Hi Morgan: Yes, but it's a matter of how hot. The Ni-Cad chemistry is what's called endothermic and the Ni-MH is what's called exothermic. This means more heat is produced at the end of charge with the Ni-MH battery and amounts to about 30 degrees C more than the Ni-Cad (100 F vs 150 F). Reference: Handbook of Batteries, chapter 29 (portable sealed Ni-MH Batteries, paragraph 29.5.1 Charging sealed Ni-MH batteries, general principles. Figure 29.16b is a plot comparing battery temperature vs % charge for Ni-Cad & Ni-MH. Fig. 29a compares cell voltage vs. % charge and shows the the -delta V for Ni-MH is smaller than for Ni-Cad so some chargers designed for Ni-Cad may not sense the -delta V on Ni-MH. A clear example are the military BB-590/U and BB-390/U batteries. The earlier BB-590/U is a Ni-Cad battery and has no provision for temperature monitoring. The newer BB-390/U has built-in temperature sensors needed for charging. I discovered "burp" charging when testing a surplus charger and it did not overheat my Ni-MH battery. The Maha C777+ terminates charging my Ni-MH battery in the over temperature protection mode and shows an error number leaving the battery over 140 deg F. There seems to be some controversy about "burp" charging but I have seen it work experimentally. A burp fast charger will not overheat a Ni-MH battery and does not require a temperature sensor. Battery Space now offers one. Have Fun, Brooke Clarke, N6GCE -- w/Java http://www.PRC68.com w/o Java http://www.pacificsites.com/~brooke/PRC68COM.shtml http://www.precisionclock.com >Date: Wed, 26 Oct 2005 19:23:37 +0200 >From: Morgan Olsson >To: "Microcontroller discussion list - Public." >Subject: RE: [EE] Charging NiMH >Message-ID: <4.3.2.7.2.20051026192008.01a8d980@127.0.0.1> >In-Reply-To: <435E62BE.8090106@pacific.net> >Content-Type: text/plain; charset="us-ascii" >MIME-Version: 1.0 >Precedence: list >Reply-To: "Microcontroller discussion list - Public." >Message: 6 > >Brooke Clarke 18:52 2005-10-25: > > >>Ni-Cad batteries have a chemistry that does not get hot when fully charged >> >> > >Of course they will if you pump energy into it when it is fully charged. > >You can not destroy energy, so whatever you pump energy in that is not used for other things (such as the electrochemical storage in the cell, or at worst abuse gassing or explosion...) is bound to be heat. > >/Morgan > > >-- >Morgan Olsson, Kivik, Sweden > >------------------------------ > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist