Thinking about a Bus/RV

[Ted]

Random thought of the day - I'd rather take a ride in your bus than in either of the two current US spacecraft, let alone any from any other country.

I appreciate the vote of confidence.

Re the air leaks, it would be cool if it were possible to fill the air systems up with orange smoke and fix all the leaks at once. And if anyone working at a spacecraft company uses that idea, I expect a coupon for a steak dinner at my choice of eatery.

I'd imagine you could do something like that. I have a couple of known air leaks that I just haven't gotten around to, which are on the auxiliary side. When I first got the bus, it leaked fast enough that it wouldn't pass a DOT check if I ever got stopped. Of course, I don't think RVs normally get that treatment, but that rule is there for a reason.

Now, while it's not the best sealed system in the world, I've had it in the shop with the air suspension at max for a month. The right rear will bleed down after a few days like this, but the left rear and the front are still aired up. For all I know, these couple of air leaks I've found and am addressing may fix that - we'll see. The front and rear air tanks will hold air overnight, going down from 120 PSI to about 75-80. I've seen them go a few days before emptying altogether.

With an air system, "some seepage is normal". But ideally my goal is that the air suspension won't bleed down, at least not quickly enough to require regular adjustments.

All this talk of the air system reminds me. Another thing I did was replace the air dryer filter. To do that, I had to empty the air system (which I'd filled up to raise that one corner that goes down so I could put my jack stands under the bus). I then needed to empty the air out to remove the air dryer filter, so I drained several of the tanks (which was due anyway). The "wet tank", which is the tank directly off the air compressor, had basically no liquid in it at all. Previously (before replacing the air compressor) it would have an oily-watery gunk in it. I already knew the air compressor was bad and needed replaced, but it's nice to see that cleared things up. I'm pretty sure that air dryer cartridge had gotten clogged up after the only 10,000 miles or so it had on it because of that, so I expect I'll see the air system fill up quicker.

 

[Half Fast]

Okay, Ted - enough of this stuff. You have more important matters to consider. When's the RX7 going to be entered in a race?

 

[Ted]

Okay, Ted - enough of this stuff. You have more important matters to consider. When's the RX7 going to be entered in a race?

This is probably our last RV trip of the year, unless we do something over Christmas. I don’t have any major/required projects on it left - just a number of little items that are varying degrees of deferrable depending on how much they bug me. Of course, we’ll see what happens on this trip - we usually find something to add to the list. The biggest thing is I want to replace the rooftop ACs with quieter and more powerful units, and that’s not a big project.

So, the plan this fall is to get my wrenching time focused on progress on the Cobra and RX-7.

When I look through the big items I did on the last bus, they either don’t apply to this one or are things I don’t want. For example, I’ve decided I don’t care about adding solar on this bus. The interior doesn’t require a redo. I’d like to do electric fans, but seeing as this one has a clutched fan and manages its temperatures so well it’s not worth it to the same degree as it was on the last bus. This is just a better product all around, so it’s been more of that first year “catch up” than having to re-engineer the dumpster fire from scratch.

 

[Ted]

I got the bus out for a test drive this afternoon before we head up to 6Y9. Despite not having done anything that should've impacted horsepower, it does feel like it was a bit more responsive and peppy than I recall. Given that it was 95F out, that really doesn't make much sense. The only thing that I can think of is I was driving it without the Jeep attached and it's fairly low on fresh water (and empty on grey/black tanks).

But, everything worked well, and the sound deadening I did for the generator inlet air is definitely working. The generator was noticeably quieter than before, which is always a good thing.

While airing up the bus from the tank I do think I found another air leak I should look into. Once again, something that I'm not worried about for the trip, but something I've added to the list. Whack-a-mole.

 

[Matthew]

In my pre-retirement days the products we built used the push-fit air connectors, it sounds like what you have. Leaks, when the hoses were properly inserted, didn’t seem to be a problem. But with age the hoses would lose some flexibility and not seal well, or poor routing would pull on the hoses. I’d see 20yr old equipment with tight air connections and brand new with leaks, though, so there isn’t always a correlation.

My favorite problem was the guys that installed the air lines were pretty much left on their own. So they routed however they felt was best and rarely labeled the hose ends. So we always spent at least a day swapping hoses until things operated properly.

I hope your bus is plumbed a little better.

 

[Ted]

In my pre-retirement days the products we built used the push-fit air connectors, it sounds like what you have. Leaks, when the hoses were properly inserted, didn’t seem to be a problem. But with age the hoses would lose some flexibility and not seal well, or poor routing would pull on the hoses. I’d see 20yr old equipment with tight air connections and brand new with leaks, though, so there isn’t always a correlation.

My favorite problem was the guys that installed the air lines were pretty much left on their own. So they routed however they felt was best and rarely labeled the hose ends. So we always spent at least a day swapping hoses until things operated properly.

I hope your bus is plumbed a little better.

For being a 23 year old bus, really the leaks on it aren't terrible. But there are some folks with them tight enough that the things will hold air for weeks at a time (as in, down to the tanks holding air - not just the airbags). I'm not there, and that part is ok. But audible leaks I want to make sure I avoid at any point.

Overall, the plumbing is pretty good on this bus. Prevost did a good job.

 

[Ted]

We got back a bit ago from our trip to 6Y9 for the Labor Day fly-in. The round trip is about 1600 miles, putting us over 111k on the bus total, and something around 14-15k since we bought it. Something that's also special (or at least of note) is that when we got home from 6Y9 last year I had a feeling that was going to be the last trip we took in that RV. And sure enough, it was. On the way home we had attempted to go look at a Prevost in person but that fell through. We basically started looking at Prevosts immediately upon getting home from 6Y9 last year (go back to page 47 for more details) and that turned into purchasing this one. On Page 49 (and mid November of last year) I took it home. So figure a bit under 10 months, that's a pretty good amount of miles.

This bus drove wonderfully when I bought it. Now, it only drives better, and is a real joy. Of course, it's complicated with a lot of systems and things break.

The last few times I'd taken it out, the bedroom slide seemed to have issues with wanting to go out and back in. The slide itself was fine, the issues were with the computer systems on it. This is a fairly complicated slide system. Unplugging the slide motor controller from the main slide controller and plugging it back in had worked previously. This time, that didn't work. So, we went the trip without the bedroom slide out - a fairly minor inconvenience as the bedroom is still very usable with the slide in - and I'll have to dig into that further. With some diagnostics I was able to determine the problem does seem to be within the rear slide master controller, as if I swapped motor controllers, whichever motor controller was plugged into the master controller for the rear was throwing an error code. That's a bit annoying, but I'll figure it out.

I left knowing I had a few fittings that leaked air, and I'll need to work on those now that I'm back home (and search for more). The system was bleeding down air fairly quickly once the engine was shut off, definitely faster than on previous trips. So I'll start with the known leaks and go from there, and try to get this sealed up better.

But perhaps the thing I was the most interested in playing with was the shunt that a friend gave me, which would let me monitor the batteries and their health. And I definitely learned a lot there.

The Prevost came with lithium batteries from Lion Energy (a company I'd never heard of previously, and haven't seen mentioned since). They're 12V, 105aH batteries, but since the system is 24V they're run with 2 batteries in series, and 4 sets of those in parallel. Running on batteries we've found that it seems like the batteries have run out faster than would be expected. Basically expect to have to run the generator daily for some period of time.

Friday evening with the shunt reporting 75% capacity on the batteries (based on the amps/watts it measures going in and out the batteries had dropped to 21V and everything shut off. Well that's weird. Got the generator fired back up, charged up to 100% after a bit, tried again. By Saturday evening they'd gotten down to 50%, and being somewhat worried about how much capacity they would have overnight, I ran the generator a bit to get them up to 60%, and then let it see how it did overnight. On Sunday I managed to get them down to about 20% before the voltage started to get lower (around 24V), around the time we were ready to leave.

A friend of mine who has his house set up with solar and batteries said he suspected that some of the batteries might've gotten a low enough voltage to engage the low voltage dropout on the BMS, which can happen with high transient currents. We did have that happening at some point, and so that seems likely. I'm not sure how much capacity is really to be expected from these lithiums (with lead acids you don't get the rated capacity, and you don't want to drain them that low with any regularity) but getting down to 20% or so of rated before things start to drop off seems more reasonable.

I also learned some system items. For example, I had thought that this bus didn't have an electric water heater, only a diesel fired one. Nope, turns out it DOES have an electric water heater, and that it pulls 70A from the batteries. This is a confusing setup. The diesel water heater has a toggle switch that goes between "Engine Heat", "Off", and "System Heat" (the latter being diesel). Then there is a separate "Water Heater" toggle switch (which, confusingly, has a "Pilot Out" indicator below it). That's what flips the electric water heater on. Conveniently, you can turn it on with the diesel heater to get the water hot faster. But, I have also been turning that on with batteries. As you can imagine, a 70A drain on batteries with a claimed 420aH capacity can hurt things quite a bit. The dynamic voltage drop with that and other large loads (think microwave/toaster) at the same time may have caused that issue with running out of power at 75% power.

I was also able to watch the power that certain things consumed. It seems like just sitting the bus consumes around 10A in general. So if you figure 420Ah total, that means that in 2 days with nothing else the bus will have run out of power. I'd like to look at getting that sitting current down if I can. I'm thinking it's probably a combination of things like the TVs taking power, but there may be some other systems that there's nothing I can do much about. I also found that the toaster takes a lot less than I thought (only about 10A), and some of the accent lights that were put in take a lot of power (15A).

I was also able to adjust some of the settings on the inverters to get better charging optimization on the batteries, where they'll now take about 120 amps (so full charging form empty in under 4 hours) whereas before it was around 50A.

My takeaway from this is more or less what I thought in general, which is that I need more battery power if I want to be able to boondock with the bus (unless I add solar, which I don't want to do on this bus). Doubling the battery capacity would be a good number, tripling would be even better.

We aren't planning another RV trip for a while, so I want to look at attacking these air leaks while I consider what else I want to work on, and wrench on some other things.

 

[CJones]

The Prevost came with lithium batteries from Lion Energy (a company I'd never heard of previously, and haven't seen mentioned since). They're 12V, 105aH batteries, but since the system is 24V they're run with 2 batteries in series, and 4 sets of those in parallel. Running on batteries we've found that it seems like the batteries have run out faster than would be expected. Basically expect to have to run the generator daily for some period of time.

There is a dude on YT - Red Poppy Ranch - that I *THINK* is using a Lion Energy off-grid setup. I used to follow him quite a bit, but he's gotten a little wonky with his projects lately, so I'm not as up to speed on his goings-on. I do know that when he originally built his house several years ago, he thought he was going to outsmart 'the man' and tried to set up full off-grid solar battery system for his house (and associated 4-person family) using regular 12V deep cycle batteries. Well, that didn't last long and he went with some off-the-shelf 'better' batteries, but I think I remember a couple of years ago that Lion Energy pseudo-sponsored him by setting him up with a 'real' off-grid battery system and controllers.

 

[Ted]

There is a dude on YT - Red Poppy Ranch - that I *THINK* is using a Lion Energy off-grid setup. I used to follow him quite a bit, but he's gotten a little wonky with his projects lately, so I'm not as up to speed on his goings-on. I do know that when he originally built his house several years ago, he thought he was going to outsmart 'the man' and tried to set up full off-grid solar battery system for his house (and associated 4-person family) using regular 12V deep cycle batteries. Well, that didn't last long and he went with some off-the-shelf 'better' batteries, but I think I remember a couple of years ago that Lion Energy pseudo-sponsored him by setting him up with a 'real' off-grid battery system and controllers.

I'm sure that I'm not the only person that has them, or the company wouldn't be able to be in business still. But it also seems that some of the "bigger name" lithium battery companies that were real hot during the Covid frenzy of making solar off grid everything have been less heard of lately, and prices are overall dropping significantly.

Annoyingly, these batteries are supposed to be Bluetooth enabled and I haven't managed to get the app to work to connect to them (not sure whether this is a me problem or a battery problem), so I don't know what the BMSs in those batteries are thinking or doing. And with 8 of them and all running in a 2 series arrangement of some sort, that means any one of those 8 could hit the low voltage threshold and then drop out, which would remove 1/4 of the battery capacity without an indication of an issue. I'm not sure which of the batteries in a series arrangement is more likely to get a more significant voltage drop, but to add into the confusion of the system, there's also a 12V circuit that pulls off of the "lower" batteries as some of the circuits in there are 12V. That probably means those lower batteries get a disproportionate draw vs. the "higher" ones, although there is also a balancing circuit which is supposed to even that out.

I'm looking at a copule of DIY battery options, although if I could get sponsored by a company to get some additional batteries to put in, that would be good as well. However when I run the numbers, if I'm paying for it, the commercial batteries are hard to justify unless I can get some screaming deals.

Some of the various other interactions between the engine charging the batteries and the generator charging the batteries I need to understand better. When I started the bus in Sidnaw Friday when it was time to leave and the house batteries were at 24V, the alternator was not seeming to charge the house batteries at all. I started the generator which got them going up to about 66% capacity, and then things stopped from there. We stopped for dinner (engine off) and when we came back to the bus the batteries were at 100%. I'm not sure if the generator started kicking in more once the engine was off or if the shunt did some kind of realization that it was wrong and reset itself. Without knowing what the battery BMSs think, that all gets hard to tell.

But again, the big takeaway is that I need to either plan to 1) run the generator daily (more or less what we'd figured already) or 2) add more batteries if I want to be able to boondock for a weekend in nice weather. Option 1 is easy, and it doesn't take all that much running to get the batteries back up to a reasonable amount at whatever time is convenient. Option 2 is nicer, but has a cost associated, albeit with very easy install.

So, more things to think about.

 

[charheep]

Are you not considering adding any solar power?

 

[Ted]

Are you not considering adding any solar power?

I have considered it, and it's something I might do at some point, but not immediately. There are downsides. Solar is a LOT of work. I definitely did it on the higher effort side last time on the old bus, but even if I did fewer larger panels (as opposed to 12x 100W panels) this would still be a high effort on this bus. I could go with less power, but honestly if I did solar and wanted it to be sufficient (an undersized array doesn't really help me much) and so I would likely, if anything, go bigger. There's also not an immediately obvious pathway I've been able to find for running wires from the roof into the battery bay. Not that it can't be done - it has been - but again, more work.

When I did the solar setup on the old bus, I think I was in it for a total of something around $2k. Adding $2k-ish worth of batteries would at least double my storage capacity. If we stayed in one place for a long time, then solar would be the obvious choice if we were trying to avoid running the generator. But that's not us, at least for now, so the batteries seem to be a more logical choice.

Or, just run the generator for a bit.

 

[Albany Tom]

I share your frustration with bluetooth in a commercial power management system. I know it's low power and unlicensed and simple, but still kind of a hack to me. Hope you get that sorted out, because as you know and mentioned, having a good battery management system is more important for lithium than lead acid.

From my sideline view, though, for extended stays without generator, I'd think there's some work that could be done to reduce your parasitic battery drain when on battery. Not just the 70A water heater, but that's an indication to me that the whole system might be eating away a lot of power.

I could be completely wrong, though, and maybe you're using dc to 120 V inverters or AC or DC fridge and you really need to run the generator a lot. I'm basing a lot of my assumptions on a previous life, where we would run a 27' trailer over a weekend on a 12V 110AH battery...but that was just minimal DC lighting and water pump, and a limited use of a 12V/propane furnace. Water heater and fridge were propane. Anyway, all of your battery and systems management stuff, if designed right, should be less than 5-10W draw by my guestimation. Microcontrollers and LCD displays sip power.

 

[Ted]

I share your frustration with bluetooth in a commercial power management system. I know it's low power and unlicensed and simple, but still kind of a hack to me. Hope you get that sorted out, because as you know and mentioned, having a good battery management system is more important for lithium than lead acid.

From my sideline view, though, for extended stays without generator, I'd think there's some work that could be done to reduce your parasitic battery drain when on battery. Not just the 70A water heater, but that's an indication to me that the whole system might be eating away a lot of power.

I could be completely wrong, though, and maybe you're using dc to 120 V inverters or AC or DC fridge and you really need to run the generator a lot. I'm basing a lot of my assumptions on a previous life, where we would run a 27' trailer over a weekend on a 12V 110AH battery...but that was just minimal DC lighting and water pump, and a limited use of a 12V/propane furnace. Water heater and fridge were propane. Anyway, all of your battery and systems management stuff, if designed right, should be less than 5-10W draw by my guestimation. Microcontrollers and LCD displays sip power.

My issue is less with Bluetooth so much as that it doesn't work in this case. If I had to pair to all 8 batteries that would be cumbersome, but it's something I could manage. The issue is I can't even seem to pair with one battery. Maybe there's something I'm doing wrong, and I need to put more effort into it.

To your other point, this bus will never be as low current draw as your trailer was. There are a lot of systems, and a lot of electric consumption. The water heater is an easy one to improve since it does have a diesel fired heater, and I now know how to use it vs. the electric heater. This is a good thing since it lets me pick and choose (with the generator on or plugged in to full hook-ups, I'd much rather let the electric work for free). But the fridge is a residential electric one, there are 3 TVs with 2 DVD players and sound system/media boxes, the cooking is 100% electric (cooktop, microwave, toaster), the toilet is a macerating electric unit, dual water pumps, the TVs have nice sound systems (including powered subwoofers). Then don't forget charging iPhones and other digital devices/accessories. Higher current draw is a fact of life with this bus. Minimizing it is possible, eliminating it is not.

I just put the bus back away after washing the front and rear of it to get the bugs off as well as some residual oil residue (which I think is leftover from my oil leak due to a poorly installed valve cover gasket). The bus has been sitting outside since Monday afternoon, so figure close to 40 hours of just sitting, minimal electric use, no devices charging, etc. the batteries were down to 59%, which is pretty good. It's been a fairly steadyish 5A draw off the batteries, the 10A is probably when the fridge is actively cooling and/or caused by various other devices plugged in, lights on, things like that.

But, I can say fairly certainly at this point that the engine is not charging the house batteries after several attempts. This is a big deal, and really explains a lot of why we show up someplace after traveling and the batteries don't seem to last long. In the summer we have the generator running while driving to power the AC units. In the fall/winter/spring, we do not have that. So, this is something I need to figure out the root cause of and address. Given some of the other dumb things that these people did when we bought the RV, I wonder if they simply disconnected the ability for the engine to charge the house batteries given the lithium upgrade or something of that sort. This is a common thing you "should do" (which I disagree with) because lithiums will just take power as fast as the alternator can feed it in most cases, and people say it will damage the alternator. I haven't found that on other attempts. So, I need to fix that.

 

[Albany Tom]

You absolutely have an impressive and complex set of systems. Re the bluetooth, if you haven't already I'd see if you can contact the manufacturer and see how they recommend pairing multiple sets of batteries. I could see them interfering with each other if the pairing isn't done some specific way. Industrial/commercial setups I've indirectly worked with have all been hardwired copper or fiber ethernet.

Re the charging, I absolutely can see that being annoying. Again about 2 orders of magnitude different, but even in the travel trailer setups it was common to not try to charge the house battery specifically because of fear of taking down the tow vehicles 12v system. For your RV, though, I agree it should be possible to throttle that with the charge controllers to set a draw level that won't overload the RV's alternator(s).

But that brings me back to the parasitic load. I'm sure what you have is within normal spec, and I get that the stove and fridge are your primary draws. But 5A, to me, still seems a lot not counting the fridge load. I'd be tempted to power down the fridge and go circuit by circuit to figure out what those draws are. If not to increase your battery run time, to increase the amount of current available for charging while driving. In the grand scheme of things, maybe not worth the effort...if you can charge at 50A or whatever, 5A is in the noise, but it would bug me. Kinda like air leaks that wouldn't bother some people bug other people who want it to be better. And don't read any of this as being critical - you put WAY more into that RV than anyone I've ever encountered, and it shows.

 

[Ted]

I do agree that the 5A parasitic load seems relatively high. I suppose that’s roughly 1-1.5A at 120V, and I’d had the same thought to go through and power down circuits one by one to see what I could reduce.

The good part is, now I’ve got some baselines to work with. People say the Trace inverters are the best, but I don’t like that their current measurements are all at the 120VAC level, rather than the 24VDC where the batteries are.

I’ll keep plugging away at it.

 

[Mikey52]

Depending on how it's wired. Do you have a 24 volt charger, or does it just use AC.

 

[Ted]

Depending on how it's wired. Do you have a 24 volt charger, or does it just use AC.

The alternator (which is 24V, not sure what it charges at) is supposed to charge the chassis and house batteries.

The inverter measures the house battery voltage but its amp readings are all on AC.