Battery switching/wiring question

[Trailbob]

I have been following these forums for a while, and have learned a lot. I have a wiring question, here is some background: I have a 2010 Hawk that is mounted on a 2015 Silverado 2500, 6.0. The truck has an auxiliary battery (blue top Optima) that is isolated from the starting battery. The camper has the original 80 ah group 24 battery, which is near the end of its life. The camper battery is connected to the auxiliary truck battery via the factory camper/trailer wiring, and a Marinco plug which I installed. The auxiliary truck battery is isolated from the camper battery by the FWC factory installed separator. The separator only allows power to flow from the truck to the camper.

I run an ARB fridge off the truck's auxiliary battery. I plan to upgrade the camper's battery in the near future to either one group 27, or two group 24s. I also plan to install a 100 watt solar panel this winter. I have wired an external plug on the camper where I can attach a portable solar panel, or the ARB fridge; this plug is wired directly to the camper battery.

I would like to be able to supplement the truck's auxiliary battery with power from the camper's battery. The ARB fridge will run the Optima down in about a day (depending on temperature, etc), so it needs to be recharged. The camper has the 30 amp IOTA charger with the smart module, and I have a Honda 2000 generator to power it. I was hoping to use the camper's charger for truck and camper battery.

My plan is to install a marine battery switch. One leg will power the separator like it is currently set up. I was going to run the second leg to the back side of the battery separator (where the truck battery is connected) so that I could bypass the separator. I could also turn the switch "off" and completely isolate the camper battery from the truck.

Currently, the camper battery hot lead is attached to the stud on the front side of the separator, and the power lead for the converter/DC panel is attached to the same stud. I plan to install a separate isolated stud for these two leads. I could also attach a future solar controller to this stud.

(Finally...) My question is: Does the above make sense, or am I missing something? If I do this, would it be worth upgrading to #8 wire from the camper battery to the - buss, and the positive distribution stud?

Sorry for the long winded explanation, but thanks for your help.

-Bob

 

[ntsqd]

I would start with what you want the resulting system to do and work backwards to what equipment needs to be added and/or wire routing that needs to be changed.

What else does the truck's aux battery do? Seems to me that you could parallel it and the camper battery to get more amp-hrs in the camper's battery system. Voltage drop would be really important to eliminate if you did go this route. What wire size is being used now and do you have any way to know what the max current through that wire is?

Also, you didn't mention it so if it is not there I would strongly suggest that a dedicated ground wire of the same size as the charge wire be run between the batteries.

 

[esimmers]

Let's make sure we understand your setup and what you're trying to accomplish.

Right now your truck has the regular chassis battery and an isolated auxiliary battery. You don't say how that auxiliary battery is connected to and isolated from the chassis battery and charging system. Hopefully it's with a continuous-duty solenoid that's triggered by power from the truck ignition switch and only connects the two batteries together when the truck is running. If instead you're using a battery separator, one that compares voltage before deciding whether to connect or disconnect, you're probably experiencing some voltage drop from the chassis battery to the auxiliary battery. This voltage drop is common to most if not all battery separators (like the one installed in FWC campers) and can result in the auxiliary battery being less fully charged.

Next, you're using the auxiliary battery to power your ARB fridge which I assume is located in the truck cab. You've also run wire from the auxiliary battery to the FWC factory-installed battery separator in the camper.

Battery separators are usually designed to be engaged only when the electrical source reaches about 13.2 volts. Otherwise the separator disconnects the load from the source, protecting the source from discharge. It seems that since you're using the factory-installed separator, the only time the truck's auxiliary battery is getting juice to the camper battery is when the truck's running and the alternator is (hopefully) pushing enough voltage to the auxiliary battery so that your camper's battery separator still sees at least 13.2 volts coming from the truck's auxiliary battery. Given that you're also pulling juice from the auxiliary battery to run the fridge and given that there will be some substantial voltage drop through the long wires from the truck's auxiliary battery to the camper's battery separator, it's quite certain that your camper is getting zero help from the truck's auxiliary battery when the truck's not running.

It seems there's no reason for the camper's battery separator with your system. The justification for a battery separator is to protect a vehicle's starting battery, but your truck's starting battery is protected by the isolation in the wiring between the starting battery and the truck's auxiliary battery. So you're not only getting a voltage drop because of the camper's separator, its also preventing ANY current to the camper battery unless the truck is running.

You are planning an external socket on the camper where you can plug in the refrigerator or a solar panel. While I'm no solar expert, I understand that electricity from solar panels needs first to go through a charge controller before being fed to a battery. Sounds like these two items shouldn't be combined in the same connection.

Here are some alternative ideas.

1. Remove the camper's battery separator and directly connect the truck's auxiliary battery and your camper battery together using heavy enough + and - wires to eliminate voltage drop between them. Then when you are using shore power or your generator to power your IOTA converter/charger, you're recharging both the truck's auxiliary battery and the camper battery and powering the fridge at the same time. It's never a great idea to charge two batteries at the same time unless they are identical batteries and wired together, but you might use that switch you were talking about to connect Battery One or Battery Two or Both to the converter/charger and the camper house circuits for additional flexibility.

2. Move the camper feed from the truck's auxiliary battery to the truck's chassis battery. Leave the battery separator in the camper. You'll get a better camper battery charge from the alternator running straight from the chassis battery because you'll avoid the loss caused by the chassis-auxiliary battery isolation. The camper's battery separator will prevent discharge of the chassis battery. Plug the fridge into the camper battery and keep it charged by your shore power, generator or solar. This alternative idea won't charge the auxiliary battery until you start the truck engine but so what? You don't need that battery while camping if you have sufficient capacity in your camper battery and a way (solar, in particular) to keep the camper battery charged.

Well, those are some thoughts. Others will join in. Welcome to the world of camper electricity. Isn't it fun!

 

[Trailbob]

Thanks for the replies. I'm not an electrical person, and am probably overthinking this.

The main things I want to accomplish are:

1. Be able to re-charge the truck aux battery via the camper's converter or (in the future) solar.

2. If practical, supplement the truck aux battery with the camper, and visa versa.


To clarify a couple of things:

-The truck aux battery is separated from the starting battery with a "smart" constant duty solenoid, which is not suppose to have the voltage drop issues of battery separator. The solenoid closes when either battery rises above a set point.

-The wiring from the aux battery to the camper via the factory tow/camper package, and looks to be #10. There is not a direct ground to the aux battery (but that is a good idea). I may upgrade this wire as a future project. I agree there is substantial voltage drop in the long factory wires.

-The external socket that I installed (an SAE) will connect a portable solar panel with its own controller (Zamp, etc), or I can connect the ARB by running the power cord out the back window and directly to the camper (I put an SAE on the ARB cord). The ARB sits in the cab. The ARB and the portable solar would not be connected at the same time. Roof top solar is another (future) project, and would have its own controller inside the camper.

I agree that the FWC separator is redundant. That was the reason for the marine switch, so I could completely isolate the camper, connect direct to the aux battery, or (not sure why I would do this), connect through the separator.

I mainly use the ARB as a freezer, which has quite a bit more draw than the refer mode. This is the reason I need an efficient method of recharging the aux battery (or the aux and camper batteries if they are wired in parallel). When we camp and fish for several days, I need to freeze the fish. During hunting season, I keep jugs of water frozen to put in coolers along with deer/elk meat. I thought the IOTA converter would be fastest way to recharge the batteries, with the generator. The solar would contribute when the generator was off. The three way switch would allow me to charge the camper batteries first, then connect the aux battery. Maybe this isn't such a great idea?

You both gave me some good things to think about I appreciate your impute. And yes, camper wiring is great fun!

-Bob

 

[ntsqd]

I think that a distinction needs to be made about battery separators. The old type uses diodes and those do have a significant voltage drop.

The newer devices saddled with that same label are some tricky electronics controlling either a constant duty solenoid or possibly an IGBT (solid state high current switch) to do the high current switching. I've not ever seen one of the newer devices have significant voltage drop.

Both our truck battery bank and the camper battery read the same voltage on our Tri-Metric when the batteries are fully charged and the truck is running. This tells me that the voltage on both sides of the BEP Marine VSR "separator" is the same. No voltage drop.

Was it me:
There are some smart combiners made that can be 'forced' to close with a remote switch. I would consider one of those between the camper battery and the truck's aux battery. When not 'forced' it will wait until the aux battery is fully charged before closing and starting the charge of the camper battery. This avoids charging dissimilar batteries at the same time - a point that I've been concerned about too. The forcing function will allow you to combine the aux and camper batteries for more total A-hrs while stationary. I would install an LED indicator light both in the cab and in the camper that is lit when the device is 'forced.' Could do this with the proposed battery switch too. It just won't have any way to tell you that it's been turned on, which could lead to charging dissimilar batteries at the same time.

Use a different plug & receptacle for the ARB's power so that you don't get them confused. Solar panel output, unless a tiny panel designed for a specific use, needs to first go thru a solar controller. The output voltage is beyond the normal upper voltage limit or very close to it for most 12VDC accessories. If you don't like the US typical "PowerPoint" (cigarette lighter) socket have a look at the DIN plug & socket used on some BMW motorcycles. I *think* Aerostitch sells them. Otherwise I think that the Marinco plugs and receptacles may be the best "cigarette lighter" type connectors.

 

[Trailbob]

Ntsqd, I was not familiar with marine VSRs. I looked them up and found they also make "dual" models that will "connect" the batteries when either the camper or aux batteries are charged to a certain voltage. This would allow charging the camper via the alternator, and the aux battery via the IOTA or camper's solar. I like your idea about replacing the FWC separator with a VSR, especially a dual model with the ability to force connect the batts to support each other's amp hours, if necessary. The manual marine battery switch I was considering may be unnecessary.

I confirmed there is substantial voltage drop between the aux battery and the camper battery. I did not yet open the panel to check each side of the FWC separator, but just checked the battery in each location while the truck was running.

Thanks again for everyone's thoughts. I'll probably tackle the project later in the fall, after hunting seasons close.

 

[pawleyk]

Not sure where you are with this, but I'm putting my vote with the dual sensing vsr. We've got the Blue Sea Systems ACR which is dual sensing and I'm sure something like that would do exactly what you want. Mine let's our IOTA converter or solar charge the truck batteries in addition to allowing the truck to charge the camper..

 

[Wallowa]

KI7AMV...where in Oregon? ....KI7ARF [not on line].

 

[DrJ]

Pawleyk,
I'm very interested in your mod about replacing the sure power isolator with a blue sea ACR.
What model did you use?
Have you noticed an improvement from truck charging to camper?

I was first bothered by the idea of the camper solar charging the truck batteries but it makes sense to me now.

I am considering this mod too.

 

[pawleyk]

KI7AMV...where in Oregon? ....KI7ARF [not on line].

I'm in Salem now, but quick to point out I'm from the dry side also..

Pawleyk,
I'm very interested in your mod about replacing the sure power isolator with a blue sea ACR.
What model did you use?
Have you noticed an improvement from truck charging to camper?

I was first bothered by the idea of the camper solar charging the truck batteries but it makes sense to me now.

I am considering this mod too.

I didn't notice any improvement just because I didn't have a camper battery or standard isolator to base it off of. I installed both the new battery and ACR at the same time.

I just like the idea of backups for my backups.. My alternator could go out and I could charge my truck battery from shore power or solar if need be. Not a great solution, but if I'm stuck in some jungle in Guatemala I'd like to have an option or two. It'll also stay topped off over long stays where we aren't driving much or at all..

Just looking things over, I'd say the greatest improvement in charging from truck to camper would be gained by replacing the charge line the dealer installed with something heavier..

Here's the link to the Blue Sea ACR I bought from Ebay.. http://www.ebay.com/itm/391375006462 and the link to Blue Sea's website.. https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A