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A few weeks ago at their dealer event in San Diego, Winnebago announced their Pure3 Energy Management System, which brings 48 volt lithium power to two new models, the Travato 59GL and 59KL.  Russ (Winnebago’s Product Manager) and Stef hatched a plan to take a quick holiday in the new rigs after the dealer event. Besides being a cool Travato meet-up with friends, we just couldn’t pass up the chance to participate in Winnebago’s prototype evaluation program for the new Pure3 Lithium system. The units were just completed in time for the show (and after the show they were scheduled for 8 more weeks of usage testing and real world analysis). Russ said Winnebago was intent on making sure that user experience would be a critical part of the prototype testing, so getting us in one coach and he and his wife Kathy in the other on the first week of testing, well that would surely be some great feedback for the design team at Winnebago.  Our plan was to start in San Diego, stop in Joshua Tree National Park, and then head up the California coast, and finally home to Utah.  We planned to do some “regular camping” at first, and some “bench testing” once we returned home.  But the life of a test pilot, it turns out, can be a bit unpredictable.

A few days into our test camp, we identified an issue with the second alternator belt that cut our trip short, and prevented us from completing our planned testing.

But remember: this is a good thing!  This is exactly why Winnebago wanted us testing the rig!  Based on our experience, they’ve identified the issue with the belt, and it won’t be affecting anyone else.  They’re also using our feedback to further dial in things like high-idle settings, autostart settings, inverter limits, and who knows what else.  We actually gave Winnebago about four pages of notes, so the production systems will be all that much better for everyone when they hit the roads.

So as you read, do bear in mind we were working with a prototype coach.  This isn’t a review of a production unit like you’d read in a trade magazine.  This prototype had not gone through Winnebago’s own usage testing yet.  But I think they knew that getting Stef and me (both very familiar with Travatos and lithium systems) into their prototype would be one of the best ways to get high quality feedback right away, giving them time to address any issues before production starts. With that understood, we’re here to tell you what we can, and what we learned from our experience.


OK.  So What Exactly Happened?

This is probably the first thing that people want to know, so I’ll start there.

The first thing to understand is that the second alternator in this rig – when the battery calls for it, is capable of throwing SIX THOUSAND WATTS at the battery.   That’s a good sized load, and turning that alternator can require quite a bit of torque.  So if the belt is not aligned properly, or if it’s not tensioned properly, or if it’s been stretched… any number of things could cause the belt to slip.  And if the belt slips, it can’t turn that big load, charging stops, the belt squeaks, etc. etc. etc.  And that’s precisely what happened in our case.

Everything was going well for the first three days.  But sometime into our fourth, the belt started slipping, and we weren’t getting any charge from the second alternator.  The temporary fix for this was really easy.  I simply unplugged a multi-pin connector and that shut off the second alternator.  After that, the second alternator was basically free-wheeling, which takes almost no power.  While we could still use most of the rig, this meant that we couldn’t use the alternator to charge the large lithium battery.

At this point, we could have limited our stay to full-service RV parks with shore power, but that wasn’t what we had planned.  We wanted to get off-grid with it!  Since we weren’t able to test the charging performance of the second alternator or auto-start, we just headed for home on day 5.

Those of you who follow our blog may recall that we also had a second alternator belt issue when we installed a lithium system in our RV, Lance.  But in that case, the belt cut through a coolant hose and dumped our radiator contents onto the highway – instantly disabling us.  This problem was nowhere near that catastrophic.  It didn’t require a tow truck.

We were talking to support people from both Winnebago and Volta all along the way, so we never felt unsafe, or abandoned.  They’ve since identified the issue as something unique to the GL prototype build due to a late-in-the-game alternator upgrade.  (The KL prototype, for example, didn’t have the issue.)  And they’ve obviously got all our feedback, so I think it’s pretty safe to say that this problem won’t be affecting anyone else.  (And speaking of everyone else, this is a good reminder to check your belts and hoses periodically. 🙂 )


How Are They Rating Battery Capacity?

They’re using watt-hours to rate the size of the battery, not amp-hours.  It’s not what people are used to, but this makes a lot more sense for a number of reasons.  I’ll give you two.

The first reason is because nobody rates the LOADS in terms of amps – or at least, not in everyday parlance.  Here’s an example:  How many amps does your hair dryer draw?  I’d bet you don’t know.  But you probably know how many watts your hair dryer uses.  Or if you personally don’t, I’d bet that someone in your house knows – and the number is likely plastered all over the device itself anyway.  So rating the battery in watt-hours makes more sense, because you can pretty quickly figure out capacities and loads.

The second reason to use watt-hours is nerdier… because two batteries with the same amp-hour capacity might not have the same amount of stored energy.  Meaning, a 100 amp-hour lithium battery at 14.4 volts has more stored energy than a 100 amp-hour lead acid battery at 12.6 volts.  Butt a Watt is a Watt is a Watt.  You can compare them directly without worrying about the chemistry of your battery and what the resting voltage is.

And now that you know that, it’s probably a good time to tell you that the battery pack in our test coach was only 2/3 the size of what will be delivered in the production Pure3 Travatos.  The batteries in the production coaches will contain an 8700 (useable) watt-hour battery.  Ours was less.

I want to commend the high road Winnebago is taking with their ratings here.  The battery is actually a 10,100 watt-hour battery pack.  Pretty much any company under the sun would want to use the bigger number in their marketing because; well, bigger is better when it comes to specs.  But Winnebago is publishing the **useable** watt-hour capacity of the battery.

You see, there’s a 10-15% (ish) reserve that the battery management system (BMS) will try to keep to avoid completely discharging the battery.  The battery is programmed to keep you from using those watt-hours.  Since you can’t use them, Winnebago is quoting the smaller, useable watt-hour number in their specs.  That’s pretty honest.


How Long Can It Run (insert something here)?

The fact that our test coach only had a 2/3 size battery was one big reason why we didn’t do any hard core “How long can I run X” kinds of tests.  The other big reason we didn’t do much of that is because the answer to those questions is always “it depends”.  If you want to know how long you could run the air conditioner, for example, it depends on

  • What’s the outside temperature?
  • What’s the humidity outside?
  • How cold do you have it set inside
  • Are you parked in the shade?
  • What else do you have running?
  • and so on and so on

But!  Since we’re rating the battery in watt-hours, there’s some simple rule of thumb math you can use to get an approximate duration for any appliance you might want to run.

Let’s say we want to run the air conditioner.  On this coach, that’s a Coleman Mach 10, and if you look it up, it says it runs at about 1410 watts.  Now, the battery is 8700 watt hours, and that’s all useable capacity.  So simply divide 1410 watts into 8700 watt-hours, and you’ll get 6.17 hours. (The units even work out correctly!)

But that calculation assumes a perfect world where there are no losses.  Since nothing is ever perfect, I’d personally downrate that by about 10% just to be on the safe side.  That leaves you with about 5.5 hours.  At the end of the 5.5 hours, either the system would shut down, or the auto-start would kick in and start charging the battery again if you had it enabled.

But that math assumes the AC runs the compressor all the time, which it hopefully doesn’t.  Once the air conditioner gets the rig to temperature, it should start cycling the compressor on and off.  When that happens, you’ll likely encounter something greater than 5.5 hours.

You can also use this approach to see how long you could run electric heat from the battery pack.  This is something we did test, briefly, and the Truma electric heat works the same off battery as it does on shore power.  There’s no difference to the end user.

On EL1 (for example), the Truma uses an 850 watt heating element.  So 850 into 8700 is about 10.2, and take another 10% off of that, and you get about 9.2 hours.  So, on EL1, I’d estimate you could run the Truma about 9.2 hours.  Subject to the same caveat that, once it got the rig to the right temperature, it would cycle on and off and you’d probably get more than 9.2 hours.

During our test-camp experience, temperatures were pretty mild, so we had little need for heat or air conditioning.  Regardless, we were able to verify the following:

  • We ran the air conditioner off of the inverter and battery pack for 15 minutes or so, until it got too cold. Operation was normal.
  • We ran the Truma on EL2 (about 1700 Watts AC) off of the inverter and battery pack for a half hour or so, and it worked just fine as well.
  • While we did not enable auto-start, we did observe the battery pack shutting itself down when the load dropped below the 10% neighborhood.


So What CAN You Tell Us About The Loads?

Determining exact loads in the coach was tough.  Winnebago has opted to go with a simple analog gauge for displaying the battery level.  This is a fantastic way to go for 99.9% of the population, but it made it difficult for me to know how much load any one item was drawing.  There was no ammeter available. (The BMS probably knows how many watts are going in or out, but it’s not talking.)  Since we called the testing off before I started hooking meters up to the rig, I don’t have a list of “this device uses this many amps”.  However, many of the devices and appliances in this rig were the same as the ones used in my previous 12 volt test.  You can see that post here.

Anecdotally, I can say that the “regular” loads in this coach are pretty small.  And here I’m talking about those things that are on most of the time, like the refrigerator, the propane leak detector… those kinds of things you may not even actively control most of the time.

As an example: once we decided to head home, we left an RV park with the battery at 90%.  We drove home over a day and a half, with no charging at all from any source.  When we got home, the battery was still at about 35%.  During that time, the fridge was always on, Stef and I each took a shower, we made a lot of coffee (about 10 minutes of microwave), and I worked and had the inverter on charging a laptop for several hours.  Plus, we ran our usual lights, phone charging, water pump, blah blah blah.

And remember – the battery bank we were using is only 2/3 what will be in the production coaches!  I think this is pretty good news on the battery capacity front.


How Was the Inverter?

I’ve previously mentioned that the inverter was adequate enough to run the air conditioner, microwave, and Truma electric heater.  We were also able to run the electric heat (Truma, on EL1) and the microwave at the same time.  We didn’t have any need for more during our test camp, so that’s as far as we got with multiple loads.  The short story is that the inverter does seem to be capable of providing the full 3600 watts of power that’s claimed.  And since it started the air conditioner, we know it can surge to even more than that.  My opinion is that the inverter is no more limiting than a 30 amp shore power supply.

I do want to describe how we use an inverter, in case any newcomers are confused as to what exactly its function is.  The inverter doesn’t produce any power.  It only consumes it, and changes it from one form to another.  The inverter is what takes the battery power, and changes it to what you might call “regular household current”.   So if you need 120 volt AC power, you’ve got it, any time you want it.

But if you don’t need that 120 volt AC power, there’s not much reason to leave the inverter on, because the inverter DOES, even at idle, produce a load.  Now it’s small, maybe just a couple amps, but it is still going to be drawing on the batteries, just by being on.  And remember, this is a 48 volt battery, so even 2 amps is a 100 watt load.

We have this same situation in our own coach, Lance.  As a best practice, we’ve gotten in the habit of just turning the inverter off if we’re not using it.  It’s one button in our coach, and it’s one button in this one, so it’s not hard, and it conserves power.


Charging from the Alternator

Before we disabled it, we learned that the second alternator requires a high-idle in order to charge the battery.  So when the vehicle autostarts, it will also kick it into high idle to initiate charging.  The battery will also be charged while driving down the road and the RPMs are up.  That second alternator is rated at six thousand watts, so if it’s running at speed, it could charge a fully depleted battery in about an hour and a half.  (That math works the same way for charging as it does for discharging.)  Our coach had a 2/3 size battery, and we observed about a 30% charge increase in 30 minutes of easy stop-and-go driving, which seems to track with expectations.

We informally tested to see how the alternator would charge the battery while also running loads.  We had the Truma heating on EL1, and were running the microwave periodically, and the battery was still charging while the engine high-idled.  Without an ammeter, it’s tough to say at exactly what rate the vehicle was charging, but we did see the needle move “up”, and we did not detect the engine getting bogged down.

But why the high idle?  I asked about this, and the feeling was, with the power required to spin up that second alternator, they didn’t want to be doing it at a lazy idle.  When I observed it, the charging seemed to kick in at about 1600 RPM, but that exact number may change.

They’re also thinking a lot about the “automobile” part of the RV.  The Volta folks told me about an additional feature that we didn’t get to test specifically.  Basically, when you’re really revving the engine – like climbing a mountain pass – the alternator will back off so you have all the power available to you when you really need it.  They take information from the vehicle’s CAN bus to determine that.


Charging from the Inverter/Charger

This works as you would expect.  The 3600 watt inverter is also a battery charger, and the vehicle charges while plugged in to shore power.  This is another area where they are still determining the final settings.

The battery charger here is powerful enough that if they just let it run free, you could trip a breaker if you plugged in to a 15 amp outlet.  People who plugged in to prep for a trip could be pretty disappointed if this happened.  There are two places where the charging can be limited: via the control panel or via a switch on the back of the panel.   Winnebago and Volta are still working to determine the best way to set these to allow for full-speed charging when you have 30 amps, and to not trip a breaker when you don’t.

You’ll want to keep in mind that the inverter is *upstream* of the Precision Circuits Power Control Center.  So setting a limit there does not affect the settings on the inverter/charger.  Also, I noticed that the charge going to the batteries would drop as you called for more load in the coach.  In other words, while plugged in, the coach loads seemed to take priority over battery charging, while still observing the overall limit.  This is what you want.

In our use, I had flipped the switch on the back to allow for 30 Amp charging (yes, I was dismantling a borrowed rig), but did not change settings on the control panel.  This seemed to keep the charging limited to 15 amps.  Even so, we were able to fully charge a nearly-fully-depleted battery from about 5% to over 90% overnight while running other loads.  (It probably charged before that but we were asleep.)


Charging from Solar

The solar charging on our test coach was not working.  We only cared about this after the alternator stopped charging.  But under normal circumstances, you might not notice solar power at all.  Here’s why:

The rig had 200 watts of panels on the top.  200 watts of solar, on the equator, on the equinox, on a cloudless day would fully charge the big battery in over 43 hours of direct sun.  That could take a week or two depending on the weather.

But remember, the alternator does the same job in AN HOUR AND A HALF.  RAIN OR SHINE.  DAY OR NIGHT.  That’s literally over 30 times faster than solar.  So basically, compared to the size of the battery and the size of the second alternator, solar charging starts to look kind of silly.

Consider also that Class B owners (at least, the ones we know) rarely stay in one place for more than a few days without moving anyway.  That mobility is one of the main draws of a Class B in the first place.  So as soon as you turn on the engine to go somewhere, you’ve dwarfed any solar charging in the first few minutes.  So under normal circumstances, we’d probably not even notice solar.  Others who use their rigs differently might find it more useful.

Probably the best use for the solar on this rig would be just to keep the battery topped off while in storage.  You could leave the big button on, and solar would keep you at or close to full.  (Or you could store it with the button off.)


Cold Weather?

We didn’t encounter any cold weather on our trip, and I don’t have my own climate test chamber, so what I’m going to relay here is information I gathered from talking to Winnebago and Volta.

The big deal is that lithium batteries don’t like to be charged while they’re freezing.  It’s really bad for them.  So on this battery pack, charging is disabled if the battery temperature is below freezing – or actually a little above, like 40 degrees or so.  The BMS does this all on its own.  There’s nothing for the end user to do.

Now, obviously, you don’t want that to happen while you’re using the rig, so to keep the battery warm, when the battery temperature drops, the rig blows cabin air into the insulated battery box to keep it warm.  That’s the same air you’re already heating to keep yourself warm, so it kind of just makes the battery box an extension of the cabin.  This all happens automatically, so once you’re up and running, there’s nothing more to do.

The follow on questions to that are; what do you do about storage?  And how do you get the rig from cold storage UP TO running temperatures?  Here’s what I learned:

  • According to Volta, the battery is good for storage at minus twenty degrees Celsius (-4 Fahrenheit).
  • It can handle occasional dips, such as overnights, down to minus 30 Celsius (-22 Fahrenheit).
  • But that’s storage, you don’t want to use the battery at those temperatures. So the BMS cuts off even DIScharging the battery at -10 Celsius (14 degrees Fahrenheit).

Those are all internal battery temperatures, not outdoor temps.  So, if you’ve got the rig stored, and the internal temperature of the battery is anywhere over 14 degrees Fahrenheit, then all you do to get going is plug in the rig, turn on the heater, and wait until things warm up.

But if the internal battery temperature is below 14 degrees Fahrenheit, then you would have to warm it up to at least that using some external method – and the Volta guy suggested a space heater right under the battery box.  And then turn on the heater and warm up the rig.

Excessive heat can also take a toll on the batteries, so as a corollary to cold weather operation, the same system works for hot temperatures as well.  We obviously didn’t test this in March, but if the battery gets too hot, it’s supposed to pump COOLER air from the cabin into the battery box to regulate things.


What Is Our Opinion of the Battery Location?

When the Travato first came out several years ago, people were concerned about the generator hanging underneath.  The ProMaster is a low-slung vehicle, and the generator just looked like it was in peril.  Well, time marched on, and – with a few exceptions – the generator placement hasn’t turned out to be that much of an issue.  The (expensive) lithium battery sits in pretty much the same place, so people are again questioning the placement.  I went out with a tape measure, and here’s what I found.

  • The bottom of our all-wheel-drive Subaru Impreza is less than 6 inches off the ground.
  • The bottom of the battery box, sitting in our driveway, was approximately 6.25 inches off the ground.
  • The bottom of the rear axle, for comparison, 7 inches off the ground.

So, with just ¾ inch of lift in the back, you will get the battery box at or above the level of the rear axle.  It seems many owners install something like Sumo Springs, which raise the rear axle about an inch.  Something like that would get the battery box over the rear axle.  But even without that, the Travato GL has better ground clearance than our Subaru (which seems weird, but I promise it’s true).

Bottom line: Me, I wouldn’t worry about the battery location.


Other Things We Noticed

The first one of these had to do with the DC to DC Converter.  That’s a device that takes the 48 volt power from the battery bank, and steps it down to the 12 volt power (14.4 volts in this case) that most RV stuff runs on.

It makes a little noise.  If it was just me that heard it, I might dismiss it, because small noises bother me.  But Stef heard it too, so it’s a thing.  It’s kind of a little hum or buzz, and it’s pretty constant.

We’ve provided our feedback on this to Winnebago, and they know they’ve got to do something about the noise from that component.  The DC to DC converter is in the same enclosure as the inverter/charger, which also makes noise.  So whatever they come up with for a solution will likely help with both of those components.

The next thing we noticed – and LOVED – were the dual paned acrylic windows.  We liked these more than I expected.  There was the unobstructed view, and the easy operation.  We were familiar with these as we have one of these windows in Lance.  But most of all what we noticed was the SOUND!  They provide a greater degree of sound isolation than the standard glass windows you may be used to.  You’ll really appreciate these if you ever have to overnight at a Flying J.  Trust us.

We also noticed that the water tank was different than the standard Travato G.  First, it’s a bit smaller.  This is because the water tank has been moved underneath the rig, and into an insulated box.  (And I actually felt around in there up through the drain hole and verified there is insulation in there.)  But since it’s moved, and some of the space is taken up by insulation now, the capacity is a bit smaller than a “regular” Travato G:  18 gallons in this one versus 21 gallons in a regular G.

Also, since the tank has moved, there’s no gravity fill.  This meant we couldn’t do something that we’re used to doing in Lance, and that’s filling through the top of the tank.

We did use the new cab blinds on a daily basis while we were in the rig.  Overall, we found the operation to be just as quick as we showed in our videos – even a bit quicker once you get the hang of it.  We did run the defroster in the mornings, and the cab blinds did not seem to affect its operation.   The darkening from the cab blinds and the new cassette blinds on the windows was sufficient to allow us to sleep in much longer than we really should have been.



So there you have it.  Besides learning a lot about the Pure3 Energy Management System in the new Travato models, we also had a blast trying one out!  We’re confident that our experience (and yes, even our problems) will be useful to Winnebago in making the new GL and KL model Travatos even better.

Despite the nits, the capabilities of the system seemed to live up to what the marketing claims.  And they totally nailed the easy-to-use aspect, so if you read this and your eyes rolled into the back of your head – don’t worry!  You don’t really need to know much of any of this in order to use the Pure3 system.  Because at the end of the day, it’s not supposed to be about temperature limits and watt-hours… it’s supposed to be about how much fun you can have with the capability.

See you on the road!