[me and my metro]

This may take a few posts from people with different backgrounds to solve. I am not an expert on batteries. Deep cycle batteries have their use and place in the automotive world. They are not a good starting battery, they are designed for slow discharge and recharge. They are designed for many deep cycles hence the name.

Automotive batteries are constructed differently and they are designed to take a quick 100 amp discharge to start then a quick 100 amp recharge to float voltage. If you have a higher starter draw and Diesel starting aids like glow plugs or intake air heaters use multiple batteries.

My newest Ford gas powered trucks have a single group 65 battery and a 150 amp alternator.

All my Diesel power equipment have multiple batteries. The glow plugs draw 200 amps and the alternator is delayed until glow plug use is over. I want to see 14.4 - 14.5 volts at idle with the batteries at full charge. If I don’t see that I still have a problem.

Checking parasitic draw on computer controlled cars is interesting. Some batteries tolerate draw better than others. 500 millivolts is a good thing to stay under. My company installed automated vehicle locators on most of our powered equipment a few years ago. This system wakes up twice a day and sends a quick text to the vendor about the vehicle. This is not much draw but If the vehicle sits for a few weeks without starting the battery will die.

Low use vehicles have either a battery disconnect or an onboard maintenance charger. The 1.5 amp size works for the single battery trucks and a 5 amp size keeps the big trucks charged.