floor O2 concentrator

[user 23166]

Hi everyone,

I'm still looking for a conversion van to start my adventure. I'm 57 and want to get to traveling ASAP....but I need some help figuring out how to set my van up with enough battery power to supply my electrical needs.

I'm not sure if I'm figuring this correctly or not.

I have a stationary O2 concentrator that I need to bleed oxygen into my cpap for 8 hours a night, I will also have a Refrigerator that will run 24/7, but haven't decided yet if I'm gonna power with electric or propane, but am including it here so I know what I need just in case.

The manufacturer says my O2 concentrator is 350 watts, my cpap manufacturer said my cpap is 110 watts, and everything I'm reading said about 200 watts for the refrigerator. 

With these numbers I came up with approximately 57AH...can someone verify if that is correct or not for me please?
It just seems like a low ball number for all that wattage.

Any idea's or answers are so very much appreciated,
Thank You

 

[highdesertranger]

Welcome wanderingwillow to the CRVL forums! To help you learn the ins and outs of these forums, this "Tips, Tricks and Rules" post lists some helpful information to get you started. We look forward to hearing more from you.

are those wattage numbers at 110v AC? in other words household current. if so you are going to have losses in the conversion. refrigerators and cpaps are available in 12v, I don't know about the O2 concentrator.

highdesertranger

 

[user 23166]

Hello highdesertranger,

Thank you for responding.

Yes, the O2 concentrator is 110V and I knew I was going to have some loss in the conversion, but I'm not sure how much. Is there a way to figure that out as well, and do you know if my calculations in figuring overall wattage to AH's were correct?

 

[Wabbit]

Convert watts to amps(EDIT: not my words, find link below)

Actually, watts is the fundamental unit of power and watt-hours is the energy stored. The key is to use the watts you know to calculate the amps at the battery voltage .

For example, say you want to run a 250 watt 110VAC light bulb from an inverter for 5 hours.
Watt-hours = watts * hours = 250 watts * 5 hours = 1250 watt hours

Account for the efficiency of the inverter, say 85%

Watt-hours = watts * hours / efficiency = 1250 / 0.85 = 1470 watt-hours

Since watts = amps * volts divide the watt hours by the voltage of the battery to get amp-hours of battery storage

Amp-hours (at 12 volts) = watt-hours / 12 volts = 1470 / 12 = 122.5 amp-hours.
If you are using a different voltage battery the amp-hours will change by dividing it by the battery voltage you are using.

From this link...
https://www.powerstream.com/battery-capacity-calculations.htm


Fun stuff!

 

[maki2]

What might be of use to you for your calculations....the various solar panel companies have put onto their websites easy to use calculators that help you to figure out your power needs. They also take into account your battery size and/or recommend battery size as well of course as the amount of solar panels you would need to match your electrical consumption.

So that is an easy, no math way to quickly check variations in you setup regarding equipment you might be considering using or purchasing. The information for the inverters you look at should also give some indication of the power it draws while in active use.

If you have the ability to create simple spreadsheets it would help you keep track of the different pieces of equipment you are considering and the values returned for it from the online calculator. Being methodical about the data collected in research does help reduce confusion and errors.

 

[Mrcap]

There are a lot of factors that will impact your results or needs.

For example;

Some of your power consumption will be during the day while solar is available and not drawing on your battery in most cases.

If you are not carrying propane otherwise you may want to be all electric.

The type of battery will determine safe percentage of discharge between charges.

The type of the solar controller has a big impact on efficiency.

Are you going to be in a sunny climate all the time?

If you want a guess? I would say a minimum of 200ah but more like 400ah of batteries and 400 or more Watts of solar.

My RV has 300ah of batteries and 500w of solar. I have a little extra in panels so I don't have to bother tilting them.

If my memory serves me there have been previous discussions about the use of these devices and real life charging scenarios so hopefully those users will chime in.

 

[user 23166]

Thanks everyone for the information, it's been very helpful, I know what setup I'm going to start with and add from there

 

[Trebor English]

The manufacturer says my O2 concentrator is 350 watts, my cpap manufacturer said my cpap is 110 watts, and everything I'm reading said about 200 watts for the refrigerator. 

With these numbers I came up with approximately 57AH...can someone verify if that is correct or not for me please?

Your watts add up to 660.  If you divide by 12 you get 55 amps.  That's when everything is on.  If you add 20% for the inverter loss you end up with 66 amps.  A quick way to figure that rather than 12 volt and 20%, just divide the 660 by ten, easy mental math.  

You only want the CPAP and concentrator, 460 watts, 46 amps, for 8 hours, 368 amp hours per day.  A small 12 volt fridge should be around 20 amp hours per day.  The 200 watt power level you mentioned, 20 amps, would only apply while the compressor runs.  If it actually runs 2.4 hours per day, 10% on 90% off, at 20 amps you get  48 amp hours per day.  That sounds like a dorm fridge running from an inverter.  

368 + 48 = 416 amp hours per day.    Two pairs of 6 volt golf cart batteries will be fully used with all that.  Since the majority is over night there won't be enough daytime use to change the math.  

Very often the power rating of a device differs dramatically from the actual use.  It may be that your equipment will use less power at the heating, humidification, pressure and liters O2 you actually use.  Get a Kill A Watt, about $20 from Amazon, Home Depot, Harbor Freight, and actually measure your overnight use.  

The peak watts still affects the size inverter you need.  Whatever your fridge uses running the starting surge is at least double that.