Wire Upgrade from Truck to Camper

[NorCalSteve]

I am not against running the refrigerator on gas while driving. If I am worried about the level of charge on my batteries, I will run the refrigerator on gas. It is not that big of a deal. I just see some room for improvement with my particular configuration. I think, once I have increased the wire size between the truck battery and the camper battery, I will learn when to run the refrigerator on batteries and when to use the gas. I am still new at this whole thing. But having fun both tweaking stuff as well as going out an using my camper! Yeah, I wish the existing wires were #6 to begin with.

I ran an experiment on the truck that I don't feel real great about because there is so much room for error but will go ahead and mention it. I set the refrigerator to DC with the truck off for a few hours just to get the battery discharged a little. The battery in the camper dropped to about 12 volts with the refrigerator still on DC. I then started the truck (refrigerator still on). I was alone so I could only idle the truck while I took measurements. The truck battery was at 13.9 volts and the camper battery was at 12.6 volts. I am comfortable saying there was at least a 1 volt drop or greater between the truck battery and the camper battery. I then ran my jumper cables from the truck battery through the cab to the camper battery. Then, the truck battery was at 13.7 volts and the camper battery was at 13.2 volts. So I might have gained .5 volts after the jumper cables were attached. I have no idea how much current was flowing so I have to be careful how I use these results.

Again, I don't expect a real great improvement but it will be fun to see what happens.

Steve

 

[pods8]

As I mentioned in another post, I ran #8 wire directly from the battery to the refrigerator.


Which battery are you referring to here? When I mentioned running a line directly to the fridge I meant from the TRUCK, it sounds like you went to your camper. If that is the case I honestly can't see the point. Why would you ever want to run a 13amp load off your camper batteries? I can't ever see a reason, you're either going to drain them or impede charging or both. You'll want to supply those amps from your alternator if you're ever going to bother with the DC mode on the fridge. So run a dedicated line for the fridge back to the truck and also a dedicated line for the batteries, if you do that I think you won't see the voltage drops you're dealing with right now at the camper battery. Otherwise you're always going to have a 13amp load off the bat contributing to your voltage drop regardless of wire size (6ga you've already got 1.5% drop at 20' in that case).

Or look at the DC-DC charger to boost the voltage back up to something useful. Wiring is cheaper though...

 

[NorCalSteve]

Hey pods8,
The 3-way refrigerator was installed by FWC. FWC used #10 wire from the camper battery to the fuse box and then from the fuse box to the refrigerator. There was a little more of a voltage drop than I wanted between the camper battery and the refrigerator when the refrigerator was operated on the 12 volts DC. So I ran #8 wire directly from the "camper" battery to a fuse and then directly to the refrigerator.' I did this rather than replace the factory #10 wire because it was pretty easy. This gave me a slightly higher voltage at the refrigerator when it operated at DC. I am happy with the small improvement this made. I think that many people who use the Dometic 3 way refrigerator don't even bother to run it on 12 volts DC. I do and it works for me (if I am careful).

 

[K7MDL]

To avoid needing to run the fridge on gas or DC while in transit, I use several "Blue Ice" plastic freeze blocks. Keeps it cold for more than a day, and when I stop for the day, I switch to propane and move the blocks into the freezer comparment. Pull them out the next morning. In cooler weather I never turn on the gas for a short weekend and use a few more freeze blocks since I need less stuff in the fridge. I do empty the fridge when not traveling and thus only carry what I plan to use on the trip which leaves me plenty of room for the extra blocks.

 

[NorCalSteve]

Cool Idea K7MDL. That is something I figured I would try sometime. I have driven in warm weather where the refrigerator creeps up to 50 degrees. It was on a trip to Texas about a month back. 75MPH in hot weather. The Blue Ice would be a great way to assist the system on those hot days. Glad to hear it helps! And my freezer usually has space for at least one blue ice block.

Steve

 

[pods8]

I think that many people who use the Dometic 3 way refrigerator don't even bother to run it on 12 volts DC.


I agree 13amps isn't something to shrug off.


Again to reiterate I think lots of good suggestions are out there now, just gotta choose what you want. Run a dedicated wire from the truck to avoid the voltage drop to the camper battery, use a DC-DC charger to boost it back up, don't use DC fridge, use ice packs, etc. Without doing a dedicated line I'd say you'll rob any worthwhile solar charging so discount that while on DC.

Just my thoughts.

 

[ntsqd]

A point of "Handy Bob's" that I came away with from reading his blog is that a .1 volt drop (or gain) isn't a small percentage loss or gain since we're not dealing with a range of zero to twelve volts. We're dealing with a range from ~12.1 volts (50% discharged) to ~13.6 volts (fully charged), or roughly 1.5 volts total charging range. Suddenly a .1V gain is a whole lot more significant when talking about battery charging. This is, I think, his foundation realization. What he builds everything else on. Once you accept that, and I don't think that it will be too difficult to do, then everything else that he has to say about wire sizing and voltage drop is a logical deduction.

My early days as a bachelor in my own home (no roomies etc.) taught me that "thermal mass" in the fridge is a good plan. I didn't have a lot in the fridge in those early days (or money to fill it with) and it was running almost constantly. Simply by filling used gallon milk bottles with water and leaving them in the fridge cut the run time significantly.

 

[White Dog]

I think ntsqd made HandyBob's point in much less space - I don't see a single rant. Thanks ntsqd.

Voltage drop is the real issue. HandBob uses the analogy of trying to blow up a tire. If you have a compressor set at 75 psi, it is quite easy to reach 50 psi in the tire. The last 10 psi takes longer than the first but it's still relatively quick. If you try to do the same with the compressor set at 51 psi, it takes forever. The volume of air (analogous to amps) is the same but the higher psi (analogous to volts) makes the process much faster. The problem is to get the highest voltage that will not damage the battery to the battery (typically (but not always) 14.8 VDC for lead-acid deep-charge wet batteries). This is impossible from the truck's alternator since it is limited to 14 VDC. Voltage drop from the alternator to the camper battery just makes it worse. Plugging in the camper will continue this process but unless it has a 'smart' charger built into it, the charge will continue at the same poky rate. The stock Iota DSL-30 that FWC uses puts out 13.4 VDC. However they do offer an upgrade module called the IQ4 which turns the DLS-30 into a 4-stage charger.

Personally, I would prefer to never camp anywhere I could plug my FWC in but that's just me. So I continue on my quest for 120 VAC independence at affordable cost.

 

[ntsqd]

Thank you for posting that link. It has proved to be the beginning of my truly grasping what a well designed and installed solar charging system is and has led to a sequence of further reading that I've learned a lot from.

My first purchase is going to be a Tri-Metric meter. After I have a handle on our usage, then I'll start sizing & spec-ing a solar system.

 

[White Dog]

My first purchase is going to be a Tri-Metric meter. After I have a handle on our usage, then I'll start sizing & spec-ing a solar system.


TriMetric is just one brand. These monitors are used quite often on boats so if you look at some marine suppliers like Jamestown Distributors you will see they have other models. This will help with pricing and features before you make a decision. Some of these will even data log to your laptop.

Good luck. Let us know what you find out

 

[NorCalSteve]

Thanks again to everyone who gave me direction on this project. I made my changes to the camper today. Things are much better but I really need to go for a drive and see how well things are working. My daughter and I leave for Glacier NP next week so that will give me time to see how things are working.

I decided, rather than replace the existing wire from the truck battery to the camper battery, I would add a new wire. K7MDL (and maybe others) said to keep it short. This made me realize that I really needed to pick the more direct route from the truck battery to the camper battery. I chose to use the Anderson Connectors at the camper but also chose to use the #6 wire from Lowes. Not using the Ancor Marine wire was probably not a good idea. Having that protective jacket built in and being a more flexible wire is nice. I bought the cheaper Lowes wire before I had decided to take the direct (shorter) route to the camper battery. I did use a hose to protect the wire but it really makes things look unprofessional, but functional. Well, no one will see it but me.

OK. Way back when I thought about doing this. I measured the voltage at the truck battery and camper battery while the engine was idling, and the refrigerator had been on DC for about 2 hours. I got 13.9 volts at the cig lighter and 12.6 volts at the camper battery. Today, just before making the final connection of the new 12 volt and ground wires (the camper battery is pretty charged but the refrigerator was on DC). I got 13.9 volts at the lighter and 12.7 at the camper battery. Then, I connected the two new wires to the battery separator and ground. Now, I got 13.7 volts at the lighter and 13.3 at the camper battery. I have not done any amp (current) measurements. I will probably make some measurements tonight.

Steve

 

[NorCalSteve]

Quick current measurement.

After leaving the refrigerator on DC for about 2 hours, the batteries had dropped down to about 12 volts under the refrigerator load and they were at about 12.4 volts when I turned the refrigerator off after the electrical current measurement. The current going from the truck charging system to the camper was 40 amps. This would break down to 25 amps charging the battery and 15 amps to power the refrigerator.

Again, a trip is needed where I can track the camper battery voltage over a longer period of time but it sure looks like I am going to get improved camper battery charging while the refrigerator is on DC. Which was my main goal.

Steve

 

[White Dog]

So adding the heavier gauge wire seems to have paid off. You gained 0.7 VDC at the camper battery which will lead to much faster charges of the battery when it is quite low. This matches with your measurement of amps. However, the voltage is still a bit low to bring the battery up to full charge quickly but hopefully the solar panel can do that.

It would be interesting to watch the number of amps going into the battery as it gets a higher and higher charge. One interesting measurement would be to see what the resting voltage of the battery is after a days driving. It's simple to do. Once you have set up camp for the night, turn off the master switch for 15 or 20 minutes so that the battery has no load or charge. If, after the rest period, the battery voltage is 12.7 or higher, the battery is full charged.

 

[NorCalSteve]

I will try to get a few voltage measurements when I stop after a long drive and quickly turn the refrigerator to gas. I leave Wednesday of next week for Glacier NP. Exactly 1000 miles (will take three days to get there) from the house to the park entrance. I won't even try and guess what the voltage will be. Just hope it is close to 12.7 volts. The truck should now do a much better job of getting the battery charged back up after I stop but leave the refrigerator on DC.

Had I research refrigerator options more carefully (at all), I would probably have got the Waeco fridge. But I am happy with how things are working with the 3-way fridge now.

I procrastinated on getting a passport so I won't be able to visit Waterton Lakes NP. Me bad.

Steve

 

[White Dog]

I procrastinated on getting a passport so I won't be able to visit Waterton Lakes NP. Me bad.


I'd let you in no problem. Canadian Border Services Agency might too. It's getting back into the US that would be the problem. You'd just have to stay and become a Canadian.

 

[NorCalSteve]

Got back yesterday from Glacier NP and the drive home via the Oregon Coast. Good time although the high elevation hikes had too much snow and a few wet days.

And I have more to learn about battery charging so chime in and help if I am off track. So, after upgrading the wires between the truck battery and the camper battery to #6 wires, I headed for Glacier. First stop was Bend Oregon, which was maybe 7 hours away including stops. I switched the 3 way Dometic fridge to DC about an hour before my departure.

My main observation was that the truck alternator started out at over 14 volts charge voltage but before I got out of town, it was down to maybe 13.6 volts. I "think" that the charging voltage from the alternator changes with temperature so, when the engine compartment gets hot, the alternator lowers the charging voltage. If this "is" the case, the alternator needs to choose the charging voltage based on the hot truck battery and not based on the camper batteries and the camper batteries will, probably, charge slower because of this. Am I correct on this?

Because of the lower charge voltage, I did not see any super charge rate on the camper batteries. But, other than below, the new wiring worked well.

Although I "thought" I was being careful about choosing the correct wire path between the truck battery and the breaker under the hood (when I increased the wire size), I was not careful enough. A piece of metal on the hood of the truck rubbed through the insulation and shorted. Yes, this was before the breaker so things got real hot. I popped the hood and removed the wire completely, which brought an end to any experiments since my camper batteries were only going to charge from the solar panel until I replaced the charred wire. This meant the refrigerator stayed on gas while driving instead of me switching to DC. Yeah, I need to be a little bit more careful.

Steve

 

[K7MDL]

Now you know why first hand breakers should be located as close to the power source as possible. They are there primarily to protect the wire and your truck from burning

That include both ends for the wire for battery to battery connections. If you cannot locate a fuse/breaker close then the path should be very protected.

The other thing that is happening to your voltage is that the starting battery is recharged fully and it wants to be floated at 13.6VDC at its terminals, adjusted for temperature ideally. The alternator will increase output current enough to keep the voltage constant as the external loads like your enine, accessories, and the camper battery draw off power. Remember the alternator has no clue there is a camper battery out there, it is only maintaining constant voltage best it can locally.