Excellent, Roger, Thank you.

On Thu, Nov 6, 2014 at 7:08 PM, Roger Stockton via EV <ev@lists.evdl.org>

> 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.
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