Quote:
Originally Posted by Scot McPherson
Do NOT top off your batteries in the AM as suggested however, that leaves absolutely nothing for your solar and wind to do. Get as much from the sun and wind as you can, then top off your batteries before you go to bed. This MAXIMIZES the amount of energy gained from solar and wind and MINIMIZES the amount of fuel you will need to burn.
|
The best practice is actually the opposite of this. You want to get your batteries to as high an SOC as you can in the AM using bulk
charging, then let the solar take over. This uses your
alternator in the
most efficient manner possible.
You don't want to waste half your day
under bulking your batteries when the quickest way to replenish over night losses is to fire up the
high current engine or gen set for 30 minutes to an hour and quickly breeze through the constant
current stage of
charging. Because the acceptance taper is the
longest part of the charge process this is best left to the
low current PV system.
Solar, unless you have a
massive array, simply can not produce the same bulk
current an
alternator can and you'll wind up at the end of the day at an overall lower SOC..
Solar is best left for the "
finish charging" through the long, slow and arduous acceptance stage. The acceptance or CV (constant voltage) stage can take as long as 4-10 hours depending upon the
battery bank type and state of
health. This is ideal for solar when you start out the day at the highest SOC possible.
The alternator is best and most efficiently used to get you from 50% SOC to 80-85% SOC
early in the day so the PV can handle the long, slow acceptance stage.
You can turn off Dino powered sources when at absorption voltage the current declines to what your solar can produce,
minus DC system loads. Running the engine in the evening means the alternator is being used less efficiently and wasting
fuel because the batteries will be at or close to absorption which means the alternator will be putting out low current, which is what the PV is best used for...
Reverse your practice and you will see a higher SOC by the end of the day, which is considerably more healthy for the batteries.
As to the original poster, two G-31 automotive type batteries are not going to be well suited for
refrigeration plus typical house loads. Of course this all depends upon how you
actually use the boat.
I have a number of customers who do one overnight per week and then tie to a
dock for shore charging until the next weekend.. These customers still run the stock alternator and survive on automotive cased "
light cycling" batteries.
If your
boat is the early to mid eighties P-34 unfortunately the stock
battery tray is horrible and can really only fit two G-31's. You'll want to find a location to fit more Ah's. Also the battery tray is
oriented incorrectly for flooded batteries and causes the plates to come uncovered from electrolyte while heeled. Bad design by
Pearson.. The only real suitable option, in that factory tray, are VRLA batteries (GEL or AGM) or you just burn through
cheap G-31's rapidly and accept it.
If you start to push beyond a few days of use at a time and are on a
mooring etc. then you'll likely want a considerably larger bank, better quality batteries, and improvements to the charging system usually including solar. A lot depends upon what your stock alternator already is. Any stock alternator can be converted to external regulation, though below about 50A you're really chasing fairy tales. If you use a
Balmar regulator with
adaptive alternator temp sensing, plus belt manager, it will charge better, charge faster and keep your batteries healthier. A
Balmar ARS-5 can be had for about $300.00 plus the alt temp
sensor and any competent alternator shop can convert your existing alt to external for a minimal fee....