Gentlemen-
I am working on rewiring my boat and thinking of battery capacities. The spreadsheet below is my attempt to consider draws and what should work. I am supposing a long fishing drift or tuna chunking but I feel like I'm just throwing darts here.
I think the big wild card is the stereo as the amp states an "Idle" current rating of 1.7A and a max of 50A. I'm also dubious at the draw for the AIS which is a Transponder system. Any suggestions or advice is very much appreciated.
I am guilty of not wanting to take the next step to bigger batteries or banks after the two Group 31s. With two Group 31 AGMs http://www.lifelinebatteries.com/marineflyer.php?id=30 I can get 250 Amp Hours. While that is skinny by these calculations it doesn't strike me as silly.
Is a low voltage disconnect like: worth considering?
All you advice and guidance is appreciated.
Stephan
If I understand you correctly you are running two group 31's. I would really add a house battery or carry portable jump starter like this one. I would not feel comfortable otherwise. Wire them all up, so that you can bring all three batteries on line to start at least one engine if needed.
Stephan,
My 31' Express had 2 Group 31 batteries in her for most of her life, with no problems. The last 10 years I added an extra group 31'for the 12v kite reels and live well pumps. I would recommend either making a new battery box for the area between the engine boxes and making it so it is not down in the lower bilge area. I've seen boxes outboard of the starboard engine also. I had 2- 454 big blocks, electric flush head, 4 cabin fans, 6 cabin lights, search light, electric horn, kite reel outlets port and starboard, 2 40 gallon live wells, macerator pump on live well discharges, under gunwale cockpit lights, 2- 2200 gph 1-2000 gph bilge pumps, 1- 3000 gph bait well pump, flood light on the back of the soft top, JVC stereo with 10 disc changer and 12v outlet for the 12volt cooler under the helm seat. As long as your alternators are good and 12v loading is spread out on a good Blue Seas or other brand breaker panel you should be fine. I had a Blue Seas 24 breaker panel with analog gauges and battery selector switch. I had a 6 breaker 110 volt electric panel just below the 12 volt panel, for 110 volt cabin and head outlets, 110 v 40 amp battery charger, 110 refrigerator and a spare for air conditioner that never was installed. I rewired the entire boat with anchor marine boat cable of various sizes all new 8 gauge green bonding wire and all new 1/0 red and black battery cables and new Cole Hersey rotary battery switches. You can install new halogen or LED cabin lights that hardly burn any juice. Just make sure that all the connections are either soldered or crimped with the correct tool and use heat shrinked terminal ends. What ever you do don't cheapen out on the electrical system, it might cost you some bucks in the beginning but in the long run it is well worth the extra expense of good wire, crimps,cable ends and the best batteries that you can find. Remember to add chafe protection where wires go thru bulkheads and support all wiring every 18" throughout the boat. Blue Seas in Riviera Beach has everything you will need, they are a wholesale company so if you know anyone in the marine business that can help you out it would be helpfull. Good luck with the project.
Pete Fallon
You should be fine running the auxilieries off of the house battery, and if wired correctly, you should not drain the engine start batteries.
As far a bilge pumps are concerned, I have each pump running off seperate batteries. If you have three pumps, one should be hooked up to the Starboard Start, one to the port start and the third to the house battery.
This will make you more than comfortable that in a bad storm when you are not there, there will always be on pump that will be running. The odds of killing all three batteries in a bad storm are pretty slim.
great tony i am very conscious of "Murphy" he has cause so much grief on the water!-----------typical "i was on vacation and rain like hell on the boat all bilge pumps on one battery not isolated ,battery went dead water came in the suppers and down it went at the dock" saw a beautiful tiara go down two years ago at dock -----------damn shame
How difficult is it to attach a smaller (or bigger) solar panel to the battery? That way, when the sun will rise again your battery will pick up again, preventing the worse case scenario,... unless there is no sun in your area, or space, I doubt it though that that Tiara didn't have any space for a small panel.
The other reason for separating everything is guests with kids. I had a friend out with his grandkids. One of the kids must of been playing with the three way switch to one of the pumps. He turned it off. We had a terrible storm that night. Thank god for the other pumps.
I had something similar happen Tony, only the boat was in the boathouse and the drip from the stuffing boxes was slowly filling up the bilge! The front pump was shut off and eventually the rear would have kept her from sinking, but after that I added a large Rule pump with an Ultra pump switch switch that is located higher than the forward pump and is wired directly to the batteries with no switch other than pulling the fuse.
I went thru a lot of the same thinking when I rewired my 31. My cruising mo is to never dock...except for the rendevous, so managing battery life was key. Actual use never seemed to match theory. My suggestion is to get a good battery monitor. I had a link 20. It worked ok...but i am sure ther are others that will work well. This way you can monitor actual usage a adjust accordongly. I agree with Pete, don't scimp...buy only good quality marine wire, and good connectors. Recomend using a rachet crimper. I used blue sea breakers and was very happy with them. You are local, so if you want, I can go over with you what I did, perhaps over a cold beer.
Giff-
Thanks for this kind offer. I would like to take you up on it.
I've been charting a boat in the BVIs where we have been running multiple refrigeration and freezer units supported by 2 hours in the am and 2 hours in the pm of engine battery charging. While I don't think much of the refrigeration and freezer units I am impressed with how simple this system is to use. There are two 90 amp alternators on the small Yanmars in this cruising catamaran. I'm doing the math of 90 x 2 hours x 2 engines to get 360 Ah charging cycles. With two cycles a day (720 Ah total) we are getting a lot of charging and just keeping up with the usage.
I'm not sure why but I am guessing that not all 720 of those Ah are completely efficiently being transferred to the batteries. Per your suggestion it does have a Victron Energy BMV-700 (https://www.victronenergy.com/upload/do ... ies-EN.pdf) battery monitor. This appears to be an excellent unit with much information but perhaps best of all a small graph in the lower right corner of the display to indicate percent charge.
I will dig in to the lower regions of this thing tomorrow and find out how big a bank there is. Perhaps 6x120Ah batteries?
Kind regards,
Stephan
I'll have to get a download on you bvi charter experience....on my short list of things to do.
On to charging batteries....your math is fine, but the physics unfortunately don't follow. Most modern chargers and alternators with "smart" regulators follow this scenerio.....constant current until you reach a predetermined voltage ( I think 14.6 volts for a wet cell battery). Then voltage is held and cuurent varies downward to hold the 14.6 volts.....thus, over the charge cycle, much less than your alternators or charger can put out. This is the dilema when yoy are away from the dock for an extended period of time. Its hard to bring your batteries up to full charge in a reasonable length of time. I tested this theory out many times with my Bertram as we would almost never dock once we left our slip. I had 2 150 amp balmar alternators and no generator. Even with the large continuous duty alternators and charging once a day, things would be fine for the first few days without an extened run, but eventully to fully charge, i needed either a several hour run, or dock power for an extended period of time. I was able to keep close tabs on things with the battery monitor. Alternate solution is a generator that you run perodically for an extended period of time. I ended up buying a Honda S2000 for my bertram. Whish i had gonnthis route out of the gate as it was a lot cheaper than my big alternators with smart chargers.
Btw, battery monitor looks nice....better than the one i had. Looks like same principal though.
Going thru all this thinking again as I update the electricals on the trawler I own now.
Let me know if you want to meet for a pint or two...otherwise, stopby my new "office".....under rhe shrinkwrap at Dickersons working on the new boat. Logging a lot of hours lately.
worth considering?
