Michael Ross wrote: > I am investigating how to test cells and packs - I will need to charge and > discharge. > > If I have a programmable electronic load, rather than purely resistive > loads, is this an unrealistic way to discharge batteries?
Thought I'd mention that while a programmable load is an *excellent* way to discharge when testing batteries, it can be pricey (typically about $2/W on the used market). If you have a load bank, or need one for other reasons, then by all means use it. If you are considering buying one just for this purpose, then carefully consider what other equipment you have or will need to acquire to go with it. If you get a load large enough to handle your needs on its own (i.e. it can handle the desired discharge current even with a fully-charge battery), and you get one equipped with a communications interface (GPIB/IEEE-488 or RS232, typically), then you may be able to use its own voltage and current measurement capabilities to avoid the need to purchase a standalone data logger or USB DAC/digital I/O device to take measurements and control things. If you already have a data logger or other means of measuring/controlling a load and charger, then perhaps consider using a passive load in parallel with a smaller electronic load, so that you can save money on the electronic load purchase. Or, you may be able to go in entirely the opposite direction and use a completely passive load bank. I started out with a battery cycler setup consisting of a bank of 12VDC Edison-base (household screw-type) light bulbs switched by a continuous duty Ford starter solenoid-type RV battery switch. A simple QBasic program on an old laptop controlled the relay for the load and another for the charger via the parallel port. An E-meter with the RS232 comms option provided voltage, current, etc. measurements to the QBasic program. Incandescent bulbs have the nice property that the current they draw varies less with voltage than would a purely resistive load, so you can get a reasonably constant discharge current simply. Unless your battery voltage is significantly below the rated voltage of the bulbs, they also provide a nice visual indication that they are on and hot. ;^> Cheers, Roger. _______________________________________________ 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)