Battery capacity and dd autopilots

[Peregrine1983]

Hey guys,

We are a Pearson 424 - 42', 23,000 lb ketch. I currently have 4 Duracell GC2's, two years old and well maintained as our house bank. I'm calculating these as having about 428ah of capacity at 12v. We have 430w of solar with an excellent charge controller. A 70 amp and a 125 amp alternator on our 58 horse diesel.

Sailing all day in 15-20kt winds and a rolling small swell our Raymarine direct drive autopilot drains the house bank after several hours. I have not timed it exactly as it varies on conditions.

I'm thinking about adding 2-4 more GC2's and adding 50% or 100% more capacity so we don't have to run the motor to charge.

Curious to hear about other people with similarly sized boats running direct drive autopilots for long periods on wet cell batteries like these.

How much battery capacity do you have and what percentage of it do you devote to the autopilot?


Thanks in advance for any input.