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.

Step 1:

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

93% efficient

Mean time before failure: Calculated to be over 5 million hours.

Short Circuit Duration: continuous, No damage.

Input reverse polarity protection (external fuse).

Step 2:

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.

Links:

400 Farad Super Capacitor Flashlight:

https://www.instructables.com/id/400-Farad-Super-Capacitor-Flashlight-Build-This-/?ALLSTEPS

http://www.futureelectronics.com/en/technologies/electromechanical/power-supplies/dc-dc/Pages/1010233-OKR-T-3-W12-C.aspx?IM=0

http://www.murata-ps.com/data/power/okr-t3-w12.pdf

My only complaints about this converter are:

1. The lead spacing is smaller than 10^th 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.

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