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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: orange on December 09, 2015, 07:13:46 AM
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It seems the super capacitors aren't so expensive anymore. Is any extra electronics needed or are they 'drop in' replacements for clock battery?
I'd buy 1F or 1,5F; 5,5Volts, are those ok?
thanks.
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Last time I looked there was not a super capacitor as a drop in replacement. They need extra electronics to be used because of inrush current and over voltage protection.
They do not have near the storage time or capacity as a battery.
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Last time I looked there was not a super capacitor as a drop in replacement. They need extra electronics to be used because of inrush current and over voltage protection.
They do not have near the storage time or capacity as a battery.
Agreed. For a start, look at something physically compatible such as this (http://nz.element14.com/cornell-dubilier/edlsg155h5r5c/capacitor-super-1-5f-5-5v-30-ohm/dp/1364211) (5.5V, 1.5F). Look at the associated datasheet for the maths. Sorting out the charging is easy enough. Regarding the backup (discharge) time for running the RP5C01 Amiga real time clock (I=15µA), you'll get 78 hours = 3.2 days backup time at best. By comparison, the standard 80mAHr Ni-MH battery will provide around 200 days or 6 to 7 months backup.
A lesser known fact about many super capacitors is that they can age rapidly. Read the datasheet mentioned above for details, but essentially this can be 3 to 4 years.
The rated lifetime of a Varta 3/V80H Ni-MH battery is around 6-7 years. So long as you replace the battery before it reaches end of life, there's a low risk of leakage issues.
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And they have a pretty fast self discharge rate.