Originally Posted by
ProDigit
I'm late in the game. But it appears to me, you could just swap the battery out with a Capacitor pack, or a 4 cell Lithium battery? (like those motorcycle LEGO battery packs)?
It's lighter, it's smaller, and it doesn't need as much charging.
It also keeps (full) charge longer.
A capacitor pack not as much, they might deplete overnight, but usually charge within like a few seconds.
Which reminds me, I bought a USB battery pack (one of those 11000mAh battery packs) and it had a built in car starter (400CCA, up to 4L engines it said). It's not meant to start a car by itself, but to aid with the battery that's already present in the car.
But use that on a 3 cylinder, 1,2L engine, and you probably don't even need a car battery.
I tried starting my 800CC motorcycle with it, after the battery was totally dead, and it worked!
So what stops anyone from just installing 2x $35 5F (rated, in reality they're 1F or 2F) capacitors, those huge water bottle size caps, and pair it with a USB battery pack for starting? That's not even 5LBS on starting gear vs 40?
Excellent question Prodigit! You can certainly replace your starting battery with something smaller and lighter. Loren did that with his very small lead acid battery that he used to reduce weight for his autocross Mirage. However, that doesn't stop the alternator from putting a load on the engine. Just because you have a smaller battery doesn't mean your alternator has to work any easier. When you're driving around and you turn your headlights on, your alternator now has to generate 110W (2x 55W) more power to supply the power necessary for those headlights. That means your engine has to burn ~220W more fuel because alternators are at most 50% efficient.
This modification completely removes all load from the alternator (except the belt, alternator fan and bearings) by telling the alternator that the battery is already full. Having a capacitor bank will not do that. Even having a lithium pack won't do that unless the new battery runs at a voltage above 14.4V. Because, as soon as the battery's voltage falls below 14.4V, the alternator starts pumping out power to maintain 14.4V. This is done by the voltage regulator that is inside the alternator.
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View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)