I thought the USPS was stopping Saturday deliveries at some point, but low and behold my Lowly 10 turn 1K ohm pot came today, Sunday, along with my Solder Wick, and Arctic Silver 5 thermal grease and a pair of flush cut wire nippers.
Never used Solder wick before, and my soldering skills are nothing to brag about, but they are improving.
Some red stuck to the black wire. I made this lead pretty long and this is by no means final. I still need to design a method to mount the new pot.
This shows which wire went where on the circuit board. I made sure that clockwise turning of the pot reduced resistance, like the original trim pot.
Looks like I used a little too much pressure and time wicking out the old solder. Macro photos reveal all.
The third leg of the trim pot was being difficult, so I just bent it over and snipped off the 3rd leg which is just a second ground. Now It is lopsided. It measured a maximum of 984 ohms after removal from circuit board. It measured 872 ohms while still in it.
Here's a less zoomed in photo.
The new pot measured a max of 1023 ohms. Wonder if it will allow lower voltages, not that that is a concern, just a curiosity. When testing it, there were a couple spots where the ohms jumped up a hundred and than back down throughout the 10 full turns, but they smoothed out the next pass and were gone on the third. The dial is not perfectly smooth to the feel, not buttery smooth, perhaps butter with a little bit of grit.
Increasing 1 single ohm with this pot is simple.
So onto the heatsinks. Many posts ago, in a universe far far away, I noticed that the heatsink was not sitting nice and flush with the casing. A straight edge revealed why.
I filed both heat sinks completely flat on both sides, and deburred the edges.
My Middle name is overkill. I then wet sanded them on a piece of glass with 220, 400,600 and then 800 grit sandpaper. They were practically mirrors when done. I managed to stop myself before busting out the finer grades of sandpaper like the 1000, 1200, 1500 and 2000.
The file also revealed the screw holes in the casing were also also raised. They got the same treatment as the heat sinks. Nice and flat and so smooth a baby's bottom would be envious.
Arctic Silver 5 is strange stuff. Never felt any grease like it, but followed their application directions to a T. It is kind of sticky and spreads with a razor blade very easily to an even thickness. I expected more difficulty in this area but it was almost rewarding.
Anyway since the heatsinks now are perfectly flat and mating with the now perfectly flat case, with the thermal grease, I expect to get higher temp reading on the exterior of the casing with the unit maxed out, indicating better thermal transfer from the MosFets.
Before, there was likely very little direct contact between the heatsink and the casing. No idea if this will affect output but should make for better longevity.
My flooded 31 is reading 36ah from full, 12.12v under a 6.6 amp load. Not as impressive as the AGM. Hoping to see higher case temps when maxed out. Kind of eager to play with the new 10 turn pot.
