Well, you don't. The Cobra CPI 480 just might be the biggest piece of shit we've ever spent money on. It failed after one month, when all it was used for, other than one short session with the Dremel tool, was charging a laptop. When I measured zero ohms across the input terminals, I knew it was toast. We took it to a repair shop in the small town of Villa de Leyva, Colombia. The repair shop was only the size of a double wide toll booth, yet there was already another Cobra CPI 480 on the shelf, waiting to be repaired.
It had the same problem as mine, a blown transistor. Lucky for me, these inverters use a pair of these transistors. The repair guy pulled the good one from the other inverter and soldered it into mine. Of course, it's obvious that Cobra has a class problem, so who knows how long these transistors will last. The repair guy recommended some better transistors that I could use when these fail, but he didn't have any in stock, so we'll be on the look out.
When we got back to the truck, I googled "Cobra CPI 480 review". PC Magazine gave it 2.5 instead of 3.5 stars because 2 out of 3 test units failed. The first one failed after 2 days, and the second failed a week later. WTF? Failure of 2 out of 3 test units should earn you 0.0 stars. PC Magazine also claimed that the Cobra was made of black plastic and aluminum. Uhh, no. It's all plastic. The middle part is just painted to look like an aluminum heat sink. In reality, it's a thick plastic thermal blanket, the opposite of a heat sink.
From the start, the Cobra irritated us because the fan constantly cycles on and off. Cobra's documentation says this is to prolong the life of the fan, which it might do, but not really important if the transistors fail because they aren't getting properly cooled! Since we have a backup fan that I pulled from our old inverter, I rewired the Cobra to run the fan all the time. I also drilled multiple vent holes and slots in the plastic housing to improve cooling.
|Looks like aluminum, but it's not. Holes and slots added to top and side.|