Michael Ross wrote: > I have heard of putting a roll of fencing in a tank to steam off heat. Is > this useful with a programmable load? Or is this just a crude way to > discharge.
Probably not, unless the electronic load you choose is designed to be used with an external load bank, or you plan to control the electronic load from a remote source rather than simply setting it to regulate the desired load current on its own. An external load bank (coat hanger or other wire in a bucket of water or fan-cooled power resistors, etc.) can be useful if you want to increase the power capability of your electronic load (or conversely, to be able to use a smaller - and cheaper - electronic load than you could otherwise). For instance, when testing a 12V battery you will typically discharge to about 10V minimum; if your desired discharge rate is 75A, then your minimum load is about 750W. If you want to be sure that you can pull the full 75A from a freshly charged battery, it needs to be able to handle the maximum load of about 15V x 75A = 1125W. If you use a resistive load to handle most of the minimum load requirement, then your electronic load only needs to be sized to handle the difference (in this case 1125-750 = 375W) instead of the full amount. > Someone mentioned needing a heat dispensing means would be needed with a > programmable load. Not unless you pick up a water-cooled load. The air-cooled loads have built in fans and will cool themselves. If you are discharging a large capacity battery in a small room, you may need to open a window or otherwise allow for some ventilation as the room will warm up. > Any recommendation of actual units to look at? I've mostly used DLP- and RBL-series units from TDI (Transistor Devices). They are often available used, and are generally basic rugged units. You don't need particularly fancy features for battery discharging as most often you will use the load in constant current or possibly constant power. In constant current mode, the TDI loads can have the load current controlled remotely by a 0-5V signal, so you can use an external means to monitor the total load current drawn by the electronic load and a resistive load and then control the electronic load to regulate the total current at the desired level. They also can be enabled/disabled remotely with a simple relay or opto so that your data logger can turn the load off when the battery voltage reaches the desired end-of-discharge voltage. Some models support IEEE-488 (GPIB) communication, in which case you can achieve all of this controllability through software control, provided you spring for a GPIB interface for your PC. I've also used loads from NH Research (NHR, this is what I have at home) and Chroma. This site provides an idea of what sort of devices are available on the used market: <http://www.alltest.net/s.nl/sc.2/category.16/.f> 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)