Adding batteries

Hi,

As wa8yxm so sagely suggested get a cpap that uses 12 volts DC. If the one you have has a power brick, it may already be a 12 volt unit.

Why not a 12 volt machine? (Save the inverter)

your GC2s (The six volt batteries) hold about 1KWH of usable electricity, with a residential fridge, You are going to be stressing them going all night,

I would double up on them and let the existing inverter power the CPAP it should have the reserve capacity. Or get a 12 volt machine.

For me RULE NUMBER one is not to mess with the TRUCK starter battery or the Truck Alternator System. These are only used to get me home.

I leave all of that as factory as I can on my camping trips.

In your case perhaps your 1000WATT INVERTER has two receptacles on it. Perhaps plug the fridge into one and your CPAP in the other one. You can use extension cords if your like...

Not all that familar with the CPAP machines but seems like I hear alot of folks saying they are dual voltgae items 120VAC and 12VDC depending which cord you are using....

You may have to investigate what type of INVERTER is needed for the CPAP machine. I suspect your 1000WATT Inverter is a MSW type and this may not be compatible with the CPAP machine... You need to check on that before plugging it into the 1000WATT Inverter. The PSW type inverters produce the same 120VAC power the Shore Power gives.

A good setup for you would be to pick up a 600WATT PSW Inverter to run your CPAP as well as all of your home entertainment items and other low wattage electronics.. Then just leave the 1000WATT MSW Inverter alone to just support your fridge when needed.

Your dual 6VDC batteries will produce around 220AHs which will hold up pretty good over night.

What you don't want to happen is tie in your truck start battery to the mix and drain both of them down over-night. Then you are DEAD IN THE WATER so to speak...

If you buildup your battery systems you also have to consider how to charge them in a timely manner. You should not run down any deep cycle battery lower than 12.0VDC over night which is approximately 50% charge state and not return them to at least 90% charge state the next day. Doing this will do harm to your batteries and you may have to replace them. You need to come up with a easy way to recharge them when they get below 50% charge state. It takes around three hours time to recharge a deep cycle battery back up to their 90% charge state using smart mode charging techniques...

In my case I must start each day/nights run on my batteries with them charged up to at least 90% charge state. When my battery bank drops to 12.0VDC I will shut them down and wait until I get them re-charged again in a timely manner.

This is what I do at any rate - I'm sure others have their own ideas what works well for them.

It all depends on how you camp off the power grid... I unfortunately consume alot of DC Power from my 255Ah capacity batteries supporting my Ham Radio ops and our Trailer needs...

Roy Ken

Is it a compressor fridge or absorption?
Actually either one needs four batteries to operate properly but the absorption fridge will hog a lot of power.

I would add a small transfer switch to connect to the single string of outlets you need to plug in the cpap.

Just connect your new 12v battery , too/parallel with the paired 6's which make one 12v
You will have a battery bank consisting of one 12 and two 6s

You can add as many batteries as you have room for, they, all connect together as one bank to feed the inverter

What you Can Not do is isolate batteries and loads, when using Only One inverter, you can not make the cpap use the 12v single and the fridge use the paired 6s unless you use Two separate inverters wired to separate batteries

I would just tap off of the outlet behind the refrigerator - get an electrician to do it if you are not very familiar with 120V power - it is simple and the most efficient way to get what you need. Adding an additional inverter just adds another parasitic load to your battery bank. Also, no inverter should EVER be connected to the chassis starting battery as mentioned by the other posters. Starting batteries are built for immediate high current draw usage followed by being immediately recharged. They are not intended to be "deep discharged" by an inverter.

Thanks to both.

I would like to end up with 2-12v batteries, (1 chassis and 1 to the inverter), and 2-6v batteries both to the coach. However as it has been pointed out, I cant hook 1-12v and 2-6v to the same inverter. So I guess this is one of the many dumb ideas.

Thanks again

Not sure I understand correctly; Are you wanting to use the 2 6V's to power the fridge and 1 12V to power your CPAP from the same inverter?
If so, there's no way to separate what battery supplies power to individual loads of the single inverter. You would need to get another inverter to separate battery draw and as sch911 indicated, it's a bad idea to draw off your chassis battery.

You want to use your chassis battery and the coach batteries to power the inverter? It's theoretically possible but, it's a bad idea. What happens when you run down the chassis battery? You can't start the MH or the generator.... Why not just add an extension cord at the outlet behind the fridge and power the CPAP with it?