Building a CPAP battery backup

[Mikey_CH47]

I am very new at this and would like someone to review my wiring diagram. I think this is what you were talking about. I believe the 200-watt solar panels are over kill but this is what I have. Please let me know if you would design this differently or am I missing something. Thank you. mike

 

[sshibly]

I am very new at this and would like someone to review my wiring diagram. I think this is what you were talking about. I believe the 200-watt solar panels are over kill but this is what I have. Please let me know if you would design this differently or am I missing something. Thank you. mike

The only thing I would suggest is to use a ring connector to the battery if you are connecting directly to battery.

 

[jpcjtrtj]

What’s the V max on the panels? Divide that into the 200 watts to see max amps from panels and the 15 amp fuse should be 1.25x your max amps.

I think you could use a 20 amp solar controller with a 30 Amp fuse on the charger side (they are $20 on Amazon). If you stick with the 40 amp controller; put a 50 amp fuse where the 40 is.

Other than that it looks fine to me. mine 25 AH runs the CPAP for about 7 days without a charge and with humidifier off. 3 days with humidifier on.

 

[MisterSandals]

25 AH runs the CPAP for about 7 days

25Ah x 12.8V = 320Wh
320Wh / 7 days = 45.7Wh/ day
45.7Wh / 8h nightly runtime? = 5.7W while running?

Less than 6 watts seems mighty low.

 

[jpcjtrtj]

25Ah x 12.8V = 320Wh
320Wh / 7 days = 45.7Wh/ day
45.7Wh / 8h nightly runtime? = 5.7W while running?

Less than 6 watts seems mighty low.

It’s 13.6 V nominal; so 360 WH (seems like I actually got a few more WH when I tested it; like closer to 380 WH) and I prolly only sleep 6 hours; so closer to 8.5-9 watts per hour; my pressure setting might be lower than others too; your mileage may vary …. But with humidifier off it has a pretty low draw on the kilowatt meter…with a 200 watt solar panel the battery will be fresh every night anyways; but I have run a week on it without a charge…

 

[Mikey_CH47]

What’s the V max on the panels? Divide that into the 200 watts to see max amps from panels and the 15 amp fuse should be 1.25x your max amps.

I think you could use a 20 amp solar controller with a 30 Amp fuse on the charger side (they are $20 on Amazon). If you stick with the 40 amp controller; put a 50 amp fuse where the 40 is.

Other than that it looks fine to me. mine 25 AH runs the CPAP for about 7 days without a charge and with humidifier off. 3 days with humidifier on.

Vmax = 1000V DC so let me see if I am understanding this:

200/1000 = .2 then 1.25 x .2 = .25
or is it:
1000vdc / 200 = 5 then 1.25 x 5 = 6.25

I tried looking this up but could not find anything that provided clarification.... So either way a 15 amp fuse would safe guard this part of the system?

Thanks so much for the input

 

[jpcjtrtj]

Your panel puts out 200 watts of power. This is the number of volts times the number of amps. There should be a sticker on the back of your solar panel… the v max should be somewhere between 18 and 40 volts +\- . 200 watts could be 18 volts times 11.11 amps or 36 volts times 5.55 amps …or any number of other configurations. In all likelihood 15 amps should be fine, but I would want to check to be sure

 

[sshibly]

25Ah x 12.8V = 320Wh
320Wh / 7 days = 45.7Wh/ day
45.7Wh / 8h nightly runtime? = 5.7W while running?

Less than 6 watts seems mighty low.

Few years back before LIFEPO4 came into my life, I used an AGM 90ah batt, heavy mother... but I could sleep 3 nights (sleep 6 hours too ) and still have a bunch left over.

 

[Cal]

Please let me know if you would design this differently or am I missing something. Thank you. mike

Are you using a ResMed machine? Does the connector have a center pin? If so, you're missing quite a bit. The center pin allows communication between the machine and the power supply.

 

[Mikey_CH47]

Few years back before LIFEPO4 came into my life, I used an AGM 90ah batt, heavy mother... but I could sleep 3 nights (sleep 6 hours too ) and still have a bunch left over.

I have been using a lead battery but I am getting too old to move it around. Trying to upgrade my system that can be recharged with my current solar generator.

 

[Mikey_CH47]

Are you using a ResMed machine? Does the connector have a center pin? If so, you're missing quite a bit. The center pin allows communication between the machine and the power supply.

I do have a ResMed machine. I also have a ResMed DC adapter kit so that the machine can run off of a 12v battery with either alligator clips or cigarette lighter socket.

 

[efficientPV]

Mine runs on a clock to save the battery in case I forget to turn it off when I leave the house on very early days. On other days it can act like a very rude alarm clock.

On RESMED machines the center pin just tells the unit that the power pack is large enough to support the humidifier. It can be faked with just two resistors.

 

[jpcjtrtj]

Hi,

I looked up the 200 watt Rich solar panel; it has a max short circuit current of 10.2 amps. Multiply that times 1.25 and you get something over 12 amps. So, your 15 amp fuse is fine. Vmax was not what i shoulda asked for.

jps

 

[jpcjtrtj]

Use Update; Full battery Sunday morning 25ah lipo4; used each night for 6-8 hours on ResMed with humidity off thru cigarette lighter; battery died Friday morning at 5 am with no charging in between. So 4.75 days solid.

 

[Rocketman]

I made a small portable battery 50ah 12v. I designed it for my sister in law in case she came camping with us - she did - but we had full hookups. I have a small inverter I was going to use with it for 120v.

Small Portable Battery - Show & Tell.

Well I finished my 12v 50Ah LiFePo4 small portable battery. I will be using the battery in my Jeep and for camping. It has eight 25Ah Fortune cells from electriccarparts.com and an Overkill BMS. I started to play with the batteries with my Batrium BMS in this thread: BMS...

diysolarforum.com

 

[jpcjtrtj]

So, i decided to rework this battery into a smaller case. Here's the result. Much more portable and fits better in the RV. Still needs to be charged every 4 days; but that works for me. . . .