Hi Roger, Thanks for the thoughtful reply.
I think I need to be a notch or two above garage testing. To provide results worth referencing. I do have to be frugal and not spend where good things can be fabricated. We want to be cost effective for clients that aren't at the million$ a year in sales level. Large OEMs can care for themselves. Since we are a functioning test lab, I have an assortment of quality measuring instruments - just not specific to battery testing. We test solar thermal collectors. Lots of radiation, temperature, and flow capability. I have a pretty comprehensive data acquisition system, National Instruments cRIO controller, 32, 5V biderectional DIO channels, 8 channels of high speed 5V bidirectional DIO, 16 channels of 24V DO, 8 channels of analog input. I have a couple 6 1/2 digit DMMs and 3 20 channel cards to use in them (slow but accurate). All that can be programmed with some sophistication using LabVIEW. I won't need PLCs. With some relays and contactors, I can probably move on to the power supplies and possibly load banks for a place to spend money. For cell testing I have an EMS 7.5V 300A 1700W supply. I have not really used it, so I don't know exactly how to control it automatically. It could do cell modules, but not packs. Then I have a couple of transformers in Lestronic II PbSO4 chargers 24V 25Amp, and 36V 30A. And I have a 480V:120V 7.5KVA transformer that ought to be useful somehow. It is a start. If I can get any funding at all, I think knowing the power and load needed for the most probable testing, and getting good equipment to provide those would be smart. I think I also want some reference standards. But, I might make them, or settle for the calibrated DMMs. Mike On Thu, Nov 6, 2014 at 7:48 PM, Roger Stockton via EV <email@example.com> wrote: > 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) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison <http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk michael.e.r...@gmail.com <michael.e.r...@gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20141106/b554aba8/attachment.htm> _______________________________________________ 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)