Over this past weekend I installed the ESC Coolers on the MK BL's on the top of the MK PDB. I used the arctic silver to seal them and let it sit for 2 days to cure even though it setups up really good in a few hours. Installation was very easy but took me about 3 hours as I removed the PDB and masked everything around the mosfets. With the 7D on the CS8 in 80 degree weather my BL's didn't reach 80 degrees until I hovered for 3 minutes. They didn't reach 90 degrees until I hovered without moving for a little over 4 minutes which I think is really good. Not too many applications where you need to hover without moving for that long of time. It's definitely an improvement but how much is hard to say because it was pretty dry air. I see a huge difference in BL temps when its more humid as I'm sure a lot others do even when its just 80 degrees out. Before I added the coolers I could reach 85 degrees in a hover of close to a minute with a GAW of 15 pounds. I also noticed that once I started getting air flow moving through the PDB via skating the copter side to side I could get the temps to cool off much faster. For those that are on the borderline edge for their BL temps I really recommend the coolers. Has anyone put the heat sinks on the bottom MOSFETS? I'm not sure if there's enough room for them in respects to having enough surface area on the MOSFETS because of the way the caps are glued. I might have to break the seal and then reglue and not sure if it would hurt the caps by breaking that glue seal. I don't want to mess with it if I don't have to. I wonder how thel bottom MOSFETS are effected with the top MOSFETS being cooler. IF you can hover for a longer time because the top MOSFETS are cooler and you do nothing to the bottom MOSFETS, I would imagine the bottom mosfets would continue to go higher. Does anyone know how MK determines the BL temp? Is it an average of all the MOSFETS? IF it averages all the mosfets that would be a good indication that the bottom MOSFETS are not increasing and that the overall temp of each MOSFET is more of a complete circuit efficiency. I also ordered the same Fan that Josh used and give it a try. I ordered 60mm standoffs for the battery tray to give me the extra clearance needed. I'm going to bolt the fan to the battery plate. I"m going to run the fan on a 2200 battery and see how fast it takes the battery down.
Dave I had them on top and bottom. Didn't move the caps for the bottom install. Just mounted them to they were up against the caps and hung a little over the opposite side. Never did really see much difference overall. Send went to 100C on a 90 degree day regardless of movement. Really like getting away from that limitation with separate ESC's like the Castle ICE series of the FF Motor control set. Flew yesterday. OT was about 30C and my ESC's measured 35C with the IR temp gun.
Dave: I raised the PDB up a bit using some neoprene tube "washers" on the 15mm hex standoffs to give extra space. There was just enough room to mount the heat sinks on the lower MOSFETs without having to shift the caps over -- the concern being less the caps but damaging the surface mount components to which the caps are effectively glued. Even if the heat sinks are offset slightly, they will provide additional radiative surface area. I can't tell you whether having the top MOSFETs cooled by heatsinks will also cool the lower MOSFETs -- the concern being I don't know what the thermal conductivity of the interposed fiber-glass circuit board is. My guess would be that it would not conduct particularly well. You don't need to mask around the MOSFETs. The Arctic Silver is non-conductive -- but don't slather on too much. As for the fan: 1. Be sure to twist the power supply wires to reduce the EMI. 2. Position it so that it's distant from the NC board with the compass, just in case there are stray magnetic fields. I would put a LiPo alarm on the 2200 battery. If you over-discharge the LiPo below 13v you'll have a LiPo paperweight on your hands. Andy.
No concern about potential Noise the fan will create? I put a small fan near my 1.5Watt transmitter because the bird was going to fly, land and observe for 4 hours then fly back, DARPA UAV competition last may, and it induced a bit of noise into my video feed, making static. I was able to get used to it but there defiantly was noise being created and this was a small 1"x1" fan. Your talking about a 120mm computer fan! Also about temps, 2 weeks ago when i was in Kuwait we hit 126. I didn't go outside unless I HAD to!
Thanks for the info on the bottom of the board. Interesting you didn't see much of a difference. Do you remember your GAW at the time?
Good idea about the lipo. I masked the board as the directions suggested to do so because the silver can induce a slight amount of capacitance. Did you notice a difference with the coolers on?
Hi Paul I wouldn't say I'm overly concerned, I view this as an inexpensive test. I"m just trying to maximize the MK stack for the rest of the summer and buying time until Synapse comes out. Until I hear otherwise I'm going to go on the assumption that Synapse might not be released until late next year (or even later) considering the success they are having with the MOVI. Releasing a new flight control system with nav and GPS is a huge undertaking that will take a lot of resources I"m sure. So I'm just going to do what I can to get by. IF I twist the fan power wires and have them come out the back toward boom 5, noise shouldn't be a concern. There's a fan on my extreme mondo that doesn't induce noise but its obviously not 120mm. If the fan causes issues then I"m only out a total of $30 bucks.
Interesting your only about a half pound heavier than me. It will be interesting to see what happens in more humid weather. The coolers probably won't be enough by themselves.
Got the fan in yesterday. The good news is that its drawing very low current. I ran it on a fully charged 4S 2200 lipo that I use to power the nav lights. I ran it for 35 minutes and it only took the voltage down 0.2 of a volt. It also pulls pretty good air through it and since the BL's will be so close I think its going to really. The bad news is that its really going to be a tight fit. I do not know if I will have enough clearance between the fan and the new ACC sensor. I'm using 55 mm standoff's for the battery plate and even went back to stock standoff's for the flight control board but its right up against the sensor. I ordered 60mm standoff's which will give me a tad more than 3/16" clearance but I wanted a little bit of space between the fan and the battery tray to help pull air through the fan. It's going to be tight.
Got the fan mounted and installed. I also installed the 60mm battery plate standoff's. I have just enough clearance between the fan and the new ACC sensor on the flight control board. I mounted the fan to the bottom of the battery plate using 1/8 aluminum. It's a bit overkill but I didn't want any flexing on the fan that would put the fan up against the ACC sensor. I also have about 3/16 of an inch between the top of the fan and the bottom of the battery plate so that it has enough space to draw air in to push down on the power board. I have it powered up and its definitely blowing a good amount of air on the Power board. I will do a full fights back to back with the fans on and with it off to see how it affects the motor temps. Just waiting for mid afternoon where the outside air temp will be the highest.