batteries in a flashlight. You'd be able to open the case without breaking it apart, just take out a few screws. And the cells would have contacts, rather than having to weld or solder them.
But we live in a disposible society, where greed rules the show. Since the batteries are overpriced and cost nearly what the whole tool cost, they know you'll be their sucker and buy an entire new tool.
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On 12/4/2015 2:02 PM, Percival P. Cassidy wrote:

It's a known problem I came across some time ago. The batteries would not stay topped off. The solution was to turn off the charger after the batteries were charged. Worked fine for quite a while, but now they discharge if left in the charger, even while turned off. So now I remove the batteries after charging and they are fine. Almost a full charge after after sitting a for a month or so.
Dan
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On 12/4/2015 5:02 PM, Percival P. Cassidy wrote:

I have an 18 volt DeWalt set. The original charger would overcharge which is evident by the fact that the battery stays fairly warm on the charger after the red light goes out. When I needed new batteries, a good deal was the 18 volt DeWalt 1/2" drill with 2 batteries and a new charger for only $99 at Lowe's ... this year it's only $89 probably because they want to get rid of all the nicad stuff in favor of LI. With the new charger, after the charge cycle, the battery cools off and stays cool. Now I only use the old charger when traveling in the motor home and I do not leave the batteries sit for any length of time.
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