[brucepick]

Was it worth it? Well, I'm an OCD fuel economy fiend so if I can increase mpg, I'm a happy man. I got a $260 "jump" on the overall cost from the money I got when I junked my old Volvo 240. What I didn't face at the start was that the whole cost would run between $600-700, far more than what I got for the Volvo. The battery was $459 + charger about $45 + about $50 shipping, if I recall. Plus cables, and some money to my buddy to run it from engine bay to the rear interior area.

Yes, nearly 10% gain in the four most recent fills. My last fill, not yet in the log, is about 53.x mpg so not quite 10% but still very nice. I think that will go up again, after I deal with weather-related changes - lean burn issues due to too much grill block for this warmer weather.

Yes there's an alternator cut. I put a disconnect switch on the main battery + terminal. The switched side of switch goes directly to the alternator [not via starter], so I can have the alt connected or not with a quick trip under the hood. The [other] side of switch goes to the battery + and to the starter, so starter is always powered by the main battery. The old oem wire from starter to alt is disconnected at the alt and taped over. If you haven't studied the circuit diagram, just understand that the new LiFePO4 cell + terminal is wired to the main fuse box from where it powers the car's electrical system. However it doesn't power the starter, as noted just above.

I first attempted an alternator cutoff by disconnecting the small four wire "control" connector at the alternator. Within a couple minutes of startup, it was putting out 14V anyway, charging the battery. So I had to resort to disconnecting the alt's main output wire instead, at the alternator. I left the control wires connector disconnected also, no sense powering the field coils etc. if I'm not running it.