Battery power required

Submitted: Wednesday, Feb 15, 2006 at 21:57
ThreadID: 30820 Views:2466 Replies:7 FollowUps:3
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I have a remstar CPAP machine that draws 3 amp on 12vDC and 1 amp at 240V. I am planning a long desert trip in the future and want to make sure I dont get caught out without power (as I then can't sleep). I currently have a dual battery system (both wet cell) in a 3.0 litre GU iii patrol and wanted to put another battery in out camper trailer connected by an anderson plug. What suggested size battery should I use and is am AMG battery the best suited? Any advice greatly received. I am in the eastern suburbs of Melbourne so recommended people would be great too!!

Thanks everyone.
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Reply By: ACDC - Wednesday, Feb 15, 2006 at 22:03

Wednesday, Feb 15, 2006 at 22:03
3 amps on 12 volt is only 36 watt but on 240 volt it's 240 watt does not sound right! have a recheck!
AnswerID: 155236

Follow Up By: MacandJen - Wednesday, Feb 15, 2006 at 22:16

Wednesday, Feb 15, 2006 at 22:16
I don't claim to know anything about this stuff! On the back panel it says
100-240v 50 - 60 Hz AC 1.0 A max
12VDC 3.0 A max

A mate told me that 3 amps is a lot of draw at 12 V. I just want to make sure I don't run out of juice in the middle of nowhere. As I said, any advice welcome.
FollowupID: 409183

Follow Up By: Mike DiD - Wednesday, Feb 15, 2006 at 23:14

Wednesday, Feb 15, 2006 at 23:14
A 12 volt fridge also averages around 3 amps.

FollowupID: 409203

Reply By: Member - Luxoluk - Wednesday, Feb 15, 2006 at 22:17

Wednesday, Feb 15, 2006 at 22:17
Same issue for me and same machine...good that it runs off 12V eh!! I have used mine for years and have never run short of power provided I am on the move most days to recharge the spare battery. Done plenty of desert trips as well and very conscious of battery failures in that situation. I run fluro light and Engle fridge plus HF radio. I would be doubtfull that a third battery is necessary unless you are fairly draining the spare with other equipment or staying put for a couple of days. My 2nd battery is the same size as the primary battery fitted to a TD troopy.
AnswerID: 155241

Follow Up By: Member - Luxoluk - Wednesday, Feb 15, 2006 at 22:24

Wednesday, Feb 15, 2006 at 22:24
I should have also added that 3 amp draw would be typical of start-up of the CPAP and a lesser draw would then prevail. The higher your pressure then the higher draw in amps. Another option is to connect an ammeter and determine the draw when operating under normal use.
FollowupID: 409185

Reply By: Derek from Affordable Batteries & Radiators - Wednesday, Feb 15, 2006 at 22:36

Wednesday, Feb 15, 2006 at 22:36
Hi Mac and Jen

AGM Batteries are great and will do the job for you. I agree with the others and think you should check the amp draw. A cheap multi meter will cost you $20.00 and will have a 10 amp load measure. Use this to check your start up amps and running amps on 12 volts. With these specs you can work out the rest.

It is always rewarding to work these things out for yourself and if you need help let me know.

Regards Derek from ABR

AnswerID: 155249

Reply By: Jimbo - Wednesday, Feb 15, 2006 at 22:39

Wednesday, Feb 15, 2006 at 22:39

email me your phone no and I'll give you a call tomorrow, easier than typing it all out.

jimbest at internode dot on dot net


AnswerID: 155251

Reply By: Sand Man (SA) - Wednesday, Feb 15, 2006 at 22:44

Wednesday, Feb 15, 2006 at 22:44

An AGM battery would definitely be the best choice for your needs.
It can be charged at the same time as the auxiliary battery is charged, although if you are leaving it in the Camper Trailer, you would be best served if you included an Arrid Twin Charge unit in the trailer, to counteract voltage drop.

I would consider a battery of at least 75 A/H rating which should give you about 3 days (or nights) of capacity. The AGM will take a deeper discharge cycle than a conventional wet cell battery and will recharge quicker.

Can't offer much advice on a retailer in Melbourne.
Perhaps a Battery World outlet would be a good start to get a ballpark price.
I think they distribute the Remco & Lifeline brands.

You can pick up a 110 A/H Remco for about $265. (Solar Online price)
100 A/H FullRiver $249 (Lake Macquarie Communications - NSW)

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AnswerID: 155253

Reply By: Member - Collyn R (WA) - Thursday, Feb 16, 2006 at 10:55

Thursday, Feb 16, 2006 at 10:55
Most probable draw is three amps at 12-volts dc (36-watts). The '1 amp at 240-volt' may refer to the onrush (magnetizing) current of a transfomer in the 240/12 power supply or something - but there's no way the steady current draw is 240 watts.

Suggest use AGM battery - ideally 100 Ah as this will give you about three nights of eight hours use without recharging concerns.
Collyn Rivers
AnswerID: 155315

Reply By: snailbait (Blue mntns) - Thursday, Feb 16, 2006 at 17:31

Thursday, Feb 16, 2006 at 17:31
hi Macandjen
I to have a CPAP machine it is a RESMED S7 lightweight which also has a water vapour attachment
I RUN 2 bats in the DEFENDER ONE IS A 75 AMP GELL the rear one is a 13 amp hr lead asid bat
i have installed a 130 amp hr in the camper trailer and when we are not moving the trailer bat lasts 2 nights i use a 300 wat inverter to run the cpap as it has to have 240 volts to run the heater in the vapour attachment
WE staid for 11 days at TOM GROGAN in the high country in Victoria
i used the rear bat from the Defender as it was charged when we went for a run
i have puchased a .5KVA GEN FOR $95.00 FROM Bunnings which i used to charged the bat in the trailer this is a verry light gen weighing 7 kg runs 12 volt as well as 240 volts and is a throw away gen if it last 2 years through it a way and buy a new one

i have used 4 gauge cable and anderson plug to give the 12 volts a easy passage to charge the bat
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AnswerID: 155395

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