Respectfully, pause charging allows even NiMH to develop a detectable voltage peak prior to overcharging. read NASA to find out that they have used pause charging on NiMH cells (up to 300V packs) on crew recovery vehicles. With conventional approaches like Maxim and Benchmarq, you are correct in saying that NiMH cells can be complicated to charge quickly and completely. Steve Halla ----- Original Message ----- From: "Dave VanHorn" To: "Microcontroller discussion list - Public." ; "Microcontroller discussion list - Public." Sent: Tuesday, May 10, 2005 4:08 PM Subject: Re: [PIC] Backup Battery > At 02:53 PM 5/10/2005, Steve Halla - LEAP wrote: >>I believe that we may be making battery charging too difficult. >> >>Heat is the single worst cause of battery failure and poor performance. >>To minimize the heat on charge build up (for any battery), pause charging >>is the most effective way to make a simple charger. Ni cells can all be >>easily charged with constant current with an LM317, terminate at peak >>voltage. Both SLA and Li can be charged to their respective fixed >>voltages, and still be safely pulse charged to provide 87-93% nameplate >>capacity. > > NIMH is a very complicated chemistry to charge, especially if you want to > do it quickly, and not damage the cells. > > Charging to peak voltage, will get you a false early termination on cells > that have sat for a while. > Read the data sheets at Panasonic and Sanyo, they will give you a good > start, and have a look at Galaxy power's chips. > The maxim "nimh" chip will cook most NIMH cells because it's constant > trickle current is way too high. > Some NIMH cells will TOLERATE C/10 trickle, others specify ZERO trickle. > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist