2007 320 sundancer. Finally got to go out today and relax on our new to us boat. Wasn't sure how long the 4 batteries last approximately with my anchor light, 2 refrigerators, garmin and stereo on? I was running my generator after 15 minutes because I was so afraid of not being able to start it because of a dead battery but it does provide some unwanted background noise if I don't need it. Especially concerned because I'm in the ocean so don't want to make that mistake. Thank you in advance.
how long do batteries last while anchored
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superwa
Active Member
Multiple hours usually. We’ll anchor at 10 am without the gen running and leave at around 4-5 pm without a problem. Are all batteries connected together? I have a separate one just for the generator, so I could run it for a few minutes if I ever get too low.
There are ways to mitigate potential issues. Depending on your boat you may be able to isolate battery banks using the battery switches, such that a starting or generator battery is always kept in reserve.
- A blasting stereo will kill your batteries almost as quickly as your boating neighbors will sink your boat.
- Never run your anchor windlass without the engines running.
- Switch all your light bulbs to their LED equivalents.
- avoid opening and closing your fridge more than necessary. Keep your next needed items in a cooler of ice.
- and did I mention, don't blast your stereo??
Regardless, it's best not to run any of your batteries completely dead, as it will significantly shorten their life. 50% for lead acid is the typical threshold. So, with a 200 amp/hour bank, you wouldn't want to use more than 100 amp/hours without charging. AGM batteries can accept a deeper discharge, so definitely worth the extra coin.
Once you figure out the available amp hours, you can calculate your approximate usage. So for example if your fridge averages 5 amps (totally made up number), and you run it for 2 hours, you will have used 10 amp/hours.
If you are in a wet slip, just disconnect from shore power and do a "dry run". Staying in the slip, turn on your anchor light, cabin lights, etc, as if you were out on the water. That should give you some insight into your setup's capabilities, without the risk of getting stranded.
- A blasting stereo will kill your batteries almost as quickly as your boating neighbors will sink your boat.
- Never run your anchor windlass without the engines running.
- Switch all your light bulbs to their LED equivalents.
- avoid opening and closing your fridge more than necessary. Keep your next needed items in a cooler of ice.
- and did I mention, don't blast your stereo??
Regardless, it's best not to run any of your batteries completely dead, as it will significantly shorten their life. 50% for lead acid is the typical threshold. So, with a 200 amp/hour bank, you wouldn't want to use more than 100 amp/hours without charging. AGM batteries can accept a deeper discharge, so definitely worth the extra coin.
Once you figure out the available amp hours, you can calculate your approximate usage. So for example if your fridge averages 5 amps (totally made up number), and you run it for 2 hours, you will have used 10 amp/hours.
If you are in a wet slip, just disconnect from shore power and do a "dry run". Staying in the slip, turn on your anchor light, cabin lights, etc, as if you were out on the water. That should give you some insight into your setup's capabilities, without the risk of getting stranded.
Last edited:
- Apr 26, 2009
- 5,821
- Boat Info
- '97 330 Sundancer, Raymarine C80 suite with radar, Mercury 310 Hypalon w/8hp Yammie 2stk
- Engines
- 2X 454 carbs w/ vDrives
Answer is it depends on what you have running. Your 320 has a "house" bank that runs most 12v stuff and starting for one engine. The other bank is for the other engine. Play around with your battery switches and figure out what runs on what. Your electrical panel also has amp meters. Your batteries are measured in amp hours so, you can estimate time to discharge by looking at the consumption rate with everything on on your meter and dividing say 50% of the capacity by that rate (assuming your batteries are in good shape).
So quick math:
If your consumption rate is 15 amps with everything on on your house bank (and that would be a LOT), and it has two 12v Group 27s with 80 amp hours each, that means about 5.3 hrs of time to drain to 50%. But fridges only run about 30% of the time or less (depending on a lot of things, might be more or less) so using 50% of capacity and full run rate amps is very conservative. If you have a massive audio amp that might consume a lot of power though.
Changing your bulbs to LED's will save a LOT of power. Anchor light bulbs are generally 10 watt so about 0.85amps per bulb. Probably two in your anchor light. LED's are generally 10 to 20% of that, so changing to LED helps a lot if you anchor at night and have to leave the anchor lights on. Same with interior bulbs. Boats use a lot of spot lights so lots of potential battery life savings there.
So quick math:
If your consumption rate is 15 amps with everything on on your house bank (and that would be a LOT), and it has two 12v Group 27s with 80 amp hours each, that means about 5.3 hrs of time to drain to 50%. But fridges only run about 30% of the time or less (depending on a lot of things, might be more or less) so using 50% of capacity and full run rate amps is very conservative. If you have a massive audio amp that might consume a lot of power though.
Changing your bulbs to LED's will save a LOT of power. Anchor light bulbs are generally 10 watt so about 0.85amps per bulb. Probably two in your anchor light. LED's are generally 10 to 20% of that, so changing to LED helps a lot if you anchor at night and have to leave the anchor lights on. Same with interior bulbs. Boats use a lot of spot lights so lots of potential battery life savings there.
skolbe
Well-Known Member
- Oct 3, 2006
- 3,549
- Boat Info
- 320 Sundancer, Zodiac 290 Wave Inflatable Tohatsu 6HP, Boston Whaler 130 Sport
- Engines
- 350 Mag V-Drive - Kohler 5ecd
I stay overnight on my 320 with no issue in the AM. I usually fire up the generator in the AM. If I am concerned I have turned the cockpit fridge to minimal cooling since it is just drinks. If your batteries are in good shape you should be fine. You do have the emergency start option. The stereo is what drains the batteries a lot.
Bt Doctur
Well-Known Member
A smarter alternative is to have a dedicated house and dedicated engine battery system
Craig
Well-Known Member
- Feb 8, 2007
- 1,044
- Boat Info
- Boatless
- Engines
- Boatless
I was out all day yesterday on the hook. 10 to 5. Ran both fridges set on 3. The jl stereo amp at lower volume and a 12 volt fan. I have 2 group 31 agm Duracells for a house bank. My victron battery monitor read 76% when I weighed anchor. I have never depleted it below 70% on a outing. I am sure I could get a overnight out of it and not go below 50%.
