2016 Grandby Battery and Isolator Install

Updates-

Had the battery tested at Batteries Plus. Guy threw the load tester on it and said it was more than good...

I also tried plugging the camper into 110 and using the converter. I had the same results. When the converter wasn't hooked to the battery, it read about 13v. After connecting to the battery, it dropped to just over 12.

I'm really not sure what it could be.. maybe something with the ground inside the camper? I'll try bypassing all the FWC wiring tomorrow and see what I can get with my own grounds.

I'll also probably pull the 120lb battery and see if I get the same result outside the camper, from jumpers maybe.
 
What gauge wire do you have running from your camper to the engine bay of the truck? It sounds like it could be an issue with the resistance and resultant voltage drop in the wire runs. This would explain why the voltage looks good when the battery is not connected (no load, therefore no current and no voltage drop in the wires). When you connect your honking battery into the circuit and it is at low state of charge, it will draw a lot of current - causing a voltage drop across the long wire runs. For example if you are using 8 AWG wire, and your battery is pulling 30A, you could be losing almost 1.3V in a 30' run.

As for the converter - this is what I would expect to see with a large battery which is mostly discharged. I don't have my FWC yet, so I don't know the details of the converter, but is can only provide so many amps into the battery, so it will take some time to bring the battery voltage up to 13.5 or what ever the float charge voltage is.
 
That actually makes a lot of sense. I'm just using the stock wiring the dealer installed. It's actually solid core most of the way, so I'm not sure of the gauge. Essentially the type of wire I'd expect to see in 110 applications.

I'd discounted the wire size as the cause because the battery didn't seem dramatically discharged at 12v and everything worked just fine when I first installed it.

I'll charge the battery back up and see if the truck can keep up with it then.
 
I've got the battery on a plug in charger at 2amps. I'll just leave it all day and see what happens.

I get the same issue with the plug in charger as with the rest, charge voltage drops as soon as it's connected to the battery.

Hopefully the big ol' battery just needs a little juice. If I get it charged up and everything works the way it should, I'll run some heavy cable from the truck to remedy the low-level charging.

I picked up a solar setup at Northwest Overland Rally last weekend, so hopefully the battery won't get drawn down as much going forward.
 
That battery is very large compared to your charging sources and it will pull the amps to charge up, thus pulling down the voltage with it unitil it charges up.

If you measure the terminals at the charge source and the battery when charging, you should a difference between them change over time. The wiring is dropping voltage and you might feel them heat up some. As the battery charges, the battery terminal voltage will begin to rise. The charger output will also rise some with it as the output current tapers off to be less then its rated output maximum. If you can watch the voltage on both ends at the same time, over a couple hours you should see both rise, and the battery voltage rising faster then the charger voltage, and the charger voltage likely will level off first. If so then everything will be OK, but heavier wire will help by reducing the voltage drop, allowing for a more efficient thus faster charge, less heat wasted in the wiring.
 
So I'm going to re-wire from the truck battery to the camper battery to help with this issue.

What size wire should I go with?

Just a regular cab truck, probably about 12' total run, taking lateral moves into account.

140amp alternator.

200a/h battery.

I'm thinking maybe 6-8ga?

That's significantly larger than FWC uses, so I'd be bypassing the internal runs also. Looks to me like they used 12-14ga.

Or maybe I'd be ok with stock wiring, as long as I make sure my battery doesn't draw down too much..

Also, I've run 2/0 welding cable to the rear bumper as a power point for my winch and jumpers.. would it be ok to tie into that on the frame and create a junction block just behind the cab for my camper power and maybe my Viair compressor, or should I run all of those to the engine compartment just for weather/water protection?

It would be nice to move all those connections to somewhere with a little more room, but it would definitely be submerged occasionally.

Everything fused appropriately of course.
 
I would use the 2/0 connection, fused of course. You will need to think about what connector (thus wire size) you will use. My camper uses 10GA wire and I ran 6GA to the truck bed connector and it is charging a pair of 79ah batteries and running my compressor fridge fine. The camper section of the wiring is short enough there is not much loss of concern. You can fix the truck section and test it, deal with the camper wire as a separate step.
 
Based on a maximum of 1% voltage drop, and 50A charging current (way overkill) - 2AWG would be fine. It depends a little bit on whether you have a good ground near the camper plug, or need to run two wires back to the battery - if you run 2 wires they need to be a little larger (maybe 0AWG) as you will have voltage drop on both the positive and negative. Either way this would be a vast improvement over the stock installation. For the truck-camper connection, Anderson Connectors seem to be the standard - these would work nicely with 2AWG wires:
https://www.waytekwire.com/item/37855/600V-2GA-Gray-Connector-Kit/
 
The winch setup is both + and - from the battery to front and rear anderson plugs. I'll probably just run a third 2/0 set of lines to just behind the cab near the camper plug location and put a matching anderson on it. That way I'll be able to jump from the center of the truck too, and have power already if I ever want to fab up a winch mount to pull things into the bed.

I'll just put an anderson on the camper side with some much smaller wire to make the last few feet into the camper and to the battery. Probably 8ga or so.

My battery's under the dinette, so I've removed about 4 feet of run over stock that way too..
 
Finally got the 2/0 extended to the spot behind the cab for the camper and the camper wiring replaced with 4ga. So now I've got (+) and (-) 4ga running from the isolator/battery ground to an Anderson connector at the cab.

No drop at all, which I guess shouldn't be a surprise with wire that size.. :)

I'll get the truck side connector bolted to the bed after it gets back from powdercoat next week.

I also wire in a voltage meter and remote led to show me the battery voltage and the isolator state. I can see it from the truck cab, outside the camper through the dinette window, and from the bed.

IMG_20160926_090418.jpgIMG_20160926_090528.jpg
 
So I have a 1983 grandby and have a blue sea battery and SI-ACR isolator. I have 14 volts coming in from the truck, but only 12 volts coming out. Originally i had 14 coming out, but not sure what changed. Any thoughts on why this is so? I also have the red round isolator switch but never installed it.
 
Fused wire coming out of it to positive source, fuse blown? Wire disconnected? Just a couple of quick thoughts.

More random thoughts..

Your 12 volts is the camper battery and can check with a volt meter at camper battery and at separator.

How long are you running the truck to see if the separator opens up to the camper battery?

Can't remember how low the camper battery can be that the separator may not open. The red rocker switch you can open it so both batteries are connected.
 
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