Michael Ross wrote: > 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.
Thanks for clarifying that this is NOT a personal project, but a commercial one. I think you will find that if you are doing testing for hire, that there is significant value in the credibility that comes with using professional grade commercial equipment versus explaining to the client that the coat hanger in that garbage can full of water really is a sensible piece of equipment for the test they are paying you to execute ;^> The cost effectiveness for smaller clients comes from *you* bearing the multi-$1000 investment in a proper active load and data acquisition and control equipment and possibly power supplies (for charging), and then recovering the cost over multiple clients and over time so that they have access to this level of test capability, when needed, for a much smaller up-front or per-instance expenditure. If you are able to consider sufficiently large electronic loads, then ones that can push the energy back into the grid rather than dissipating it as heat become an option. This capability doesn’t really become available until you are looking at loads of at least 6kW, and you should check with your local utility to see what sort of barriers will face you in trying to connect such a load before buying. > 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. Great! For battery testing you generally don't need particularly fast scan speeds. I'm not sure just what your 6.5-digit DMMs are, but they sound similar to the Agilent units I use for battery testing. It is particularly nice that they can directly measure pack and cell voltages as well as shunts and thermocouples for monitoring temperature. As long as the number of channels you are scanning isn't too great, it is possible to get at least a few readings per second in the uncommon event that your test requires it. More typically, recording data at 1-10 second intervals is plenty fast for battery cycle testing. > I won't need PLCs. Also great, though I referred to use of a *PC*, same as you will use to run your LabVIEW application to control things ;^> > 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. The power supply sounds like it could be useful, especially if equipped with IEEE-488 and if a LabVIEW driver is available for it. The transformers sound less promising, at least for this purpose. Really, it comes down to the sort of clientele you will serve and what sort of testing they require. They may want you to test specific cells/modules, either recharging them using a provided charger or using your programmable supply to implement some specified charge regimen. You may need to consider investing in water baths to maintain consistent temperatures throughout the test pack, and/or an environmental chamber to allow testing at elevated or reduced temperatures. If you are going to test Li chemistries, especially at high rates and/or elevated temperatures, investigate the safety requirements for appropriate fire suppression and ventilation, etc. If you will be testing flooded lead acid, investigate the spill containment and personal safety requirements (eye wash, emergency shower, etc.), as well as hydrogen sensing equipment and ventilation requirements. A properly equipped (inert gas purge, explosion proof locking door, suitable pressure relief fearture, possibly reinforced to handle the weight of larger (especially lead-acid) packs, etc.) environmental chamber runs about $60K, so once again part of the value provided for smaller clients is the ability for them to avoid the need to make this sort of investment in test equipment. > I think I also want some reference standards. But, I > might make them, or settle for the calibrated DMMs. The route you choose may depend on what you already do for other equipment in your lab, however, the approach we've taken is to maintain the calibration on the DMM/data acquisition units and rely on them to control the loads and power supplies so that the loads and power supplies themselves don't need to be kept calibrated. Cheers and good luck! 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)