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palerider wrote:

KatyDidAgain wrote:Good point about how long it would take to charge a laptop. I just read that the average laptop draws 72 kwh, but mine plugged into the kill-a-watt only draws 18-20 kwh -

while trying to figure all this out, it helps to make sure you understand, and use the terms right. else it can be very confusing.

I *think* you're meaning 72 watts, and 18-20 watts. a kwh is a KiloWattHour, a WattHour is a measure of total power used over time, one watt, pulled for one hour. so if you had your laptop on for an hour, it would use 18-20 WattHours, or .018-.020 KiloWattHours, since Kilo means 1000.

Volts electrical pressure, amps is the amount of electricity flowing, more needs bigger wires... watts is roughly amps times volts, so it's a measure of electrical power. and WattHours is a measure of electricity used, or, capacity, in the case of batteries. often times, batteries are specified as "amp hours" so to get watt hours, you have to multiply amp hours by the voltage of the battery, to get watt hours.

that's why amp hours of those little lithium battery packs can be so deceiving, since they're saying it's 10 amp hours, but they often mean at something around 3.5 volts, (the voltage of the internal lithium battery) not 12v which is what you really care about when trying to power a cpap.... so 10 amp hours at 3.5 volts is 35 watt hours, but if you compare that to a 12v battery, it's only 2.9 amp hours@12v. not enough for a cpap. (they often use marketing and say that the battery has 10,000 milliamphours, just to be able to use a bigger number, but that's 10,000 thousandths of an amp hour... or, 10.

It was a typo. I meant watts, not kwh. But still, the explanation is helpful.

You might want to figure out where it will sit at night while you are using it. Look at the bed/night stand of something like a Thor Palazzo 33.2. Most convenient for us hose heads.

I would recommend adding an additional DEEP CYCLE battery to your system.
More storage, all in the same place.

KatyDidAgain wrote: kill the humidity

I suggest you do home trials without humidity to see how your body responds. If you do OK, then think about how the ambient humidity at some of your campsites compares to your ambient humidity at home. If you camp in a very arid area, your experience without the humidifier may differ from the experience in your home trials.

BTW, I do not use a humidifier when the ambient humidity is 35% or higher.

I do agree with your husband on the 50" TV.



LOL. In the last few years I have gone from a full size tv to a small monitor to the lap top.

But, sports .... keeping my big screens.

I intend to do this in the near future. I will go with the 12V cpaps to make life easier and not have to worry about conversions. I intend to use as many same or similar makes , models, and parts as possible to make things interchangeable and have spares. So even tho she needs a cpap I will set up a bipap for her also. Esp. when it comes to power cords identical makes/models is a big help. And don't forget spare fuses.

You cant really add batteries to an older battery(s) as the older batteries will limit the performance of the entire battery bank. If you intend on making your battery bank larger it is always recommended that you replace all batteries at the same time with batteries that as best as you can determine were manufactured at about the same time.

CapnLoki wrote:Taking advantage any charge source is good, but it takes several hours to charge a computer and in the end you've only taken in a few amp hours. A big house bank can accept much more power so you should really focus on keeping that happy. If you want to think emergency backup, remember the cars alternator can put 30-50 amps into a deep cycle backup battery.

Hi CapnLoki,
My husband and I have been living on our boat at the dock for the past year, getting ready to start down the ICW from the Chesapeake to Florida. (Yeah, I know we're getting a late start -- that's a rant for a boating forum.). Using our CPAPs in the slip with shore power has not been an issue. Both of our CPAPs Are the AIEOEverrest travel CPAPs with the travel batteries and two charging systems: a regular 110 outlet and a Sabre (or cigarette lighter) charger. (Unfortunately, we have no 12 volt sockets.). The Everest has been discontinued a few years ago due to a warehouse fire and the company is no longer in business. We are attempting to figure out how many amps the CPAP draws in use.

We have a 1000 watt true sine wave inverter, but my dear husband is at a loss in figuring out how to install it. He also has a few 12 volt sockets, but hasn't installed them. We have three battery banks, one for starting the engine and two banks of house batteries, each with two batteries and 225 AH per battery. From the upthread discussion, it seems that our house batteries would be sufficient to power both CPAPs overnight, and we will be running our engine daily on the ICW so recharging the house batteries should not be an issue. We also have a Honda EU2000i generator, although I don't have a clear idea how long it would take to actually charge a CPAP battery.

Now to the question -- I think. Would installing two 12 volt sockets for the two CPAPs be enough to get us underway? Must they be on separate fuses? Is there some other question I should be asking? Is there a thread I should be perusing for ideas/answers or more questions? Thanks for any help you can give us.

Randy in Maine wrote:I bought this cord to run the cpap off the battery....24 volt machine on a 12 volt battery. IMO it is more efficient to go DC to DC as opposed to DC to AC to DC.

https://www.cpap.com/productpage/resmed ... hines.html

Very true, but using a 12 volt XPAP off of !2 volt DC, is the most efficient way to get the job done, even using a 110 volt AC cord requires a down converter circuit to power your machine, (it's just built in or a cord wart. If your vehicle power is 12 volt, it pays to use 12 volt toys, if you are worrying about power costs. Jim

Ruby Vee wrote: Hi CapnLoki,
My husband and I have been living on our boat at the dock for the past year, getting ready to start down the ICW from the Chesapeake to Florida. (Yeah, I know we're getting a late start -- that's a rant for a boating forum.). Using our CPAPs in the slip with shore power has not been an issue. Both of our CPAPs Are the AIEOEverrest travel CPAPs with the travel batteries and two charging systems: a regular 110 outlet and a Sabre (or cigarette lighter) charger. (Unfortunately, we have no 12 volt sockets.). The Everest has been discontinued a few years ago due to a warehouse fire and the company is no longer in business. We are attempting to figure out how many amps the CPAP draws in use.

I'm not familiar with the Everest products but I gather they used a 19v supply, meaning a special battery and power supply. While they may be some advantage to this for airplane/hiking applications because its similar to computer lithium packs, there is no great advantage over a Respironics Series 60 which can run nicely directly from 12 volts. Not saying you should throw away the Everest, but maybe you should keep your eyes open for a deal on a Respironics. BTW, I never bother to even bring a humidifier on the boat, though there's been a few autumn nights when I missed it.

Ruby Vee wrote:We have a 1000 watt true sine wave inverter, but my dear husband is at a loss in figuring out how to install it. He also has a few 12 volt sockets, but hasn't installed them. We have three battery banks, one for starting the engine and two banks of house batteries, each with two batteries and 225 AH per battery. From the upthread discussion, it seems that our house batteries would be sufficient to power both CPAPs overnight, and we will be running our engine daily on the ICW so recharging the house batteries should not be an issue. We also have a Honda EU2000i generator, although I don't have a clear idea how long it would take to actually charge a CPAP battery.

I use my 2000 watt inverter only briefly when running the microwave or the coffee grinder. The overhead of keeping it turned on is just too high. I have a collection of smaller inverters for running other devices, and I try to get devices that can run directly from 12 volts. I guessing that your "two banks of house batteries, each with two batteries and 225 AH per battery" is actually 4 Trojan T105's (or equivalent) 6 volt batteries for a total of 450 Amp hours. That is what I have, although last time around I went with slightly bigger T125's for a total of 480. If you really mean 4x225 or 900 Amp-hours then you have the largest bank I've seen on a small cruiser. In any case, your two CPAPs shouldn't use more than 10 amp-hours a night, so you're not coming close to straining the batteries if they are getting recharged during the day. BTW, it generally pays to combine all the house batteries into one large bank. The starting batteries are kept separate.

I also have a EU2000i, but I only run it a few times a year. Its really backup for the alternator.

BTW, the answer to "how long does it take to charge a battery?" is almost always 1 to 2 hours to get up to 85%, a few more hours to get to 95%, overnight to 100%. This is a traditional truism based on the acceptance rate of batteries. Modern lithium packs can be designed for fast charging, but most products do not have aggressive chargers.

Ruby Vee wrote: Now to the question -- I think. Would installing two 12 volt sockets for the two CPAPs be enough to get us underway? Must they be on separate fuses? Is there some other question I should be asking? Is there a thread I should be perusing for ideas/answers or more questions? Thanks for any help you can give us.

Yes, the 12V sockets should be installed. And ultimately this will be the best solution since your goal should be to have equipment that runs efficiently from 12V. At last count I have 2 sockets in the galley, 3 in the saloon, 2 at the nav station, 2 in the master berth, one at the instrument wiring, and one in the cockpit; plus two double USB chargers built in. It seems every year there's a new need!

The question shouldn't be "how many fuses" but "what size wire?" Run one heavy wire, I think I use 12 gauge for all my sockets. If its a real long run, consult the voltage drop chart in the West Marine catalog. If you don't use humidifiers, the current should bounce between zero and 2 Amps for each pump, so worst case in a momentary hit of about 5 amps. I'm guessing your "Accessory" breaker on your panel is 10 to 15 amps, which will protect the wiring against shorts. (If you do use humidity, you really have to work out the details, because the heater may go on full to warm up the water. With two units, this could be 10 Amps!)

So this is a little late to get started so make sure you bring a few cold weather clothes. When we went down in 2000 we did Thanksgiving in Myrtle Beach and there was a hard freeze (burst pipes on the dock on T'day morning!) and the freezes followed us all the way to Florida.