One relatively cheap way of doing high power cycle testing is to cycle power between a large battery bank and the test battery using a bidirectional DCDC converter.
The DCDC is simple since it's just a switching pole with an inductor and some controls. A DC motor controller with regen capability can be used as the DCDC converter, the controls should have a constant torque (current) mode for it to be useful. On Fri, Nov 7, 2014 at 9:54 AM, Michael Ross via EV <ev@lists.evdl.org> wrote: > Thank you , Lee. > > Some concerns about cost may drop away because I am not aiming at > automotive EVs - for now , maybe never. > > Because I need to go for some grant funding, I have to be aimed at > manufacturers - job creation is what everything is about these days (I > don't disagree). The automotive manufacturers will likely build their own > labs. But, the LEV (and smaller) market is in need of some help. > > I think electronic loads are a good idea, but I will have to roll my own > stuff for a while; that will be a good learning experience I am sure. > > Just guessing, I suspect I can do a lot with 50A of current and load. > 6000W is pushing 10 HP. Electronic loads that size would be costly. > > I need to sort this out better though. I am trying to put together a > survey to collect information about testing people need but can't do, > testing they would far out if the cost was right, and so on. I need a > range of packs sizes in this space. I know there is still some lead acid > being used, so I probably need to consider that, but the arc of the future > is probably Lithium batteries. > > I am already set up to use National Instruments DAQ and Keithley DMM > instruments. I already program extensively in LabVIEW, so we will stick > with that (also the university has a site license for it). We get an > academic discount on hardware and NI has an extensive array of choices. > > I am still interested in seeing DIY setups - that is always very > instructive. > > > > > On Fri, Nov 7, 2014 at 12:30 PM, Lee Hart via EV <ev@lists.evdl.org> > wrote: > > > Roger has some excellent advice here. It reflects a lot of what I do > > myself. :-) > > > > Roger Stockton via EV wrote: > > > >> Thought I'd mention that while a programmable load is an *excellent* > >> way to discharge when testing batteries, it can be pricey... > >> > > > > Indeed. Programmable loads get very expensive if you are dealing with > high > > power (high voltages and/or high currents). They are also effective room > > heaters. Good in Minnesota winters; but bad in Arizona in the summer when > > you're already paying to air condition. > > > > 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. > >> > >> A simple QBasic program on an old laptop controlled the relay for > >> the load and another for the charger via the parallel port. > >> > > > > This is the approach I use. I have a couple of $50 DAQ118 analog/digital > > I/O modules that plug into my PC. They have several 12-bit analog inputs > > (to read voltages, currents, and temperatures), outputs (to throttle the > > charger, and digital output channels (operate relays to select various > > loads). > > > > They are run by a PC with software written in QuickBASIC. I have an old > PC > > that is too slow for anything modern; but has a parallel port and is > > rock-solid-reliable and can run tests for days. > > > > These modules were bought in 2002. I'm not sure if they are available > > today, but there are lots of equivalents. > > > > I also have a Keithley 576 Measurement and Control system. This is a > > stand-alone data acquisition controller. Rather tedious to set up, but > lots > > of channels, high precision, and very versatile. > > > > I use these with a commercial battery charger for charging, and a custom > > made load box that basically consists of a bunch of big power resistors, > in > > a box, with a fan, and relays to select the load resistance in a stepwise > > 1-2-4-8 sequence. > > > > I started out with a battery cycler setup consisting of a bank of 12VDC > >> Edison-base (household screw-type) light bulbs > >> > > > > Light bulbs are a good *and* cheap load resistor. :-) As Roger says, they > > have the useful feature of drawing a roughly constant current despite > > changes in voltage. This is a simple way to get an approximately constant > > load current despite the sagging voltage as the battery discharges. > > > > I've used car headlights (about 4 amps each) and taillights (about 1 amp > > each) as load resistors for 12v battery testing. > > > > 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. > >> > > > > This describes the most common load tester I use. I have a few E-Meters / > > Link 10 / ProLink meters (all the same meter, but sold respectively by > > Cruising Equipment / Heart Interface / and now Xantrex). These measure > > volts/amps/watts/amphours/watthours/time/temperature and send the data to > > a PC via an RS-232 serial port. I have a QuickBASIC program that logs, > > plots, and prints the data. > > > > The "controller" is an old Manzanita Micro "Rudman Regulator". It has an > > output that switches a relay to select between charge and discharge, and > > trimpots to select the max and min voltage at which to switch between > > charge and discharge. This setup has been documented in the EVDL > archives. > > > > I also built my own stand-alone battery tester/cycler, which includes the > > charger, constant-current load, and metering for volts, amps, amphours, > > temperature, etc. It is documented at > > > > http://www3.telus.net/nook/balancerland/cycler/index.htm > > > > This stuff is not exactly "hard" to build yourself, either from scratch > or > > cobbled together using whatever you have on hand. But it does take a fair > > amount of time and effort to sort it all out and figure out how to use > it. > > -- > > A designer knows he has achieved perfection not when there is > > nothing left to add, but when there is nothing left to take away. > > -- Antoine de Saint Exupery > > -- > > Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.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) > > > > > > > -- > 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/20141107/65c7de7c/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) > > -- www.electric-lemon.com -------------- next part -------------- An HTML attachment was scrubbed... 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