Quote:
Originally Posted by cr45
Is this for a LiFePo piggybacked with Ultra Capacitors?
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While I do run supercaps, that's just because I have them, not because they're needed. 7.4Ah starts and runs the car fine, but might be a little close for comfort in a daily driver. It would be very easy to kill a battery that size if any accessories were left on for any period of time.
On previous cars (admittedly with Pb batteries), I've found that while the supercaps help cold cranking, once you stop cranking they suck so much current from the electrical system that the engine sputters (possibly starving the ignition coils). Three of the four cars (old and new -big and small) I tried them on had this problem.
Only happens on the first start of the morning though, after that starting performance was improved.
Point is while supercaps can help smooth out peak current demands, they can present a massive current demand themselves.
Smart alts present challenges of their own.
The smart alt on my 875cc Fiat is rated for a max output of 160A! Well above what such a car would normally have. LiFe batteries have a max charge rating of 30A per 7.4Ah. You'd need quite a big battery to safely accept the full alternator output.
You might also find the alternator is no longer 'smart' once you change chemistry, because the internal resistance readings will be well out of spec. The alt might go into fail safe mode (just holding 13.8v) - this would be a good thing as you wouldn't see full alt output under braking. From memory, my Fiat's alt still worked correctly with the LiFe.
On the other hand, Lotus sells a LiFe option for it's Elise (14.4Ah I think). I'm fairly certain that it comes with a Toyota/Denso smart alt and that it's highly unlikely that they do any reprogramming.