Inverter extention cord question

[yawnny]

I am moving my 105 AH battery from the garage to my upstairs "computer" room, which is next to my bedroom. I don't want to move it directly to the bedroom because there is really no place to keep it without worrying about tripping over it. I intend to leave it connected to a batteryminder plus to insure a constant charge. I have a 600 watt true sine wave inverter which I use to power my S9 during power failures. I know the the S9 can run directly from a battery, but I'm working with what I've got.

I used to carry the battery in from the garage during power failures and hook it up in my bedroom, but mysteriously the darn thing has gotten heavier over the years.

My main question is; it is roughly a 30 ft run of wire from my "computer" room to my bedroom. It seems like it would be OK to make my own extension cord from a 30 foot piece of lamp wire from the hardware store? I know that the S9, especially with the humidifier off is going to run way less than 600 watts. Rolling up 30 feet of lamp cord would make a small package, easily stashed in a drawer. There is no voltage drop in a heavier gauge 50 ft long indoor outdoor cord, but it is harder to stash. Are there rational reasons not to use a lamp cord extension cord with such a low load? Please excuse my ignorance and be nice.

[greg-g]

It would be preferable to leave the inverter next to the battery and run a regular extension cord to your bedroom.
Without going into the mathematics, you either have low voltage and high current, or high voltage and low current. The voltage loss in the cable is proportional to the current, hence as long as its safe its preferable to have a short low voltage wire and a longer high voltage cable.

[yawnny]

It would be preferable to leave the inverter next to the battery and run a regular extension cord to your bedroom.
Without going into the mathematics, you either have low voltage and high current, or high voltage and low current. The voltage loss in the cable is proportional to the current, hence as long as its safe its preferable to have a short low voltage wire and a longer high voltage cable.

Sorry about the lack of details. The battery is going to be virtually next to the inverter, in the "computer" room, connected by 4 feet of #4 AWG cable, fastened to the terminals on each end by crimped connectors, with threaded nuts. The 30 feet of lamp wire will be carrying 117 volts of AC current from the inverter, not 12 volts DC.

[greg-g]

The current carrying capacity of the lamp cable should be more than adequate, the S9 AutoSet only draws a maximum of 90 watts which is no more than a typical lamp.
Its up to you to determine the electrical safety of your actions, I can't see a problem, but I'm in Australia.

[mdboze]

You said you want to make your own extension cord from a 30 foot piece of lamp wire.
Please do not mess with AC power. 600 watts can kill and cause fires if not wired correctly, or if done with the wrong wire guage.

Can you simply use a standard off-the-shelf, pre-made 25 foot extension cord from the hardware store? (one for outdoor lawn & garden use perhaps)

Regarding running the AC power 30 feet. No problem. If this were DC voltage, that would be different.


I am an Electrical Engineer, and I design medical devices. Tell me more details of what you have in mind.


S9 AutoSet only draws a maximum of 90 watts (from greg-g)
Where you live? is your native power 115V AC ? or 220V AC? (what type of power do you have standard) 50 or 60 HZ ?
How often do you lose power?


Michael.

[jamiswolf]

MDBoze wrote: is your native power 115V AC ? or 220V AC? (what type of power do you have standard) 50 or 60 HZ ?

They do teach you to read in Electrical Engineering school? Read the thread. It's very short.

Mdboze wrote: Please do not mess with AC power. 600 watts can kill and cause fires if not wired correctly, or if done with the wrong wire guage.

You know Dude, having an EE say this is very much akin to our Doctors telling is we aren't smart enough to change our own cpap settings.

If we have a lamp cord go bad, we go to the hardware store and buy a new cord or cord end. A screwdriver and a little wire stripping. It's so easy an EE could do it.

But I do have one warning Yawwny, be sure to price the lamp cord before you buy it. Sometimes they overcharge for that stuff and it might be cheaper to buy a ready made extension cord.
Jamis

[yawnny]

In no particular order, 117 volts, 60 cycles. The power probably goes out 6 times a year, usually at night. If I use a standard, heavy gauge extension cord, it WILL BE appropriated by someone for some other purpose at some point, whereas a lamp cord could be rolled up and keep in a drawer. If it turns out that lamp wire is considerably more expensive, I will go with a pre-made cord, and try to find a good hiding place for it.

My major concern was that I would lose an excessive amount of current over 30 feet lamp wire. I don't particularly want to buy 30 feet of wire and find out that it is unusable. I do have a couple of smaller, modified sine wave inverters which would probably cause less of a draw on the battery, but I am a bit leery of feeding odd shaped waves to the S9.

[nanwilson]

Yawnny
I bought a small hand cart at Costco for under $20, works fine to roll my battery around the house. I actually keep the battery on the cart & its usually in my motorhome ready to go camping, now its almost winter I wheeled it into a corner in my bedroom, all set up waiting for a power outage.

[jamiswolf]

Hi Yawnny,
Just because a regular extension cord looks heavy duty, don't be mistaken into thinking it has large guage wires in it. Many are merely 14 guage which is a pretty skinny wire.

Here's a voltage drop calculation page. Pretty straightforward...

http://www.paigewire.com/volt_loss_formulas.htm

Jamis

PS And apologies to Mdboze for being rude. Your post struck me the wrong way...and I hadn't had my morning coffee yet.

[archangle]

Extension cords pose certain hazards, but the hazard using one for your CPAP machine is about the same as using the same extension cord for something else. Extension cords going from room to room in the house present trip hazards. They also present hazards from getting worn from being stepped on, pinched in a door, etc. This is especially bad if you leave the extension cord running through hallways, etc.

Are the two rooms adjacent? Is there somewhere you can drill a small hole in the wall and run the cord through there without being too conspicuous and keeping the cord out of the way or out of view? For instance, if there are closets in both rooms?

Don't be stupid. Buy a good pre-made extension cord. Get one that's made for that kind of usage. It should say SJ, SJT, SJTO, or SJTW molded into the cord itself. They're cheap enough and less likely to burn down your house because you stepped on it and crushed the insulation on one of the wires.

In terms of the extension cord getting stolen, use a cable tie and tie it to something somewhere along its length.

[mdboze]

PS And apologies to Mdboze for being rude. Your post struck me the wrong way...and I hadn't had my morning coffee yet.

No problem, I didn't take it personally.
And, Yes, coffee is a must for most of us here, especially after a night of mask leaks, or a bad AHI night.

having an EE say this is very much akin to our Doctors telling is we aren't smart enough to change our own cpap settings.

Very funny comparison.
Like we would listen to a doc who says "no more changing your settings, or analyzing your own results" lol

I remember a few years ago how my DME insisted on not letting me have or even look at the provider manual when my BiPap AutoSv first arrived.
My attitude was... I paid for it ! The machine and manual belongs to me, not you. (that didn't help).
Eventually found it all online.


Michael.