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Old 07-27-2017, 12:45 PM   #1
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Help me understand 12VDC and 120VAC

I get that the converter in the TT converts the 30A 120VAC camp plug into 12VDC for the camper to run its 12v systems, including charging the battery. And I also get that generators generally have a 12VDC > 120VAC inverter for normal 110/120v plug use.

There are a few things that I'm still confused about regarding battery power vs. shore power vs. propane power vs. generator power (electrical is not my strong suit). I'm hoping these aren't dumb questions and/or I missed a sticky thread somewhere.

My TT (23BHM) user manual has two charts in the electrical section labeled 12-volt system and 120-volt system. I assume the first chart is a list of things that can run off the 72ah TT battery (Exide Edge Dual Use Grp-24), and the second chart is a list of things that can run off electricity when hooked up to a 30A 120v outlet. My refrigerator is listed on both - on 12-volt, it shows a 3.0 amp draw and on 120-volt it shows a 6.0 amp draw.

Questions:

  1. My storage facility offers 110VAC (120) outlets and electricity for $5/mo. Each building is on a 20A circuit breaker, and mainly used for trickle chargers. If I were to plug in using a 30A-to-20A or 30:15 "dog bone" converter, could I run my refrigerator for a period of time assuming my 6.0 amp load (from the chart above) + the other vehicles plugged in didn't trip the 20A circuit breaker?
  2. If that doesn't work, could I run it off my 72ah battery for a period of time (3.0 amp load from above), and then hook up shore power to recharge the battery when I leave/when we reach our campsite?
  3. The propane section indicates the refrigerator uses 1,200-1,500 BTU/hr. If neither of the above work, should I just turn on the propane system and have the refrigerator use propane to cool until I can access 30A shore power? Can you travel with this turned on?

Sorry again if these are dumb questions - it is our first TT and we're trying to learn the process of cooling the refrigerator and loading it with cold/frozen food. I have a couple more question specific to a generator.

  1. Since the generator natively produces 12VDC which is then converter via inverter to 120VAC, is there a way to have the generator and TT 12v systems directly connected to avoid the DC > AC > DC loss?
  2. Do most 2k generators have a 30A plug or should we plan on a 30A:110v "dog bone" converter for generator use?
  3. Does the generator (and/or solar, if we were to add that) directly power 12v or 120v systems directly, or simply provide charge to the battery which then produces the power via the converter?

I'm trying to make sure I understand the correlation between power usage (per device) vs. all the possible power sources, and frankly my head is swimming a bit at the moment.

Thanks in advance for any and all help.
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Old 07-27-2017, 01:11 PM   #2
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Originally Posted by gravedgr View Post
I get that the converter in the TT converts the 30A 120VAC camp plug into 12VDC for the camper to run its 12v systems, including charging the battery. And I also get that generators generally have a 12VDC > 120VAC inverter for normal 110/120v plug use.

There are a few things that I'm still confused about regarding battery power vs. shore power vs. propane power vs. generator power (electrical is not my strong suit). I'm hoping these aren't dumb questions and/or I missed a sticky thread somewhere.

My TT (23BHM) user manual has two charts in the electrical section labeled 12-volt system and 120-volt system. I assume the first chart is a list of things that can run off the 72ah TT battery (Exide Edge Dual Use Grp-24), and the second chart is a list of things that can run off electricity when hooked up to a 30A 120v outlet. My refrigerator is listed on both - on 12-volt, it shows a 3.0 amp draw and on 120-volt it shows a 6.0 amp draw.

Questions:

  1. My storage facility offers 110VAC (120) outlets and electricity for $5/mo. Each building is on a 20A circuit breaker, and mainly used for trickle chargers. If I were to plug in using a 30A-to-20A or 30:15 "dog bone" converter, could I run my refrigerator for a period of time assuming my 6.0 amp load (from the chart above) + the other vehicles plugged in didn't trip the 20A circuit breaker?
    Quote:
    Yes you should be able to. It depends on how many people have their campers plugged in. My camper with fridge running is plugged into a 15A circuit at the house for a few days before we go. One thing I would mention is if you are running the fridge for weeks at a time, it may ice up. I know we ran ours for a few weeks because we were going out every weekend. Once we had a period where we were not going out we unplugged it and let it defrost.
  2. If that doesn't work, could I run it off my 72ah battery for a period of time (3.0 amp load from above), and then hook up shore power to recharge the battery when I leave/when we reach our campsite?
    Quote:
    Unless your fridge is a 3 way it doesn't run on 12V. For instance mine runs on propane which needs 12V to run the brains. OR 120v which by the way is still using 12V for the brains. If it were me I would be hesitant about leaving it run on 12V if it is a 3 way. Just mainly because of the draw on the battery. Sure you can recharge it but it is hard on them if it was drawn down really low.
  3. The propane section indicates the refrigerator uses 1,200-1,500 BTU/hr. If neither of the above work, should I just turn on the propane system and have the refrigerator use propane to cool until I can access 30A shore power? Can you travel with this turned on?
Quote:
It will actually cool quicker on propane. Is it stored outside? Sure you can leave it on propane but it will still need 12V for the brains as mentioned.
You are also consuming propane but if you are fine with that OK. You don't need full 30A to run it. Really you can likely run pretty much anything in your camper on a 15A circuit except the AC. Well maybe the microwave if other stuff was on at the same time. I run my indoor fridge, outdoor fridge which is 110V only and converter with no problem on 15A circuit.

Sorry again if these are dumb questions - it is our first TT and we're trying to learn the process of cooling the refrigerator and loading it with cold/frozen food. I have a couple more question specific to a generator.

  1. Since the generator natively produces 12VDC which is then converter via inverter to 120VAC, is there a way to have the generator and TT 12v systems directly connected to avoid the DC > AC > DC loss?
    Quote:
    My Yamaha has a 12V cable with alligator clips which I could connect directly to the battery to charge it. However it doesn't monitor charging so you could over charge it and damage the battery as there is no monitoring. Just plug into the 120v and let the converter do what it does best.
  2. Do most 2k generators have a 30A plug or should we plan on a 30A:110v "dog bone" converter for generator use?
    Quote:
    Most generators have a twist lock connection so you will need a dog bone anyhow. Even if a 2K generator has a 30A plug (Honda 2000 Companion has one) keep in mind it can't provide 30A. So this means don't plan on running your AC on a 2K generator unless it is paralleled to a second unit. There are some ways people have gotten around this but don't plan on it out of the box.
  3. Does the generator (and/or solar, if we were to add that) directly power 12v or 120v systems directly, or simply provide charge to the battery which then produces the power via the converter?
Quote:
Depends on how you hook things up. Most people with a generator plug into the 120V outlet. SO then you are using 120V through the converter to the 12V stuff. You could hook the 12V to the battery but as I mentioned above you run the risk of overcharging. Solar provides 12V to the battery.
If you go with a bigger 12V system get a controller. Just like with the generator to 12V you don't want to overcharge. To go from 12V to 120V you need an inverter. However can you run an AC off 12V batteries with an inverter? Sure you are going to need lots of heavy batteries and lots of solar panels to do so and this would be very expensive. It is lighter and cheaper to just go with a generator but then you have noise. Microwave is your second highest draw appliance. TV isn't too bad and you can get away with that for a while on 12V with an inverter. You do want to size the inverter to your load though. For instance no sense in running a 1000w inverter to power the TV which needs maybe 90w of power. You will just kill your battery faster than needed.

I'm trying to make sure I understand the correlation between power usage (per device) vs. all the possible power sources, and frankly my head is swimming a bit at the moment.

Thanks in advance for any and all help.
Basically just think of anything that produces heat or cold is going to be a big power draw appliance. Things like TVs are pretty low.
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Old 07-27-2017, 01:22 PM   #3
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Really you can likely run pretty much anything in your camper on a 15A circuit except the AC. Well maybe the microwave if other stuff was on at the same time. I run my indoor fridge, outdoor fridge which is 110V only and converter with no problem on 15A circuit.
Just a side note: We parked our 5'r in front of the house for a couple days and ran the 50A -> 15A (110v) to the house off an extension cord. I had a 15K AC unit blowing full blast, the TV on, the stereo on, the fridge on and all the lights on and didn't blow a circuit. I will suggest using a 12 GA contractors/heavy duty extension cord for RV use due to the power you're drawing. Otherwise, you may end up melting a prong and causing a short. Bottom line is you can run quite a bit off a 15A circuit.
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Old 07-27-2017, 01:31 PM   #4
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Originally Posted by Packerbacker_TX View Post
Just a side note: We parked our 5'r in front of the house for a couple days and ran the 50A -> 15A (110v) to the house off an extension cord. I had a 15K AC unit blowing full blast, the TV on, the stereo on, the fridge on and all the lights on and didn't blow a circuit. I will suggest using a 12 GA contractors/heavy duty extension cord for RV use due to the power you're drawing. Otherwise, you may end up melting a prong and causing a short. Bottom line is you can run quite a bit off a 15A circuit.
I have the Progressive Industries EMS-HW30C (the internal one with remote display). When hooked up to my 15A circuit running my outdoor fridge, inside fridge, lights (but they are 12V and my 2017 is full LED), bathroom vent fan (again 12V) and I want to say the remote display was reading I was pulling about 13A if I remember what I was seeing the last time I tried it.

Were you plugged into the garage by chance? Many time garage circuits are 20A. That would explain how you got away with it. The TV isn't a huge load. Lights not necessarily. I don't know what the RV fridge pulls but the where you run into problems with the AC is when the compressor kicks in. Once it is running they don't pull much. It is getting over that hump. On 15A I could probably run on that (I also have a 15K AC) but I might have to have the fridge on propane or as long it didn't cycle while the AC unit kicked in as that would likely trip the breaker. I would also have to unplug my outdoor kitchen fridge.

I do agree run a heavy gauge cord if you try this or better yet plug directly into the outlet with a dog bone if possible.
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Old 07-27-2017, 02:13 PM   #5
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Thank you for all the information and the detailed responses! I'll to clarify a few things below.

Quote:
Yes you should be able to. It depends on how many people have their campers plugged in. My camper with fridge running is plugged into a 15A circuit at the house for a few days before we go. One thing I would mention is if you are running the fridge for weeks at a time, it may ice up. I know we ran ours for a few weeks because we were going out every weekend. Once we had a period where we were not going out we unplugged it and let it defrost.
We were only thinking of driving up the night before and packing everything but the cold food items, and turning on the fridge. Then when we drove up for our hookup, we'd just need to load the cold food in an already cold fridge.

Quote:
Unless your fridge is a 3 way it doesn't run on 12V. For instance mine runs on propane which needs 12V to run the brains. OR 120v which by the way is still using 12V for the brains. If it were me I would be hesitant about leaving it run on 12V if it is a 3 way. Just mainly because of the draw on the battery. Sure you can recharge it but it is hard on them if it was drawn down really low.
I'm not sure. It is a Norcold 6 gallon. The manual lists its power draw in amps (12-volt chart), amps (120-volt chart) and BTU (propane chart). I don't know if that makes it a 3-way or not.

Quote:
It will actually cool quicker on propane. Is it stored outside? Sure you can leave it on propane but it will still need 12V for the brains as mentioned.
You are also consuming propane but if you are fine with that OK. You don't need full 30A to run it. Really you can likely run pretty much anything in your camper on a 15A circuit except the AC. Well maybe the microwave if other stuff was on at the same time. I run my indoor fridge, outdoor fridge which is 110V only and converter with no problem on 15A circuit.
It is an inside fridge. The only thing the 23BHM has outside is a shower and TV mount/hookup.

Quote:
My Yamaha has a 12V cable with alligator clips which I could connect directly to the battery to charge it. However it doesn't monitor charging so you could over charge it and damage the battery as there is no monitoring. Just plug into the 120v and let the converter do what it does best.
I was looking at the Yamaha 2k, but now I'm looking at getting a pair of 2k from Costco with the Yamaha engine. The noise is slightly higher, but they support connecting them to increase output and are half the price.

Quote:
Most generators have a twist lock connection so you will need a dog bone anyhow. Even if a 2K generator has a 30A plug (Honda 2000 Companion has one) keep in mind it can't provide 30A. So this means don't plan on running your AC on a 2K generator unless it is paralleled to a second unit. There are some ways people have gotten around this but don't plan on it out of the box.
We will only be camping using shore power for at least the first few months. We usually go to Expo East (www.expeditionportal.com) and tent camp. We had hoped to convince friends to camp elsewhere and drive to the expo for the day (they are all teardrop campers), but I don't think that is happening. Even if we wanted to chance parking in the field they use to host people that are camping (big "IF"), we'd need to have generator AC while at the RV.

One option would be the 2 inline 2k's mentioned above, or something like a Micro Air easy start.

Quote:
Depends on how you hook things up. Most people with a generator plug into the 120V outlet. SO then you are using 120V through the converter to the 12V stuff. You could hook the 12V to the battery but as I mentioned above you run the risk of overcharging. Solar provides 12V to the battery.
If you go with a bigger 12V system get a controller. Just like with the generator to 12V you don't want to overcharge. To go from 12V to 120V you need an inverter. However can you run an AC off 12V batteries with an inverter? Sure you are going to need lots of heavy batteries and lots of solar panels to do so and this would be very expensive. It is lighter and cheaper to just go with a generator but then you have noise. Microwave is your second highest draw appliance. TV isn't too bad and you can get away with that for a while on 12V with an inverter. You do want to size the inverter to your load though. For instance no sense in running a 1000w inverter to power the TV which needs maybe 90w of power. You will just kill your battery faster than needed.
No plans to run A/C off battery (shore or genny). I expect furnace will be propane only. Just about everything else we'd like to have options for propane, shore, genny and/or solar eventually for ultimate flexibility.
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Old 07-27-2017, 02:15 PM   #6
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Just a side note: We parked our 5'r in front of the house for a couple days and ran the 50A -> 15A (110v) to the house off an extension cord. I had a 15K AC unit blowing full blast, the TV on, the stereo on, the fridge on and all the lights on and didn't blow a circuit. I will suggest using a 12 GA contractors/heavy duty extension cord for RV use due to the power you're drawing. Otherwise, you may end up melting a prong and causing a short. Bottom line is you can run quite a bit off a 15A circuit.
Thanks for that tip. I bought some HD cables earlier in the year for camping and power tool use, so I'll check the gauge on them.
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Old 07-27-2017, 02:16 PM   #7
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Were you plugged into the garage by chance? Many time garage circuits are 20A. That would explain how you got away with it. The TV isn't a huge load. Lights not necessarily. I don't know what the RV fridge pulls but the where you run into problems with the AC is when the compressor kicks in. Once it is running they don't pull much. It is getting over that hump. On 15A I could probably run on that (I also have a 15K AC) but I might have to have the fridge on propane or as long it didn't cycle while the AC unit kicked in as that would likely trip the breaker. I would also have to unplug my outdoor kitchen fridge.

I do agree run a heavy gauge cord if you try this or better yet plug directly into the outlet with a dog bone if possible.
Funny you should ask - Yes, I did plug into the 110V outlet on the outside of my garage. I assume the circuit is 15 or 20A but won't know for sure until I check the breaker box. I do admit, it does seem a bit frivolous to run all that simultaneously but it was our first time so we were testing everything. Realistically, the AC for comfort while you're in it, the fridge to get ready for the trip and some lights to see what you're doing. When we're camping, we're normally plugged into a 30 or 50A outlet.
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Old 07-27-2017, 02:56 PM   #8
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Thank you for all the information and the detailed responses! I'll to clarify a few things below.

We were only thinking of driving up the night before and packing everything but the cold food items, and turning on the fridge. Then when we drove up for our hookup, we'd just need to load the cold food in an already cold fridge.

Quote:
Yeah that is a good plan. If you are going out the next weekend you are fine leaving it run all week but after a month or two you might need to do a defrost cycle.
I'm not sure. It is a Norcold 6 gallon. The manual lists its power draw in amps (12-volt chart), amps (120-volt chart) and BTU (propane chart). I don't know if that makes it a 3-way or not.

Quote:
Like I said the brains are always going to need 12V no matter if you are on propane or 110v shore power. That is likely why it is listed. There are 3 way fridges but if you have a Jay Feather 23BHM that is the other camper we were considering when we bought the JF 25BH. It would have the same fridge I have. Unless your propane is on the 12V alone won't do anything.
I want to say the 3 way fridges are more expensive and I would expect to see them on motorhomes more so than a travel trailer.
It is an inside fridge. The only thing the 23BHM has outside is a shower and TV mount/hookup.

Quote:
The outdoor kitchen is one of the reasons we went with the 25BH over the 23BHM so I knew you didn't have one. I just mentioned it as I was commenting on what I run on my camper while plugged into a 15A circuit.
You don't have the outside fridge so you don't have that load.
I was looking at the Yamaha 2k, but now I'm looking at getting a pair of 2k from Costco with the Yamaha engine. The noise is slightly higher, but they support connecting them to increase output and are half the price.

Quote:
Also look at the one from Harbor Freight. I think they are the same generator which is an inverter which can be paralleled. I was talking with someone else about this generator. The key point is you might get your AC to run on a 2K. I know our camper has the optional 15K AC and I was questioning if it would run on my 3K Yamaha but it does. Also take note in generator specs. For instance I have a Yamaha 3000is. But that is 3000w surge I think it is only rated to 2800w continuous. Many times generators can take a power spike like when a compressor kicks in at a load higher than the number used as the model number. What I mean by this is some manufacturers have a 2000w but it is a 2000w sustained and 2300w surge. Others, like my Yamaha have a 3000 but that is 3000 surge and 2800 sustained. It makes it hard to do an apples to apples comparison. Just look at the specs.
We will only be camping using shore power for at least the first few months. We usually go to Expo East (www.expeditionportal.com) and tent camp. We had hoped to convince friends to camp elsewhere and drive to the expo for the day (they are all teardrop campers), but I don't think that is happening. Even if we wanted to chance parking in the field they use to host people that are camping (big "IF"), we'd need to have generator AC while at the RV.

Quote:
This is the nice thing about those smaller 2Ks that can be linked.
If you know you don't need the AC you only have one generator to lug around and it is likely more fuel efficient than a single larger one.
One option would be the 2 inline 2k's mentioned above, or something like a Micro Air easy start.

Quote:
That is what I was referring to when I mentioned people get AC units to run on smaller generators. With a big enough capacitor you can get past that spike to start the compressor. Though I think the AC units in the newer campers already have larger caps so you might be fine.
No plans to run A/C off battery (shore or genny). I expect furnace will be propane only. Just about everything else we'd like to have options for propane, shore, genny and/or solar eventually for ultimate flexibility.
I wasn't clear if you were looking at AC on battery/solar. Sure it can be done and some do it and are happy because they don't want the noise. My generator is very quiet, granted not as much so if the AC is running but we are fine even if we can cool things off a bit before bed.
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Old 07-27-2017, 03:01 PM   #9
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Funny you should ask - Yes, I did plug into the 110V outlet on the outside of my garage. I assume the circuit is 15 or 20A but won't know for sure until I check the breaker box. I do admit, it does seem a bit frivolous to run all that simultaneously but it was our first time so we were testing everything. Realistically, the AC for comfort while you're in it, the fridge to get ready for the trip and some lights to see what you're doing. When we're camping, we're normally plugged into a 30 or 50A outlet.
Of course local building codes and age of your house would possibly change what is done on what circuit but around here bathrooms, kitchens and garages all get 20A circuits. Not sure how far back that goes as our house built in the 60s is all 15A. At least it was, we did a remodel two years ago in the kitchen and main bath so they are both 20A.

Yeah I hear you on wanting to test stuff out. We didn't run the AC for a while after getting the new camper. It was too cold out to try it. Being we are in MN we ran the furnace a lot more than the AC. That brings up another point. I haven't run the AC while on my 15A but I am 90% sure I have switched the thermostat to fan. Now the compressor wouldn't have been kicking in but I think I did have that going when I was seeing in the 13A range. I assume the A reading on the Progressive is accurate.
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Old 07-27-2017, 03:05 PM   #10
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On the generators. Here is where we were talking about those Costco ones that are also at Harbor freight.

https://www.jaycoowners.com/forums/f7...tml#post549935
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