accrete said:
. And a small 110ah AGM house battery will typically see only ~20-30ah draw down during our week long times away from town. The drive back in charges it back up.
Many people assume their alternator breaks the laws of Physics and can recharge a battery to 100% full quickly.
It takes time at absorption voltage. 14.4v ish must be held in the neighborhood of 4 hours before the battery can be considered fully charged.
Most vehicles will not hold ABSV for this long
Most vehicles will not be driven for 4 hours when the battery is depleted.
Most vehicles house battery systems are not wired thick enough so that proper absorption voltage( if even allowed by the vehicle's voltage regulator) actually makes it to the distant battery.
AGMS are degraded by not returning to 100% charge regularly, more so than flooded deep cycle batteries.
Do not assume that an alternator is going to truly fully recharge any depleted battery.
Surface voltage of the battery after driving is NOT indicative of state of charge, especially on an AGM. Surface charge voltage fools most people into thinking their battery is much more charged than it actually is.
After an outing, one should have a plug in or Solar method to truly fully recharge their battery, otherwise its cycle life will be compromised to some degree. It depends on its state of charge when put to rest as to how much and how fast degradation occurs.
Whether upgrades to meet the batteries demands for ideal service life are worth it, is another matter. If 300 cycles to 50% is acceptable as opposed to 500 cycles then one can worry about other things. Just don't fall into the Magical alternator mindset which permeates society.
Time at absorption voltage is required to fully charge any battery. There is NO way around this. Not enough time and not high enough absorption voltage, well don't kid yourself just because you see 13.2v when you turn the engine off.