Alternators, Batteries and Breakers

NorCalSteve

NorCalSteve

Senior Member
Joined
May 28, 2012
Messages
198
Location
Chico, CA
I have added a computer to my Hawk camper, which gathers camper data. Every 5 minutes it records inside temp, outside temp, refrigerator temp, freezer temp, HW heater temp, refrigerator condenser temp, and battery voltage. I also put a GPS up in the fan area and gather location and speed data as well. I do have the solar panel option. This was a good decision for me.

While on my last adventure from Northern California to Texas and other places, I started getting low on Propane. Since I am still learning how long I can go on a tank of propane, I started getting nervous and decided to switch the refrigerator to DC for a day of driving, which I did a while before leaving the campsite. As I was driving down the road, I realized that the graph of my DC power showed the battery voltage jumping from about 12 volts to about 11.5 volts. This occurred about 6 times in a two hour period. It "seems like", after the battery charged a little, this cycling went away. The voltage measurement is taken pretty much at the refrigerator and not at the battery. More on that later. My "guess" is that the breaker under the hood of the truck for the camper must have been tripping. After the batteries in the camper charged some, it stopped tripping and things were fine. If I learn more about this, I will post it. For now, I will make sure the batteries are charged before I put the refrigerator on DC and add another 12 amps or more to the pull on the alternator. If the breaker is cycling, I figure this is not a good thing. It was also a warm day so the breaker was probably pretty warm under the hood. If I see this happening again, I plan to jumper the breaker long enough to see if it goes away by doing that.

While on the subject of using the refrigerator on DC, I decided to beef up the wiring to the refrigerator. With the refrigerator on and car off, I measured the voltage at the battery (12.6 volts) and at the refrigerator (11.7 volts). So I was loosing 0.9 volts in the wiring, breaker, fuses, etc.. This also means, the coolant heater in the refrigerator was running at 233 watts, instead of 250 watts or more. I ran 8 gauge wire directly from the battery to the refrigerator. Currently it is connected without a fuse (little dangerous), but I plan to add a fuse at the battery.

After the change, the battery was at 12.3 volts and the refrigerator was at 12.1 volts. This means the coolant heater was running at about 152 watts (with the engine off). I am not sure why the battery dropped from 12.6 volts, before to 12.3 volts after but I did like only seeing a 0.2 volt drop between the battery and the refrigerator. I have not tried driving anyplace with the refrigerator on DC but I think it is going to be an improvement. I have a short camping trip planned for this weekend. I will post anything I learn.

Steve
 
I have added a computer to my Hawk camper, which gathers camper data. Every 5 minutes it records inside temp, outside temp, refrigerator temp, freezer temp, HW heater temp, refrigerator condenser temp, and battery voltage. I also put a GPS up in the fan area and gather location and speed data as well. I do have the solar panel option. This was a good decision for me.
Wow! Most excellent -- cool stuff. :)
I think that's more data acquisition than the space shuttle had.
tongue.gif

_____________

Great idea on making the DC draw for the fridge more efficient, as efficient as that sketchy system can be.
When I had a 3-way fridge (before I switched to a compressor-type fridge) I gave up on running it on DC when driving and only used propane, finding that under DC power it barely kept up, barely kept it cold, on a hot day driving.
 
The DC function is pretty worthless in my mind. As mentioned it doesn't work well and HAMMERS the amps. The only business 12V power should have in regards to fridges is for compressor fridges.
 
On the advice of my Roadtrek vet traveler Mom and step-dad (from Upper So. CA: New Brunswick 1X, Alaska 3X + more local trips, currently on the road to Flaming Gorge via Bend, OR) we switch to DC when driving and flip back to propane when going to be stopped for any significant time. This is partly why I wired & breaker'd for 80 amps to the camper battery with a 3% voltage drop. Doing it this way makes refuel stops simple and the alt can more than keep up with all of the demands. Our Dometic seems to be able to hold "Max" just fine on DC, but it can't get it there very fast on it's own. I pre-cool with shore power.

I too am interested in what you're using for your D/A.
 
My plan is also to only use DC on the refrigerator when driving. And I am researching a replacement breaker that can handle a little more current. Any inputs here would be appreciated.

The computer addition in the camper is ongoing and has been a challenging project for me. For the computer, I am using a network wireless access point (usually used for home networks) that has a USB port and has been reprogrammed with an open source operating system call "OpenWrt". It is a Linux based operating system. The sensors are from a family of "one wire devices" that are currently made by a company called Maxim. I purchased a USB adapter that can send and receive the One Wire signals from the devices. It also turned out that someone had written drivers for the USB adapter device that was part of the OpenWrt operating system. This project was not an easy task and my now being over 60 made it much harder. Much of what I needed was already available in the Linux based OpenWrt operating system but there are many small programs that I had to write to make everything work together.

Each temperature sensor is capable of operating with only two wires, power and ground. The power line is also a bi-directional data line. So I have strung two wires to each sensor in a single string. Each sensor has a unique address and they are all on the same twisted pair. The voltage sensor works the same way but it needs 5 volts to power the analog to digital converter.

I suspect that if FWC saw my mess of wires, they would cancel my last 5 months of warranty. I tried to tie into the water level sensor but gave up on that for now. This was a challenging project for me. If someone likes programming computers, knows a little about the Linux operating system (I am no expert), is comfortable with a soldering iron and likes getting frustrated when things don't work, I would be happy to share more details of the project online or offline.

I have also installed two fans for the refrigerator. I compare the temperature on the condenser with the outside temperature. At about 40 degrees difference, the computer will turn on the fans. They are both low RPM computer fans and I can not hear them when they are on. At about 20 degrees temperature difference, the computer will turn the fans off.

Steve
 
For my breaker I went with one of these from Blue Sea: http://bluesea.com/category/3/10/productline/overview/432
I specifically wanted a manual reset, but they do offer other options here: http://bluesea.com/category/3/10

For camper systems monitoring it sounds like this is more my speed, if I ever get deep pockets. Though it does not appear to do any logic operations, so it won't meet your fridge fan control type demands.
http://bluesea.com/products/1800
 
My plan is also to only use DC on the refrigerator when driving. And I am researching a replacement breaker that can handle a little more current. Any inputs here would be appreciated.

The computer addition in the camper is ongoing and has been a challenging project for me. For the computer, I am using a network wireless access point (usually used for home networks) that has a USB port and has been reprogrammed with an open source operating system call "OpenWrt". It is a Linux based operating system. The sensors are from a family of "one wire devices" that are currently made by a company called Maxim. I purchased a USB adapter that can send and receive the One Wire signals from the devices. It also turned out that someone had written drivers for the USB adapter device that was part of the OpenWrt operating system. This project was not an easy task and my now being over 60 made it much harder. Much of what I needed was already available in the Linux based OpenWrt operating system but there are many small programs that I had to write to make everything work together.

Each temperature sensor is capable of operating with only two wires, power and ground. The power line is also a bi-directional data line. So I have strung two wires to each sensor in a single string. Each sensor has a unique address and they are all on the same twisted pair. The voltage sensor works the same way but it needs 5 volts to power the analog to digital converter.

I suspect that if FWC saw my mess of wires, they would cancel my last 5 months of warranty. I tried to tie into the water level sensor but gave up on that for now. This was a challenging project for me. If someone likes programming computers, knows a little about the Linux operating system (I am no expert), is comfortable with a soldering iron and likes getting frustrated when things don't work, I would be happy to share more details of the project online or offline.

I have also installed two fans for the refrigerator. I compare the temperature on the condenser with the outside temperature. At about 40 degrees difference, the computer will turn on the fans. They are both low RPM computer fans and I can not hear them when they are on. At about 20 degrees temperature difference, the computer will turn the fans off.

Steve


:LOL:Wow, I read this tecno type thread (or try and understand this and read it) and realize how much I don't know after almost 7 years of keeping my fwc working-somehow it seems-I always put my 3 way on batt when i drive -thought that is what i was supposed to do and use propane when parked and use my solar to keep the batt up when parked or when something like when the frig crashes (as it has before) or I put the TV/sat dish up to watch my Giants or 49er's. I just feel real stupid trying to understand what I don't know, but keep it up, sometimes (allot of times) i understand enough and learn something from these discussions so please keep them up because I not bitching just wishing I knew more so i can i do more with my fwc and keep having fun out there! Now if we were talking about keeping unstuck-then I could put my two bits in and feel on safe ground. That make sense???
Smoke
 
Thanks ntsqd for the breaker info.

That monitor looks interesting. I still want a better water level device than 4 lights. For the new breaker, I was hoping they made a 50 amp breaker that would be a direct replacement for what I have now (I assume it is a 30 amp). It looks like 80 amps is probably the better way to go. Again, thanks!

And thanks Smoke.

Playing with computers is my hobby. Although it is getting harder to do as I get older and my brain gets slower, I still have fun trying. And, on the other hand, I wish I had the ability to do so many of the physical modifications that others are doing to their campers. It is pretty cool! I really admire many of the camper mods I see posted here and wish I had the tools and ability to do the same thing.

Oh yeah, I think first pitch is about 7:30pm tonight!

Steve
 
...I always put my 3 way on batt when i drive -thought that is what i was supposed to do...

Yes, that's the mfg. recommendation -- for safety (i.e., CYA for the mfg).
 
For us it works well. The key is to not forget and let it run too long with the engine off. A fuel stop I leave it alone, but a grocery store stop or similar I switch it to propane.
 
Propane with a reignitor isn't the end all be all but works pretty well. I ran mine for a 2 week road trip that covered 3000mi that way, never had it blow out while driving, only once did I come back to the camper parked in the wind at Bodie, CA did I hear the clicking of the ignitor signifying it was trying but unable to respark it. Some folks don't like the idea of driving on propane but I didn't mind (they have propane engines after all) so it worked well for me while dealing with the 3way platform. New camper is getting a compressor fridge though so it'll be an non-issue.
 
Just a couple of quick thoughts.

I just picked up our new Grandby with the Dometic/Waeco compressor fridge. My initial view is pretty positive but I reserve final judgement until I've used it for a long hot trip. It certainly gets the fridge cool and freezer cold. In cooler spring temperatures, it doesn't seem to run very much but that's kind of a guess because it is very quiet. I was a bit worried about the noise because I hadn't actually seem one before we placed the order. However, I had to put my ear up to it in order to tell if the compressor is running. Stay tuned for comments once I make a longer trip later this summer.

Voltage drop is one of those things that is often overlooked in 12 VDC wiring. It deserves a lot more thought and the correct wire gauge chosen accordingly. In the boat-world, a 10% drop is usually considered the maximum for non-critical circuits, 3% for critical equipment. Here is a handy online calculator for calculating voltage drop and hence picking the right wire gauge (Voltage drop calculator). Don't forget to size the fuse/breaker for the wire gauge not the appliance draw.
 
Congratulations on the new Grandby! I remember looking at it at the showroom and it is one sweet camper!

And thanks for the voltage drop calculator. I measured .2 volts drop to the refrigerator on about a 12 foot wire run of 8 gauge wire and the calculator says 2.2 I meant .22 volts (corrected). I saved the link for more use later.

So tomorrow, I look at the wire from the battery to the camper and decide if I might want to boost the size some. I went camping for the last two days and swear that the breaker between the battery and camper was tripping a few times just after I hit the road. I stopped at a rest stop and bypassed it. I have not seen the problem since doing that. So a larger breaker is in the works. And yes, one with a small voltage drop across it would be good.

Just adding a slightly larger breaker really should do the trick but I still might switch from 8 gauge to 6 gauge if it does not look like a major undertaking.

Steve
 
I find this discussion very interesting. Most of it, the Linux bits etc., may be useful in my next life. Too old to learn that stuff now but who knows what the afterlife will bring. But thicker wires to the fridge is something I could consider. Mostly I find the DC works while driving but not always. The key is to remember what state the fridge is in when you stop. Has anyone designed a reminder system that works? I was thinking one of those invisible fence dog collars I could wear.
 
I started a post last night that talked about the heaters in the Dometic fridge on DC compared to AC. I started getting carried away and deleted the message but; On AC, the manufacturer says the heater is 175 watts. If the refrigerator power, at the refrigerator, is 12 volts. the heater should be running at 150 watts when on DC. If the power at the refrigerator is 13 volts (charging while driving?), the heater would be 175 watts. I am assuming that the refrigerator does not regulate the 12 volts to the heating element. I am also going to assume that at some point, and I have no idea when that is, hotter does not help.

Since I run the refrigerator on DC only while driving or on a ferry that requires it, I can't really figure out how to measure how well the fridge works while on DC. There is no doubt that the refrigerator does not do real well while I am driving down the road on gas or DC. And this is where the compressor refrigerators must do better. I park my truck and camper next to the driveway on a slope. I dug two holes for the wheels to drop into while parked. The nice part is that it makes it real easy to step into the camper without an extra step! I had to do this so the refrigerator would operate while my camper is parked at home. I need to get some miles out of my Dometic fridge before I consider switching to a compressor refrigerator. They do look inviting for someone with a solar panel (and does not camp often in a dense forest).

I do think running 8 gauge wire directly from the battery to the refrigerator is better than the factory wiring I am getting, maybe 0.7 volts more at the refrigerator, which should mean more heat from the heating element when on DC. Your mileage may vary. If someone decides to do this, be careful! Shorting out a 75 to 150 amp-hour battery can start a fire. I did add a 30 amp fuse to protect from shorts on the wire between the battery and the refrigerator. I think I will replace the fuse with a breaker of some sort but breakers do drop the voltage across them. According to the manual, the refrigerator has its own fuses.

Steve
 
Remembering to switch back to gas at the destination is going to be a big problem for me. On my first big outing with the camper, I left my door mat at one campsite and my home made wood blocks at the next campsite. I need to make a checklist and stick it on the steering wheel. I have always latched the top but have had closer calls than I would like to have had. The Hawk camper has a latch on the ceiling that you engage after you drop the top. I forget that one about 20 percent of the time, although I am getting better.

Steve
 
Most of us have some amount of CRS:rolleyes: After packing up my camp I drive forward a truck length, get out and give my camp and vehicle a second lookover. I have found things that way. Rain is the killer for me. I'll ignore lots of stuff to stay dry :eek:
 
And thanks for the voltage drop calculator. I measured .2 volts drop to the refrigerator on about a 12 foot wire run of 8 gauge wire and the calculator says 2.2 volts. I saved the link for more use later.

Steve


Steve, are these numbers correct? You measured a .2 volt drop but the calculator predicted 2.2 volts? If that's the case, I'm deleting the calculator from bookmarks. It's way off.
 
Dang! No they were .2 and .22 so well within my measurement error. Sorry about the decimal place error! The calculator works great! I will fix my post. I hate it when I do that!

Steve
 
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