Join Date: Jul 2001
Thanked 18 Times in 17 Posts
Rep Power: 15
Re: replacing starting battery
I faced the same decision last year. Like you, I use an LED anchor light which I raise in the rigging, rather than the all around white light at the top of the mast. The LED light shines softly on the boat to make it more visible, and meets the CFR for an anchor light.
My boat had two group 27 batteries; one 10 years old, and the other 7 years old. I replaced them with two group 29 batteries (105 AH), and use one for the house, and the other for the start. I can use either as a start, or house. A marine deep cycle battery works fine for starting a diesel.
Someday, I will combine these two batteries, move them to another location, and add a small, cheap, start battery.
eh's description is a classic example of the evolution of boating electrical support systems.
2 separate banks (a bank being a single to any multiple of batteries) was the older style. The currently preferred arrangement is as large a house bank as possible with a separate either start or reserve smaller bank. Reasons are explained in Charlie's book.
Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)