Electric Heater

[Donald Tyson]

Some of you were able to break down how long something would run on the batteries I have (two 27 size AGM storage). Is this even possible to run a ceramic heater for more than a couple of hours. Would I be tremendously wiser to take a slip and use shore power for the three nights I'll be there. Kim and I are planning to visit New England during the second week of October...probably the Newport area or Mystic. We don't have a Wallace or similar.
I've heard that a cast Iron Frying pan over the Alcohol burner works well but I can't imagine it to be for any duration to speak of and safety would be questionable. While we could probably just tough-it-up and do without heat for three nights it may be nice to have it as well.
Thoughts?

[djy887]

I've used a 'Mr Heater' portable buddy heater. Obviously using ANY sort of heater requires an elevated sense of awareness/safety. This is a good unit with an auto-shutoff on tipover. I set it on the floor on wooden cutting board...with a at least of foot of space around it in all directions. I kept it on a middle to low heat setting. I cracked a window to try and minimize condensation. And it worked it quite well.

https://www.homedepot.com/pep/Mr-Heater-Portable-Buddy-9-000-BTU-Radiant-Propane-Indoor-Outdoor-Space-Heater-F232000/205527178?clickid=QTXxLPwC2xycRaT1-QVhLRShUkpzOR3gExx4zI0&irgwc=1&cm_mmc=afl-ir-2003851-1420157-EdgeBingFlow

[Flashyfish]

A 12 volt 300 Watt electric heater needs 25 amps of DC power to work. With an average storage battery, you would be lucky to see an hour of heating before voltage dropped too low to continue functioning. I don't know if a 300 watt heater would make much difference.

[thataway]

To run a 120 V AC heater would require at east a 1500 watt inverter (12V DC to 120 V AC). On low these heaters pull 800 to 1000 watts. (80 to 100 amps 12 V DC) At this level, you are looking at about an hour max for two group 27 batteries.

A 12 volt 300 watt heater woud pull somewhere near the 25 amps (as per Flashyfish.). That would last about 4 hours, but would not really give you enough heat.

I don't like the Mr heater or Mr. Buddy. They do have oxygen sensors, but CO remaoins an issue. You can buy expensive CO meters for airplanes or less sensative househod types.

Best are the forced draft/blower type which are used in trucks and RV's. There are boat specific boat units both real Esphar or Chinese/Russian copies.

In AK we used the electric at the dock and the Wallas stovetop when on the hook. It took the chill off, but not "warm".

I have pronoucned dead all too many who have used CO producing heaters in boats and RV's....Each was a tragedy in itsef.

[Tom Hruby]

As mentioned by others, two 12 V batteries will not provide enough power to heat the cabin overnight in October in Massachusetts. In my 22' cruiser I have found that I need about 500 watts to keep the cabin temperature above 65 degrees when the outside temp fall to the low 50's. Even with electric heating I still need to keep some windows open to keep the carbon dioxide levels from our breathing below 800 ppm. Carbon dioxide levels above that can lead to headaches. Any combustion based heaters without adequate ventilation will raise CO2 to toxic levels within minutes. FYI the CO2 levels we breathe out is about 40,000 ppm. Two of us in our cabin with everything closed will raise the CO2 levels to 1500 ppm in less than hour (actually measured).

Since I don't like the noise of heater fans running I am using a convection heater with a thermostat and two settings 700 and 1500 watts.

My 48 V battery bank for propulsion holds 20kWh or energy, and I do have a 48V to 120V inverter. Even with that I probably could not heat the cabin for more than a day or so. But in colder weather we do plan our cruising from marina to marina with shore power.

[robhwa]

Though it varies, your body will produce about 100 watts of heat sleeping, or about 800 watt-hours through the night. Add a partner, and you have twice that, or more energy than a 100 amp 12 volt battery LiFePO4 battery will provide in that same time, and you don't need to recharge the heater. You can sleep warmly if you add insulation, and a mummy-style sleeping bag works fine for me. I have two that zip together, and we've been relatively comfortable in -30F winter Alberta. Add a couple of dogs, and you're golden. You really need to be careful with buddy-type heaters, which I do use, but only with great ventilation in the cockpit of my boat and in deer blinds. I also am extremely cautious about propane, which is heavier than air and can fill you cabin and cockpit if it leaks. Propane emissions produce both CO2 and water vapor, and the water vapor condenses on cold surfaces. It is best to put combustion air outside of your cabin, and to guard against the possibility of CO poisoning which Bob mentions. Webasto diesel heaters are a gold standard and well worth the investment if you use your boat in colder areas and/or places. I just took a trip south from Prince Rupert, BC, Canada, and it was always a joy to step back into a warm, dry cabin after fishing outside in the cold rain.