Using a car as an electrical source

[truck71]

Heading to the Silverstone Classic at the end of the month- will be camping. Totally forgot I'll need a power source for my CPAP sleeping machine, is there something that I can use to run from my car battery (Merc E class, current model)?

[bristolracer]

You could try an inverter
Just check it will cope with load

[GlenMH]

Also bear in mind that car batteries are not the same as leisure batteries and are harmed by deep discharge. It might be cheaper to buy a leisure battery to power your CPAP machine.

[marshalla]

First thing to do is check the power requirements for the CPAP. Many of them are designed with travel in mind and are capable of running from a 12V source - removing the need for an inverter.

If yours can run from 12V a leisure battery is a much better option than the car battery for the reasons given above + the fact that it removes the risk of you flattening the car battery.

[truck71]

Great thanks, where would you advise buying a leisure battery? Do you simply charge it fully and then draw from it until it's dead?

[davepoth]

I'd be inclined to get something like this:

https://www.amazon.co.uk/Portable-Compressor-Inver...

since it includes all of the bits you'll need (battery, inverter) as well as some other stuff that will be handy if you accidentally discharge the car battery over the weekend.

[GlenMH]

truck71 said:

Great thanks, where would you advise buying a leisure battery?

Halfords or your local caravan/motorhome dealer will have them in stock.

truck71 said:

Do you simply charge it fully and then draw from it until it's dead?

Yup

[Kenty]

I run mine from a 12v battery ( from a golf buggy) in the caravan, the problem is the plug into the CPAP machine which is hard to find. If you find another way let me know!
FYI the battery will last for 3 nights' the CPAP uses very little power.

Edited by Kenty on Sunday 10th July 12:28

[surveyor]

chap in our party tried to run a machine off an inverter.

Not sure if my battery is tired, but it did not like it at all.

[truck71]

surveyor said:

chap in our party tried to run a machine off an inverter.

Not sure if my battery is tired, but it did not like it at all.

I was planning on using an inverter, what issue did he encounter?

[surveyor]

truck71 said:

I was planning on using an inverter, what issue did he encounter?

Not enough juice to provide the power....

[GlenMH]

Why on earth are you planning to convert 12V DC to 240V AC back to 12V DC again if you can run it from a leisure battery?

[truck71]

GlenMH said:

Why on earth are you planning to convert 12V DC to 240V AC back to 12V DC again if you can run it from a leisure battery?

No idea. I'm just not sure how to get the power from the leisure battery into the CPAP machine, it has a standard three point plug and the leisure battery I assume will come with two terminals. I'm up for an idiots guide as to how to do this (me being the idiot).

[anonymous-user]

Pleasure battery

[marshalla]

truck71 said:

No idea. I'm just not sure how to get the power from the leisure battery into the CPAP machine, it has a standard three point plug and the leisure battery I assume will come with two terminals. I'm up for an idiots guide as to how to do this (me being the idiot).

Make and model of the CPAP, please - we might be able to find a manual which tells us what the power inputs are.

[truck71]

It's a Resmed S9, sticker says 24v DC, 1.25A (FG) 3.75A (Sys).

Thanks.

[marshalla]

truck71 said:

It's a Resmed S9, sticker says 24v DC, 1.25A (FG) 3.75A (Sys).

Thanks.

One of these : https://mysleep.resmed.com/GB/en/Sleep-Apnoea/Acce...

and a 12V leisure battery will do a much better job than playing around with inverters.

(the official power supply says it comes with croc clips for connecting to a battery, but you might like to get one of these as well, just in case : http://www.ebay.co.uk/itm/12V-Car-Portable-Cigaret... )

Edited by marshalla on Tuesday 19th July 22:52

[truck71]

marshalla said:

One of these : https://mysleep.resmed.com/GB/en/Sleep-Apnoea/Acce...

and a 12V leisure battery will do a much better job than playing around with inverters.

(the official power supply says it comes with croc clips for connecting to a battery, but you might like to get one of these as well, just in case : http://www.ebay.co.uk/itm/12V-Car-Portable-Cigaret... )

Edited by marshalla on Tuesday 19th July 22:52

Superb, you're a gent. Cheers.

[dartissimus]

truck71 said:

marshalla said:

One of these : https://mysleep.resmed.com/GB/en/Sleep-Apnoea/Acce...

and a 12V leisure battery will do a much better job than playing around with inverters.

(the official power supply says it comes with croc clips for connecting to a battery, but you might like to get one of these as well, just in case : http://www.ebay.co.uk/itm/12V-Car-Portable-Cigaret... )

Edited by marshalla on Tuesday 19th July 22:52

Superb, you're a gent. Cheers.

I've come to this very late, I'm off to Beaulieu in early Sept, and two years ago got plenty of complaints.

I now have a Resmed S9, and have just bought their inverter and now need a suitable battery.
I thought a jump starter battery pack would be Ok, but bearing in mind that the Resmed S9 is 24 volts and 90 watts, for two nights without recharge, I would need a 35amp hour+ sized battery.
Expensive, is there an alternative?

Edited by dartissimus on Friday 22 July 13:45

[truck71]

dartissimus said:

truck71 said:

marshalla said:

One of these : https://mysleep.resmed.com/GB/en/Sleep-Apnoea/Acce...

and a 12V leisure battery will do a much better job than playing around with inverters.

(the official power supply says it comes with croc clips for connecting to a battery, but you might like to get one of these as well, just in case : http://www.ebay.co.uk/itm/12V-Car-Portable-Cigaret... )

Edited by marshalla on Tuesday 19th July 22:52

Superb, you're a gent. Cheers.

I've come to this very late, I'm off to Beaulieu in early Sept, and two years ago got plenty of complaints.

I now have a Resmed S9, and have just bought their inverter and now need a suitable battery.
I thought a jump starter battery pack would be Ok, but bearing in mind that the Resmed S9 is 24 volts and 90 watts, for two nights without recharge, I would need a 35amp hour+ sized battery.
Expensive, is there an alternative?

Edited by dartissimus on Friday 22 July 13:45

Quick update, the solution suggested by Marshalla worked a treat, the adapter came with croc clips so no need to get them separately.
As for the battery I bought the cheapest leisure battery in halfords and it was fine over two nights (59.99iirc).