battery cable size

[highdesertranger]

I think everyone is making this confusing. again you are fine on the C-Pap.

you need to go with the 35amps from the converter. I believe you said 2ft run. the chart shows 12 gauge but remember that is marine wire. I like overkill if it was my system I would go with 6 gauge and I would still use marine wire.

I do believe both the solar and the converter are undersize for those batteries. I would go with 400 watts of solar and a 45 amp converter.

I just realized you are calling the C-Pap adapter a converter. but in another post you said you will use the 35amp converter to charge the batteries when solar is not enough. are you planning on installing a converter/charger?

highdesertranger

 

[Elbear1]

Converter takes 120v power and converts to 12v (despite the wording of your cpap adapter). Inverter takes 12v and converts to 120v.

A good easy way to get wire is at tractor supply in the welding section. Its 4 or 2 gauge and good for any wiring you need around batteries.

 

[Qxxx]

Willow, since you're wiring 2-6V, 225AH batteries in series, that's equivalent to a single 12V, 225AH battery. Most people use 100W solar for each 100AH of 12V battery, so you should more properly be using two 100W panels in order to keep the batteries up, especially if you add the inverter down the road and start loading the batteries more, say with lights and computer and whatever.

EDIT: the other thing is, then you should definitely think about putting fuses or circuit breakers into the battery lines. Don't want the wires melting and the van burning down.

 

[Elbear1]

Sorry but 200w is still just a 10 amp charger. 10a vs 225ah bank with 4-7hr window is not going to cut it once they they start to sulfate after 6 months on the road. Cant expect to have a big bank with a tiny little charger for daily use. Or you can expect to get way less than half the life out of them. Again c/10 plus load is proper charger size.

 

[user 23166]

Excellent. Just for reference, it might have saved a lot of flailing around if we'd had the PDF reference a while back . Just saying.

However, the file actually gives specs for 6 or 8 different devices. On looking at the last unit on page 7, Airsense 10 with ClimateAir and humidifier (yes/no??), it shows 5.37A at pressure 16, or 65W. IOW, right what I estimated.

Buying the 12V DC-DC converter is a good option. Other things you'll notice, on page 5, it indicates using a 300W inverter, again just what I said. And on page 3, it shows the DC-DC converter you are apparently buying. You'll notice how "thin" those wires are, not hardly 2 gauge. Now you got it all. Have fun and keep on trucking.

:thumbsup:

 

[user 23166]

Youre going to have problems with that setup. Once you break them batteries in youre going to need 500w or more.

The advice you always hear of you draw say 35 amps and thus you need 35 amps in solar to replace it is horrendously false. The batteries dont charge linearly like that. The older they get the worse it becomes. Size battery to needs then size solar to battery. I.e. you need to charge about 1/8th (c10 + load) your bank.... 22.5a + load = 500w to achieve 14.8v and even then you will struggle without perfect sun and a backup source.

A small lithium battery might be better for you than a bunch more panels. They are nearly linear like that.

P.s. youre wiring in series. Series-parallel would be if youre hooking up 4 6v to be 12v. 2 in series plus 2 in series then those would be paralleled for 12v 450ah.

I was wondering why I could never find a photo of 2 batteries wired in series AND parallel.

Well, since I can't afford a bunch more panel OR a lithium battery at this moment, I guess I'll drop the solar part and just stick with a generator and shore power :-/

 

[user 23166]

I think everyone is making this confusing.  again you are fine on the C-Pap.

you need to go with the 35amps from the converter.  I believe you said 2ft run.  the chart shows 12 gauge but remember that is marine wire.  I like overkill if it was my system I would go with 6 gauge and I would still use marine wire.

I do believe both the solar and the converter are undersize for those batteries.  I would go with 400 watts of solar and a 45 amp converter.

I just realized you are calling the C-Pap adapter a converter.  but in another post you said you will use the 35amp converter to charge the batteries when solar is not enough.  are you planning on installing a converter/charger?

highdesertranger

Resmed, the cpap manufacturer calls it a converter...I would use that to connect my cpap directly to my batteries.

I was also planning of installing a 35 amp (now 45 amp like you suggest,) in a couple months

 

[user 23166]

Willow, since you're wiring 2-6V, 225AH batteries in series, that's equivalent to a single 12V, 225AH battery. Most people use 100W solar for each 100AH of 12V battery, so you should more properly be using two 100W panels in order to keep the batteries up, especially if you add the inverter down the road and start loading the batteries more, say with lights and computer and whatever.

EDIT: the other thing is, then you should definitely think about putting fuses or circuit breakers into the battery lines. Don't want the wires melting and the van burning down.

Thx, Qxxx,
I just figured out that in order to run a battery bank in series AND parallel, you need 4 batteries ... I have some more thinking to do on whether I want to start with more panels, or just use a generator and shore power to start off with

 

[vangotransit]

In Telecom when building series batteries and parallel batteries you use busbars it 0/1 to 0/4 wire
I tend to use 0/2 for everything

 

[user 23166]

Sorry but 200w is still just a 10 amp charger. 10a vs 225ah bank with 4-7hr window is not going to cut it once they they start to sulfate after 6 months on the road. Cant expect to have a big bank with a tiny little charger for daily use. Or you can expect to get way less than half the life out of them. Again c/10 plus load is proper charger size.

but what if i'm only using 20% of the battery bank everyday?

i'm not going to be sucking up 225 AH's a day, not even close...20% is only 45 amps, and I won't have to worry about sulfating right away, in a couple months when I'll be getting a smart charger

 

[Qxxx]

Thx, Qxxx,
I just figured out that in order to run a battery bank in series AND parallel, you need 4 batteries ... I have some more thinking to do on whether I want to start with more panels, or just use a generator and shore power to start off with

Yes, 2-6V in series, or 4 in series-parallel. The business I mentioned about 100W of solar per 100AH is what people quote for AGM batteries, lead acid may require more solar for best results like ebear says, I don't know for sure. Need to research it.

When wiring your 2-6V'ers in series, best to use heavy buss wire like others said, in order to plan for the future. Has anyone given a link to off the shelf preassembled buss wires?

The other thing is, besides the DC-DC converter for the CPAP, you might also get the regular AC-DC wall-wart so you can use it when you have regular mains power.

 

[user 23166]

Yes, 2-6V in series, or 4 in series-parallel. The business I mentioned about 100W of solar per 100AH is what people quote for AGM batteries, lead acid may require more solar for best results like ebear says, I don't know for sure. Need to research it.

When wiring your 2-6V'ers in series, best to use heavy buss wire like others said, in order to plan for the future. Has anyone given a link to off the shelf preassembled buss wires?

The other thing is, besides the DC-DC converter for the CPAP, you might also get the regular AC-DC wall-wart so you can use it when you have regular mains power.

TY, mine already came with one :thumbsup:

 

[Qxxx]

Ah so. BTW, just for reference, if you click on "Specs" on this page, it shows  the 120VAC wall-wart for the unit puts out 24VDC at 3.75A. This is a 90W power supply for a 53W device; it's typical for electrical design to use a 2:1 or so safety margin, so right on.
https://www.cpap.com/productpage/resmed-airsense-10-autoset-humidair#specs-tab

Also, this indicates how the DC-DC converter works. It takes 12VDC input and puts out 24VDC. The CPAP unit no doubt has a 24V air pump. In general, DC-DC converters can take about any voltage input, 3-48VDC whatever, and put out about any voltage in the similar range.