I do not want to use a battery in my circuit. My circuit would contain some charged super-capacitors and voltage regulators.
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2 Answers
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You can, but there some some gotchas that you need to be aware of.
- Supercaps are rated for low voltages, often 2.5-2.7V. Any you find rated higher than that are either not really supercaps, or are multiple supercaps in series in the same package. If you put them in series yourself, you'll need to do some analysis to determine whether balancing is necessary. Balancing can drastically increase your leakage.
- Cell relaxation is a real phenomena. If you charge a supercap up to its rated voltage, and remove power, with no load, it will discharge to ~60-70% of its rated voltage in less than an hour. This effect can be minimized by holding the cap at the charge voltage for a period of time.
- Leakage current can be significant. Check the datasheet of your caps to see what the leakage current is, and under what test conditions it was measured.
answered Sep 25, 2016 at 2:15
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\$\begingroup\$ Thank you. That makes sense. I want to use those charged super-capacitors for low power switching purpose. \$\endgroup\$ Sep 25, 2016 at 3:00
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You can. You will have to make sure that you charge this supercap correctly. Although it's not a battery, some rules apply. Mainly you have to control/limit charge current.
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\$\begingroup\$ How can I control/limit charge current? My planned Circuit follows like this Super-capacitor, Voltage regulator, Op-amp/Transistor for switching, LEDs. \$\endgroup\$ Sep 25, 2016 at 2:56
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\$\begingroup\$ @Mat_python Gregory is talking about charging the capacitor, not discharging it. That will probably work fine for discharging. But supercapacitors start "flat", unlike batteries, so you're not going to get any power out of one without charging it first. \$\endgroup\$ Nov 1, 2016 at 8:58