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Discussion Starter #1
Have seen some good photo posts on battery hookups, but in trying to run some cables came up with few questions:

Our aux battery is on the floor right up against the higher cabin floor behind the drivers seat.

1) in trying to run cables out of the veh battery box under the cabin floor to under the drivers seat - there is form between the cabin floor and the frame - did others cut away this foam or simply allow the floor to press the wires down into the foam (wondering if this might damage the wires). To cut away the foam it looks like the whole rubber floor might have to be removed which does not look easy to do vs the panels. How did others do this ?

2) some of the photos show use of fuses at the veh battery terminals but we intend to use breakers instead (allows easy cutoff and eliminates need to carry around extra fuses). The plastic veh battery case looks like we could fit the breakers on the battery ends and would require glue or screws into the plastic - any ideas on this ? Or we could put the breakers under the drivers seat where we plan on putting a 1500 w inverter (should get good cooling under the seat open ends).

3) someone showed a metal container box they bought for under the seat but can't find that post now. Anyone else have experience as to attaching things under the seat ?

our isolator specs a #6 wire at least 6ft total between veh batt - isolator - we plan to have a 100 a breaker between each batt and the isolator. Then run a #2 ground cable between each batt with a 100a breaker in the middle. We will then have separate #2 cables running from the aux batt to 150a breakers to the inverter which should only be about 12-18 inches long total. Then run #12 wires from aux to DC panel.
 

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You should have a proper sized fuse at each end of your + cable (as close to the end as possible) forget the - cable, it's a waste of time and money, simply connect a ground strap from the aux battery to the body. No need to remove the seat or floor mat just the plastic trim pieces in the step area and edge of the floor mat. There is a plastic channel with two slots underneath the mat on the side that you can run the + cable thru for protection but you may have to reroute the smaller wires that are there to the the other slot. If you open it up it is very apparent and easy to do.

This is how I did it
 

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I did much the same as KOV and used a breaker at the battery as you are doing. At present I have a 50 amp breaker that seems to be working but I plan to go to an 80 or 100 amp breaker or fuse. I did not run a black ground wire but grounded the battery beside itself to a good bolt through the van's body after grinding an area to get a perfect connection. Fuse both ends of the + cable to avoid a short in that wire burning up your campervan. Then feed the inverter back to the spot under the seat and protect the wires by placing them under the floor or in flex conduit. I used 4 AGW wire for both the battery connections and the inverter connection to safely carry up to 200 amps at the distances you have. I also ran the 4AGW up to my distribution panel as it was near the ceiling and the total wire length was about 12 feet. I suggest you go a size or two larger to the panel as drawing 80 amps is easy in the future and 12 would be a bit small.
 

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Have seen some good photo posts on battery hookups, but in trying to run some cables came up with few questions:

Our aux battery is on the floor right up against the higher cabin floor behind the drivers seat.

1) in trying to run cables out of the veh battery box under the cabin floor to under the drivers seat - there is form between the cabin floor and the frame - did others cut away this foam or simply allow the floor to press the wires down into the foam (wondering if this might damage the wires). To cut away the foam it looks like the whole rubber floor might have to be removed which does not look easy to do vs the panels. How did others do this ?

2) some of the photos show use of fuses at the veh battery terminals but we intend to use breakers instead (allows easy cutoff and eliminates need to carry around extra fuses). The plastic veh battery case looks like we could fit the breakers on the battery ends and would require glue or screws into the plastic - any ideas on this ? Or we could put the breakers under the drivers seat where we plan on putting a 1500 w inverter (should get good cooling under the seat open ends).

3) someone showed a metal container box they bought for under the seat but can't find that post now. Anyone else have experience as to attaching things under the seat ?

our isolator specs a #6 wire at least 6ft total between veh batt - isolator - we plan to have a 100 a breaker between each batt and the isolator. Then run a #2 ground cable between each batt with a 100a breaker in the middle. We will then have separate #2 cables running from the aux batt to 150a breakers to the inverter which should only be about 12-18 inches long total. Then run #12 wires from aux to DC panel.

Here is a chart of the AWG needed for various loads and distances. -> http://assets.bluesea.com/files/resources/newsletter/images/DC_wire_selection_chartlg.jpg


Your 1500w inverter can sustain 125 amps (1500w/12v) and probably can handle more for surge, usually double that for many inverters.
 

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Discussion Starter #5
Here is a chart of the AWG needed for various loads and distances. -> http://assets.bluesea.com/files/resources/newsletter/images/DC_wire_selection_chartlg.jpg


Your 1500w inverter can sustain 125 amps (1500w/12v) and probably can handle more for surge, usually double that for many inverters.
thks for chart - best one we've seen.

Yes, planned for 120a which is why going with #2 . Probably should have bought 1000w inverter since really only using for 900w microwave (orginally planned for charging house battery thru AC charger but went with isolator instead).
 

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Discussion Starter #6
@kov - thks for photo - somehow missed that existing channel.

Had thought about grounding to frame (obviously easier) but then on isolator install diagrams they showed connect neg to both batteries. Yes, fuses are more compact and easier but breakers give both disconnect and reset advantage - don't want to be stuck somewhere with blown fuse or carrynig spares but since it really shouldn't happen maybe the fuse is okay. Anyway bought the breakers so plan to use them.
 

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You should ground to the chassis to save costs and time. Besides the metal chassis is going to carry more current then any gauge cable.

However at the battery you should add additional short ground to the chassis.. was goes out must come back.
 

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The chart fails in one way. The minimum wire length is 20 feet. All this wiring in our vans is often for much less distance and the same size wire can carry much more current with low loss at 3 ft or 7 ft which are more representative distances. Not that the chart is wrong just encourages us to run larger wire than necessary. For example 4AGW which I use mostly can carry 200 or more amps for up to 15ft. and much more for 4 or 5 feet. Even 10 AGW can carry 200 amps for 3 ft! (I might not do that)
 

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I might recommend going larger than recommended as equipment runs better/cooler and more efficiently at higher voltages. All wire has resistance no matter what size and you loose a bit of voltage the smaller you go. You can conserve a bit of battery power by running larger wire to everything thats has a motor, heating element or large load.
 

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The chart fails in one way. The minimum wire length is 20 feet. All this wiring in our vans is often for much less distance and the same size wire can carry much more current with low loss at 3 ft or 7 ft which are more representative distances. Not that the chart is wrong just encourages us to run larger wire than necessary. For example 4AGW which I use mostly can carry 200 or more amps for up to 15ft. and much more for 4 or 5 feet. Even 10 AGW can carry 200 amps for 3 ft! (I might not do that)

I have heard that 3% loss or less should be the goal. I think the 10% is only for extremely long runs when one has no choice... something that is unlikely to happen in a conversion van unless one has a portable remote solar panel tied to the van so that the van can park in the shade.
 

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Discussion Starter #12
You should ground to the chassis to save costs and time. Besides the metal chassis is going to carry more current then any gauge cable.

However at the battery you should add additional short ground to the chassis.. was goes out must come back.
not sure what you mean - the isolator box has a thin neg wire that will go to ground. Then we will cable via breaker from the aux neg to the chassis - is this what you mean ? or something else ?
 

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Breaker should only go on the power side. What I meant by the ground is that if you add something on the power side then you should balance it out by adding the same on the negative side.
 

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Ideally, you want to have two conductors, one for the positive, and one for the negative. They should be taped or tied together every 6 inches in order to hold the conductors right next to each other. This increases surge capability and reduces inductance. This is especially helpful if you are planning to run the engine at times while inverting for heavier tasks.

It is probably not that big a deal if you are only running it to charge the auxiliary.

This scenario is even more important for the run from the auxiliary to the inverter, where the increased surge capability is beneficial for obvious reasons, and reducing the inductance improves the inverter's wave form, and reduces wear on it's filter capacitors.

That is "ideally." No problem just grounding to the chassis either, it just isn't optimum.
 

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From what I've read, except for an initial surge, inductance doesn't have a whole lot of impact on DC circuits.

The wiring diagram for my isolator indicates that chassis ground is the way to do it. (Battery Doctor 150A Wizard)

Should be OK either way, the PM chassis has a whole lot of ampacity! :D

outdoorvanman, that small grounded wire is there to allow the electronics in the isolator to work. That's not the ground being discussed. By the way, on my Battery Doctor 150A Wizard, I put a switch on that small ground wire so I can turn the aux charging off. I do that when I'm hooked up to AC and my converter/charger is doing the aux charging job instead of the van alternator.

Ed
 

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Cut...... By the way, on my Battery Doctor 150A Wizard, I put a switch on that small ground wire so I can turn the aux charging off. I do that when I'm hooked up to AC and my converter/charger is doing the aux charging job instead of the van alternator.
I did the same sort of switch on the feed side of the solenoid to allow the solar to charge the batteries all the time.... Except when I need a bit more juice from the van or the converter.
 

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Discussion Starter #18
From what I've read, except for an initial surge, inductance doesn't have a whole lot of impact on DC circuits.

The wiring diagram for my isolator indicates that chassis ground is the way to do it. (Battery Doctor 150A Wizard)

Should be OK either way, the PM chassis has a whole lot of ampacity! :D

outdoorvanman, that small grounded wire is there to allow the electronics in the isolator to work. That's not the ground being discussed. By the way, on my Battery Doctor 150A Wizard, I put a switch on that small ground wire so I can turn the aux charging off. I do that when I'm hooked up to AC and my converter/charger is doing the aux charging job instead of the van alternator.

Ed
We expected to use the postive breaker switch as on/off charging. Is there any reason to put the switch on the neg wire ?

I still don't understand catilins comment on the aux batt ground - shouldn't the aux neg ground still have a breaker/fuse on it since ground is common between batteries, isolator ? Thought I had read that somewhere.
 

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Airstream trailers, the Rolls-Royce of camper trailers, historically fused both (+) and (-) sides of their house battery so with enough things going wrong at the same time - accident, interior constructions shifting around, if the house battery (+) terminal itself gets shorted to ground there is a safety provided; also the fuse lends protection in the event 240/120VAC surge gets into the low voltage wiring, or a tow vehicle power circuit finds the shortest return path is through the house battery (since there is a second power circuit from the tow vehicle involved). Remember most of the time these incidents alone may not be enough to open the fuse BUT if the system is in use, trailer occupied and ongoing activities the extra input would open the circuit. For me at least it's details like that that make sleeping in a 50-year-old trailer possible...
 

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We expected to use the postive breaker switch as on/off charging. Is there any reason to put the switch on the neg wire ?

I still don't understand catilins comment on the aux batt ground - shouldn't the aux neg ground still have a breaker/fuse on it since ground is common between batteries, isolator ? Thought I had read that somewhere.
Switch should always be on the positive side of the battery. It's the side that's possibly charged and the side that provides electron flow.

I don't have access to my computer right now so I can't illustrate...and of course after all these posts I may have lost sight what you're doing exactly.

What I meant by the ground wiring is that it's not necessary to route a ground wire all the way back to the main battery. BUT you should upgrade that main ground to "balance" the load. Meaning, 2ga on the positive, then put a short 2ga on the ground side to chassis.
 
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