Wire Upgrade from Truck to Camper

NorCalSteve

NorCalSteve

Senior Member
Joined
May 28, 2012
Messages
198
Location
Chico, CA
I have been following the Multiple Charge Sources thread, among others, and am pretty sure I want to run larger wire from the truck battery to the truck bed connector.

First, I have a 100 amp alternator, two 75 AH batteries in the camper, I have a solar panel (80 watt? factory installed)and I want to run the refrigerator on DC while driving. Dometic says the DC heater in the refrigerator is 0.96 ohms, which would be about 13.5 amps when the battery is at 13 volts (about this voltage when driving). From my last drive, I really don't think the battery is getting much of a charge (if any) while driving with the refrigerator on DC. With the refrigerator on, and no sun, if the alternator delivered 20 amps to the camper battery, only about 6.5 amps would be available for charging the battery. The rest would go to the refrigerator.

There are different approaches to upgrading the wiring and I need help. I will have even more question after a few answers and new options are posted but here goes.

I am thinking "adding" 8 gauge to the existing factory 10 gauge wire going from the truck battery to the camper connector (leave the 10AWG and add 8AWG in parallel. Or replacing the 10 gauge with 6 gauge wire.

My local Lowes store has 8 gauge and I am pretty sure 6 gauge wire available by the foot. I am worried that this wire is not designed for the automobile application I need it for. I am looking at something like this. Bottom line, would this work and, if not, what is a good source for 8 and 6 gauge wire?

I think a new connector at the truck bed is needed because my current connector will not accommodate the larger wire (and I hope, current)? Hard to see exactly what is up there. I have seen one or two connectors mentioned here. Does anyone have any input for me on this as well? I am just guessing I need a new connector at the truck bed.

Also, if I missed an existing thread that discusses this, pass it on!

Thanks!

Steve
 
leave the 10AWG and add 8AWG in parallel.

If you do this try and gang them together into the same terminal ends. That way if corrosion decreases the efficiency of a terminal it ends up the same for both leads.

what is a good source for 8 and 6 gauge wire?

6 and 8 are common for trolling motors on fishing boats. Look to the marine shops...

Or, use a good set of heavy gauge jumper cables.

I think a new connector...


Check out the plug/socket setup for jumper cables. You could probably see one on your local police cars.
 
I found 8 ga. wire by the foot, connectors, 30amp inline breakers, a marine grade male/female plug, and a solenoid at my local NAPA and everything works great on my recent rewire. I ran the wires through a black garden hose piece from my marine plug in the bed all the way to the solenoid under the hood and and it seems pretty solid. Might be worth checking out.
 
I had hit two auto stores near my home and did not have any luck with wire. I have to admit that I have not looked at plugs at any of those two stores. I see a NAPA store pretty close to me and will see how well they are stocked.

The hose idea for the wires sound great. Just need to make sure it won't melt under the hood. I did replace the breaker under the hood of the truck with a 70 amp breaker. I also replaced the breaker between the battery and the fuse box in the camper with a 70 amp breaker. No special reason for picking 70 amp breakers. 50 amp probably would have been a better choice. I just wanted more than 30 amps. They both are manual reset breakers but I monitor the camper battery voltage while driving so I would know if either breaker tripped.

Thanks!

Steve
 
I used this wire: Ancor 6ga. Duplex It's not the least expensive option, but with the silver plated strands corrosion is much less of a concern.
I have, but have not yet installed, this connector: Anderson Power Cable Connector. Note that you need two of the complete assemblies to make a connection, and also note that connectors of the same size but different colors will not mate together. I plan to use the two holes in the connector to bolt one half to the truck's bed. The other half will come out of the camper via a J-Box screwed to the side of the camper with a weather-tight strain relief.

I miss Chico. CSU-C, ME&M '00
 
I used the Anderson power pole connectors. I really like them, they're a good positive connection. Get a good crimper to attach the wire to the poles. The only thing I need to rig up is a better way to hang the connector when the camper isn't on the truck. It just lays in the box with a plastic bag tapped around it... I ended up using 4ga wire. My local Princess Auto (I'm going to guess Harbour Freight for the southerners??) had welding 4ga cable by the foot, and 4 was the smallest diameter they had. I have it hooked up to my Blue Sea ACR relay under the hood of my truck.

If my battery wasn't a piece of garbage, I'd get a proper DC-DC charger. I'd recommend this system for you. With the ACR, you can wire in a ON/OFF switch and when the battery is nearly charged, you can top it off with your solar. Seeing as the ACR has quite a large capacity, it will easily handle your fridge while driving.
 
I used the Anderson power pole connectors. I really like them, they're a good positive connection. Get a good crimper to attach the wire to the poles. The only thing I need to rig up is a better way to hang the connector when the camper isn't on the truck. It just lays in the box with a plastic bag tapped around it... I ended up using 4ga wire. My local Princess Auto (I'm going to guess Harbour Freight for the southerners??) had welding 4ga cable by the foot, and 4 was the smallest diameter they had. I have it hooked up to my Blue Sea ACR relay under the hood of my truck.

If my battery wasn't a piece of garbage, I'd get a proper DC-DC charger. I'd recommend this system for you. With the ACR, you can wire in a ON/OFF switch and when the battery is nearly charged, you can top it off with your solar. Seeing as the ACR has quite a large capacity, it will easily handle your fridge while driving.



I see no point in using the manual on/off switch for charging control, if the solar has more to offer and the battery is willing to take it, it will just happen. If the truck has more, it will be the one. If the battery is full, it's voltage will rise and none will try to charge it (since they are all regulated). This scenario is being overthought me thinks. :)

I do have a manual override on my ACR located under my driver seat, with an LED status light. It is handy for testing or powering off the camper for testing or disconnecting when the truck is still running. I run my ham radio gear in the truck off the camper side of the battery also. I can force the ACR to turn off and that is handy at times for my radio work.
 
Currently, the Anderson connectors look great. The 120 amp connector can use different wire size contacts which will accept #4 or #6 wire. It is good to know the different color connectors are keyed differently.

The Ancor Marine wire looks expensive ($120+ for my wire run) but you do get both wires and a jacket around them. If I buy #6 wire from a local store, it will be probably around $75+.

Following this and other threads have made me realize that there is still lots to learn. Different batteries, different battery chargers, different solar panel controllers. So many ways to do things. Still lots for me to learn!

I ordered an amp meter so I can attempt a before and after measurement. I don't expect a big improvement in charge current. Since I am only replacing the wire from the battery to the camper connector as well as the connector (for now). The wire going into the camper will still be #10 and I will still loose a few tenths of a volt here.

I will replace the wire first and the connector later. I have a trip to Glacier NP coming up in early July and will probably put off replacing the connector until after I return. I will do a little more research before I either buy the Ancor Marine #6 wire or go with #4 wire.

Thanks everyone for helping me locate all these possible options.

Steve

CSU Chico 1978 moved to Boise for about 30 years and back in Chico. HOT here!
AKA KD7RO (no longer active)
 
The Ancor Marine wire looks expensive ($120+ for my wire run) but you do get both wires and a jacket around them. If I buy #6 wire from a local store, it will be probably around $75+.


The link I had above was for 6ga tinned wire for $1.24/ft ($2.48/ft for the pair) with free shipping in case you didn't follow it.
 
Thanks pods8,

I am not sure why I missed the link. Sorry about that. That wire also looks like a great choice. I plan to hit a couple of local stores tomorrow or Friday. I want to look at the physical size of 4 and 6 AWG wire to make sure I know what I will be dealing with. Mostly to take a close look at how big 4 AWG wire is.

Steve
 
Going back to the original objectives, NorCalSteve wants to run his fridge (13.5 A) and presumably charge his battery too. Ideally, 10 A into the battery would be nice. This means 23.5 A total into the camper. Is this possible within practical limits?

On my truck, the run from the truck's battery to the camper battery is about 15'. Using the voltage drop calculator on the Nooutage website, I've calculated the voltage drop for the wire gauges being discussed at the wished-for current 23.5 A. The drop for #8 is 3.2%, for #6 is 2.0% and for #4 is 1.3%. Assuming NorCalSteve's truck alternator regulator cuts out at 14 VDC (typical), this means 13.55 VDC at the camper battery if #8 wire is used, 13.72 VDC for #6, and 13.82 VDC for #4. Any of these wires will probably be fine for the fridge but even at 13.82, typical 'float' voltage, it is going to take a long time to completely recharge the battery. And for long battery life, complete charging is important. Up to about a 75% charge will be fairly quick but the rest will be slow and largely the responsibility of the solar.

I have also worked out the benefit of doubling up additional wire with the existing #10. Assuming the wire meets AWG standards, the cross-sectional area of the existing #10 wire is 5.26 mm2. AWG #8 wire has a cross-sectional area of 8.36 mm2, #6 13.29 mm2 and #4 21.14 mm2. Adding a #8 wire to the #10 would result in about the same cross-sectional area as a #6 but adding a #6 would still be only 88% of a #4. I also seem to remember reading somewhere that doubling wires to reach the same cross-sectional area as a bigger wire doesn't quite work out. There are some additional losses somewhere. However, that may be just an incorrect memory leaking through. Someone can correct me.

The conclusion is it is relatively easy to run the fridge. However, increasing the wire gauge will not have a spectacular impact on recharging the camper battery to full charge. Automotive alternators and regulators are just not designed to quickly charge remote batteries to a full charge. Bigger wires will help with the first 75% of the charge but the last 25% is at the mercy of voltage drop. It's kind of like filling a swimming pool from the bottom. As the water gets deeper and deeper, the back-pressure on the water coming in through the hose gets higher so the top quarter of the pool fills slower than the bottom quarter.
 
Thanks White Dog for taking the time to work out those numbers. And thanks for the voltage drop calculator. Great stuff! And, as much as I hate to say it. I am probably wasting my time trying to make things much better by making the wire between the truck battery and camper bigger. Yeah, I will get a small improvement but probably not enough payback to make it worthwhile.

I spent a good amount looking for a DC-DC battery charger that could deliver some current but there does not seem to be anything available. I have also considered an inverter to a 30 or 40 amp charger but that kind of scares me. Too much electronics. Having a true AGM battery charger sure sounds like a good thing. I do realize the importance of maintaining the proper charge on my battery.

I still might go ahead and replace the power and ground between the battery and camper with something like #6, just because that is such an easy undertaking. It is about 21 feet from the truck battery to the plug in the back of the truck (left side). So maybe another 6 feet to the battery? I only plan to do the 21 feet to the truck bed first.

Is there a reason for going from a battery on the right side of my trunk to the left side of my truck to run the wire to the truck bed, and then back to the right side of the camper to get to the battery? I probably should look at that and see if I can run the wires down the right side of the truck instead of the left side. If I can, that would be a much shorter run!

Although you were nice enough not to say it, I am not going to get what I want from this modification. I do realize my distance is longer so my numbers will be a little better. My search for the perfect charging system for my truck continues. If I do beef up the wires, I will post anything I find out. I know it will be a little better than it is now.

Steve
 
Yup, I'm afraid whoever decided 12 VDC was the right voltage for vehicles didn't do us any favours. If we used 24 VDC, these problems would virtually all go away.

A couple of things I'm going to try. I think I'm going to spring for a Trimetric battery monitor. With it I will be able to see where my power is coming from and going. It's a bit pricey but if I can double the life of my batteries it will pay for itself. Besides, I'm just like tinkering with this stuff. Another interesting detail surfaced today. HandyBob talks about how even a small shadow on a solar panel can make a big difference to output. I ran the battery down on my FWC a bit today then reconnected the solar panel. I was curious what its output was early (okay relatively early) in the morning. At 9:00 it was showing 2.4 A (I have a DC amp meter) which is less than expected since the theoretical output from the panel is 5.6 A. I remembered what HandyBob said about shadows so I checked the panel and it was pretty clean except for one corner where rainwater had collected and evaporated leaving a pretty thick layer of dust. I cleaned the panel and the output jumped to 3.5 A, a 45% increase. HandyBob was right - keep the panel clean and out of the shadows.

I have used Ancor wire for years. I used to wire marine survey launches in a former life. It is a good product although more expensive than regular automotive wire. If you are used to automotive wire, you'll find Ancor very flexible because it uses many more fine strands in the twist. The tinning makes it virtually corrosion proof when used in RV applications.

Good luck with the project. Let us know how it turns out.
 
You are right White Dog about 12 versus 24 volts. That is one of the many things I have just learned. I have always loved to play with electronics most all of my life but, since getting my Hawk camper, I now realize how little I know about 12 volt systems in cars and RVs. I am learning more about what is out there but I still have much to learn about trade-offs between different approaches. I read HandyBob's article yesterday morning. Great stuff! I always just figured my battery was fine if I just let the truck charge it whenever I go someplace but that is not true. I do have the solar panel but only a few hours of sun each day reach it where it is. I would trust the solar panel controller to top off my battery before my Walmart 6 amp charger. I have a .5 amp computer running in the camper all the time so I am not sure how often the solar panels are able to top off the battery with the short sun time it gets.

My DC amp meter arrived today! I will have fun using it to better understand where the current is going and see my small improvements on any wiring changes I make.

I figured I would go ahead and replace the wire run from the battery to the truck bed but since you said your run was only 15 feet, I think I will look at if I can route the wire to the other side of the truck. Try and do it right the first time.

Steve
 
Do what you can to keep it short. It might almost get you the effect of installing a more expensive thicker wire the long way. Saves you money and works better and lighter keeping it short.

I use the separate red and black wire off the rolls and use inexpensive split loom for protection where needed. Works fine, secure the wire so it does not flop around. If you are trying to terminate the heavier wire like #6 into a truck bed mounted connector, it can be rough to turn the corner in between the truck bed outer and inner walls. I chose to splice in a very short section of #8 into my bed mounted connector. It is no big deal since the camper is #10 thereafter.
 
In my personal opinion don't bother running your fridge on DC and then you can move on with life. That's just my personal opinion but running a fridge relighter is easier in my book. Assuming you still have a desire to run the fridge on DC then consider running a dedicated line from your truck to it, then you're not trying to charge your battery off the same line that's delivering all those amps to the fridge and is already experiencing the associated voltage drop.

Or since you mentioned DC-DC charges of higher amps not being available (which is not accurate): Its not the cheapest solution but promariner makes a 40amp DC-DC charger: http://www.pmariner.com/productFeature.php?ProductNum=05504 Runs $350-400 online.
 
Thanks pods8,

The refrigerator runs great on DC. As I mentioned in another post, I ran #8 wire directly from the battery to the refrigerator. I am pleased with those results. Since the refrigerator now gets close to 13 volts while driving, I figure the refrigerator heating element is now running at about 175 watts, rather than 150 watts or less before the rewire (again, while driving). It seems to me to be working better now. My wire run to the camper battery is just over 25 feet. Shorter would be better.

Getting more charging current to the camper battery seems like a good thing. Refrigerator on or not. And I am enjoying making the modifications and the help I am getting from you and others.

As far as DC-DC converts, I tried to word the unavailability of a high current DC-DC converter in a way that someone might reply and show me one that would work for me. I did not mean to say that they did not make it. My mistake. But thanks! That is exactly what I am looking for. And yup, pretty pricy! I saved the link and will continue to look for an alternatives like this to add to my camper in the future. If there are other high current DC-DC chargers available out there, please post them.

Steve
 
If there are other high current DC-DC chargers available out there, please post them.


That one (which is also branded as sterling in the UK) and the 7.5amp powerstream are the only ones I know off from my looking in the past. The powerstream used to have a 7.5amp/15amp switch on it from my reading, 15amps would be a nice sweet spot for the price point but that isn't offered any more.
 
A simple option might be to leave the fridge off in the morning while you are driving. It should stay cold for 2 or 3 hours. This will let the battery soak up as much power from the truck as possible when the charge is at its lowest in the camper battery. By lunch, the solar panel will be doing most of the battery charging so turn the fridge back on for the afternoon to bring its temperature down before you stop for the day. Of course you will have to remember to turn the fridge on at lunch for this to work ;)
 
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