In article ,
"Roger Long" wrote:

Calder points out how battery life is increased by minimizing
discharge level. No matter how many batteries you have in the boat,
you'll get maximum life by putting them in one bank. Keeping a
starting battery isolated and in reserve is obviously a necessary
compromise for most craft. However, with a 20 hp diesel, modest
starting loads, and the ability to hand start, I'm thinking that the
simplicity of a one bank system might make sense for a daysailing,
short cruise boat, that is docked with shore power. If the batteries
did get run down away from home, I'd be willing to hand start in
penance.

The key question is whether a two cylinder diesel like a 20 hp Yanmar
2QM can really be hand started or if it is an "only when your life
absolutely depends on it" kind of operation. I don't have much
experience with engines under 200 HP so I'd appreciate the benefit of
actual experience.

We have a fairly recent 2GM20F. No provision for hand-starting.

But a single bank is feasible, at least on the Chesapeake during the
season, with the addition of a small solar cell. Ours is 12w. On last
year's cruise, the battery was dead flat one morning. Switched
everything off but the solar cell and we could start by mid-morning.
Since it tops things off between weekends, we only need to use the
engine for motive power. Have never had healthier batteries; the one I
expected to replace was rejuvenated.

Eventually, we will have a dedicated engine battery with absolutely the
shortest possible leads. House bank will normally be isolated by a
simple on/off switch, the cell keeping it healthy. Won't be able to fry
the alternator by tossing a switch.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/