A 12v power question

[winchman]

I need to run a medical device (CPAP Machine) in the motor home.
I was going to install a separate 12v leisure battery to power it, this will be charged when the vans on hook up or when I remove the battery at home.
The manufacturer quotes AC power consumption100-240v 50/60Hx, 2.0-1.0A
I have tried to email for the 12v load but as yet no reply.
So any thoughts on what power it would be around 12v and what size battery would be required used for a max of 3 days 12 hours a day when off grid?

 

[the snooper]

Have you got a clamp meter ? If so you can measure it

 

[winchman]

Have you got a clamp meter ? Uf so you can measure it

I know but I was hoping to fit it all before it arrives and the current rented machine ( different make) goes back

 

[the snooper]

Ah sorry didn't realise you didn't have it yet

 

[daedalusminos]

So your motorhome has an inverter to convert from 12V to 220V?

 

[winchman]

So your motorhome has an inverter to convert from 12V to 220V?

No everything in it is 12v.
The new unit has a 12v lead

 

[daedalusminos]

Ahh OK, well it should have a 12V DC spec have you tried to google the model?

 

[wyn]

Would a "Battery power station" be any good.

could charge it from the vehicle or solar or 240v.

Eco flow, bluetti, jackery type of thing.

 

[the snooper]

Found this

 

[winchman]

Would a "Battery power station" be any good.

could charge it from the vehicle or solar or 240v.

Eco flow, bluetti, jackery type of thing.

Just too cumbersome. I can fit a battery and charger in the garage and bed is directly above it so a simple install. the portable type power stations are expensive I believe compared to a leisure battery?

 

[ajlelectronics]

It seems to be 240W so 20A at 12V.

 

[the snooper]

It seems to be 240W so 20A at 12V.

Could be a bit less, I guess the manufacturer will have some headroom in the mains power supply

 

[winchman]

It seems to be 240W so 20A at 12V.

Thanks thats a lot but the details given arnt showing over what time but if its 20A for 12 hours I would b]need some serious battery power?
Lets see what the manufacturer comes up with well assuming they reply?

 

[the snooper]

Do you have make and model number ?

 

[ajlelectronics]

arnt showing over what time

From switch on until switch off. Yes, that is going to need some serious battery banks.

 

[Seadog]

It seems to be 240W so 20A at 12V.

Which is a ludicrous amount. But the figures don't lie.

 

[winchman]

Do you have make and model number ?

Dream station 2 cPAP

 

[Seadog]

6.67a from what I can see.

 

[the snooper]

Gives you some specs for 12v here

12V DreamStation 2 CPAP Car Auto dc travel charger

Buy cheap and high quality Genuine DreamStation 2 CPAP Car Auto dc travel AC Adapter Charger Power Supply from lps-gopower.org with 1 year warranty.Free shipping to worldwide.

www.lps-gopower.org

 

[voipio]

Found this

The person that wrote that spec doesn't seem to know the difference between instantaneous current drain (A) and cumulative current drain [or charge] (Ah)!! The figure for inverter power is confusing.

Trying to interpret the figures, the current drain from a 12V supply, by a 30W CPAP machine, is 2.7A which seems reasonably close to the calculated 2.5A and, over 8 hours it will consume 21.6Ah of charge.

Or for @winchman 's use case of 12hours per day over 3 days, for a 30W CPAP machine, we're talking of 2.7A x 12h x 3days = 97.2Ah. That would require 200Ah worth of leisure battery capacity, based on discharging the battery to 50% of capacity (discharging a lead acid battery any more than that will tend to shorten the battery life). A 60W CPAP machine would require double that i.e. 400Ah of battery capacity, if there is no hookup.