Adding Secondary 12v battery for Electronics

Have a yellow top Optima deep cycle battery specs below:

Open Circuit Voltage (Fully charged): 13.1 volts
Internal Resistance (Fully charged): .0025 ohms
Capacity: 75 Ah (C/20)
Reserve Capacity: BCI: 155 minutes
(25 amp discharge, 80°F (26.7°C), to 10.5 volts cut-off)

I am figuring out what capacity from full 100% to 0%. The loading being a 10 Amp or 100 watts. I came across the Peukert Exponent for a battery where the amp-hours and reserve minutes are known.

Reserve Minutes 155
Reserve minute amps 25
Amp-Hour Rating 75
Amp-hour Rating Time 1.25

Peukert Exponent 0.83

Battery capacity 75 amp-hours
Time for specified capacity (20 or 10 typ) 1.25 Hours
Discharge rate 10 amps
Peukert exponent 0.83
Acceptable depth of discharge 100 percent
Peukert amp-hours 37.3 amp-hours
Amp-hours available at discharge rate 55.2 amp-hours
Life at discharge rate to specified DOD 5.52 hours

Any Battery Wiz know if this is the correct math?

If correct it will provide 5.52 from full charge at 10 amps.

Battery will be Charged via Main battery Positive connection and grounded there as well. Which I suspect is charged by the DC to DC Converter from HV batteries.

There is a charging controller that will isolate the secondary battery from the main battery if it drops below 12v. Otherwise it runs it in Parallel and charges in Parallel.

Peukert's law - Wikipedia, the free encyclopedia