Two Battery

You have two batteries connected in series. The positive terminal of a battery is connected to a bulb

then the positive terminal of the capacitor. The other battery is connected through a switch to the negative terminal of the capacitor. A DMM (measures voltage) is connected across capacitor (in series with the capacitor), whereas the other DMM is connected to the terminals of the bulb. The question is: How does the voltage change over time to capacitor, and the light bulb?

The voltage across the capacitor will increase with the following function after the switch is closed: Uc Batt = U * 1-e ^ (-t/tc) The voltage across the lamp: BATT U – Uc Uc = voltage across the capacitor. Batt U = t = time voltage battery in seconds tc = time constant = capacity in Farads multiplied by the fire resistance in ohms (in seconds) the first time after the ignition, the fire has the full voltage and the capacitor has zero voltage. After some time the lamp has a zero voltage and the capacitor is charged the full Battery Voltage.

(Q & A) How To Install 2 Batteries – BASIC – Adding A Second Car Audio Battery w/ Isolators & Relays