Adding an Inverter; got a question

Bentspoon · 04-02-2017, 10:57 AM

I have a 24' Coachmen Freelander. In this unit there is no inverter. The AC outlets are dead if you are dry camping. My wife uses a CPAP machine and that demands AC power, so dry camping has been a dilemma. I have looked at things carefully, made measurements and determined that a little 600W true sine wave was the one for me. So I added one wired directly onto the battery pack with in-line fuse.The Freelander has a manual transfer switch. That is, I have a 30A plug and I can plug it into shore power or the generator output or not. Now I have a 4th choice - the inverter. But I must take care for I cannot be charging the battery with the AC generated by the battery. Therefore before engaging the inverter I must throw the "battery disengage" switch. It is my theory that the batteries are now isolated and driving the inverter which is driving the converter for 12V. I have tried this and everything seems to be fine.
Now for my question. In this latter configuration, The converter has gone into boost mode and is telling me that it is pumping 14.4 volts. I haven't measured that yet, but I assume it is right. It makes sense in that there is no battery connected. My question: can anyone see any harm in this - continuous boost mode with no battery? I assume all the appliances/lights can tolerate the range of voltage or I couldn't charge in normal mode. I wonder of the charger/converter is damaged by this but I think not. I would appreciate any input
Bentspoon

CHICKDOE · 04-02-2017, 11:12 AM

a couple of comments for what they are worth. as I understand the ac output from the inverter is wired to the ac distribution panel and from there to the outlet that runs the cpap machine. if so this would allow the converter to have power. this is why you have to disconnect the batteries so the converter does not try to charge them. it seems to me there is a good probability that at some time you will be running the inverter with the batteries still connected to the converter. is the inverter solely for the cpap machine? if so, would it be possible to run a dedicated 110 vac line from the inverter output to a new receptacle dedicated to the cpap machine. or does your inverter have a 110 vac pass thru capability? or can you get a small 110 vac transfer switch ($50)? you could install it in the 110 vac line from the inverter to the distribution panel branch circuit that runs the cpap machine. it would automatically power the cpap machine from shore (or generator) power if it was present and would only connect the inverter to the cpap machine if shore power was not present. this would isolate the inverter 110 vac output from ever connecting to the distribution panel (and thru it to the converter).

llr · 04-02-2017, 11:12 AM

You don't want to disconnect the battery. You need to turn off the converter, probably on its own breaker.
With only a 600 watt inverter be sure no other AC is on. For that size inverter I would just run the AC straight to the CPAP and not connect it to the trailer AC input

ScottBrownstein · 04-02-2017, 11:15 AM

Bad idea. You are now supplying the entire 12 volt load of the coach from your 600 watt inverter by running a converter. It won't hurt the converter, as it is designed to run without a battery lead (although I am surprised that it is at 14+ rather than at 13.6). So this means when you turn on a light to go to the bathroom, the power for the light (and your pressure pump) first comes from the batteries, then to the inverter, then to the converter and then to the pump. Not even close to ideal.

Better idea is to install a small inverter transfer switch that only feeds the outlet breaker in your coach. That way you do nothing but turn on the inverter. When the switch sees power coming from the breaker (either generator or shore power) it drops the inverter output and switches to the main source of power. Two versions attached.

dmdomokos · 04-02-2017, 11:26 AM

I use a 1500 watt inverter to power out trailer from the shore power plug. I leave the batteries connected BUT turn off the converter via its breaker. The inverter like yours is directly connected to the batteries. Now I can run everything in the trailer. But be careful on what you use as it will drain your batteries.

ScottBrownstein · 04-02-2017, 11:32 AM

Hopefully you do not have a 110 volt hot water heater and it is turned on.

dmdomokos · 04-02-2017, 12:02 PM

No, I keep the water heater on propane AND the refrigerator. The inverter has a wattage display so I can check to see if I am drawing power I don't know about. My kid figured out the AC was on one time and had all kinds of stuff plugged in. I check to make sure wattage is zero before turning on anything.

ScottBrownstein · 04-02-2017, 12:14 PM

I thought about that too! The inverter would just crash and come back, if it is a decent one. This whole thing is strange to me. I you pull the wire off the breaker that powers the outlets (15 amp) and put in a $50 transfer switch you can forget about all of that. The only issue is whether the inverter is turned on, the rest is totally immaterial. You either always have power at the outlets, or you don't. Fact is, when you connect to shore or run a generator, you can leave the inverter running since it draws virtually nothing and your converter is running anyway.

Many of us can live with the "don't forget to turn this off, and then turn this on..." but besides me, my family could never do it. $50 to do it right and sustainable.

RMWSierra · 04-02-2017, 12:58 PM

My CPAP will run on 110-240 vac or 12 vdc.

SidecarFlip · 04-02-2017, 03:33 PM

Seems as though someone made something simple, very complex.

My wife and I both have CPAP machines, Res Med S8's to be exact. We both sleep in the RV and we both run our CPAP every night(with the humidifier on, I might add).

I run a 1000 watt 1500 surge AIMS Power PSW invetrer (same as a Xantrex but with a lower idle current draw and like the Xantrex), it's remote switchable.

The Inverter is hard wired to the battery bank (fused with a 100 amp MEGA fuse and fuse block) and the output of the inverter is delivered to a 110 volt plug in the bunk area that we can plug into (marked Inverter Only).

We power up the inverter before bed time, plug in and go to sleep. Never had an issue with depleted batteries in the morning and never had an issue with the inverter.

Don't even think about it anymore. Just turn it on, green light illuminates, plug in the S8's, mask up and go to sleep.

ScottBrownstein · 04-02-2017, 04:34 PM

SidecarFlip Sure that works, but when you are plugged into shore power, then what do you plug your CPAPs into? Or do you run your inverter anyway? For an additional $50, your CPAP outlets would always work as would a bunch of others for phone chargers and your TVs and such. Nothing that the average journeyman electrician could not have done for you. Maybe complicated to talk about, but really easy to use.

SidecarFlip · 04-02-2017, 04:48 PM

I just use the inverter, shore power or not. Just let the converter keep the battery bank charged. No point in making it complex.

I rarely run shore power anyway.

ScottBrownstein · 04-02-2017, 04:52 PM

Hey...to each his own. If it works for you then it's perfect.

Jim in Halifax · 04-02-2017, 05:31 PM

Quote:

Originally Posted by llr

You don't want to disconnect the battery. You need to turn off the converter, probably on its own breaker.
With only a 600 watt inverter be sure no other AC is on. For that size inverter I would just run the AC straight to the CPAP and not connect it to the trailer AC input

My inverter is wired to a "dedicated" AC BOX (labeled as such) strictly for my beer fridge in storage area when in travel mode.... At CG I move plug to a normal 110v AC receptacle in storage area....Wire your CPAC the same way......

Tom48 · 04-02-2017, 06:03 PM

Quote:

Originally Posted by Bentspoon

I have a 24' Coachmen Freelander. In this unit there is no inverter. The AC outlets are dead if you are dry camping. My wife uses a CPAP machine and that demands AC power, so dry camping has been a dilemma. I have looked at things carefully, made measurements and determined that a little 600W true sine wave was the one for me. So I added one wired directly onto the battery pack with in-line fuse.The Freelander has a manual transfer switch. That is, I have a 30A plug and I can plug it into shore power or the generator output or not. Now I have a 4th choice - the inverter. But I must take care for I cannot be charging the battery with the AC generated by the battery. Therefore before engaging the inverter I must throw the "battery disengage" switch. It is my theory that the batteries are now isolated and driving the inverter which is driving the converter for 12V. I have tried this and everything seems to be fine.
Now for my question. In this latter configuration, The converter has gone into boost mode and is telling me that it is pumping 14.4 volts. I haven't measured that yet, but I assume it is right. It makes sense in that there is no battery connected. My question: can anyone see any harm in this - continuous boost mode with no battery? I assume all the appliances/lights can tolerate the range of voltage or I couldn't charge in normal mode. I wonder of the charger/converter is damaged by this but I think not. I would appreciate any input
Bentspoon

Not liking what the Converter is doing. When we ran our old coach that way it was easy, I simply unplugged the converter.charger. result no paracitic loads from converter. New coach the converter is hard to get to.so I discovered WOW, ONE flip of a circuit breaker/switch and converter is out of the loop. I suggest not let it sit running AT ALL.

ALSO BOTH OG MY C-PAP machines had a power brick and the output to the machines on both was 12dc and the manufacturer offered a 12v Battery hookup kit. Works very efficiently.

SidecarFlip · 04-02-2017, 07:14 PM

Quote:

Originally Posted by Jim in Halifax

My inverter is wired to a "dedicated" AC BOX (labeled as such) strictly for my beer fridge in storage area when in travel mode.... At CG I move plug to a normal 110v AC receptacle in storage area....Wire your CPAC the same way......

Glad I don't drink beer..lol

Bentspoon · 04-02-2017, 07:50 PM

Lots of input - thanks. Some clarification - the 21RS (my rig) does not have 12 volt outlets. Yes it is true. The CPAP machine will run on 12V but there is no outlet and stringing wire and drilling holes is an undesirable solution for me. Plus I plan to run a TV for a couple of hours as well. The installed TVs are all AC. I think the best Idea I heard was to throw the charger circuit breaker and let the batteries provide 12V. This is more efficient to be sure but the inverter provides 95% efficiency and I would assume the converter is close to that efficiency so both methods work but why lose 10-15%. If I get some gumption I might try to profile both methods. By the way I am pretty sure of my loads and will be running 20-25A max out of the batteries at any one time and 50Ah should be a reasonable night for us. I have 75Ah capacity. (two 75Ah batteries)
Thanks everyone
Bentspoon

SidecarFlip · 04-03-2017, 07:09 AM

One thing needs to be clarified and that is..

Not every CPAP / BIPAP machine is the same, in fact, everyone is different as far as input is concerned. While most will operate on 110/60, some will operate on 220 and on 50cps and 60 cps depending on configuration and most will run on 12 volts but the polarity input is different on different machines.

Trawlerphil · 04-03-2017, 03:57 PM

Check the bottom of your CPAP machine. You may find it will run on DC with their power cord.

KMP44 · 04-03-2017, 04:21 PM

Quote:

Originally Posted by Bentspoon

Lots of input - thanks. Some clarification - the 21RS (my rig) does not have 12 volt outlets. Yes it is true. The CPAP machine will run on 12V but there is no outlet and stringing wire and drilling holes is an undesirable solution for me. Plus I plan to run a TV for a couple of hours as well. The installed TVs are all AC. I think the best Idea I heard was to throw the charger circuit breaker and let the batteries provide 12V. This is more efficient to be sure but the inverter provides 95% efficiency and I would assume the converter is close to that efficiency so both methods work but why lose 10-15%. If I get some gumption I might try to profile both methods. By the way I am pretty sure of my loads and will be running 20-25A max out of the batteries at any one time and 50Ah should be a reasonable night for us. I have 75Ah capacity. (two 75Ah batteries)
Thanks everyone
Bentspoon

Throwing the breaker on the converter and plugging the inverter into your 30A inlet will work - but it leaves opportunity for high draw items to be turned on. If somebody mistakenly sets the thermostat to cool, your AC can try to turn on. Or the microwave and 110v side of the water heater would have power.

Scottbrownstein's suggestion with a transfer switch and only running your outlet circuit off the inverter is how I set my system up. Its a pretty easy install and wouldn't cost much to have an electrician do either. Its a simplified version of a sub-panel system.

If the current setup works for you, go with it but its worth considering a transfer switch to have your outlets automatically switch between shore power/generator power and battery automatically without anything else inadvertently being powered.

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