[PUP] Energy resource management ( was PPM in general - what should it be ?)

[2elnav at netbistro.com]

John Marshall wrote
> We cook with propane, and rarely fire up the electric oven, although
> we do microwave a bit.
>
> In warmish weather, our major current drain is refrigeration. In
> winter, in the PNW with short days and heating needs, lights and
> heating dominate.


REPLY
Once we get past the obvious issues of sea keeping ability, hull strength
and integrity; the biggest ongoing issue facing all cruising boats is how
to manage the available energy resources. This ranges from the most fuel
efficient cruising speed to getting the maximum return on genset run time.

When fuel was cheap and refueling stations plentiful, it was not as much
of an issue. The new reality seems to be, fuel is getting much more
expensive and many of the smaller fuel docks may not continue to stay in
business.

It has for a long time been considered a given that you stop the generator
when the battery is recharged to about 80% of full charge. Once you get
into the later stages of absorbtion and float charge, the  genset is no
longer efficient in terms of amp hour output for fuel consumed input.

I do not propose to question thi, but the one thing about this practice
that is a downside is the fact not all of the lead sulfate is reversed
back to lead and lead oxide during each charge cycle. The remaining 15% -
20% remains as lead sulfate and the longer it remains so, the harder it is
to reverse. The accumulation of lead sulfate will eventually lead to
battery failure. Even periodic equalization will not totally remove the
most stubborn remnants. And frequent equalization has its own issues in
terms of damage to the battery.
Boats that frequently tie up to shore power can overcome this because the 
duration on shore power will enable the charger to complete the float
stage and hopefully reverse all of the accumulated lead sulfate. But what
about cruisers who routinely stay at anchor for days on end, then make a
short hop to another anchorage?

The float stage must be maintained for several hours to remove the last
vestiges of lead sulfate. Battery engineers make the assumption that the
charging regime is done without simultaneously depleting the same battery
bank with an ongoing load. Unfortunately this is the norm for cruising
boats.
One solution might be to split the house bank and bring one half up to
float charge with wind or solar panels while the other half is used to
support hotel load on board. This may or may not be workable, depending on
how big the hotel load is.
Has anyone developed a good routine?

best regards
Arild