The one I'm looking at holds two standard size 12 volt batteries. I have to run a CPAP @ 3.75 amps and an oxygen concentrator @ 7.9 amps for about 8 hours. I don't know if two standard size batteries could handle this and hoping someone could help me out. Thanks so much, DJ

Have no idea what you mean by "standard size batteries". Deep cycle 12 volt batteries are Group 24, Group 27, Group 31, sometimes also a Group 29. The greater the Group number the larger the battery is but also the greater is it's capacity. Since a CPAP draws quite a bit of power, especially if you need it's humidifier running also, I'd go with the larger Group 31 if there's sufficient space to mount them. Otherwise you might want to switch to a pair of 6 volt GC-2 batteries which in series will offer about the same capacity as a pair of Group 31 12 volt batteries wired in parallel, and although taller will have a much smaller footprint, about the same as a Group 24 12 volt battery.

Are those amps at 12V-DC?I'm guess yes. If they are 120v-AC, not a chance.Assuming 8hr use between charges...that's around 96amp-hr...assuming nothing else is drawing a couple golf cart batteries should do the trick but that assumes you have a means to completely recharge the next day.

Looking at your old setup, a pair of GC=2 and solar, how did that do?If you were not drawing that down to less than 60% of a full charge, then cutting it in half is about your minimum. Two GC-2 batteries with 210-230 amps will allow for the needed 64 amp hrs for the O2 concentrator and the 32 amphrs for the CPAP but you will need to top off daily, not getting back over 90% with that will leave you lacking after only a day or two.

If you add in what the rig is using for the fridge etc you will most likely be pulling 13 amps. Mulitply that by say 10 hours equals 130 AH down. You need more like three group 27 or four GC2 6 volts. You also need to consider your draw between no sun and bedtime if on solar.If topping off 100% on generator at bedtime then go back to about 130 ah draw down. As mentioned, if you are drawing them down far it takes a considerable amount of time to completely charge so you go into the next night full. If not they will start dropping more and more. As you do this check the specific gravity at times to be sure you aren't walking them down by not fully charging. You don't need to dip them constantly, you just need to dip enough to be sure your energy management program is working.

The QUACKS had me on an O2 concentrator that sucked 520 watts at 1.2 liters. Is a 12 volt concentrator -The New Miracle-? Flapping and whirring through the night?I just cannot imagine a 12 volt concentrator. Would be like a 12 volt microwave.The humidifier uses four times the power of the CPAP blower. So that's a factor.Methinks you are on the wrong trail. Two 24's will allow around 85 amp hours total With standard gizmos online after dark you will be taxing group24 batteries to the max. I suspect the O2 unit is 120vac. A pipe dream.Might want to start thinking about a 1500 watt generator that can run 8 hours.

Downsizing to smaller rig, battery capacity | Good Sam Community

MEXICOWANDERER
Explorer
Apr 22, 2019
generally it doesn't get below 40 here most times.

The air going into the CPAP?

At 54F the heater is at 100% duty
_DJ_1
Explorer II
Apr 22, 2019
Thanks everyone. Guess I will stick with what I have. Just tired of dragging a trailer around. My current set up works good running both machines. Volt meter at 12.9 when I go to bed and 12.4 when I get cup. This is with four Trojan T145's, 450 watts of solar and a couple hours of gen run time for a kick start in the AM.

I am having trouble with the Xantrex Inverter/charger tho. But I should start a different thread for that.
wa8yxm
Explorer III
Apr 23, 2019
Some "Standard Size" numbers
GC-2 (six volt you need two in series) about 210-230 amp hours you can safely use half that.

Group XX.. Most of these are MARINE/deep cycle you should not use more than 25%
24 about 70-75 AH
27 just under 100
29 Just over 100
31 About 130 I'm guessing you have 27 or 29 as your "Standard"

A pair of GC-2 would give you more amp hours total and way more usable Amp hours.

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