Quote:
Originally Posted by gascort
If my logic is correct, my Optima Yellow Top D34/78 has 55AH of capacity. It has been fine to get me to and from work. Since this new battery I'm adding in series is 4V out of the total 16, it will only be providing 1/4 of the amps to the circuit, so its 9AH * 4 = 36 effective amp hours relative to what the optima was providing.
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Nope.
If you have the batteries in series, the current flowing through each will be the same. To use a plumbing analogy, voltage is like pressure, and current is like flow rate (how many electrons pass a point per second, if you like). So if you draw 18A while driving, your 55Ah battery will last 3 hours, and your 9Ah battery will last 0.5 hours. The best case scenario is that your 16V will slowly droop as the batteries discharge, and after 0.5hr, the 4V battery will be at 0V and the system will be at 12V. The worst case scenario involves internal resistance rising in the 4V battery.
If your starter draws 200A, the terminals on your 4V battery need to be rated for 200A as well.
Hmm, that leads to an interesting idea. Why not just place a 2.3V NiMH battery in line with the fuse that goes to the ECU, or whichever system you're trying to fool? You won't blow out headlights or anything. If all you need to fool is the alternator warning light bulb, the battery would probably go weeks between recharging.