Basic help please

[tex4judy]

We have purchased a Sprinter 170" extended with the 7' inside head room; and are building a Class B RV. Our intention is to install the Nations 270 Amp Alternator instead of a diesel generator. (We're doing our best to avoid propane.)

I understand the solar panels and controller, the lithium battery bank, and the shore power. We're prepared to install the high capacity inverter, etc.

My question (and it's hard to get info from Roadtrek when we're building our own): Does the 270 Amp Alternator feed the batteries, the batteries feed the inverter, and then on to the AC distribution panel? Or does the Alternator feed the inverter directly? And the batteries are charged from a converter fed from the AC panel?

I know this may sound basic to many, but my background is engineering on ships and boats and some of the new electrical/electronics equipment is an educational opportunity for me. Thanks in advance for your help.

tex4judy

[avanti]

Originally Posted by tex4judy

My question (and it's hard to get info from Roadtrek when we're building our own): Does the 270 Amp Alternator feed the batteries, the batteries feed the inverter, and then on to the AC distribution panel? Or does the Alternator feed the inverter directly? And the batteries are charged from a converter fed from the AC panel?

Typically, there is only a single DC system. I.e., the battery, alternator, inverter/charger, solar charger, and all loads are essentially all connected together. Think of it as a bus with all sources and sinks of current all connected in parallel. The battery in effect serves as a "load balancer" absorbing spare current when it is available and contributing it when necessary. The inverter/charger is a source when it is plugged in to shore power and a sink when it is inverting.

[tex4judy]

Your description is very helpful. So I can run DC current from the Alternator to the Inverter in the same connections where the battery is hooked up? And not worry about "unmanaged" charging of the batteries?

[BobB]

Originally Posted by tex4judy

......and it's hard to get info from Roadtrek when we're building our own...
tex4judy

And you probably won't get any. Other manufacturers may be more helpful.

Originally Posted by tex4judy

I know this may sound basic to many, but my background is engineering on ships and boats and some of the new electrical/electronics equipment is an educational opportunity for me. Thanks in advance for your help.
tex4judy

Electricity is not my forté. BUT there are a lot of knowledgable people here. So my advice is - before you buy anything - work out the electrical design on paper, then post it here for review and comment. Much easier and cheaper to make mistakes on paper than in your new van.

See the thread "Roadtrek E-Trek Battery Replacement" and you'll get the idea.

[avanti]

Originally Posted by tex4judy

Your description is very helpful. So I can run DC current from the Alternator to the Inverter in the same connections where the battery is hooked up? And not worry about "unmanaged" charging of the batteries?

Pretty much. At least that is what is commonly done, and it seems to mostly work out ok. You DO need to configure all the chargers so they are all singing from the same song sheet wrt charge thresholds, etc.

One issue that is a little subtle is where to put various disconnects, fuses and circuit breakers. There are non-obvious failure modes (e.g., suddenly removing the batteries from a running alternator) that can be nasty. This topic has been discussed here at length.

[avanti]

Just to be clear: The alternator doesn't literally connect directly to the battery. There needs to be a regulator/charger between them. Lots of people (including RT) use the Balmar MC614H, which is an excellent choice.

[tex4judy]

Perfect. Thanks. As I said, needing basic help.

You are also correct that there is good discussion here. Some have questioned running an A/C with the Secondary Alternator, but my numbers say it will start and run as long as the initial surge amps aren't too high. Any personal experience with that? The E Trek is set up that way.

[gregmchugh]

I agree with the idea that you document your design in detail and post it for review before you start buying stuff and building it. The devil is in the details in terms of wire size, circuit protection, balancing battery types/capacity, inverter size, and charging systems (solar, engine, inverter charger) with your energy usage profile. You can build up the system incrementally but a full design will help avoid finding out later you have issues.

There are examples of design schematics for similar systems you could use to start with.

[avanti]

Originally Posted by tex4judy

Some have questioned running an A/C with the Secondary Alternator, but my numbers say it will start and run as long as the initial surge amps aren't too high. Any personal experience with that? The E Trek is set up that way.

I do it all the time. Trust your numbers. If you have a dedicated 270 amp alternator with properly-sized wiring, it is a no-brainer.

[booster]

There are many, very detailed, discussions here about the different systems, how they work, and why folks chose to do them the way they do. Many of the questions you have brought out have been addressed from many different views, and that is a very good thing.

IMO, some of the important things to dig in to.

There are good reasons to chose a single alternator setup, and also good reasons to chose a standalone setup. It comes down to personal choice to some extent, how the van electronics react to big alternators, and if you feel the need to be able to stop the alternator charging to the coach. Especially with the lithium, I don't think a lot of the questions have for sure answers at this point.

The devil is in the details with charging, with AGM having one set of concerns, lithium a different set. Again, the lithium tech is new and not fully resolved, so most certainly will have to take a best guess on what is best, worst, OK on some of the issues. In all types of setups, it is possible to ruin batteries in a short time if done poorly. Environmental concerns have recently been a big topic for both hot and cold. Several folks are working on lithium systems on the forum, but only davydd has any real amount of time on them, and his time is still pretty short.

Interactions between all the systems have been proven to cause a lot of us issues. You have to have 3 charging systems that do what they are supposed to without keeping the other two from doing the same. Advanced RV appears to have put together a very sophisticated central control system to do that with the lithium batteries, but doing it with individual components will be tougher. Even with the much older AGM tech, there are very few components that play well together, and they still have oddities to them.

Above all, you will need to have a very good monitoring system, especially for initial checkout and tweaking.

IMO, the last thing you want to do is believe what the sales guys tell you about their stuff as we have seen piles of bad, distorted, and outright inaccurate information. Trust, but verify, as they say, no matter who says it.

Good luck on your project, it will be fun to see it progress!

[tex4judy]

OK - have worked on this as much as possible (not retired) and am getting ready to post a diagram of our proposed Electrical set up.

Here is a installation question: in the marine world all wiring is stranded. Solid single strand wire, like 12-2 house wiring is too prone to being kinked in installation, being flexed, stressed, or corroded in a marine environment. It seems to me that an RV would have some of the same concerns. Does anyone use "stranded only" wire; or is that overkill?

[Bruceper]

Automotive electrical uses stranded wire, not solid. Coach manufacturers may have installed solid wire for 120 volt systems, but strictly speaking that is not automotive use.

There is, or should be, no flex in the house of your motorhome. So stranded wire would not be needed in 120 volt applications.

[avanti]

I have always been taught that best practice dictates the exclusive use of stranded wire in all RV applications. There may not be "flex", but there are certainly vibrations. The risks may not be high, but neither are the costs. I vote "stranded only".

[skagitstan]

Our in-process Transit conversion uses stranded for all wiring, DC and AC.
We expect to be on rough unpaved roads a lot, and I would rather deal with unexpected vibration up front.

Other than cost, there is no real downside to using stranded.


As an aside, my conversion write-ups (including electrical work) are a bit behind on this site. To many of my entries are picture heavy, and the site only allows 4 pics linked in one post.
Check my blog if you want the latest blathering.

Stan

[booster]

I agree that even though many/most of the RV builders use solid Romex for the 120v systems, it is just not all that good an idea. Boats require stranded for a reason and that is flex breakage from bounce, primarily. Personally, I have had poor luck with crimp connections on solid, also, so that makes the whole process difficult to wire besides.

For an occasional signal low voltage wire that is not critical, possible, but not anything important, and they would need to be tied up tight.

[tex4judy]

I can see that I've fallen in with like minded men. Will post our proposed Electrical Diagram soon. Thanks

[BobB]

So tex4judy - With the back and forth on stranded wire, there is one more question. Are you going to use automotive stranded wire or marine stranded wire?

For RVers out there, there is a difference. On Marine stranded wire (by someone like Ancor Marine) "Each strand has a tin coating for extra corrosion resistance (note the “silver” look when you strip it)." Often I have read this referred to as "tinned" wire. Whether it makes enough difference to use on your RV, I don't know. Anyone have an opinion on that? Also Ancor states their wire has some other attributes (type 3 vs type 2) making it better.

My guess is marine costs a bit more than automotive. I need to do some re-wiring this spring, but will probably go with marine, since a I find it very easy to deal with West Marine.

[skagitstan]

I'm using untinned wire. I figure if Annie ends up floating in salt water, I've got bigger problems than wire corrosion .

[BobB]

Originally Posted by skagitstan

I'm using untinned wire. I figure if Annie ends up floating in salt water, I've got bigger problems than wire corrosion .

LOL!!

For RV use and conditions, I don't think one is necessarily better than the other. But there is another thread on this forum about learning from boat builders and just wanted to point this out. I have use Blue Seas switches for battery disconnects and I know others use marine-rated charger/inverters.

[avanti]

The eBay seller "acdcelectricparts" is an excellent source of high quality large gauge wire.

items in ACDCELECTRICPARTS store on eBay!

They often have "end of roll" remnant lengths available at good prices.