Folks, I'm working on plans to rebuild the "as is" battery system and electricity generation system on my new to me 1987 Irwin 38 CC.
As is is pretty basic.
4 Group 24 batteries installed in the compartment in the center of the salon floor. 320 ah total, new in 2009.
A DC start battery in the engine compartment. Age unknown.
A 12v analog gauge on the distribution panel.
A 20amp Xantrex charger.
A Yanmar 44 jhte with a presumed 55 amp alt.
Against that I'm running (end state in three years) a 12v refridge, maybe a ice maker (Rum sucks when warm), autopilot, full array of wind, speed depth sensors, tank monitors, radar as needed, chartplotter and all the normal lights and various odds and ends one finds on a cruising boat.
My assumed daily load is 200 AH. The fridge is half that - subject to an upgrade and insulation re-do (and a monitor to eliminate that guess work).
My goal is to never have to run the main engine just to charge batteries.
To run that right now I'm looking at 2 x 240w Kyocera panels - but that might go to three - two on the bimini, one on the davits.
I'll add the ubiquitous Honda 2000 generator for odds, ends, and the Cruisair air conditioner I want to add.
I'm not planning on a wind generator - might add it after we go cruising if we feel short of juice.
So - my first question(s) to the experts
Should I give up on the group 24 space and just put a big bank of 8d's in the engine compartment (it's not really a room on a I38 cc, but it's big enough to put in 4 8'd and still have lots of air circulation.
I don't think mixing and matching is a good idea so how do you rate the idea of 1 bank for the refridge, 1 for the 'house' - with an ACR to bridge if needed. Could I mix battery types if I did this, wet for the easy to get to fridge bank, AGM's for the house bank?
How large a MPPT do I need to get to control 480W of panel going into either one 800ah or two 400ah ish banks? How much larger if I go with 3 panels?
The math I did (not a good thing to watch me do) came out to up to 50amps of juice in good sun. Is that even close?
What are the ramifications of keeping the dinky 50amp altenator when my bank is 800ah - I've heard you can burn the bejesus out of a alt if the bank is more than 4x the output.
I am no expert C, but here is what I would do and have done. BTW - I am assuming we are outfitting this for cruising. With that assumption:
If I had your access and space, I would probably go with wet cells. I would go with 6v batteries (the 'golf cart'" versus 4 or 8 d's. That way if you lose one battery, you can still keep much of the bank intact. It also costs a lot less. Our house bank is 840 ah (theoretical), giving 420 ah theoretical for 50% SOC. Our realiastic use is probably pretty close to 200 ah/day now without any 110. We do not burn anywhere near 100 ah on our fridge. We are ballpark 45-55 ish depending on temperature and what we run. THis is a ballpark guestimate but probably not far off. Other than really isulating your fridge, keep it stocked and access it from the top as much as possible to save electricity. Another trick is that when packing, keep the meals and things you will go to first on top. We also place things in exactly the same space everytime so that we can go straight to it when reaching in - therby minimizing our time letting out the precious cold air.
If you have a lot of space, I guess you could use the icemaker. Mom and dad have a portable one that runs off of 110v and draws 2 amps, I think (20-25 ish at 12v). It makes ice in like 7 minutes! It recyles the water as it is doing it. It is really cool. They wanted to get us one, but we declined. For one thing, we don't have the space (it is large). Second, it is a large power draw. You will need to run her ballpark 30 minutes to make ice for all four of us. Instead, we have finally made the aluminum ice cube trays work. Basically, we keep a ziplock bag filled with ice and when it runs out, dump the trays and refill with filtered water. It makes big ice cubes which actually is nice because they last longer in the heat. SOmetimes, we will go to the marina and get ice too. It runs from 2/bag - $3 bag depending on your location. Gonna have to buy a lot of ice to equal the cost and elec useage of that ice maker. My opinion as a cruiser (which mom and dad are too... so you are seeing two different view points).
I would choose an Outback MX60 MPPT charge controller for those panels. Here is your real world in southern lats: I have 4- Kyocera 130w panels for 520 watts total. I generally see 200ish ah/day out of them on a decent day. On some days, I will see 220+. Cloudy days, not much. I have no really good data here, but after two days or so of clouds, I am looking for alternative charging (my diesel generator). SO using that ratio: 520w = 200 ah/day or every watt = .38 ah/day. So, using your 480watts, you are realistically looking at 185ish ah/day total on average. Do note: I have a solar arch and ZERO shading. If you put those panels on your dodger and they shade at all, you will see drastic drops in that output.
Instead of ditching your current charger, you might also consider doing what I did: I have two completely indpendent systems. My starter/generator battery can be brought in or out of the main bank. It has a small charger (xantrex 10amp) and that is all it needs to charge. I would use a agm or dry cell type battery (Optima). You could do the same and use your current charger for this side bank. For the rest of the bank, I would go with a Xantrex type Charger/Inverter. I know there are other options, but I use the Xantrex Prosine 2.0 Inverter/charger and the thing has worked flawlessly. It watches your power coming in, whatches out for the batts (temps, high and low voltage), and can be custom set to your specific charge routine (my lifelines). I also like it because I can set the 110 in voltage breaker size, so that when running other things off that circut (a air conditioner, for instance), the charger will not pump or draw more amps than what you have the breaker size programmed for. It automatically switches to inverter seemlessly when unplugging from dock power or generator which keeps you from ever having to reset all your clocks or other sensitive electronics. Also, per TOm Neale, the power it puts out is very clean (electronics). Lastly, it automatically switches off of inverter if it sees power coming in so you are not inverting while charging. Its a great system and has worked without incident since circa 2006. The inverter has made our life aboard and at anchor very comfortable. DO be aware though, te cabling for that thing are 0000 or larger. The cabling is a pain to run and expensive.
I have an 80 amp alternator on my engine. No way it is going to charge that bank without running a long time. However, with a large solar array, it is less of an issue. I have never turned on my main to charge the batts. It is inefficient and loud and heats up the down-below. I have, however, turned on the main to warm the water or made a good excuse to go somewhere for warm water. Since you are getting a generator, just think of the main as your backup. You will run your generator at times to charge the batts. But it is good to do this anyways since doing a good recharge is good for your batts. And quite candidly, you will find that you are moving (via motor) a lot more as a cruiser than a weekender. Why is another discussion.
I am not a big fan of wind. Can discuss this if you want, but instead just go a large solar array with a backup or two (gen and main).
I would not screw around with one bank for fridge, one for house, etc. Instead, just one large bank that you have to watch and manage. I would not worry about lights too much. THe new LED's really drop the use. Under sail, our autopilot and radar are the killers, fyi.
What else can I help with? Again, these are my opinions and real world observations as a cruiser. BTW, when are you heading off? Are you going to come down to the islands? WHat's your itin?