The battery on my Vue ISS lasts about a week now. I have a spare ISS and compared the battery current draw whilst charging the capacitors, indoors without the solar cell going.
The battery of the problem ISS charges the supercap (after it's fully charged) every second or so at 25mA whereas the charge top up on the good ISS lasts a lot longer before it drinks a lot less from the battery again. So I decided to replace the supercap, hoping this will solve the problem.
Being a G version ISS (round cables instead of ribbon cables) everything is potted at the transmitter so I decided to dig out the supercap using a a router. Unfortunately on the second pass I slipped a bit and also took out part of two adjoining capacitors.
The reason for this post is to let people know that it would have been possible to just dig out the supercap after one pass and not have the extra work of replacing the two 1000uF 6.3v caps.
Attached is a photo of the mess I made which I hope others can avoid.
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I plan to replace the 10F supercap with one rated at 50F which should give approximately 7 days' worth of charge (according to an ebay listing). Interestingly, this link compares the storage capacity of a 3000F capacitor bank to a 2500mAh AA rechargeable battery and they're nearly equal.
https://www.instructables.com/id/Supercapacitor-Solar-Box/ [ You are not allowed to view attachments ]