Hi Jay, and welcome to the EVDL. Here's the technical manual for Saft STM-180 batteries:
http://www.evdl.org/docs/STM5-180tech.pdf Unlike some of Saft's other NiCds, I'm pretty sure these were designed for road-going electric vehicles. They were used in the Chrysler TEVans, if I'm not mistaken. They were also used in E-buses back in the 1990s. Some of the used ones on the market a few years ago came from those buses, but be careful, those buses worked their batteries hard. They're really easy to charge, but the profile is very different from other batteries, so you need a flexible smart charger. Maybe the Brusa chargers can still do it; they were used for these batteries for 15-20 years ago, but it looks like the current Brusa ranges may not be able to handle pack voltages < 200v (and they're really expensive). Maybe Delta-Q? Roger, what do you think? Othewise you may have to make your own charge controller. But as I said, the profile isn't tough to implement. You don't need individual cell or battery regulators. NiCd batteries love to be overcharged and are happy when they're gassing freely as long as they don't overheat. Just charge and discharge in a series string. There are two tricks, if you can call them that. One is that time plays a role, so the charger (or some circuit you design) has to keep track of it. The other is that the threshold voltage for a change to phase 1 to phase 2 has to be adjusted for battery temperature, so you need a temp compensating charger (or your homemade controller has to deal with it). There should be a pocket in the side of the case of each module (battery) somewhere for the temperature sensor. Choose a module in the middle of the pack to fit the sensor. If your pack is split, you might want to use two sensors and average them. Briefly, here is the procedure. 1. Zero a timer. Start it counting up. 2. Charge at constant current of 36 amps (can be as low as 27a) until the voltage reaches 8v / module. That voltage is at 20 deg C; adjust it DOWN 0.02 volts per module for each degree celsius the module temperature is above 20 deg C. 3. When the battery reaches threshold voltage, reverse the timer and reduce current to 7 amps. Ignore voltage in this phase. 4. When the timer reaches zero, stop charging. (In other words, charge at 7 amps as long as you charged at 36 amps.) Did I not say it was easy? Be sure to follow the manual's procedure for watering! Do not add water before charging, even if you can't see water in the cells. Don't worry, it will magically appear as you charge. NEVER use any watering equipment that you've ever used for lead acid batteries. Traces of acid will destroy your NiCd battery. As a reminder, when you assemble your pack, don't put more than 10 modules on each watering circuit. (Voltage across it can't exceed 60 volts.) I know, the warnings are scary, but these are very sturdy batteries and will serve you well for many years if you take good care of them and charge them properly. Their cycle life is typical 2500-3000. When they're worn out Saft can (theoretically) rebuild them for another 2500-3000 cycles, though I don't know anyone who's actually had this done. You're lucky to have found them, IMO. David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
