Maybe what it is, is the signal from pressing the stick in your dash that re sets the computer is a positive negative positive pulse , that is at a continuous positive level till it is pressed, then if you disconnect the battery there is no problem as there is no signal so the computer does not re-set .
But when you start the engine with a low battery the draw from starting the engine is enough to drop the voltage to a thresh hold that makes the computer think its got a positive negative positive pulse.
i therefor wonder if the battery is ok if the problem can be resolved by simply adding a capacitor in to the circuit to smooth the effect of the voltage drop as it is only happening for a short period of time, while engine is starting.
However from the fact the open circuit voltage of my battery was 11.9 this morning the battery is prob screwed according to the description of open circuit voltage i found below from wikipedia.
The open circuit voltage, is measured when the engine is off and no loads are connected. It can be approximately related to the charge of the battery by:
Open Circuit Voltage (12 V) Approximate charge Relative acid density
12.65 V 100% 1.265 g/cm3
12.45 V 75% 1.225 g/cm3
12.24 V 50% 1.190 g/cm3
12.06 V 25% 1.155 g/cm3
11.89 V 0% 1.120 g/cm3
Open circuit voltage is also affected by temperature, and the specific gravity of the electrolyte at full charge.
The following is common for a six-cell automotive lead-acid battery at room temperature:
Quiescent (open-circuit) voltage at full charge: 12.6 V
Unloading-end: 11.8 V
Charge with 13.2–14.4 V
Gassing voltage: 14.4 V
Continuous-preservation charge with max. 13.2 V
After full charge the terminal voltage will drop quickly to 13.2 V and then slowly to 12.6 V
Wait at least 12 hours after charging to measure open circuit voltage, the resting time allows surface charge to dissipate and enables a more accurate reading.
