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Discussion Starter · #21 ·
The bigger concern, in this instance, seems to be space rather than cost. Different needs arise to add or remodel than during original construction. I'd also be surprised if it wasn't more cost for the larger wire and charger than for a small inverter and the extension cord likely already being carried.

Putting the dc-dc charger up front needs much larger wire, plus likely oversized to combat the voltage drop since it should be located near the house batteries. Large wire, possibly smaller than with the charger upfront, still needs to be run if space was made to place it in the rear by the house bank. It doesn't sound like there is easy space to run this wire.

Inverters are also cheaper than they once were, especially smaller msw ones. Either case gives multistage charging. Maybe it's less efficient, but it's spare alternator juice not battery storage so it doesn't really matter in my mind. You're not 'wasting' anything. The dc-dc is probably the best option if you're starting from scratch. The second inverter is definitely an option for an after the fact add-on.
Exactly what I was thinking.
 

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I haven't thought through all of the details of trying this, but there is a person on YT that did precisely this with their van.

As far as I know, he is still using that approach as he is pretty good about updating if anything changes, though he does say that he only really uses it as a backup to the solar, so maybe it only gets used... almost never...


His website with much more info is:


His site has lots of really excellent info on it overall for approaches to things and also for sourcing materials, etc.
 

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Discussion Starter · #23 ·
That's almost exactly what I was considering. I'd just use an extension cord (that I already carry) to make the 120v connection.

Thanks. Probably will hold off for now, but if I need it I may give it a shot.
 

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2018 2500 159-HR
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Thats not a bad idea. I do have access to under the driver's seat. I would have to pick up a negative lead somewhere as well.
The negative lead's pretty close, actually, as the van battery's negative terminal is bolted to the chassis just to the left of the front of the driver's seat, under the floormat. In my rig I repurposed the D-Ring bolt that's just below the rear of the driver seat as my central grounding point and run a 4 AWG from it to the battery's chassis bolt (which is probably an unnecessary extra step, but it shortened the 4 AWG negative run to my DMT-1250, and I centralize all my DC load grounds there too).

Here's a shot from early in the build; the uncrimped black 4 AWG wire is bolted on the other end to where the van battery bolts into the floor/chassis:
71150
 

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I have my van fully built so adding a DC to DC charger is possible, but not ideal. Also fairly expensive. Particularly for the rare situations where my solar can't keep up with my usage.

So... was thinking is there any reason I can't mount a small inverter up front and run a 120v power cord to my existing inverter/charger that's all ready to charge my batteries?

Figure a small 300w inverter could be mounted under the cup holders and permanently hooked up to the battery. I could then plug into that.

I know there are a lot of losses going from 12v to 120v and back to 12v, but that shouldn't be a big deal. With 300w I should still get 20 amps or so per hour charge. Probably could up that to a 500w inverter if it fits.

Thoughts? Am I missing anything? Yes, in my build I'd have to run a 120v extention cord from front to back but that's ok. It would only be while driving and only when absolutely necessary. Most of the time solar is fine. I figure this would cost $100 vs much more for a DC to DC charger and large Guage wire id have to run under the van.
I think you will be happier if you charge your leisure batteries via your alternator. It will cost about $300 to set up, but will be a high quality long term solution. One issue to consider: If you intend charging lithium batteries do not charge directly. Use a dc to dc charger.
 

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Discussion Starter · #26 ·
Update: I pulled a 1000w inverter from my trailer (replaced that with a 2000w unit) and did a test. I only connected to the battery with 12 awg wire because thats as large as I had on hand but it worked fine at 15 amps. Inverter fits under the front seat so I'm going to order some cable and a fuse and do a permanent install.

From what I reread above and elsewhere it seems the stock alternator should be fine at 50 amps draw?

Only issue i see is i need to be careful with my plugs. I'm backfeeding an outlet so I have a exposed plug when the inverter is on. I'm going to buy a bare socket side plug to keep on there when not in use just in case someone turns the inverter on.
 

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Discussion Starter · #27 ·
Further update. I ran heavy gauge wire and ran the inverter for 45 min while driving - sending 30 amps/hr to the batteries. Worked well except the inverter kept shutting off unless I was on the throttle. So only working during highway runs. Seems weird because I thought the alternator would keep up but regardless for my emergency uses this should be a fine solution. For the most part my solar keeps up with my uses. YMMV.
 

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2019 159 High Top - White, of course!
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I don't see how you are backfeeding a plug. You connect a regular extension cord (I assume cut off and connected semi-permanently to the inverter-charger. Where is a backfed outlet? The inverter-charger should handle the input and output, and the smaller inverter doesn't ever have any backfed outlets.

Instead of a plug, you can always just use Anderson Power Connectors (aka forklift plugs). They start at 50a and run up to 350a (as I recall). These are handy when you want to connect high load cables or wires but easily disconnect them when not being used.

I used one on the power cable to a large amp (mounted on a subwoofer box), so I could remove it quickly and easily when I raced the car. It worked perfectly and flawlessly for 14 years (until I sold the car - I have no doubt it still works flawlessly). I mounted the cable from the battery to a trunk-mounted, permanently affixed connector (bolted to the floor of the trunk), and the mating connector with a handle, and the other end of the cable connected to the amp mounted on the sub box. They are really handy, and really robust.

They make smaller PowerPole connectors for lighter wires and smaller loads.

Here is a picture of the typical forklift connector. I believe that is a 350a model. You can also add handles to make disconnecting the larger ones easier.

Hand Guitar accessory Finger Wood Thumb


Output device Rectangle Gadget Bumper Office equipment
 

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I don't see how you are backfeeding a plug. You connect a regular extension cord (I assume cut off and connected semi-permanently to the inverter-charger. Where is a backfed outlet? The inverter-charger should handle the input and output, and the smaller inverter doesn't ever have any backfed outlets.

Instead of a plug, you can always just use Anderson Power Connectors (aka forklift plugs). They start at 50a and run up to 350a (as I recall). These are handy when you want to connect high load cables or wires but easily disconnect them when not being used.

I used one on the power cable to a large amp (mounted on a subwoofer box), so I could remove it quickly and easily when I raced the car. It worked perfectly and flawlessly for 14 years (until I sold the car - I have no doubt it still works flawlessly). I mounted the cable from the battery to a trunk-mounted, permanently affixed connector (bolted to the floor of the trunk), and the mating connector with a handle, and the other end of the cable connected to the amp mounted on the sub box. They are really handy, and really robust.

They make smaller PowerPole connectors for lighter wires and smaller loads.

Here is a picture of the typical forklift connector. I believe that is a 350a model. You can also add handles to make disconnecting the larger ones easier.

View attachment 77810

View attachment 77811
 

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Discussion Starter · #30 ·
I don't see how you are backfeeding a plug. You connect a regular extension cord (I assume cut off and connected semi-permanently to the inverter-charger. Where is a backfed outlet? The inverter-charger should handle the input and output, and the smaller inverter doesn't ever have any backfed outlets.
I have a regular outlet on the input side of my "house" inverter/charger. It is usually only live when feeding power from an external source. From the new inverter I installed under the front seat I run an extension cord to it. I made up a male by male pigtail that I use to make the final connection between the inverter and the outlet. That sends power to the input of the "house" inverter/charger. Of course I'm careful not to turn on the inverter while a live male end is exposed.
 

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