C385 Alternator/Voltage Regulator

I recently became the owner of C85#71 and took my first extended cruise on her last month. I discovered that the two 4D batteries she came with aren’t enough to keep up with the load when I run both the refrigerator and the freezer (which seem to pull an average of about 5 amps, or about 120 amp hours in a day, too much for the 160 amp hour rated battery.) I don’t have a genset, so the only way to recharge the house bank when not plugged into shore power is to run the engine. But at the rate the original alternator charges up, it takes at least a couple of hours to top off the house bank.

I understand that part of the problem is that the internal regulator on the alternator isn’t designed to do a rapid recharge of a house bank. I’m considering installing an external voltage regulator, and maybe replacing the alternator. The alternator that came with the boat is rated at 125 amps, bigger than the 55 amp version I gather was standard on some of the earlier hulls. The current alternator should be plenty big, but I don’t know if it would be possible simply to put on a Balmar or other external regulator, rewiring the alternator to take the internal regulator out of the circuit. Or would it be better to replace the alternator, too? I’d appreciate any advice.

3 thoughts on “C385 Alternator/Voltage Regulator”

  1. HI,
    We are owners of C385 #71. Did you do an alternator or battery upgrade? This year was our fist year, and this is an upgrade we are considering.
    Thank you
    Ken and Lynn Baehr

  2. Congratulations on your new boat. I am sure you will love it. We love ours.

    I had the original lower capacity alternator and a single bank of batteries. I found that setup inadequate for the way we were using the boat, spending two or three days on the hook while cruising. With both the refrigerator and freezer running, as well as the power draw from the inverter I installed, the batteries just couldn’t keep up, and it took forever to charge them with the engine.
    After having to call BoatUS to get a jump start, one morning, I decided something needed to be done, so I replaced the alternator, added an external voltage regulator, put the house batteries in parallel, and added a starter battery, I can now charge the house bank with an hour or so of running the engine, and I’m quite happy. I will ultimately replace the flooded batteries with AGMs but I hope not to have to do that for a couple of years.
    Good luck.

  3. Thanks for the Information!
    We recently purchased hull #53 that came with the 2 4D flooded and 2 fridge units. Will look at at an alternator/voltage regulator future upgrade. For now were adding a start battery and solar panels.
    Hope to eventually do some limited cruising and was also considering adding a wind generator. Has anyone added a wind generator to their 385?

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