> While shopping for a car charger for a Blackberry Storm, both the > Verizon store AND several electronics mega-stores warned me against the > cheap chargers (and at Verizon, only their model would do). Their > argument was that the cheap ones would 'force' more current into the > phone than was good for the battery and severely shorten the life of the > battery. This will only happen if either - The design of the device is bizarrely incompetent or - It's a built in design feature intended to cook your batteries if an "unapproved" charger is used so they can sell more batteries, sell their own chargers, scare users off doing the same AND make it all your fault into the process. Both of the above are possible. > However, one service tech who seemed trustworthy did claim to personally > know that the non-Verizon charged units came back with batteries that > wouldn't hold a charge any more. He could only speculate on the > engineering reason. As above. > It would seem unwise to design a phone with the battery directly > connected to the usb +V. Some sort of regulation is required, if only to > prevent exploding LiIon batteries. Absolutely. Any device that did that would be so incompetently "designed" as to be arguably criminal. About the best "excuse" for doing that, if it was done, would be to say "it's not actually a USB port - it just uses the same plug - it needs a proper charger to work". ie what part of "don't don't be evil don't you understand?" > There is also talk of 'fast charge' adapters, versus regular. Hmmm. If the battery is LiIon of some sort then this should only be possible under the device's own control A given LiIon battery has a manufacturer fixed maximum charge rate. It MAY be possible to exceed this rate with known and acceptable consequences (for some values of "acceptable") BUT the device should be the controller of this behaviour. Following suffixes are mine: Normal LiIon practice is to charge at Ichg_max until Vbat_max is reached, then hold the voltage at Vchg_max until Iterminate is reached. The battery "decides" the voltage profile during the 1st phase and the current during the second phase. Ichg_max is usually 1C but some makers or chemistries allow 2C and some specialist designs coming to market allow MUCH faster. At the end of this phase charge capacity is about 60%-80% of max. Some "=3Dfast chargers" terminate at this point - you get faster time to "charge complete" but less capacity. Rate is better than full charge as you get say 2/3C in about 1 hour whereas last 1/3C takes typically another 2 hours so is on average 4 times slower rate (ie 2/3C : 1 hour versus 1/3 C : 2 hour). A "simple" test is possible IF you can access battery terminals during charging. Possibility depends on device and your ingenuity. With a "standard": LiIon/ LiPoly cell, if Vbattery is > ~4.2V at "normal" temperatures then "you have problems". If Iin is > 1C usually or maybe 2C (manufacturers spec needed) when cell hits the 4.2V pedestal then "you have problems". If Vbattery EVER exceeds 4.3V you have BIG problems. Even at 4.3V you are running on the edge. As temperature rises Vbattery max should be slightly reduced. Maybe 4.1V at 40C if 40C is in spec for cell used. > So.. Is there any truth embedded in this 'street' knowledge? Potentially yes as above. But only through extreme incompetence or evilness on makers part. > I can't see how one could 'force' more current into the phone, except if > it was a constant current supply (or maybe +12v on the usb cable), but > that would violate the usb spec. Even then, the internal regulator > should prevent problems. Am I missing something? Not apparently. BUT the "internal regulator should" may not apply if the cell is directly connected to a "not really a USB USB connector" as above and the "real" charge control is external. > How is 'fast charging' accomplished? As above. It isn't, OR the device does it with special care OR it is just early termination. > Now the funny part. I started using a non-Verizon adapter. It charges > other usb rechargeable things fine. The Storm says it likes it fine too. > No excess heat generation during charge. Done a few times over a month > and suddenly the battery went from 24+ hours on a charge to 12, then 7, > then 3, then 1 hour life per charge over the course of a week or two. I > never had =A0LiIon degrade like that. It's about a year old. Class action time? > Not sure if iPhone and Blackberry share the same type supply design (the > Storm seems to need more than a simple cable to charge as does the > iPhone). It seems a lot like cause and effect. I'm not willing to buy > into that until I can see an engineering reason though. iPhone DOES use "proper" USB connection on power leads but uses non standard resistor voltage level setting on "data" leads to set charge rate. This is "safe enough" ([tm] if you understand what is needed and do it. Odds are SOME people will start making iPhone chargers with data lines hard clamped in flat out charge mode. Battery life will suffer. Phone life may. Russell McMahon --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .