Mutau Ranch

Reserve is how much you can comfortably use before your safe floor — 100% when full, 0% at the floor (time to recharge).

It's built from a few numbers:

• 675 Ah — rated capacity when the batteries were new.
• ≈500 Ah — estimated real capacity now (they're ~7 years old). The gauge uses this so the % isn't over-optimistic.
• 50% floor — for battery life we treat half the real capacity as "empty"; going below shortens their lifespan.
• 43.2 V cutoff — the charge controller hard-stops here to protect the bank. You never want to get close.

These are estimates. The real aged capacity is a best guess until it's measured over some deeper cycles.

Surge loads are a different story. A big motor starting — like the 3 hp water pump — can briefly sag the voltage down to the cutoff and trip a shutoff even when Reserve looks fine. That's about instantaneous power (and older batteries sag harder), not stored energy — Reserve tracks energy, not surge muscle.