For the majority of people this post will be worthless but for the more technically inclined/amateur electronics engineers it might be worth noting.
Ok in one of my previous posts I mentioned that I had ordered some ultra low E.S.R capacitors that I had intended to tie into my MMM to further increase the total capacity.
(For the results skip to the end to avoid the technical blabber)
The MMM has built into it a total of 3 35v 390uF Capacitors that i'm fairly sure are also low E.S.R. capacitors. Upon reading with my Fluke 115 actual capacitance was in the neighborhood of around 1290uF. That's actually more than rated so that's good.
Now to my experiment...I figured if the MMM is so deathly (read: death=fire) afraid of ripple current why not help the situation so I used two 35v 680uF Ultra Low Esr Caps that I ordered from Jameco as a pack of 10 and wired them in parallel to net a total of 1360uF, actual measured of about 1421uF, which are again higher than rated so also good components.
Alright taking into account that just as in the case of resistors and their parallel resistance being reduced by half, I figured if two caps are connected in parallel then just the same their E.S.R. should theoretically be reduced as well. (Here is the formula if you would like to see it for resistors).
For equal resistance values;
This is for unequal value resistors;
Ok so on with the experiment.
So after wiring in all the caps in and getting everything connected to my satisfaction (took some extravagant soldering techniques that resembled a yoga position trying to hold everything in place without being burned) I came up with a total capacitance of 2714 max. Im sure my CC UBEC also played a part in that last figure also to some extent. I doubled the overall capacitance in the circuit.
So far with the results I haven't been able to do any extesive testing nor did I get temperature readings of the esc before doing this mod so I cannot give any hard evidence of lowering the temperatures any but what I can say is that after just about 5 minutes of running with a gearing of 18/56 with 4s through my front yard in some low grass/damp mossy areas with really good traction, the external caps that I added actually do get above ambient temperatures showing that they are in fact doing their intended purpose of helping to filter out ripple. But whats more interesting is that if these caps are getting slightly warmer than ambient then its no wonder that the MMM can fail due to ripple current because as the internal caps heat up with their own internal heat and heat from the fets as well, the electrolyte starts to boil off decreasing the available capacitance and fail. As the caps fail the MMM loses its built in ablity to filter ripple current. Its just a chain reaction that starts at the front (battery input - caps) and causes failures longer down the line (motor phases - FET's)
Sorry for the long read, my friends tell me I like to go into detail too much, I tell them without details the world is just a dull fuzzy place