These ultra or supercaps are pretty cool alright, had been playing around with them a bit some time ago.
They are indeed used as backup instead of batteries and would seem ideal, but here are a few things to consider:
- they are low voltage components and most of them only work up to about 2.5V. They are really fragile when it come to overvoltage too, so be careful. I suppose using two in series would give the 3.6V used by many Macs.
- most Macs (I think???) aren't able to charge backup batteries, so you'd have to manually charge the cap /wire the correct voltage to the battery holder. Like normal caps they can be charged virtually instantly if the resistance of the charging circuit is low.
- this would probably only work if the computer is used relatively frequently, having a Mac sitting in the attic for years will most likely drain the cap quicker than a battery (even though caps have high energy densities, the capacities are usually lower than batteries).
- biggest problem though is that the voltage across the cap drops as it discharges so at what point will the circuit stop working? At 3V? I have no idea but you would probably need a voltage regulator as well. How long will a 1F cap last? I have measured the current draw in an LC to be 20uA, but it depends on the resistance of the load / circuit and the cut-off voltage at which point the circuit / voltage reg stops working. Would be interesting though!
Would be a nice project
They are indeed used as backup instead of batteries and would seem ideal, but here are a few things to consider:
- they are low voltage components and most of them only work up to about 2.5V. They are really fragile when it come to overvoltage too, so be careful. I suppose using two in series would give the 3.6V used by many Macs.
- most Macs (I think???) aren't able to charge backup batteries, so you'd have to manually charge the cap /wire the correct voltage to the battery holder. Like normal caps they can be charged virtually instantly if the resistance of the charging circuit is low.
- this would probably only work if the computer is used relatively frequently, having a Mac sitting in the attic for years will most likely drain the cap quicker than a battery (even though caps have high energy densities, the capacities are usually lower than batteries).
- biggest problem though is that the voltage across the cap drops as it discharges so at what point will the circuit stop working? At 3V? I have no idea but you would probably need a voltage regulator as well. How long will a 1F cap last? I have measured the current draw in an LC to be 20uA, but it depends on the resistance of the load / circuit and the cut-off voltage at which point the circuit / voltage reg stops working. Would be interesting though!
Would be a nice project