ajlelectronics
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Where are you getting 30W from with 240V @ 1A? If it is only pulling 30W, why does it want an Amp connected to the mains?
- Thread starter winchman
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Where are you getting 30W from with 240V @ 1A? If it is only pulling 30W, why does it want an Amp connected to the mains?
Many devices having power ratings given as 240V @ 1A rarely seem to consume that in normal use, except sometimes during start up.
The 30W comes from the "datasheet" posted by @the snooper. Looking at some CPAP specs, 30W would be at the low end, with some CPAP machines consuming up to 100W.
There's a useful source of info here:
In terms of "bang for buck" I still go to Lead-Acid for the Campervan batteries. A lot simpler to charge & look after, with no inbuilt BMS electronics etc.
I know Lithium is "flavour of the month" now for some while, & yes they certainly have their place - but I don't see that they are always the "right" option.
As for power consumption ref 240v to 12v - its really just good ole Ohm's Law.... so if the load to be supported at 230vac is 1A, then that same load off 12v (approx 20x lower volts) needs approx 20x more Current.
(Yes there's the differing ACTUAL cell volts, plus the Efficiency losses if running through an inverter etc - but as a rule of thumb quick calc it's close enough)
I know Lithium is "flavour of the month" now for some while, & yes they certainly have their place - but I don't see that they are always the "right" option.
As for power consumption ref 240v to 12v - its really just good ole Ohm's Law.... so if the load to be supported at 230vac is 1A, then that same load off 12v (approx 20x lower volts) needs approx 20x more Current.
(Yes there's the differing ACTUAL cell volts, plus the Efficiency losses if running through an inverter etc - but as a rule of thumb quick calc it's close enough)
CompoSimmonite
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I've run my CPAP off a 12v battery / inverter / mains PSU for several days without a problem
winchman
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Message from the manufacturer
"Please note that DS2 12v DC power supply has 90W."
So my school boy science and maths
90w divided by 12 = 7.5A so at 10 hours use thats 75AH? So would need at lease 150AH
battery looks like it will be a non starter.
"Please note that DS2 12v DC power supply has 90W."
So my school boy science and maths
90w divided by 12 = 7.5A so at 10 hours use thats 75AH? So would need at lease 150AH
battery looks like it will be a non starter.
Erie Fred
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For example:
www.directhomemedical.com
I see 6.3 watts typical 27 watts peak.
I think the humidifier (optional) is not heated.
AirMini AUTO Ultra-Portable APAP Machine Package
Check out the deal on AirMini AUTO Ultra-Portable APAP Machine Package at Direct Home Medical
www.directhomemedical.com
I see 6.3 watts typical 27 watts peak.
I think the humidifier (optional) is not heated.
hotponyshoes
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That just sounds like the psu is capable of delivering 90w. Ie. It's got 90w printed on the back of it.
I doubt a cpap uses that.
A horse one will last at least 4hrs on a car size battery
90W would be the maximum rated power of the DC power supply. It's a bit like having a typical domestic A.C mains supply that's rated, or capable of 100A, or 25kW. The electrical goods in the property will only draw from the mains what they need to draw e.g. a single 40W incandescent equivalent lamp, rated at 4W, would only draw 4W, or 0.017A.
6.3W would be far more manageable using a leisure battery. 6.3W drawn from 12V is 0.525A which, over the 3 days, 12 hours per day, would be 0.525 x 12 x 3 = 18.9Ah.For example:
AirMini AUTO Ultra-Portable APAP Machine Package
Check out the deal on AirMini AUTO Ultra-Portable APAP Machine Package at Direct Home Medical
I see 6.3 watts typical 27 watts peak.
I think the humidifier (optional) is not heated.
winchman
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I have just ordered a 190AH Battery so will give it a go.
Like this one but a bit cheaper.
Like this one but a bit cheaper.
EnerSys PowerSafe (12V190F) 12v 190ah AGM Battery - Ideal for Solar Off grid Etc | eBay UK
Find many great new & used options and get the best deals for EnerSys PowerSafe (12V190F) 12v 190ah AGM Battery - Ideal for Solar Off grid Etc at the best online prices at eBay UK! Free delivery for many products!
www.ebay.co.uk
ajlelectronics
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I have just ordered a 190AH Battery so will give it a go.
Like this one but a bit cheaper.
EnerSys PowerSafe (12V190F) 12v 190ah AGM Battery - Ideal for Solar Off grid Etc | eBay UK
Find many great new & used options and get the best deals for EnerSys PowerSafe (12V190F) 12v 190ah AGM Battery - Ideal for Solar Off grid Etc at the best online prices at eBay UK! Free delivery for many products!www.ebay.co.uk
The key will be taking a current reading once installed.
winchman
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Thanks I will fit it and install a volt meter but I will also measure what the correct draw is once I fathom out how best to do it, one top tip I have had is leave the humidifier off as it draws less power.
winchman
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It looks like it should work.
There's also this kind of thing, as an alternative, that is slightly easier, wiring wise. Just two wires in and two wires out. Current sensing is performed internally. There's no external current sensor required:
www.ebay.co.uk/itm/388525872582
Erie Fred
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I think you will find there is no one answer.
Depending on your sleep, it will ramp up & down the pressures, and so will the amperage draw.
winchman
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Would that have to be in circuit all the time? So creating a small Drain?
Problem with that sort of thing is that it has it's own current draw and it will flatten a battery if you forget to disconnect it.
winchman
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Thats why I was looking at the Ali express one more expensive but I would assume I could just turn the control box on when I wanted to see what's going on then turn if off to save some power? I am only an amateur electrician though?
I have one of the Watt meters shown in the eBay listing above and, without anything else connected, it draws a measured 9mA from 12V so, theoretically, a 195Ah battery would power that for well over a year down to 50% battery charge remaining. The battery's own internal self discharge current would be somewhat higher. The Aliexpress item would also need to remain powered up, in order to retain its measurements.
