I dropped a teaser about this a few weeks ago, so now it’s time I finally came clean with all the details. Since that time, a number of folks at Winnebago’s Grand National Rally, and on the Lake Superior Adventure have seen Lance in action, so some of this has already leaked out. That’s OK, it’s all pretty cool stuff.
I had been thinking about a system like this for a long time. My interest with it probably began when we visited Advanced RV in Ohio. These days, there are lots of people adding lithium batteries to RVs. Advanced-RV has been doing it for a while now, and their installs work very well, from all reports. They approach RV power as an integrated system (rather than just installing a bunch of parts and hoping for the best). They put a lot of work into that integration, and I think their success is due to that. I wanted to emulate this systems approach when upgrading our RVs power.
I had two major goals here. The first one was the same as many people: I wanted to do away with the generator. In our case though, it wasn’t because the generator was loud. (OK. I mean, yes, it was loud, but we could deal with that.) It had more to do with the fact that after almost a year, we had only 13 hours on the generator – and 10 of them were just to exercise it. Exercising the generator was pretty much the whole reason I added an auto-generator-start module. So from a usage perspective, the generator was a big “meh”.
The other strike the generator had against it was its unwillingness to start at higher altitudes. I’m thinking of our trip to the Fishlake National Forest in central Utah. At 9000 feet, the generator just refused to start. We didn’t actually need the generator, we just wanted to see if it would start (and we could hear a Honda 2000 not too far away). I know there are carburetor kits for high altitude that would have helped. But a couple months later, we were camping on the beach in California at sea level. Considering where the generator was mounted, messing with the carburetor as we changed altitude seemed like a real pain for something we barely used.
The other major goal I had was that I really don’t want to think about it too much. We all know I like to tinker with the RV, but after reading about lithium batteries and inverters for the better part of two years, I’m over it. I want things to work without my having to constantly monitor and tweak them.
Now, that doesn’t mean I don’t have a healthy curiosity in the data and the results. But you may be disappointed in this post if you’re expecting to read things like:
“By decreasing the float voltage from 13.6 to 13.4 volts, I was able to increase the remaining capacity at one year by 3.2%. This translates to an increased lifespan of 4398 full discharge/charge cycles – up from 4261. Those extra 137 discharge/charge cycles will likely be an even greater number since I never let my batteries get below 84.9% full or experience temperatures above 90 degrees Fahrenheit. ”
So, fair warning to battery purists: don’t gasp in horror as you read about me deliberately draining the expensive battery until the coach went dark. (Yes. I did. And it was awesome.)
Given my aforementioned apathy toward battery capacity and charging system discussion, it won’t come as a surprise that I let someone else design the system for me. (I’m an aerospace engineer – not electrical!) In this case, it was the good folks at Xantrex (a division of Schneider Electric) who did the heavy lifting on the design side. I can’t say enough good things about the system they’ve put together.
They took the lead in contacting suppliers of components that were already on the market and working with them to gather information, size components, adjust parameters, work out communication protocols, and basically make sure everything would work together as a system when it was all said and done. Though the components were all sourced from different vendors, they’ve so far worked together flawlessly. All they’re missing is a catchy name. So just pick one word from the first column and one word from the second, add them together, and let’s pretend that’s the name. (I’m going with “Amp-Camp”!)
But the folks at Xantrex didn’t stop at just designing the system and sending me a parts list. They actually showed up at FitRV HQ and helped me install and remove stuff. This was a good thing. Since the amounts of stored electricity we’re talking about can be potentially harmful, I was glad to have the assistance and extra eyes for safety.
The system they put together consisted of the following components.
Second Alternator for the ProMaster
This proved to be the most difficult and cautionary piece of the whole puzzle, mainly because this involves messing with the engine of your ProMaster. I’m good with wood, and OK with electrical and plumbing, but I’m no mechanic. So I had to find help to install this – hopefully without blowing up my warranty. Fortunately, the team at Larry H. Miller Dodge in Sandy, UT agreed to take on the task.
The alternator kit is already used in other ProMaster based RVs. It comes with everything you need to complete the installation. Here is the kit as I unpacked it on my bench and immediately decided there was no way I was going to mess with it.
The installation is pretty involved. You have to drop the air conditioner compressor, install a pulley; install a bracket; add the second alternator and belt and tensioner; cut and re-route coolant hoses, and somehow get it all back together. Here’s what it looked like halfway through, with the bracket installed and the compressor hanging loose.
And when it’s all done, it looks like this.
It took a whole day to get it installed, and I was pretty happy with the results for about 50 miles. Then this happened.
While heading up Parley’s Canyon toward Park City, Lance’s dash lit up like a Christmas tree, and things severely overheated pretty much all at once. We made it up (barely) and coasted down the other side to wait at a gas station until we could get a tow.
What had happened was that the new hose and belt routings were just a bit too close to each other. The belt, after 50 miles or so, cut through the radiator hose, and spewed all the coolant onto the freeway. Boom! Instant overheating.
Fortunately, the crew at Larry H. Miller Dodge are real stand-up folks. They owned the problem and fixed it at no additional charge. They also took ownership of the next two problems which had Lance leaking coolant: a warped thermostat housing, and a damaged water pump. They fixed these as follow-on issues to the original mistake. So, other than having to go back and forth to the dealership a few more times than I had planned, it all worked out well in the end. Since then, we’ve put about 2000 miles on Lance, and everything has held up, so we’re pretty confident that all those problems are behind us.
This alternator also came with a voltage regulator attached. This is a key part of the system, and it does two things. First, it ensures that the alternator’s output is properly matched to the lithium batteries. This is a problem for single-alternator systems. The chassis alternator is designed to charge the starting battery, but that charge profile likely isn’t optimal for the house batteries – especially if they’re lithium. So by having a second alternator with a properly regulated output, the lithium batteries can have it their way, and the rest of your chassis electronics can have it theirs. Everyone is happy.
The second important feature of the voltage regulator is that it has a control circuit on it which will allow the NeverDie Battery Management System (BMS) on the Lithionics battery to “turn off” the alternator when it decides it’s full. This did require running a control wire from the battery to the voltage regulator, but it works – I’ve seen it in action. Working out that bit of communication is why I was glad to have Xantrex designing the system for me. It’s not likely that, as an individual, I could have worked that out between the three suppliers involved.
Zamp Solar Charge Controller
Our Travato was already sporting 300 watts of solar panels connected to a Zamp solar charge controller. But that controller was programmed for AGM batteries, which require a different charge profile than our new lithium battery.
Fortunately, Xantrex had been working with the people at Zamp as well. In the year since we purchased our Travato, Zamp had already come out with a lithium-ready controller. But Xantrex had worked with them further to tweak the charge profile to match the other components in the system. When receiving power and set for lithium, the Zamp system delivers bulk and float charges as specified by Xantrex (14.6 and 13.4 volts, respectively). As a bonus, this new charge controller will handle 40 amps as opposed to the previous 30.
This battery is what really makes all this possible. It’s a 420 Amp Hour battery from Lithionics, with an on-board battery management system. It’s a lithium battery, which brings some special considerations.
I had always been worried, when thinking about lithium batteries, about the potential for damage from the cold. You see, lithium batteries can be damaged by charging them at temperatures below freezing. Since we like to take our RV out in cold weather, and since the stock battery and generator locations in our Travato are underneath the body of the van, this was a problem. I had assumed that we’d be using the generator mounting location for this battery, and was thinking of heating blankets, insulation, and whatnot.
The Xantrex guys actually thought up this mounting location, and we’re glad they did. We lost one drawer of storage in the pantry, but what that bought us was automatic climate control for the battery for zero effort or expense. It’s genius, and similar to how I passively heat the water lines in the winter.
This did require a bit of cabinet modification, and some angle aluminum that I riveted together to keep things from moving when underway. Also, this battery has two user-operated button controls, which I mounted on the cover I had to build.
The control with the lit circle is the master battery on/off switch. It comes in very handy when you’re working on the RV and get nervous about the rather large energy store on your 12 volt system. This is different from the Winnebago-installed coach master switch because this one just controls this one battery. With this switch off and the coach switch on, for example, you would still have power from solar (assuming the sun is out). It’s kind of interesting, and I promise you’ll only forget the difference between the two once…
The second button is the “reset” switch. I only need it when I drain the battery to the point where the BMS shuts things down. This button is how you get your battery and electrical system “booted up” again. Yes, I’ve done this already. We’re getting to that.
And, since I’ve mentioned it a few times, let’s discuss the on board NeverDie BMS. It protects against overcharging, over discharging, and a host of other things. But it’s mainly those first two I’m concerned with. I’d mentioned before that it has a circuit that is tied to the voltage regulator on the second alternator. It does, and it’s the BMS that decides “I’ve had enough charging, thank you,” and kills the alternator. That keeps the battery from facing massive overcharging on a long road trip, for example.
On the discharge side, the BMS prevents running the battery all the way into the ground. It shuts down the battery when it’s about 90% discharged. Yet it retains enough reserve charge in the battery that it can be re-booted, as I mentioned above.
Xantrex Freedom SW Inverter
Naturally, Xantrex designed the 120 volt side of things around their own inverter, the Freedom SW 3012 with their System Control Panel. This is a true sine wave inverter with a 3000 Watt continuous output and a surge current rated at 80 amps. It’s a beast of an inverter/charger, but fortunately, it fits in the space where the previous Magnum inverter lived.
The 80 amp peak rating is the key driver here, as it will reliably start the air conditioner in our Travato. That air conditioner has a “Locked Rotor Amps” rating of 63, which represents the peak cold-start load. With a rating well above that, the Xantrex inverter has started our air conditioner many times now without complaint.
Beyond that, the Freedom SW is also a charger, which eliminates the need for the converter, and so we removed it, along with the transfer switch. The other thing to note is that Xantrex has updated the software in their inverter to work properly with lithium batteries. They updated the inverter on the fly using the ports on it, so we have the very latest revision.
Coleman Mach 10 Air Conditioner
Let’s talk about the elephant in the room. This is what it’s all about! When everyone talks about using large lithium batteries and large inverters in their RV, all they really care about is powering the air conditioner. Anything else you typically run in an RV can get by with much less battery or inverter capacity. The success of any RV power system is going to be measured by how long it can run an air conditioner.
With this in mind, some time ago, we had swapped our Coleman Mach 8 air conditioner for a Mach 10. Besides being just a hair taller, the Mach 10 runs at only 12-13 amps (@120v) versus the 15-16 amps the Mach 8 is rated for. When you’re trying to squeeze all the performance you can out of your batteries, those 2-4 amps matter, because they translate to 20-40 amps at 12 volts. That’s a 60 to 120 Amp-Hour savings over 3 hours, which is huge.
Our goal with the battery and inverter setup is to run the air conditioner for three hours without having to run the vehicle. Three hours represents the longest race I typically compete in (during which Stef might be stuck hanging back in the RV). It’s also about an hour longer than we ever ran the generator at once during our first year in the Travato. After three hours, we’d be fine to run the engine for a while to recharge.
One additional benefit of the Mach 10 vs the Mach 8 is that it’s approximately 50 billion times quieter*. The reduced volume is very noticeable on the outside, but not so much when you’re trying to sleep 18 inches from the air distribution box inside.
* Claim is pure hyperbole, and not verified.
Wiring and Monitoring
We wired all of the high-amp runs in the van with 4/0 welding cable, and used 300 amp fuses where appropriate. This is thick copper, and with the battery at mid-ship, none of the runs are super long, so I’m not worried about any voltage drops. Also, the welding cable is extremely flexible, so we had no difficulties in fishing it where it needed to go.
And have a look at that! To me, it looks something like what I imagine the first electric chair looked like. But what I do want you to notice is the presence of the shunt, which is part of what provides extremely accurate battery monitoring via this:
Our monitoring needs are met by this Victron battery monitor. I’m a big fan of hyper-accurate battery monitoring. If you’re going to monitor the battery, you might as well do it right. I installed a Trimetric in Das Bus. Our Magnum setup also had a shunt-based battery monitor, and now we have this Victron.
In addition to the basic amps in/amps out monitoring, it also gives state-of-charge (SOC), and estimated runtime based on the current load. I’ve also set it to alarm at 10% of usable capacity remaining.
The other item we have is this switch.
This switch performs a very important function: it keeps the two 12 volt electrical systems (chassis and house) separate. You see, from Winnebago, the house and chassis batteries are connected when either of two conditions occurs:
- The engine is running.
- The “Battery Boost” switch is pressed.
With a highly regulated lithium battery setup, I pretty much NEVER want the first condition to connect the batteries. But I may one day briefly want the second. This switch interrupts the circuit that activates the solenoid at the rear of the coach that connects the batteries. As long as the switch is off, the batteries will never be connected. If the switch were “on”, the two electrical systems could be connected and I could then use the boost switch.
There is also the potential that if one or the other of my alternators fails, I could turn on the switch and run both the vehicle and house with the other alternator. It’s kind of like a weird backup alternator. I don’t know if I’d ever do that unless it was a huge emergency, but it’s interesting to think about. Realistically, what I’ll probably do is put some sort of covered missile-launcher-style switch there instead so we never accidentally turn it on.
The Electric Travato in Daily Use
So when you hook all this stuff up, how does it run, day to day? In a word, fantastic! In normal use, you really never need to pay much attention to things, so if you’ve been overwhelmed reading this far, never fear. About the only thing you really need to know is which button to push to turn the inverter on and off. I’ve taught Stef which one it is, so life is good.
We’ve tried things like running the rear air conditioner while driving. That works just fine, and we’re still charging the battery when we do. The one problem we did encounter was traveling across Montana in 100+ degree heat. After running the rear AC from the inverter for a few hours, it got pretty hot cooped up in its little cabinet. Eventually, it shut itself down. But five minutes later, it turned back on again and everything was humming along. It was a pretty graceful recovery in my opinion. I’m considering some sort of venting for that cabinet – but it’s not a high priority since it only happened one time under extreme conditions.
I’ve run the inverter all day while I worked and Stef drove. No problems encountered, and I have no concerns about running the inverter hard for extended periods.
We’ve run the microwave and the air conditioner at the same time from the inverter, and that worked just fine, too. In the event we ever really did start using lots of juice, the EMS built into the coach by Winnebago would shut something down before we got into trouble, if the inverter itself didn’t stop the foolishness first.
I did weigh the RV before and after. There was not much change. Here we are “before”. But remember, I already had a smaller inverter installed.
And here’s the weight after. 20 pounds lighter overall, and some of that weight shifted forward a bit.
In the big scheme of things – that’s not much of a change, weight wise. We lost the generator, converter, transfer switch, and two AGM batteries. We added a big battery, a larger inverter, and quite a bit of 4/0 cabling. I would have thought the weight would have changed more.
As far as charging, without paying much attention to it, the batteries stay pretty close to full the entire time we use the rig. The combination of solar and driving keeps us pretty topped off. So I’m well on my way to meeting that “don’t pay much attention to it” goal. And I think Stef’s already there.
Some Actual Testing Results
All right, all right. What fun would it be if I didn’t share some real numbers and results? The litmus test of this whole thing is “how long can it run the air conditioner?” So let me get this out of the way.
3 hours and 19 minutes.
Here are the particulars of the test:
- Outside Temperature: 88-82 degrees
- AC Run Time: 3 hours 19 minutes (Some cycling of AC in second hour and after. But never less than 80% duty cycle even in those hours.)
- During this time, 2.6 Amp-Hours were contributed by the Zamp solar system. (I had parked in the shade to keep that to a minimum.)
- Ending event: Lithionics BMS shutdown. The coach went completely dark.
- Voltage was 11.87 Volts according to the Victron monitor approximately 10 minutes before shutdown. I didn’t catch it right at shutdown.
- Amp-Hours extracted: Greater than the 377 AH drawn from battery according to Victron monitor approximately 10 minutes before shutdown.
So basically, the BMS called the show over with just less than 10% of charge remaining, as expected. I’d like to be able to say I was surprised about something here, but everything worked exactly as advertised.
Restarting the coach from that dark state was very simple. I plugged in the coach. Everything is still dark at that point, because with the battery off, the inverter/charger didn’t recognize that there was anything to charge. Then a quick press of the reset button, and everything lit up and the battery started charging. It’s a good thing that the BMS leaves itself a little room to restart on shutdown. I suppose I could have attempted the startup with the engine and second alternator running instead, if shore power was not available.
During this test, the Victron battery monitor was very accurate as it counted down, both in time remaining and in percentage. Both of those hit zero just before the shutdown event. And it alarmed at 10% of usable capacity remaining just as programmed. If I hadn’t been determined to see how far I could go, I would have applied some charging when that alarm went off.
But besides that one test, here are some other data points for those who want to know.
The Coleman Mach 10, running through the Xantrex inverter, burns 11amps AC, which translates to 101 amps DC, according to the Xantrex Control Panel. I would have said 102 ((118 x 11)/12.7), but whatever.
When I took this picture, the Zamp solar charge system was contributing about 1.0 amps. (Again, parked in the shade.)
The battery monitor at this moment was showing 112.5 amps going out of the battery
So with a little math, we can calculate: Amps out of the battery + Amps Contributed by Solar – Inverter Output – 2.5 amps for lights, etc = losses. 112.5 + 1 – 101 – 2.5. I come up with 10 amps of losses when running the AC. With just the inverter on and no AC running, it uses about 3.8 amps. So all that means, it would seem, is that the system is over 90% efficient. Xantrex only claims 90%, so it seems they’re actually better than they claim.
I’ve mentioned that we’ve run the microwave and AC with no problems. But just to see how far I could push it, while the air was on, I plugged in an 1800 watt induction cooktop and turned it up to 10. Besides boiling water in 90 seconds, I got a peak of 280.1 amps being drawn down from the batteries!
That’s a crap-ton of juice. All the other loads are minor compared to the air conditioner and that cooktop, and I’ve already written a post where I explore the other 12 volt loads in the coach, so that’s as far as I’m going on the load side for now.
On the charging side, when the Xantrex is plugged in, it delivers its programmed 100 amps to charge the battery.
With the Xantrex unplugged, and the alternator running at idle, I get 172.6 amps in.
That’s not quite the 280 amps at idle in the brochure, but it’s pretty darn good.
And if I rev up to 2000 rpm, we get this for a charge from the second alternator:
And finally, if I need to charge the batteries in a big hurry, I can always power the Xantrex charger and run the engine. When stacking this way, at idle, I get a pretty substantial charge of 234 amps from the two combined. If I rev the engine, the charge seems to peak at about 250 amps, and it won’t easily go higher. I suspect there’s a limit somewhere of a 250 amp charge rate, though I don’t know exactly where that’s coming from. Perhaps the BMS. I don’t know that I’d ever really NEED to charge things that quickly, but it’s cool that I can. This would charge the batteries in about an hour and a half-ish I guess.
Well, it’s an RV, so it’s never really “done”. So what do I plan to do now? Well, the first thing I intend to do is something with this:
This is a True Induction cooktop. It’s the same kind Winnebago uses in some of their coaches. We’re going to have a “boil-off” of sorts, and assuming the induction cooktop wins as we expect, I’ll be mounting it up in place of the propane cooktop. Stef and I rarely use more than one burner at a time, so I doubt we’ll miss the second burner.
This cooktop is rated at 1800 Watts. That’s actually a larger load than the air conditioner if we crank it all the way up, as I did in this testing. It’s still well within the capabilities of the Xantrex inverter, so I’m not worried there. That will leave just the Truma (which is staying, for sure) and refrigerator (hmmmm… maybe…) as consumers of propane on board. Propane capacity is the limiting factor on our winter camping now, so every little bit should help.
The other thing I really want to do is to rig up something to protect the second alternator. As you can see, it sits sort of low up front:
I’m a bit worried that I may pull into a parking space with one of those cement curbs in front of it and whack it. Either that, or run over a tire snake on the freeway or any number of careless scenarios that would have me damaging the very precious second alternator. As cool as Lance’s nose ring is, I think I may have to swap it out for something more substantial that hangs a bit lower.
I’m also not too crazy about the plastic splash guard under there. I do want something there to protect from spray and particularly salt in the winter, but I’m not sure that piece of plastic is it. I also wonder what the plastic is doing to airflow around that alternator. More research needed here.
Anyway – now you know what I know. The generator’s out, and we don’t miss it, so we met objective one. And now that I’ve written this post, I’m even further down the road on the “don’t think about it” objective. Thanks for reading!