Upgrading to Inverter in a '76 Argosy

[yousty7]

Hi all,

This is my first post on the forum, but I've been absorbing tons of information here the last 2 months since my purchase. How lucky we all are to have a site like this. My trailer is a 1976 Argosy Airstream rear bath which I am converting into a mobile food trailer. I just got the OK from the local heath department to move forward with my plans, so I am very excited to get started.

I have a background in construction, so I believe I can handle all of the upcoming mod's, but one area that is a little different for me is RV electric. I was hoping one of the experts on here would give my electrical plans a quick critique for any inefficiencies before I buy everything this week.

I would like the optionality of going "off-grid" with my trailer for 3-5 hours at a time if necessary. The only things that will require electricity on an on-going basis are a 2.6 amp upright freezer, 12v LED house lights, 12v vent fans and 12v LED signage and water pump.

I am going to start out by doing this off of 2 Trojan T-105 6v batteries, wired for 12v. The batteries will be connected to a 2000W Tripp Lite Pure Sine Wave Inverter/Charger (8A/80A) which will thus be hardwired to the existing 30amp breaker box.

Doing it this way, I can leverage the existing breaker box and all of the existing outlets to draw off my batteries. I will have the option of adding solar down the line once I have some extra money to invest.

I was unsure of what size fuse I needed between the battery bank and the DC appliances. I haven't been able to find an internet resource that explains will the sizing for fuses in that regard. Do I need an 80 amp fuse here to match the capacity of the inverter?

Also, any other suggestions or thoughts would be really appreciated. When it comes to RV electric, it always seems there is an added layer that needs to be considered. I believe what I have planned matches my power needs and keeping the costs for this upgrade around 1k.

[yousty7]

So I've been restoring this trailer since December and all the electric is in. All the 120v outlets work great.

I've yet to get the 12v working though. I believe my issue is around 2 white wires coming from the back. One may have been grounded to the frame and got loose, the other was definitely in the old uni-volt.

The white ground which was in the univolt I put in the grounding bar going into the inverter. The other I removed a bit of skin, cleaned the metal and screwed back into the frame. I am not 100% sure this is correct, and as my 12v still does not turn on, I don't beleive it is.

As I said, 120v works fine, inverter is acting normally and I get 12v power coming from all the ports in the DC box.

I've attached some pictures of the set up. Is anyone able to offer an opinion?

[Jarrod White]

Do you have a converter (univolt or replacement)? I don't see one in your pic. The converter charges batteries and then there is a fuse board that connects batteries and converter and distributes 12v power. I recommend intellipower for the converter if you're adding one or as upgrade to univolt.

[yousty7]

Hi Jarrod,

Thanks for replying. The inverter you see in the picture is actually a inverter/charger. I've seen mentioned before that people save the fuse from the old univolt (still have it) but I never understood why they use that fuse specifically.

Amazon.com: TRIPP LITE APS2012SW 2000 Watt 12 Volt Inverter / Charger Pure Sine Wave 120 Volt 8A/80A Hardwire: Electronics

[Aage]

Originally Posted by yousty7

Hi Jarrod,

Thanks for replying. The inverter you see in the picture is actually a inverter/charger. I've seen mentioned before that people save the fuse from the old univolt (still have it) but I never understood why they use that fuse specifically.

I believe that they meant you might be able to recycle the fuse panel, not just a fuse. I don't support doing that due to the fact that in my own case, the metal in the fusebox that was on my original Univolt had lost its temper, which caused a dramatic spike in the resistance of the fuse panel, and might have actually caused a fire had I not replaced it.

So, in my opinion, it's recommended to replace the 12V fuse box with a new one.

[yousty7]

Ah gotcha, Aage. That's pretty much what I've done then. I have tested 12v coming out of all the fuses in the new panel, the power is just not reaching the lights or anything else.

[GeocamperAS]

You bought an "inverter" not a "converter".
The link you posted shows an inverter with a 12 volt or 120 volt input and a 120 volt output.
You need a converter with a 120 volt input and a 12 volt output.

When your camper is NOT plugged into shore power (120 volts), the 12 volt system works off of the batteries. When it is plugged into shore power the CONverter will take the 120 volts AC and reduce it and convert it to 12 volts DC.

An INverter takes the 12 volts DC and produces 120 volts AC. This would be used for running a coffee pot or a TV off of your batteries.

[TG Twinkie]

An inverter provides 120 volt AC power not 12 volt DC power. While it has charging capability. Not sure of the capacity.
My first observation is: you do not have large enough wire for a 2,000 watt inverter if you intend on using it to it's rated capacity. Which will be in the neighborhood of 167 amps on the DC side. 16 amps of capacity on the AC side. Not counting the losses of the conversion process.
IMHO you do not have near the battery capacity for an inverter of that size.
Not having any personal experience with an inverter. My educated guess is. In order to charge batteries. You must provide 120 volt AC power to the inverter. Ie shore power.
Since the inverter uses 12 volts DC on the input side and provides 120 volt AC on the output side. There is no source of power for the charging side of the inverter/charger.
If you want to use the 12 volt system. You need to provide power to that system from the batteries thru a properly fused circuit. While the inverter/charger will charge the batteries. How long will it take? And does it have the capacity to charge batteries as well as provide 12 volt DC power to the circuits. A minimum of 45 amp load capacity is what I would think it would require.
I believe a transfer switch will be involved in order to prevent back feeding to the power company.
Good luck



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[Jarrod White]

I suspect your inverter will handle the duties of a converter since it charges the batteries. You haven't posted a pic of your new fuse panel and I do not see it your diagram. You need positive and negative going to it and all of your negatives to your 12v together and then the positive leads coming off the fuses to the different 12v uses. If you have it wired like this, your 12 volt lights should work.

[yousty7]

Thanks all for the reply, very much appreciated.

Jarrod - I have the new DC fuse panel in both pictures as you described it should be done (now I'm 2nd guessing myself). In the bottom picture, I have it labeled as DC. I tested each of the wires coming off the fuse panel (pink, purple, yellow, blue) and they all read 12v on the meter.

I feel like it has to be something small so I didn't want to have to drag it to the shop, but it seems like I may have to.

[TG Twinkie]

What are you referencing your meter to When you read 12 volts?
Are you missing the common/ ground connection? Since nothing works.
You need to have the negative (common/ground) on the batteries connected to the skin/frame of the coach.


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