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tact50
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Thank you for your responses.. my question now is how to most effectively test the house batteries. If the house battery is full, the inverter is on, and I’m using no other source of power- how long should my batteries last if I’m only using a small oxygen concentrator and C-PAP machine? 
 

The batteries seem to only last 1.5 - 2 hours max. That doesn’t seem right to me but I’m not sure. Please share your experience… thank you in advance !

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Ted

I can run my norcold fridge, c- pap, bedroom furnace fan ( Aqua hot on electric) for 8 hours before I need to charge up the house batteries,  in 1.5 hours with Generator on, batteries are back up to full charge, I just came home from the east coast and was living in the coach for a month and this was the routine.

Hope this helps

Wayne 

1999 Signature Caesar 

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4 minutes ago, wayne.cerven@gmail.com said:

Ted

I can run my norcold fridge, c- pap, bedroom furnace fan ( Aqua hot on electric) for 8 hours before I need to charge up the house batteries,  in 1.5 hours with Generator on, batteries are back up to full charge, I just came home from the east coast and was living in the coach for a month and this was the routine.

Hope this helps

Wayne 

1999 Signature Caesar 

Please share with us what batteries you have.

I have 4 6V Fullriver DC250’s that are 7 years old in a recently purchased Dynasty, 1 c-pape on at night and a couple of lights for using the camode,fridge is on LP,  they last all night no problem but I’m wondering when it’s time to replace too!

 

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House batteries 4 /6 volt Duracell golf cart batteries, 2 /31magna starting batteries, 4 years old, clean all posts and spray on battery protector once a year, top up house batteries with distilled water after they're charged every six months .

If I get another year out of them I will be more then happy, 7 years they owe you nothing,great run, time to replace.

Wayne 

1999 Signature Caesar 

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19 hours ago, tact50 said:

Thank you for your responses.. my question now is how to most effectively test the house batteries. If the house battery is full, the inverter is on, and I’m using no other source of power- how long should my batteries last if I’m only using a small oxygen concentrator and C-PAP machine? 
 

The batteries seem to only last 1.5 - 2 hours max. That doesn’t seem right to me but I’m not sure. Please share your experience… thank you in advance !

You need to tell us the exact batteries you are using - Manufacturer and Model number.  The manufacturer provides a load test (discharge profile).  The basic way to test the batteries is to fully charge them.  The data sheet for you batteries defines fully charged as when the voltage is set to the manufacturer specified volts and the charge current drops to less than the manufacturer specified Amps.  For Example: If you had the Fullriver DC250 mentioned above, the values are 14.7 volts and 5 Amps when they are fully charged.

Then you need to disconnect the charger, and either disconnect all loads.  If your loads are continuous at the same value, you can use them.  I use a space heater point out the window as a load.  Most batteries have several profiles, but the most common one all has is the Amp-Hrs at 20 hour rate of discharge.  In the case of the DC250 above, that is 250 Amp-Hours.  The DC250 Discharge Table shows that the battery should last 20 hours at 12.5 Amp up to 5 hours at 40.8 amps.  NOTE: These values are for a single battery.  Since you'll likely have four batteries in a series/parallel arrangement, that means that at 12 Volts, you should have 500 Amp-Hours and the 40.8 amps discharge should take 10 hours until the batteries reach 10 VDC (again for the DD250).  So, find something that will discharge at about 40 Amps (as I stated, I use a space heater and an dimmable halogen work light to fine tune the current).  The current will vary as the voltage varies, but the intent is to determine if your batteries are okay, not to certify their actual capacity.  So, with a 40 Amp discharge, the battery bank should last 10 hours, if the batteries maintain full rated capacity.  If the only last 9 hours, then you can say that they have 90% of the original rated capacity.  I would consider this okay.  But if they only last 4 or 5 hours, I'd consider replacing them.

I don't know how much current a small oxygen concentrator draws, but my CPAP can be as little as 0.5 Amp (at 120 VAC) without the humidifier turn on to over 5 Amps with the humidifier at maximum.  Remember that 5 Amps at 120 VAC is about 50 Amps at 12 VDC.  That would mean that the CPAP would draw over 50 Amps (assuming the humidifier was on full time, I have not conducted studies to determine the percent of time it is actually on) itself.  When dry camping I generally turn off my humidifier.  If you O2 Concentrator was similar, that is 100 Amp load, and would only last about 5 hours on a new set of batteries.   I don't think you really have that much load, but without know the actual numbers, and the actual batteries, it is hard to say.  But a rough load test as described above will give you a rough idea of you batteries capacity.

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