Friday, January 18, 2013

Sample Simulated Charging runs

Have been making good progress and thought I would share some early results.  The following graph shows  the results of a charging run using the UNO based DC Generator simulator as the 'load':

Example Watts delivered by Smart DC Generator Controller (Top line)

This shows many details, but the one to focus on is the top line.  It is the amount of Watts being delivered by the generator into the battery.  (Remember, this is all using a UNO based DC Generator and Battery simulator, see next post below).    Other lines shown include Alternator AMPs, Battery Voltage and  several internal values (including that area the bottom - this is an indication of how much the controller is 'backing off' of the Field PWM drive.)   Sorry for not removing the extra items, just got lazy.

Over all I am very happy., though some issues can be seen.  If you focus on the Watts you can see some spikes in it - I need to work to fine-tune those out.  It might be an artifact of the Simulator (and esp as the Simulated battery charges in 30 minutes while a really battery would normally take a few hours), or it could be because the sensitivity levels in the controller are too high.

And here is the best news:  take a look of this simulated run where the controller was configured to respond more like how one of the normal '3-stage' regulators behave:
Example of Watts typically delivered when using a common 'smart' external 3-stage alternator regulator.
Note the triangle of 'Unused Capacity'

Notice that triangle of 'Unused Capacity'?   That was one of the basis for this project:  to eliminate the wasted resource and increase the overall system efficiency.  As Watts is the true indication of a load being placed on the Kubota engine by increasing Amps during the early stages of generating (while the battery voltage is down) we are able to increase the energy delivered into the battery, and thereby reducing overall generator time.

Over a typical charge cycle we might be able to reduce generator run time 10%.   And there is another opportunity for increasing overall system efficiency:  Alternators are more efficient at lower RPMs.  Because we measure Amps this controller can be used with a much larger alternator and intelligently 'cap' it.  For example, I will be looking at swapping out the current 135A alternator for a 200A unit - changing the pulleys to spin this new alternator at about 1/2 the speed.

Stay tune for this one, but early indications is by spinning a larger alternator slower I can gain 10-15% in overall system efficiency.   Combined we will cut generator time by up to 25%, AND saved 15% or so in fuel cost at the same time!

Well worth the effort!

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