Well i do not know what the original Volvo battery had for CCA (cold cranking amps)capacity but i am sure it was probably more than 320.

A good rule of thumb is to have a battery with a CCA that is about twice the number of the Cubic inches of the engine.

my replacement battery has 650 CCA and according to the auto supply the original was 625 CCA

My terminals were/are always kept clean, and i use the felt rings to help reduce corrosion build up.

Cables are kept tight and never loose.

as far as the car starting with or without a good battery, i do believe that the battery not only supplys starting power, but completes a circuit for recharging. At least that is how Aircraft systems work. (I am a FAA licensed Aircraft Tech,did this for many years) IF the battery is bad and a cell has high internal resistance that will not complete a circuit or is a weak link in hte circuit, then it will never charge and will also cause other electrical problems like no ignition. that is why Aircraft use two of everything.

A small capacity battery or charging system like the one in the minivan did not have enough spare amps to turn over the engine only run the lights and stuff.

try jumpstarting your car with a tiny battery and let me know if it starts.

The 850 GLT has lots of electrical goodies that may not necccessarily be operating-on but they do have power being supplied to them and this does not include the systems that are powered up and on- 2 ECU's dash lights interior lights ignition, fuel, etc. that creates alot of current draw and then throw in the starter it must pull 100 amps easy by itself.

the alternator should power all accessories with the car runniung and the battery disconnected, i have not tried this but i may have a weak alternator.

So all i know is a small car/small batttery would not jump my 850, but a big A$$ truck with big A$$ battery would.

Dan