Outback Power Flexmax 80 Modification

As mentioned in my previous review, my FLEXmax 80 did need some work done last week, due to the failure of the internal fan. It failed simply because it was running at full speed since the beginning of November and the temperature inside the garage was higher than normal.

Because I run solar panels for the length of the entire vehicle, Gigi is always parked under the sun. While the entire unit is insulated, the garage has no windows, but only two louvres one on each side of the vehicle. That does provide some cooling, but not much, especially if there is no wind. As it turned out, the temperature inside the garage has been hovering around the 40-45 degrees the entire summer.

While that is not a real problem, as the F80 can still run at those temperatures, it does start to derate at 40° Celsius, but more importantly, those temperatures are not really healthy for the rest of the electronic components inside the unit. I need it to either make the room cooler or aid the F80 cooling capacity. In the end, I opted for both solutions.

Regarding the garage, I managed to install a radiator fan into one of the louvre that will be controlled by the usual thermal switch.. For the F80 I had to work a bit harder and spend a bit of money to make it “compatible” with my garage internal summer temperatures.. As mentioned in my review, the F80 is made of very thick aluminium and for a good reason; the entire unit body does act as a massive heatsink. While this solution is more than adequate for home’s installations, in my case, between the internal garage temperature and the temperature produced by the unit, things got a fraction too hot.

In the first picture you can clearly see that a thick aluminium plate going all the way from the back side of the unit to the front part. That’s why when the unit is on, the entire assembly gets hot as the outside shell is the actual heatsink. Because of this feature, it was pretty easy to add more cooling capacity to the unit. At first, I got from Jaycar two of the larges one they sell (Part N. HH8532), thinking that it would have been enough. To install them I simply drilled 5 holes in the F80 back shell, by paying attention of where the internal components were located near the frame, and then using some mushroom head bolts to screw them into the corresponding five threaded holes that I made into the heatsink. I also applied a nice amount of thermal paste between the two before tighten the bolts.

Thinking that it would have been enough, I re-installed the unit, and while there was a nice improvement, it was simply not enough as with the garage door closed, the unit was still getting around the 53°. Just to recap those temperatures..

The garage room got too 44° at its peak. The F80 also produce its own internal heat and the wall the unit was mounted on, also has a bit of heat refraction from the outside has there is no insulation in that part (rear of the vehicle). All this combined was taking the F80 at a working temperature of 61°, way too much for it to work properly. The fan was the first thing that did fail, so I did replace it with the same unit (NYW06025012BSS).

After waiting for the hottest part of the day I went to check the temperature of the modified F80 and found that it was still working at around the 53°. So I decide to go for the full Monte. Back to Jaycar for two more heatsink (they can slide on each other and make a single unit), and two new fan as well (YX2523).

Back to the unit I glued the two extra sink in position and then installed the two new fan. For powering the new fans, I originally intended to use the AUX port of the F80, but upon checking the manual, I realise two problems with that. Firstly the AUX only provide 200mA of power but more importantly there are no setting related to temperatures, but only power or states of the unit, making the AUX completely useless for this situation.

I also realised that I had no 12Volts in the Garage but only 24 and 240Volts. Luckily I had kept one of the two Power converter that were originally installed under the dashboard. Finally, I connect the two new fan to a thermal switch located on one side of the F80 that is set at 40°.

The unit now in the hottest part of the day sit on 42°, that while is still a bit too high, is nowhere near the 61° it endured previously. I’m waiting now for some new thermal switch that are actually set at 35°. I will replace the 40 with the 35 and see if it makes the difference. I haven’t connected the radiator fan mounted on the louvre yet, but if I can’t to 40° with the modification, I will then finish the connection and see how it goes.

In the last two pictures, you can see the top and bottom of the extra heatsink and how they slide into each other. The fan would have probably been enough to hold them together, but because of the Australian road’s conditions, I didn’t want to take any risk, and cement glue the two half sink together.

If you too, have a F80 or a F60 unit in your vehicle, you may want to check the working temperature at the hottest part of the day as you may need to help the unit cooling a bit, so not to derate too much and loosing most of your solar power. In the manual there is no description of how much or how quick the derating of the unit goes, but it just mentions that it start at 40° on page 5 under features..

Please also note that the FLEXmax 80 does have the error “Over Temp” that will be displayed if it gets way too hot. When the unit was working at 61° C, it still did not display such error, and yet at page 93 of the manual it states that the operating temperatures are 40° to 60° … Frankly, unless my laser temperature thermometer is faulty, I’m not willing to find out at which temperature it does/will display the error!