Generator vs Battery/Inverter/Solar

[chobe2]

We have just purchased our first truck camper - a used 2007 Lance 845 and have a couple questions that I hope you can help us out with. The camper is still at the dealer and we're considering having a couple modifications done before we pick it up. It has an empty generator compartment in the back that we could have a propane generator installed in. Or...I've seen online that another person used this space for 3 extra batteries and an inverter plus I believe they had a solar panel. What are the pros and cons of these two systems? Any thoughts?

[zcookiemonstar]

Battery cable and welding cable are not the same. Battery cable strands are each about the size of an 18-20awg wire. Welding cable strands are fine like hairs on your head.

Stranded wire in general should be used on anything that that moves, flexes, shakes, or vibrates because a solid wire can crack in and of these applications. All RV/Trailer or vehicle wiring should be stranded wire.

[jimh406]

Here's one explanation although I doubt it will matter much for our normal uses.

Here's a long discussion with a lot of links. http://forum.allaboutcircuits.com/threads/stranded-vs-single-conductor-resistance.55795/


http://www.rowand.net/Shop/Tech/WireCapacityChart.htm

Stranded vs. Solid Wire

This one is a bit of a mind-boggler, but it's important. When electricity flows through a wire, it mostly flows on the surface of the wire, not through the middle. This effect is more pronounced on high frequency AC than it is on DC or low frequency AC. This means that a "wire" of a given size that made up of many smaller strands can carry more power than a solid wire - simply because the stranded wire has more surface area. This is one reason why battery cables in your car and welding cables are made up of many very fine strands of smaller wire - it allows them to safely carry more power with less of that power being dissipated as heat. However, this "skin" effect is not as pronounced in a typical 12V DC automotive application, and the wire and cable used there is stranded for flexibility reasons.

When looking at a chart or description of wire capacity, take note of whether it is referring to stranded or solid wire - some charts may not specify but instead assume a default based on the typical wiring used in a given application. For example, almost all automotive wiring is stranded while almost all home wiring is solid. For most applications, flexibility or the lack thereof will be more important, but for very high frequency AC applications, stranded wire might be a requirement.

[zcookiemonstar]

Reddog1 wrote:

zcookiemonstar wrote:
... Just remember it's not just the size of the cable. The thinner the strands the more resistance you will have. If you were to use welding cable because it is nice and flexible you will not get as much voltage as with a heavy stranded cable/wire. Sorry don't have a link to prove that.

I have very limited knowledge on electricity, but it is my understanding the reverse is true.

Wayne

I am not an Electrical Engineer but have been wiring automated machinery for over 20 years. This is what the Engineers I have worked with always told me.

[billtex]

dmaxpuller wrote:


Totally agree on the gas part. Its just that the one part of TC camping is the storage.
Built in generator, one less thing to haul around. We did that on our last Lance, and using it in wet weather was iffy.

If storage really is a challenge...then the portable makes much more sense; carry when you need to...leave it home when you don't. Don't have that luxury with a built-in.

[dmaxpuller]

mbloof wrote:
Personally, I'd go with a Yamaha/Honda 1K or 2K (if you want to run the air) over anything that runs off propane. While a built in generator offers on/off switch simplicity for operating the generator propane can be a limited resource that your heating, cooking, hot water and most importantly the fridge/freezer require for operation.

Where I live propane is not sold at every gas station and a 1 gallon gas can is much easier to fill then the on board propane tanks. When the generator and gas can is empty you'll still be able to use all your propane appliances however if you run out of propane you'll need to refill to use most of the appliances.

Totally agree on the gas part. Its just that the one part of TC camping is the storage.
Built in generator, one less thing to haul around. We did that on our last Lance, and using it in wet weather was iffy.

Have never had a issue with propane. The water heater does not use much, the frig, probably a little more. But if ya pay attention, you could go a couple of weeks. We have done it on numerous occasions.

2 cents worth.

[mbloof]

Personally, I'd go with a Yamaha/Honda 1K or 2K (if you want to run the air) over anything that runs off propane. While a built in generator offers on/off switch simplicity for operating the generator propane can be a limited resource that your heating, cooking, hot water and most importantly the fridge/freezer require for operation.

Where I live propane is not sold at every gas station and a 1 gallon gas can is much easier to fill then the on board propane tanks. When the generator and gas can is empty you'll still be able to use all your propane appliances however if you run out of propane you'll need to refill to use most of the appliances.

[dmaxpuller]

If the funds allow, go with a built in generator, (propane 2500 watt), get the solar also. We had our Solar Panels installed at AM Solar in Oregon. 320 watt system.

The only time we really use the generator is if we by some chance need the microwave, but the DW uses it for the hair dryer. Have run the AC a couple of times when it was really hot using the generator. Other than that, we have 150 watt inverter that runs all other stuff, if needed. i.e. TV, XM Sirrus radio, etc.

The best bang for the buck is getting the batteries. I installed 2 Trojan wet 6 volt batteries. The are the best, IMHO.

Good luck, its only money:W

[mbloof]

Personally, a 6-8AWG wire from the truck is more than enough for my use.

A quick look at my battery(s), total capacity and recommended charge rate (usually 10/C to 20/C) show that my 100AH deep cycle (for example) would like 10-20A maximum charge rate. (some sealed batteries want as little as 4/C charge rate)

If the run of wire, connectors and other items between the trucks alternator and the house battery are unable to deliver the full 100A of charge current the alternator can provide I have no problem with that.

Then again, YMMV.

[HMS_Beagle]

My Ford alternator is spec'd at 157 amps max, keeping in mind that is almost certainly a cold rating and so it will not achieve that in practical use (warm).

#6 AGW at 100 amps over 25' is about a 1.2V drop, easily compensated by any good external regulator. The wire is rated to do this. Lifeline spec's their batteries at 5C charge, but they will never accept that unless near completely discharged, and then only for a couple of minutes. At 50 percent SOC, they will accept around 0.5C, that will drop to 0.2C and less at 80 percent SOC. Most campers have one or two batteries, so around 200 AH of capacity, 100A charge is all you can ever practically use. I have a 440 AH 24V Lifeline AGM bank on the boat, when run down to 40 percent SOC it will charge at around 280A for a very short period. That bank is now going on 11 years old.

If you used LFP batteries, then a larger alternator could be used, but the costs of the system might exceed the value of the camper :).

In my camper, I haven't gone that far. I have 200W solar on the roof with a good MPPT controller, a proper 3-stage shore cord charger which I never use, and a #6 charge cable from the truck charging the 220AH Lifeline batteries through a Balmar DuoCharge controller. I do not attempt to run an electric stove or air conditioning from it, but for all other uses it works fine, normally charged only from the solar.

[rwiegand]

Doh! I'm embarrassed. :S
Thanks.

Unfortunately, transformers don't work with DC electricity.

[DiploStrat]

HMS Beagle wrote:
With a separate alternator and remote voltage sense, you would not need the large cable. #6 AWG will carry 100 amps safely, but there will be a voltage drop. Remote sense is a separate small wire (#18) running from the battery terminal to the regulator sense input, the regulator increases the voltage output of the alternator until the battery terminal is at the required set point regardless of voltage drop in the charge cable. That system would also regulate the house battery according to its needs exclusively. Equalizing the state of charge between house and start batteries in not really ideal - you do not want to bring the start battery down to the same SOC as a discharged house battery.

How far to go to finesse the system is debatable. People have been camping with a simple #10 wire in their 7 pin harness doing the charging for decades. But there are much better ways available.

I am quite familiar with remote sensing, having used it on my Sterling Alternator to Alternator charger and using it on my solar controller.

You are correct. Assuming the right gear, you can raise the origin voltage to compensate for losses in the circuit. Sterling, CTEK, and others do this all the time. In the end, all still require large cables to deliver large amperages. In my tests with the Sterling, the two 125A alternators on the truck were providing 190A at the batteries - and the 1/0 AWG cable was getting very hot.

Obviously, with a separate, dedicated alternator, you can play with the voltages and amperages as much as your heart or pocketbook allows. I'm not sure that any commercially available gear will get you enough voltage boost to push 100A DC through 20 feet of 6 AWG, but I could be wrong.

Equalizing the SOC between the camper and starter battery is exactly what you want; you want them both at 100%. This is what you will achieve with a decently sized intelligent relay and properly sized wiring. You can, indeed, accomplish this with smaller wire, but it will take much, much longer. A battery will charge as long as the charge source is higher than the voltage of the battery.

As a practical matter, your Ford probably has at least a 200A alternator - heavier wiring will get you a much better charge rate than you will get though a classic 7-pin setup.

In my case, cooking electrically and running heat or air conditioning, I want the fastest charge I can get. Lifeline specs up to a 5C charger. With a 600Ah battery bank, I am not going to find a 3000A charger, but the difference between being able to deliver 150A+ at a proper 14.4v and, say, 25A at 13.5v is considerable.

As always, YMMV. My numbers are based on two years of field use and a lot of logging. Call me in eight years to see if I make a full ten years on the batteries!

To return to the original question:

-- Can you live without a generator? Yes, many high end campers (e.g. Earthroamer, Earthcruiser, some Tigers) do exactly that.

-- Is it enough to simply add a few more batteries? Probably not. You will need to be able to charge them and your inverter may not be large enough.

-- Is it worth it for YOU? Only you can answer. I hope that the information that I have offered is correct and helpful.

😉

[ticki2]

billtex wrote:

ticki2 wrote:
http://www.silveradosierra.com/electrical/voltage-fluctuate-on-the-dasboard-meter-t19680.html#p18011...

This may shed some light on the subject , at least as far as GM . Apparently my 02 is too old for this feature . t might also explain why some GM owners are having trouble charging coach batteries from the truck .

thanks Bob...I never knew that!
I stay in T/H most of the time...unless running really flat/long...

Not sure if it matters...but does this apply to gas/diesel or both?
I didn't see in the article.

Tx, Bill

I am not sure . Here is the article from 2005 . It includes Silverado under 8600GVW .

http://acdelcotechconnect.com/pdf/imtn_V12I305.pdf

Guess you could check with a voltmeter at the 7 way charge pin .

[HMS_Beagle]

With a separate alternator and remote voltage sense, you would not need the large cable. #6 AWG will carry 100 amps safely, but there will be a voltage drop. Remote sense is a separate small wire (#18) running from the battery terminal to the regulator sense input, the regulator increases the voltage output of the alternator until the battery terminal is at the required set point regardless of voltage drop in the charge cable. That system would also regulate the house battery according to its needs exclusively. Equalizing the state of charge between house and start batteries in not really ideal - you do not want to bring the start battery down to the same SOC as a discharged house battery.

How far to go to finesse the system is debatable. People have been camping with a simple #10 wire in their 7 pin harness doing the charging for decades. But there are much better ways available.

[Reddog1]

zcookiemonstar wrote:
... Just remember it's not just the size of the cable. The thinner the strands the more resistance you will have. If you were to use welding cable because it is nice and flexible you will not get as much voltage as with a heavy stranded cable/wire. Sorry don't have a link to prove that.

I have very limited knowledge on electricity, but it is my understanding the reverse is true.

Wayne