12 volt electric heat

[Ixneigh]

Abstract; by 2 in the afternoon on an average day my solar system is dumping power. If I got a 3rd battery specifically to operate a 12 volt 600 watt electric heater, it might warm up my bathroom a little if I ran it for 30 minutes. These heaters are pretty cheaply purchased online. I could top off the battery by plugging a jumper into a cigarette lighter socket.
My question is, is this a practical idea and, what is the smallest battery that would provide 30 minutes of service?

Ix

[Stickinthemud57]

I am not knowledgeable enough in battery types and technology to answer your question, but I will offer the following thoughts;

-600 watts is a lot to ask of a battery, and one would need an inverter of fairly good size and cost to convert your DC to the AC that most electric space heaters use.
-Drawing 600 watts for 30 minutes will, I think, push the limits of most 12V lead-acid car/boat type batteries and doing this a lot would likely shorten the life of such a battery.
-There are several very affordable propane space heaters that use oxygen depletion sensors that purportedly make them safe for indoor use. You might want to look into these. Here is an example:

https://www.amazon.com/Mr-Heater-F21510 ... r=8-8&th=1

[Ixneigh]

Oh I should have specified these are heaters that operate on 12 volts, at 600 watts dc. I figured it’s much safer than 110 volts.
Apparently they are intended to defrost windows in the winter.

[Ixneigh]

Oh I should have specified these are heaters that operate on 12 volts, at 600 watts dc. I figured it’s much safer than 110 volts.
Apparently they are intended to defrost windows in the winter.
Re: purportedly safe, but I think
I’d need a real wood stove type Charlie noble to feel comfortable with heating with flame

[Russ]

Years ago I had a 12v hair dryer. It was a joke. Probably consumed 600w but sucked the battery down and didn't put out much heat.

Wait............you are in the Florida keys. Heat? I would think you'd be looking for cooling ideas.

[Ixneigh]

In The winter we have a few coolish days. Maybe twenty of them. That’s why I’m installing a wood stove or anything more complex than a portable unit.

[Be Free]

I'm going to assume that you want to run this heater in the morning or perhaps in the evening to take the chill off the head and that you are going to use the "excess" power in the afternoon to replace this power in the new battery.

600W / 12V (nominal) = 50 amps

50 amps for 0.5 hours = 25 Amp hours

Ignoring Peukert effect a 50 Ah deep discharge (not dual use) lead acid battery would work but I doubt that you can find one that small that can take a 50A discharge rate for 30 minutes. The limiting factor is likely going to be the 50A rate rather than the battery capacity. Any deep discharge lead acid battery that can be discharged at 50 amps continuously that is at least 50 Ah will work.

Regularly pulling a lead acid battery down to 50% state of charge will shorten it's life. Quickly bringing it back to full charge will help.

A 125 AH battery would only be pulled to 80% SOC and would be less stressed. It's also more likely to be able to take to 50A discharge rate.

A 50 Ah lithium battery would probably be able to handle the 50A discharge rate and would not be stressed at 50% SOC. If you are not already set up to charge lithium then this would be a very expensive heater.

Regardless of which chemistry is used, you will need to replace (a bit more than) 25 Amp hours in the battery with excess solar power each afternoon if you want to be ready for the next cycle.

Do you have enough excess solar capacity to do this?

[Ixneigh]

This is why I love this forum. There are some really smart people flogging about in these little boats.
I have not braved the lithium train yet on my boat. I’m currently experimenting with a simple system powering this little EV cart



If it doesn’t catch fire or do anything else scary I might consider redoing my boats batteries with lithium when the Optima AGM batteries bite it (they are on their last legs now)
The 50 AH battery I have in the EV cost 109.00 dollars. I set up the EV with a charge regulator and a 100 watt solar panel
and it can go a few miles a day just on solar. The motor is a 350 watt 24 volt scooter motor which is connected to a step up 12 to 24 volt converter. So this is a similar draw.

Regarding charging capacity. In cooler weather I might be able to do this with a 225 watt solar array. In warm weather running the electric icebox, not so much. I don’t shower every day when I’m just laying about on the boat. I found certainly connect the heater battery to the system for a few hours during the afternoon.

Ix

[Be Free]

This is why I love this forum. There are some really smart people flogging about in these little boats.
I have not braved the lithium train yet on my boat. I’m currently experimenting with a simple system powering this little EV cart



If it doesn’t catch fire or do anything else scary I might consider redoing my boats batteries with lithium when the Optima AGM batteries bite it (they are on their last legs now)
The 50 AH battery I have in the EV cost 109.00 dollars. I set up the EV with a charge regulator and a 100 watt solar panel
and it can go a few miles a day just on solar. The motor is a 350 watt 24 volt scooter motor which is connected to a step up 12 to 24 volt converter. So this is a similar draw.

Regarding charging capacity. In cooler weather I might be able to do this with a 225 watt solar array. In warm weather running the electric icebox, not so much. I don’t shower every day when I’m just laying about on the boat. I found certainly connect the heater battery to the system for a few hours during the afternoon.

Ix

Are you trying to reinforce the upper Keys resident sterotype?

re: your scooter
350 W / 24 V = 14.6 A but since you are pulling this from a 12V battery then the battery has to supply a bit over 29.2 A (there is overhead for the step-up converter). If the scooter battery is lead then you should get around 45 minutes run time at full speed if the battery is fully charged and still delivering 50Ah. If it is lithium you should get about 2x the run time. Is that pretty close? A 100W panel should be just about perfect for keeping a 50AH battery charged as long as you are not pulling it down to 50% every day.

I'm at the same place you are with the switch to lithium. I have a large lead house bank that is past "last legs", probably closer to "one foot in the grave". I'm actually doing the cost/benefit analysis for a switch to LiFePO4 right now. Seven years ago lead was the clear winner; lithium is definitely in the running and may actually win out this time.

In the summer you won't need to run the heater will you? The icebox will be the major draw in the summer but it will not run nearly as much in the winter. You have the additional advantage that the solar panels will work better in the winter (when they will run cooler). A 225 W solar array should put out around 15A for battery charging. You should be averaging close to 6 hours of usable sunlight at your latitude so that is around 75Ah on a clear cool day with newish panels and a good charge controller.

[Gazmn]

I'm at the same place you are with the switch to lithium. I have a large lead house bank that is past "last legs", probably closer to "one foot in the grave". I'm actually doing the cost/benefit analysis for a switch to LiFePO4 right now. Seven years ago lead was the clear winner; lithium is definitely in the running and may actually win out this time.

In the summer you won't need to run the heater will you? The icebox will be the major draw in the summer but it will not run nearly as much in the winter. You have the additional advantage that the solar panels will work better in the winter (when they will run cooler). A 225 W solar array should put out around 15A for battery charging. You should be averaging close to 6 hours of usable sunlight at your latitude so that is around 75Ah on a clear cool day with newish panels and a good charge controller.

I took the plunge a year or 3 ago with Lithium. I have a true 400hr house system with a 4K inverter and newer dual zone fridge I normally keep as a single. I haven’t posted in a while. Perhaps I’ll get it together for latest mod posting. It’s awesome.

Re: heating, why don’t you just use a propane buddy for the occasional chilly evening

https://www.amazon.com/Mr-Heater-F2320 ... 51BZU?th=1

[rsvpasap]

I think you'll find the reviews from people who have owned 12 volt heaters are generally not great. Also, at 600 watts (50 amps DC), a 100 amp hour lead acid battery will provide an hour of heat, maximum, under perfect circumstances with a fully charged battery. A 100 amp hour LifePo4 battery will provide a little more than an hour and a half of heat at 600 watts. Not meaning to state the obvious, but then you have to recharge it to do it again tomorrow.

The other option involving no installation is a portable propane heater. These come with risks you should investigate thoroughly. These risks include the possibility of depleting the oxygen in an enclosed cabin as well as filling a non-vented cabin with toxic combustion gases.

I've tried the Mr Heater Buddy. In my opinion, it's not a good solution because (1) It puts out 4,000-9000 BTUs of heat which is too much under most circumstances for a 26 ft boat especially in South Florida even on the coldest days, (2) in my personal experience with the Mr Heater Buddy the low oxygen alarm is so very quiet that it is not sufficient to provide a warning, (3) they burn a lot of propane and create a lot of condensation, (4) though people sometimes mistakenly refer to them as "catalytic heaters" there is actually nothing catalytic about them, i.e., they do not catalyze the propane into heat, instead they burn the propane in a fire.

After much (much!) experimentation with heaters on boats and campers, in my opinion, the best solution for occasional heat that does not require an installation is a Camco Olympian Wave 3 heater. https://www.google.com/search?q=Olympian+Wave+3+heater

It is actually catalytic, i.e., there is no flame except for the initial pilot light which goes out once the catalyzing process begins. Otherwise, the heat is produced by catalyzing the propane in conjunction with platinum. It provides 1600-3000 BTU, giving you the ability to leave it set on low for extended periods that will raise the temperature of the cabin 15-20F, great for those days when it's chilly but not snowing. It will raise the temperature in the cabin 30 - 35F running on its highest setting.

One pound of propane provides 21,500 BTUs of heat. Thus 1 lb bottle of propane will provide somewhere between 7 - 13 hours of heat with the Olympian wave, depending on how you have it adjusted. Compare this to the Mr Heater Buddy which will provide 2.5 - 5 hours of heat for the same amount of propane.

I've attached a photo of the stand I built for my Wave 3. This included

- small piece of plywood
- short piece of 4-in diameter PVC tube
- black spray paint
- adhesive (5200) to attach the PVC to the plywood
- screws to attach the heater to the plywood.
- propane adapter to use the heater with 1 lb bottles https://tinyurl.com/y6j4r88n

Also I drilled a small hole in the stand and another in the table in my 26x to attach them with a bolt so I can rotate the heater in any direction I like, but the heater will not bounce off the table even in the rough conditions.

The Wave 3 seems to create very substantially less condensation than the Mr heater Buddy, but that could be primarily due to the fact that it consumes so much less propane.

Finally, note that a variety of vendors now sell legally refillable 1 lb propane bottles. I have a number of these and just refill them as needed. In my area, this ends up costing approximately 85 cents per pound for propane.

Finally, if for some reason you find the Mr Heater brand more appealing, they also sell a line of catalytic heaters which are essentially copies of the Wave heaters, but they are more expensive than the Wave. https://www.mrheater.com/product/heaters/catalytic.html

[In the interest of full disclosure: I primarily use this heater as a supplemental heater in addition to the diesel heater in the boat on those occasions when it is very cold, below 35F. I have recently installed a vented propane heater to use in addition to the diesel heater for those situations. Nonetheless, I found the Wave 3 to be a great solution for occasional use.]

[OverEasy]

Hi All!

I’ve used a 12 volt DC forced air ‘hair dryer’ type defroster in an old ‘beater’ SUV..
It works just fine when the engine is running but with just the starter type battery it will quickly drain it flatter’n a pancake.
I’d look for a different approach if it were moi…..

A solar hot water heater using a thermal siphon in a closed loop system comes to mind if you just want a little bit of heat to warm the bath area. There is a weight aspect that one would need to address though.

I’ve contemplated a hydronic heating system for us from time to time.
One scenario would be that the system is empty until at a location and moored or anchored.
Then flood the system and seal. ( That way the heat transfer water is just temporary)
Set the solar heat collector in place and let it do its thing for a couple hours to warm up the incabin ‘temporary’ holding tank.
After the sun sets close off the valves to the collector (as it would otherwise act as a radiator cooling your newly acquired heat reservoir.
When moving on one just drains/pumps out the water and moves along.

Best Regards
Over Easy

[dlandersson]

Must be nice

In The winter we have a few coolish days. Maybe twenty of them.

[OverEasy]

23F last night…….brrrrrr….. and it’s just still Fall here…..

[Be Free]

I was in West Virginia last week and someone suggested that I should have a winter coat on instead of the hooded sweatshirt I was wearing.

I told them that where I come from what I was wearing was a winter coat.