northforktug130
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Can charger be on at dock all the time.
Will it overcharge or have negative effects
Will it overcharge or have negative effects
Battery charger
- Thread starter northforktug130
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Submariner
Channel Surfing
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northforktug130
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Great . Thxs
northforktug130
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Thxs great
Submariner
Channel Surfing
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What model year and model boat do you have?
northforktug130
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2014 27
Rode Trip
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Different battery types, different answers. That's probably why Submariner asked what boat he had. Lead acid and AGM batteries are perfectly fine being left on a float charge long term and it's the best way to store them. Lithium batteries prefer to be stored long term between 50-80% charged depending on the manufacturers recommendation. As far as occasionally overnight, it's perfectly fine to do that with lithium batteries. Even weeks is ok keeping your lithiums fully charged, you just don't want to store them for 3 months fully charged, you would want to run them down a little and then disconnect them.
Robert
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We are mostly day boaters and the only is the 24/7 and refrigerator. We lose about 5% a day on lithium house bank. Should I let it get to 30 or 40% and then charge or just leave the charger on?
Thanks
Bob
Thanks
Bob
Rode Trip
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My understanding of lithium batteries, and I don't personally have them on my boat yet so Submariner can probably give better advice, is that you would be better off to let them discharge to 30-40% and then charge, rather than keeping them on a float charge all the time. They can handle a lot of charge cycles without a problem, but spending long term on a float will hurt them eventually.
Submariner
Channel Surfing
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Battery charging differences between AGM and LFP (LiFePo4, Lithium).
AGM (and FLA, Flooded Lead Acid) batteries, have 3 stages of charging. Bulk, Absorption and Float. Bulk stage gets the batteries to around 85% state of charge, accepting a lot of current (like, 20-30amps per 110ah battery). The absorption phase is where the battery slows down accepting charge. It takes a lot of time (6+ hours) to get through the absorption phase. When we're out boating, we rarely would have enough time on the water to make it through the absorption phase with just engine charging or even a portable generator. The float stage is to keep the AGM/FLA batteries topped off. This is what AGM/FLA need. It's best to leave AGM/FLA on a battery charger all the time at a dock to get the most life out of them.
LFP really only has two stages, Bulk and Absorption. LFP will accept an enormous amount of charge compared to AGM. (100+ amps per LFP battery). On Channel Surfing, I have a single 320 amp-hour LFP battery (Lithionics is who makes it). It will accept up to 150 amps for charging. This enables LFP to charge a lot faster than AGM. However, with an outboard engine and 420 watts of solar and a 60 amp shorepower battery charger, the best I could ever hope to see is about 120 amps of charging if I idled the engine at the dock, on shorepower with the battery chargers on, at noon in June for max solar output (wishful thinking, really). Usually I'm around 15-80amps of charging. The Bulk stage for LFP goes up to about 95% state of charge at which point the battery charger will switch to the absorption stage. Absorption with LFP lasts less than 60 minutes, depending on the brand of the battery. If you left your boat for months and month (off-season storage), you may lose some capacity, over time, by leaving LFP fully charged on a battery charger. A few weeks here or there, a month here or there, no biggie. I leave Channel Surfing on a battery charger, especially through the off-season when solar isn't nearly as useful. We use our boat usually once a month in the off-season (October - March).
However, if I were to store my boat for 2+ months, and I was out of the water, I'd disconnect shorepower, run the inverter to power the microwave. I'd heat up a cup of water until I saw the state of charge fall below 95%. Then I'd shut off all the power on the boat (house and engine switches would be turned off). I'd pull the 24x7 fuses (being out of the water, I'm not worried about the bilge pumps). I'd then configure my solar controller to "disabled" so it doesn't charge the house battery. This would leave the LFP battery at 95% (or less. Anywhere between 45 and 95% is good for long term storage.). Then it's like the LFP battery is partially charged, sitting on a shelf, with no loads on it, and no charging. It can sit like that for 6+ months.
During boating season, (June-October) I take a different approach. Since Channel Surfing is stored outside in full view of the sun and I have 420 watts of solar, I will often just not connect to shorepower. I'll let the boat sit, week to week, not on the battery charger, with most things powered off on the boat, but I leave the 24x7 fuses in and working, I leave both refrigerators running. I leave the engine and house power turned on. Consumption occurs throughout the night, solar puts it back in the next day. The boat will usually cycle between 80 and 100% state of charge via LFP at night, and solar during the day. A few days of rain will come in, maybe I get down to 50%. Doesn't matter. LFP would rather be in a partial state of charge most of the time, being used, where AGM would rather be in float, fully charged, most of the time. I will go weeks, 3, 4, 5, 6 weeks without running my battery charger... during boating season.
LFP can handle a lot of cycles... AGM is usually 300-600 cycles, while LFP is 2000+ cycles for it's lifetime. The Victron battery monitor I have keeps tracks of cycles. At 3 years and 3 months with my LFP setup, I'm at 66 cycles as of today. We use the heck out of our house bank. It's not uncommon for us to get down to 30% state of charge. LFP can be safely discharged down to 20% state of charge while AGM needs to be 40% or higher.
Channel Surfing has 320amp-hours total. Stats, February 2022 - May 2025, as reported by my BMV-712 battery monitor.
Keeping AGM/FLA on a battery charger at shore is the best practice. LFP on a battery charger at shore is also 'ok' to do. Long term storage, drain the LFP below 95% SOC, and isolate them from charging and loads. Else, don't worry about it and enjoy using the boat.
Also note, there's a lot of time (especially during boating season) where I plug into shorepower, but I don't turn on my battery charger. With my solar setup and LFP house bank, I will let them cycle daily as described above. But then we can run multiple appliances at 120volt on the boat all at once. Hot water heater, microwave, cofee maker, and other kitchen appliances she brings. The entire boat is powered off 12 volts, except for the switches in the AC panel, which are all 120volt (port and starboard outlets, grill outlet, water heater, microwave). Running the inverter to make 120volt power, we can only run a single 120volt appliance at a time.
Since I redesigned the electrical on Channel Surfing to convert from AGM to LFP, and I had to re-wire the boat to accomodate, there's one other feature I have which I utilize if I need to store the boat in the water, during the off-season (when I need bilge pumps powered off the house). I will drain the LFP battery down to less than 95%. I then open the 250 amp DC breaker directly in front of my LFP battery. This completely isolates the LFP from all charging and all loads. I have a push-button on/off switch on my Lithionics battery. I turn the LFP battery off. It can sit like this for 6+ months. But the boat is now dark, without power. I then will parallel the engine and the house (remember, my house bank is completely isolated by that 250 amp DC breaker being open), disable my solar controller and disable my engine to house DC to DC charger (as both are configured for LFP, not AGM). I connect to shorepower and run my engine battery charger (20amp) only. (I have a second, 60amp battery charger dedicated to my house bank which I leave off). This puts all 12 volt house loads being powered by the engine battery, and the engine battery (and thruster battery) being charged by the 20 amp battery charger on shorepower. So really, all 12volt loads are being powered by the 20amp battery charger. The boat can operate like this at the dock for 6+ months, bilge pumps work, refrigerators work, lights work, etc...
Lithionics has a counter in their BMS that keeps track of how long the battery is kept at 100% state of charge. Lithionics uses this number for warranty claims (to reduce their liability). So I put forth some effort (not a lot), to slow down that number from incrementing as described above.
I don't worry about my engine and thruster batteries which are both AGM. They stay fully charged, most of the time, while I'm operating the boat.
For additional details:
Or look at our website.
www.letsgochannelsurfing.com
AGM (and FLA, Flooded Lead Acid) batteries, have 3 stages of charging. Bulk, Absorption and Float. Bulk stage gets the batteries to around 85% state of charge, accepting a lot of current (like, 20-30amps per 110ah battery). The absorption phase is where the battery slows down accepting charge. It takes a lot of time (6+ hours) to get through the absorption phase. When we're out boating, we rarely would have enough time on the water to make it through the absorption phase with just engine charging or even a portable generator. The float stage is to keep the AGM/FLA batteries topped off. This is what AGM/FLA need. It's best to leave AGM/FLA on a battery charger all the time at a dock to get the most life out of them.
LFP really only has two stages, Bulk and Absorption. LFP will accept an enormous amount of charge compared to AGM. (100+ amps per LFP battery). On Channel Surfing, I have a single 320 amp-hour LFP battery (Lithionics is who makes it). It will accept up to 150 amps for charging. This enables LFP to charge a lot faster than AGM. However, with an outboard engine and 420 watts of solar and a 60 amp shorepower battery charger, the best I could ever hope to see is about 120 amps of charging if I idled the engine at the dock, on shorepower with the battery chargers on, at noon in June for max solar output (wishful thinking, really). Usually I'm around 15-80amps of charging. The Bulk stage for LFP goes up to about 95% state of charge at which point the battery charger will switch to the absorption stage. Absorption with LFP lasts less than 60 minutes, depending on the brand of the battery. If you left your boat for months and month (off-season storage), you may lose some capacity, over time, by leaving LFP fully charged on a battery charger. A few weeks here or there, a month here or there, no biggie. I leave Channel Surfing on a battery charger, especially through the off-season when solar isn't nearly as useful. We use our boat usually once a month in the off-season (October - March).
However, if I were to store my boat for 2+ months, and I was out of the water, I'd disconnect shorepower, run the inverter to power the microwave. I'd heat up a cup of water until I saw the state of charge fall below 95%. Then I'd shut off all the power on the boat (house and engine switches would be turned off). I'd pull the 24x7 fuses (being out of the water, I'm not worried about the bilge pumps). I'd then configure my solar controller to "disabled" so it doesn't charge the house battery. This would leave the LFP battery at 95% (or less. Anywhere between 45 and 95% is good for long term storage.). Then it's like the LFP battery is partially charged, sitting on a shelf, with no loads on it, and no charging. It can sit like that for 6+ months.
During boating season, (June-October) I take a different approach. Since Channel Surfing is stored outside in full view of the sun and I have 420 watts of solar, I will often just not connect to shorepower. I'll let the boat sit, week to week, not on the battery charger, with most things powered off on the boat, but I leave the 24x7 fuses in and working, I leave both refrigerators running. I leave the engine and house power turned on. Consumption occurs throughout the night, solar puts it back in the next day. The boat will usually cycle between 80 and 100% state of charge via LFP at night, and solar during the day. A few days of rain will come in, maybe I get down to 50%. Doesn't matter. LFP would rather be in a partial state of charge most of the time, being used, where AGM would rather be in float, fully charged, most of the time. I will go weeks, 3, 4, 5, 6 weeks without running my battery charger... during boating season.
LFP can handle a lot of cycles... AGM is usually 300-600 cycles, while LFP is 2000+ cycles for it's lifetime. The Victron battery monitor I have keeps tracks of cycles. At 3 years and 3 months with my LFP setup, I'm at 66 cycles as of today. We use the heck out of our house bank. It's not uncommon for us to get down to 30% state of charge. LFP can be safely discharged down to 20% state of charge while AGM needs to be 40% or higher.
Channel Surfing has 320amp-hours total. Stats, February 2022 - May 2025, as reported by my BMV-712 battery monitor.
- Deepest discharge: 254amp-hours (20% state of charge)
- Average Discharge: 160amp-hours (50% State of charge)
- Charge Cycles: 66
- Total amp-hours drawn: 28,164ah.
Keeping AGM/FLA on a battery charger at shore is the best practice. LFP on a battery charger at shore is also 'ok' to do. Long term storage, drain the LFP below 95% SOC, and isolate them from charging and loads. Else, don't worry about it and enjoy using the boat.
Also note, there's a lot of time (especially during boating season) where I plug into shorepower, but I don't turn on my battery charger. With my solar setup and LFP house bank, I will let them cycle daily as described above. But then we can run multiple appliances at 120volt on the boat all at once. Hot water heater, microwave, cofee maker, and other kitchen appliances she brings. The entire boat is powered off 12 volts, except for the switches in the AC panel, which are all 120volt (port and starboard outlets, grill outlet, water heater, microwave). Running the inverter to make 120volt power, we can only run a single 120volt appliance at a time.
Since I redesigned the electrical on Channel Surfing to convert from AGM to LFP, and I had to re-wire the boat to accomodate, there's one other feature I have which I utilize if I need to store the boat in the water, during the off-season (when I need bilge pumps powered off the house). I will drain the LFP battery down to less than 95%. I then open the 250 amp DC breaker directly in front of my LFP battery. This completely isolates the LFP from all charging and all loads. I have a push-button on/off switch on my Lithionics battery. I turn the LFP battery off. It can sit like this for 6+ months. But the boat is now dark, without power. I then will parallel the engine and the house (remember, my house bank is completely isolated by that 250 amp DC breaker being open), disable my solar controller and disable my engine to house DC to DC charger (as both are configured for LFP, not AGM). I connect to shorepower and run my engine battery charger (20amp) only. (I have a second, 60amp battery charger dedicated to my house bank which I leave off). This puts all 12 volt house loads being powered by the engine battery, and the engine battery (and thruster battery) being charged by the 20 amp battery charger on shorepower. So really, all 12volt loads are being powered by the 20amp battery charger. The boat can operate like this at the dock for 6+ months, bilge pumps work, refrigerators work, lights work, etc...
Lithionics has a counter in their BMS that keeps track of how long the battery is kept at 100% state of charge. Lithionics uses this number for warranty claims (to reduce their liability). So I put forth some effort (not a lot), to slow down that number from incrementing as described above.
I don't worry about my engine and thruster batteries which are both AGM. They stay fully charged, most of the time, while I'm operating the boat.
For additional details:
Or look at our website.
House Battery-Lithium | LetsGoChannelSurfing
www.letsgochannelsurfing.com
Last edited:
Submariner
Channel Surfing
- Joined
- Feb 2, 2020
- Messages
- 1,620
- Location
- Everett, WA
- Website
- www.letsgochannelsurfing.com
- Fluid Motion Model
- R-27 (Outboard)
- Hull Identification Number
- FMLT2702C021
- Non-Fluid Motion Model
- https://tinyurl.com/yrv84xdm
- Vessel Name
- Channel Surfing
- MMSI Number
- 368187810
You can always, regardless of whether the boat is an LE with AGM and LFP, or a NW edition with AGM/FLA batteries, run the battery charger all the time. It won't over charge the batteries.
How you put the boat away for long term storage differs for AGM and LFP.
Submariner
Channel Surfing
- Joined
- Feb 2, 2020
- Messages
- 1,620
- Location
- Everett, WA
- Website
- www.letsgochannelsurfing.com
- Fluid Motion Model
- R-27 (Outboard)
- Hull Identification Number
- FMLT2702C021
- Non-Fluid Motion Model
- https://tinyurl.com/yrv84xdm
- Vessel Name
- Channel Surfing
- MMSI Number
- 368187810
I'd already figured out he had to have a classic model, as he'd asked about a key fob. The outboards all have keys. 🙂
He'd been asking a lot of questions in the forum about all kinds of topics, but never stated what specific boat, and model year he had. I wanted to know so I could best answer other questions he's been asking as well.