Velera wrote:
So if you do the math on what you are presenting here, You have about 150 ah of usable power between recharge cycles--because you do not want to take them down much more than 50% I would assume. The 100w solar will be very valuable to "top off" your batteries from the deficit your "smart" regulator will leave (because--no matter how you set it--it is going radically reduce the charge rate as it approaches "full" voltage--look at what amps are actually going in after the first hour and what you % of charge is on your monitor--if it does not stop charging altogether from heat sensors on the alternator or battery if you have those options) but the solar will not really provide much of your basic needs. Seems like you are set up with moderation as you say and should get along nicely. I do like most of what Mainesail says, but we disagree on some of his details. He is selling stuff now and I don't blame him but it has sort of gotten him back in the retail business pushing more is better and I will never understand his love of Balmar stuff considering the number of failures he has reported--except that it is very good looking and grossly overpriced. I have met him in a Maine anchorage a couple years ago--his boat looks as nice as you would expect. If you ever want to simplify things, you could lose the starting battery. I assume your bank is divided (? or maybe not with three batteries?) in two banks. You are very unlikely to have a dead cell in both batteries and if you flatten both batteries you can get a small diesel started again by cutting out the bad battery out of your system with the switch and letting the other rest for a few hours. It will start. I have never had a starting battery in my boats in 45 years of cruising (just two banks that I ordinarily run together 99% of the time). I have flattened batteries a couple times accidentally and had a bad cell once, but no real problems.
The big thing you can do to manage power is to deal with your refrigerator demand. Not sure what you have done, but the T37 box is very well insulated except some of the tops are not sealed or properly insulated. Also, the compressor should be in the coolest place possible. In the tropics I used to open the lazarette cover over night so the thing was not fighting engine heat. Also, I put a bigger computer fan on the compressor and put a tiny one (these use much less current than the OEM and move more air)in the box to keep the cool circulating off the bottom (and put a cork in the drain so the cool does not run into the bilge). All this reduced my compressor run time by at least 30%. Froze my beer in Panama. So you can increase your electricity production or manage your energy sometimes. For most of us, refrigeration is more than half of your energy budget.
FWIW
Ray
150ah seems about right for three G31 AGM although the Odyssey Extremes can go down lower than 50%. I think the literature says 30% but I wouldn't do that. My reserve is separate with the ACR between. Not going to use it unless I really need it. My sense of the solar is it will be great for topping off when there are no loads or extending my main bank a bit. I will be adding 2" insulation to the frig top and a small fan. I have the drains plugged. Compressor is under the sink and the fan housing is against the sail locker bulkhead that I cut a hole through for cool air. The compressor is a new Dometic CU100 so pretty efficient.
The fact that I'm limited to a 3/8" belt on the alternator is a bit depressing frankly. Why Tartan chose a 3/8 there and a 1/2" for the water pump is beyond my comprehension. I considered carefully your recommendation of a very simple alternator arrangement but got nervous about cooking batteries.
I have already replaced all interior and running lights with led and will also replace all my mast lights when the rig comes down in March. The masthead light was a major draw (over 2a I think) and I should save several ah at night with led.
I installed a robust electronics package (MFDs, AIS, instruments, etc) so that will be a larger load than I used to have considering old stuff was broken.
Thanks!