The big test

Phasma

Phasma

Phasma2128
Sep 17, 2016
691
West Michigan
Boat Info
2003 360 Sundancer
Engines
Mercruiser 8.1s Horizon
Two weeks from today we leave on our annual big cruise up north to the islands. Typically we have always used transient slips as we hop up the coast. This year we plan to be on the hook for 3 of the nights. Over the past year or so I have replaced light bulbs with LED, replaced the aging battery bank with 4 new gel batteries and fundamentally updated the electrical system. This weekend I am planning to disconnect shore power and shut down any un-needed systems. I want to see how many hours 4 gel batteries will last using just the basic systems while keeping two small fridges and a freezer cold. Doing this at the slip has the obvious benefit of plugging the boat in if the batteries die. I do this in the interest of curiosity and the element of safety. We’ve never used our boat on the hook for any amount of time. I am assuming I will need to use our generator a couple of times a day. Hopefully I can get at least 8 hours out of them before they are dead. Anyone tried this before? Any guesses as to how many hours I should get?
 
I generally run the gen in the AM for an hour or two to cook breakfast and use any other appliances......at the same time charging the batteries and heating up the water tank....I repeat the same procedure in the evening - I don't like to run my batteries too low when on the hook, you never know when you may need to start the boat and retrieve the anchor quickly if circumstances dictate it.
 
I would say you'll have no problem running for 8+ hours. This past weekend, I ran 2 refrigerators, a 12V fan, played my stereo off and on, and LED lights at night for Friday, Saturday, and part of the day Sunday. I would run my generator in the mornings for about a half hour to heat water. No problem starting up Sunday afternoon and pulling anchor.
I have 2 banks, with 2 batteries each bank, that are 2 years old.
 
Hey Phasma,
Just as an aside and because I'm curious and an engineer...What is the max percentage of discharge your Gel batteries can hit before they are kaput for good? I know all batteries have a discharge rate at max output up to a Percentage of full charge, whatever that may be. Most batteries after one or two full discharges will never reach 100% re-charge, but they will get very close, and once you go past the red zone they will not hold a charge for very long.
I would monitor closely to see how low they can and do go.
You have done due diligence, and wisely upgraded known current suckers (Lights, etc.) which will help immensely. Chillerators are known Current suckers. And rightly so. Moving heat and making things cold is difficult.
Any fans or AC running? Remember to save your starting battery (no Cheating):)
Since I don't know the profile of the batteries you are using, and I have no experience with being on the batteries, I'm going to guess a solid 6 hours. Depending on outside temperature, and how many beers per hour. (opening and closing the fridge)
 
We used to hang on the hook quite a bit with our 360, and like Mike, we would run the gen to do breakfast and let it run for about an hour and a half, same thing in the evening at dinner time. You shouldn’t have any problems going all night with your fridges on, we never turned them off. You are one up on me in the lights department, I never changed the boat over to led, just the anchor light.
My current boat is entirely led except the running lights.
If you get up in the morning and leave your anchorage early before running your Genny, start your non-house bank engine first and then use the emergency start solenoid to help with the other engine, or just use the emergency start from the get go. It’s not good for the starters to crank on low voltage.
We enjoy anchoring very much and when traveling long distances, we anchor most of the time, reserving marina stops only for times when weather could be a serious threat, provisioning, or we get the itch to go out to dinner. Have a safe trip.
 
Curious why you chose Gel over Agm? Cycle life?
 
Recommended by mechanic. Primarily cycle life was the justification. Delayed discharge. A single charger for a single type of battery also played into the decision
 
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