Partial comment: You MUST NOT tricklle charge modern high capacity NimH cells. The boundary is around 1800 mAh for AA cells. Below that it is (or was) typically acceptable. Older lower capacity cells had a mechanism/chemicals to allow reecombination of the H2/O2 generated at end of charge. As energy capacityrose this was removed to make more room for active material. A modern NimH MIGHT survive C/100 trickle according to a few manufacturers, but MOST say DO NO TRICKLE CXHARGE. (I looked at many such specs a few years back). My too many times given advice on this my Stack Exchange maybe related answers Including https://electronics.stackexchange.com/a/56843/3288 https://electronics.stackexchange.com/a/123750/3288 https://electronics.stackexchange.com/a/300627/3288 https://electronics.stackexchange.com/a/41648/3288 https://electronics.stackexchange.com/a/207003/3288 _____________________ After spending too much time and effort trying to treat NimH AAs well in portable solar charged equipment I decided that LiIon is a much nicer chemistry to manage (without any comment on its dangers). Moderrn NimH and LiIopn are of ABOUT the same energy densities in AA cells = .. LiFePO4 wrt NimH: superior charging managability, better whole of life cost per energy stored. wrt LiIon: much better safety and whole of life cost per energy stored and cycle life somewhat lower terminal voltage, lower mass and volume energy density, I'd use LiIon or LiFePO4 rather than NimH if possible. Russell Unrelated : Yee ha Starts at 3m 45s for will-be-obvious reasons. Watch from start in due course. I MUST go there !!! https://www.youtube.com/watch?v=3DrB4HVn6Rnmk&feature=3Dyoutu.be&t=3D345 On 6 June 2017 at 08:27, David C Brown wrote: > I am building a simple charger for NiMH batteries. It will have a fixed > rate constant current source and I intend to vary the charge rate between > different cells and standard/trickle rates by pulsing the charger.. A we= b > search suggests that this is a well accepted technique but the one piece = of > information I am struggling to find is the pulse rate. My gut feeling i= s > that something between 1Hz an 100mHz would be about right. can anyone > confirm this? > __________________________________________ > David C Brown > 43 Bings Road > Whaley Bridge > High Peak Phone: 01663 733236 > Derbyshire eMail: dcb.home@gmail.com > SK23 7ND web: www.bings-knowle.co.uk/dcb > > > > > *Sent from my etch-a-sketch* > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .