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Question for battery experts: proper inverter?

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Question for battery experts: proper inverter?

#1 Post by Iziskal » Thu Jan 03, 2019 7:49 am

I've got a major 4x4 camping trip coming up in a couple of weeks. I have a deep cycle 50aH battery and one of those 18aH jump starters with ac outlet. I'd rather save the jump starter in case I need to do some actual jump starting, so I'm trying to make sure I have a suitable rig to run my cpap (without humidifier) off the deep cycle battery for maybe one, definitely not more than two, nights between charges.

I've already spent a ton on equipment and I'd rather not spend any more. Soooo ... what I have lying around the house is:

- the 50aH deep cycle battery
- a cable that has clips to attach to the battery on one end and a cigarette lighter-style outlet on the other
- a cigarette lighter inverter that claims to be rated 200w
- a trickle charger to charge the battery (and that I can plug into the ac outlets on my much larger inverter in my truck)
- AC adapter only for my APAP

I may try to mod a normal plastic battery box to make a pretty package, or I may just leave it as is.

My question is, can someone who understands batteries tell me if this set-up will work? I know I lose about 10% efficiency with the inverter as opposed to ordering a DC adapter https://mechanicguides.com/best-power-inverter/ , but will I still have enough juice to last a couple of nights? Finally, will a 200w inverter provide enough power to run the apap w/o humidifier?
Last edited by Iziskal on Tue Jan 08, 2019 6:07 am, edited 1 time in total.

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Re: Question for battery experts: proper inverter?

#2 Post by MikalE » Thu Jan 03, 2019 1:12 pm

That depends upon how much current the device draws. If the device is rated in watts, you will have to convert to
amps and compare this figure to your 50 amp hour battery capacity.

50 amp hours is not a large battery.

That rating means it will power a device drawing one amp for 50 hours. Theoretically.

It will power a device that draws 10 amps for 5 hours, and so on.
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Re: Question for battery experts: proper inverter?

#3 Post by exTPfan » Thu Jan 03, 2019 2:32 pm

It all depends on how many watts the cpap requires. This should be noted on it. I assume the battery is 12 volts, so 50aH means it can provide 12x50=600 watt hours. If the cpap requires 50w, it should run but only (theoretically) for 12 hours (in practice, significantly less).

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