Quote:
Originally Posted by Ecky
Edit: my electrical theory is a bit weak but isn't it the case that since capacitors self-discharge, leaving one connected to the battery all the time would eventually drain it?
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The self-discharge is minor, and rapidly decreases as you back away from the peak rated voltage. 6-series connected BCAP model capacitors are rated to 16.2 volts. Assuming your LiFePO4 is maintained around 14v by the alternator, that works out to 2.33v per 2.7v rated capacitor. The drain will be practically nothing. I bet your alternator would shoot for an even lower voltage; somewhere around 13.5v.
Your biggest concern is the electrical draw when the vehicle sits unused. Pretty easy to measure your phantom power load and then divide your battery mAh capacity by that number to determine how many days of sitting parked the battery would sustain.
I had put together a very crude spreadsheet back when I had more time to work on this stuff. I'll try to update it and make it more user friendly sometime.
Check out the TSX tab on the spreadsheet below. My car draws 21 mA when parked. On a 4200 mAh battery, I can park for 6 days before needing to start and charge. On a 20,000 mAh battery, I can go a month.
https://docs.google.com/spreadsheets...it?usp=sharing