Intro: 93% Efficient DC to DC Converter
I needed a better way to charge Super capacitors so I wired up this DC to DC converter. I was using a linear regulator which would have worked fine except I was regulating 12 volts (off a car battery) down to 2.5 volts. The regulator was getting frying hot and was very inefficient.
This converter is one from the Murata OKR series. I used part number
OKR-T/3-W12-C. Here are some of the specifications:
Input voltage: 4.5 - 14
Output voltage: 0.591 - 6
Output amps: 0 - 3
Output watts: 15 max
Mean time before failure: Calculated to be over 5 million hours.
Short Circuit Duration: continuous, No damage.
Input reverse polarity protection (external fuse).
It works great. It does not even get a little bit warm in my application. I charge a 12 volt car battery in the garage with a 5 watt solar panel on the roof. I charge the super capacitors (400 farad and 2600 farad) using this dc to dc converter. In input and out put jacks are RCA type. I had to use 3 resistors to come up with the correct resistor value for 2.5 volts out.
400 Farad Super Capacitor Flashlight:
My only complaints about this converter are:
1. The lead spacing is smaller than 10th inch so I had to solder wires to the pins.
2. It would be helpful if Murata made one just like this one but with a higher input voltage like 24 volts so I could run it directly off a solar panel.
3. When charging up a super capacitor for the first time or charging a super capacitor that has been discharged below about 0.4 volts. The chip does not operate at that low of a voltage. If you get no output due to these conditions you can charge up the capacitor with a D cell battery. I charged a 400 farad capacitor flashlight with a d cell when the capacitor was run down to about 0.3 volts. I had my flashlight switched on during charging and the LEDS turned back on in less than 30 seconds. I finished the rest of the charging with the dc to dc converter after that. I use the super capacitor flashlights all the time and I am charging up one of them at least once or twice a week. I have only needed to do the D cell jump start once in the last year. That was because I left it on all day by accident. The flashlights are good about letting you know it is time for a recharge because the start to get a little dim.
See all of my instructables here: