Thinking about a Bus/RV

[Ted]

I feel like this is the perfect chance to mold up a P-51 belly scoop under that bay . . .

You realize that bay is also directly in the path of crap coming up off the rear tires, right?

 

[MauleSkinner]

I feel like this is the perfect chance to mold up a P-51 belly scoop under that bay . . .

Do it right and it could produce thrust like it did on the P-51.

 

[Ted]

Do it right and it could produce thrust like it did on the P-51.

That cooling fan I removed was certainly big enough to produce thrust...

 

[SoonerAviator]

You realize that bay is also directly in the path of crap coming up off the rear tires, right?

That's what mud flaps are for!

 

[Ted]

I've done a bit more thinking on this, and I think I have an idea in place as far as the controller mounting and wiring.

The solar controller has some mounting requirements that are challenging to meet in the bus. Even on a 40' bus with lots of underbay storage, we use it pretty fully. And, this unit will produce a good sum of heat.

So, I'm going to mount it here (just mounted off the floor) which is in the rear most bay:

This doesn't meet the distance requirements on top and bottom, but I think it's a good location, and I have plans.

I'm going to add cooling fans repurposed from servers behind it (the back of the unit is an aluminum heat sink) which will add forced air flow to it, and that should take care of cooling. I'll add a hole on the other side to provide an airflow source, and that should keep air flowing freely. The fans will be connected to a thermostatic switch which will turn them on when the controller reaches a certain temperature (temperature TBD) and should address the cooling issues just fine.

What I think this also will do is simplify the wiring. The back of the bus has about a 6" cavity where wires can pass through without going through the interior, and that should make it easier to wire from the roof.

At least, it sounds like a good idea...

 

[Albany Tom]

I like it! I bet the distances are conservative, based on the device being a fire hazard if it has an internal melt-down. With the walls around it being metal (it appears) I don't see it being an issue. Looking at that pic, I think my only concern would be flooding if water can get into the compartment.

 

[Ted]

They also don't have any requirements for forced cooling, and they don't specify what "good ventilation" is. So I'd agree the numbers are probably conservative. However that bay is plastic/fiberglass, so there is a potential material concern there. The battery bay is metal, so that's theoretically better.

I've been thinking about and looking at lithium batteries more. The size and weight seem to be the big things that are appealing, size especially. With two 400AH lithium batteries (so 800AH) I'd essentially be doubling what I have already. According to my friends who run lithium (and what I've read) the real benefit is that you can discharge lithium a lot further before needing to recharge, which is good for how we use it since that may likely happen.

I still want/need to get the solar hooked up first, and I want to run a trip or two with it before buying batteries. But I think I'm getting it figured. Need to get some time on the roof to put it all together.

 

[jsstevens]

If you're going to use the fans to force air into the back of the unit, put them at the bottom. If you're going to suck air out, raise the unit as far as you can (to allow airflow in at the bottom) and put the fans at the top (which should have the advantage of less crud getting splashed into the fans). I'm probably telling you stuff you know, but just in case. The key is air exchange over the heat sinks, not just air movement. So give thought to how the air will flow and always remember hot air rises so the tendency will be for the air coming off the heat sinks to rise.

Sorry if I'm being Captain Obvious here, but I've seen some really bad result from poor cooling for electronics-including a power supply that unsoldered it's own diodes from heat once.

John

 

[Ted]

I agree with your statements, Captain.

I've got a few ideas in place, once the fans that my friend is giving me show up I'll work on that implementation. But I also need to get the panels drilled down to the roof.

 

[tmyers]

How are you attaching your panels, I have been researching this as well

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[Ted]

How are you attaching your panels, I have been researching this as well

I'm going to be using rivnuts to hold them in place, at least that's this morning's plan. Originally I was going to use the self tapping screws they provided with the brackets, but those stripped out easily. So, rivnuts it is.

And if that doesn't work, I'll try something else.

 

[jsstevens]

You could always epoxy a sheet of 1/8” steel to the roof and drill and tap.

Come to me for over-engineered, impracticable solutions anytime.

 

[MauleSkinner]

Come to me for over-engineered, impracticable solutions anytime.

I built a captain’s bed for my daughter. As I was taking it apart for her most recent move, I noted how overbuilt it was, a talent that I got from my grandfather.

 

[tmyers]

There is a video out there for well nuts, wouldn't a rivenut just crush the luan?

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[Mxfarm]

I built a captain’s bed for my daughter. As I was taking it apart for her most recent move, I noted how overbuilt it was, a talent that I got from my grandfather.

a skill that unfortunately is evaporating

 

[Ted]

That’s a good idea, Tim. I may try a couple of rivnuts and see how those work, but those well nuts might be a better option for this application.

 

[tmyers]

That’s a good idea, Tim. I may try a couple of rivnuts and see how those work, but those well nuts might be a better option for this application.

a skill that unfortunately is evaporating

I watched two videos, the first one shows how one you tuber used a channel system to mount his solar panels. This would allow for easy removal / replacement, the second shows how a well nut reacts to the luan board. I think I want to attach the channel using the well nuts and then the panels to the channel. I do not like the glue or tape option because at some point I may need to remove it and with tape or glue you are counting on TPO, EPDM, or Filon to withstand the uplift from 70 MPH driving. Call me a worry wart, but I like mechanical fastening, and wood screws into 1/4" luan won't provide much resistance. The downside to the Well Nuts is the size of the hole that needs to be drilled and making sure you don't drill into any wiring. Thoughts

Actually after watching all of Tito's video I am less fearful of the HD tape he used, however when he lifted on it either the Filon or the whole roof moved, which would also happen with the well nuts

 

[MauleSkinner]

I think I want to attach the channel using the well nuts and then the panels to the channel.

I think attaching to a thin substrate like luan would make the attach fittings as important as the hardware…using some sort of rail or channel system would require a lot more force to pull the fasteners loose, as you’d have to pull them all at once. Individual brackets with one or two fasteners can pull a lot easier.

whatever the fastener system (@Ted , please post some pictures of what you do), I’d be a lot more comfortable with rails/channels than smaller brackets.

Of course, 1/2” through bolts all the way down to the chassis frame would be best.

 

[Ted]

Of course, 1/2” through bolts all the way down to the chassis frame would be best.

That… might be excessive. Even for me.

 

[Spring Ford]

I was wondering if leaving an air gap under the solar panels might significantly reduce the solar heating received by the RV? Like on the old Land Rover Safari which had a raised separated roof thingy.

 

[Ted]

I was wondering if leaving an air gap under the solar panels might significantly reduce the solar heating received by the RV? Like on the old Land Rover Safari which had a raised separated roof thingy.

Yes, the panels are off the roof by a couple of inches. This is one of the reasons I wanted to do the solar. It should help with interior comfort and cooling.

 

[Ted]

I watched two videos, the first one shows how one you tuber used a channel system to mount his solar panels. This would allow for easy removal / replacement, the second shows how a well nut reacts to the luan board. I think I want to attach the channel using the well nuts and then the panels to the channel. I do not like the glue or tape option because at some point I may need to remove it and with tape or glue you are counting on TPO, EPDM, or Filon to withstand the uplift from 70 MPH driving. Call me a worry wart, but I like mechanical fastening, and wood screws into 1/4" luan won't provide much resistance. The downside to the Well Nuts is the size of the hole that needs to be drilled and making sure you don't drill into any wiring. Thoughts

Actually after watching all of Tito's video I am less fearful of the HD tape he used, however when he lifted on it either the Filon or the whole roof moved, which would also happen with the well nuts

There's definitely more than one way to skin the cat, and I'll also be the first one to admit I'm not sure which one is best.

I've used VHB tape in the RV, and I've had mixed results with it. I've used it in some applications and it's worked well. In some cases the bond seems to not last, and in others it bonds to the paint, and then if the paint comes off, then the parts with it. We've tried using it to hold a small DVD player upsidedown in our RV bedroom, and it has not worked at all. I'm not sure I'd trust it to hold solar panels on the roof at highway speeds, at least with channeling that has all those holes in it. Water will pool in them and that's also not a great thing. Really, I just see more problems with that mounting solution the way he's executed it. But, I also still think it'll probably be fine.

One of the things I liked with using the 12x 100W panels is that I'm still using connection points for each panel, so there's a much smaller area it has to support (read: less force that the fasteners have to absorb), especially without support in the middle.

It is a really clean install, definitely looks nicer than mine does. He has enough room to get past the panesl but it'll be a bit harder than I have with how I've set mine up.

I think I still like either the rivnuts or the wellnuts, but I think the question is which. Assuming my roof is fiberglass over luan (which I guess it probably is) the rivnuts will probabbly just break the luan whereas the wellnuts will work better and self seal. So, I think I should I look at those more.

 

[tmyers]

I have worked out a preliminary lay out with 8 x 200w panels, two sets of 4 in series and either two runs to the charge controller or parallel them down to the charge controller

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[tmyers]

Ibdid like howbhebused the rivnuts on the solar panels

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[Ted]

I have worked out a preliminary lay out with 8 x 200w panels, two sets of 4 in series and either two runs to the charge controller or parallel them down to the charge controller

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I’m going to plan to run three separate wire sets down, and combine them at the controller. This will let me run breakers for each bank. Helps with diagnostics and better failure modes.

More wattage panels is good if they’ll fit. For me that wouldn’t work, too many things on my roof.

Ibdid like howbhebused the rivnuts on the solar panels

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Go home Tapatalk, you’re drunk

 

[tmyers]

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[GaryM]

If you're going to use the fans to force air into the back of the unit, put them at the bottom. If you're going to suck air out, raise the unit as far as you can (to allow airflow in at the bottom) and put the fans at the top (which should have the advantage of less crud getting splashed into the fans). I'm probably telling you stuff you know, but just in case. The key is air exchange over the heat sinks, not just air movement

Cowl flaps! You know you want to add cowl flaps to your RV. Here is your excuse.

 

[Ted]

Cowl flaps! You know you want to add cowl flaps to your RV. Here is your excuse.

No. No, I am not doing cowl flaps. No.

 

[Ted]

The first batch of well nuts that I ordered from Amazon arrived this afternoon, so I was able to start doing some playing around with them. They will definitely work, so I ordered enough to complete the project along with stainless steel screws and lock washers.

Here's a visual of how they look compressed through a piece of aluminum compared to a rivnut:

The roof of my RV is luan over insulation, topped with aluminum sheet. That's pretty good construction, but it's still a construction that's not thick enough for rivnuts or self tapping screws to work safely, in my opinion. And I am definitely not a believer in using VHB tape for that.

I really like these well nuts. They feel like they have a very good bond, and with lock washers, the screws shouldn't have any concern of backing out. They provide what would probably be enough waterproofing, but I'm going to put the self-leveling roof sealing over them anyway. So, I think that'll work pretty well.

I also spent a little time working on some of the solar panel controller wiring. That's not much at the battery side, and so next comes down to material to figure out mounting it. Which... I may have just remembered some scrapmetal I have that would be perfect for that. Now I have to see if I can find it.

 

[tmyers]

I didn't realize there was aluminum in your roof assembly

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[Ted]

I didn't realize there was aluminum in your roof assembly

Originally I didn't, either.

 

[Ted]

Last night I managed to get all 12 solar panels bolted down to the roof with the well nuts, and then went over them all with the self-leveling lap sealant, which should keep everything sealed up. One issue with putting them down before applying the lap sealant is that it's hard to get to the inside edge. Sometime today I want to take a look and see if, being self-leveling, it managed to look like it surrounded the holes well.

However really, the well nuts are supposed to seal on their own merits, so adding the sealant is just an extra layer of protection. On an RV roof, that's never a bad thing.

 

[CJones]

Last night I managed to get all 12 solar panels bolted down to the roof with the well nuts, and then went over them all with the self-leveling lap sealant, which should keep everything sealed up. One issue with putting them down before applying the lap sealant is that it's hard to get to the inside edge. Sometime today I want to take a look and see if, being self-leveling, it managed to look like it surrounded the holes well.

However really, the well nuts are supposed to seal on their own merits, so adding the sealant is just an extra layer of protection. On an RV roof, that's never a bad thing.

I used 3M 5200 behind the few rivets I replaced on our aluminum Jon boat recently. Boat people seem to swear by the stuff. Slightly less "somehow gets on everything" than Pro Seal.

 

[Ted]

I used 3M 5200 behind the few rivets I replaced on our aluminum Jon boat recently. Boat people seem to swear by the stuff. Slightly less "somehow gets on everything" than Pro Seal.

I used Dicor Self-Leveling Lap Sealant, which is what RV guys swear by for roofs. It seems to work, the stuff is all over.

 

[Ted]

Got a few little details done over the weekend, although was mostly working on house projects. With the sealant dry, I was able to get the vent fan covers on. They definitely make the interior darker, but I think will overall be a net benefit.

With the side markers having a peculiar wiring setup that doesn't work with LEDs (the diode portion, specifically, as the current flow reverses with and without the lights on) I just reverted to incandescent bulbs/fixtures. However I bought new ones, since the old ones were original. They needed to be sanded down a little for the smoke lenses to fit over them without breaking, and I need to buy amber bulbs so that they're the right color. But with all of this work (and better wiring, better grounds, etc.) now the timing of the flashers is more consistent and even on/off time as opposed to a long on followed by a short off.

Finishing up the solar wiring and finishing up the wiring for the extra fans is pretty much all I have to do before our next trip. We're not doing as much traveling as originally planned this summer, but overall that's not such a bad thing. We like going places when they aren't as crowded and being on the road when it's 100 degrees out is... hot. Plus it's given me time to get these jobs done right and not rushed.

 

[Albany Tom]

Re the LED's, I know it's after you switched them, but you could put a full wave bridge in front, and that would let them light in either polarity. It's a bit of a hack, because you'd lose 2x the forward voltage of each diode, but depending on how the lights are designed it might not make any visible difference. Ok, even with that, it would be a hack. Schottky diodes would be less drop.

 

[Ted]

Re the LED's, I know it's after you switched them, but you could put a full wave bridge in front, and that would let them light in either polarity. It's a bit of a hack, because you'd lose 2x the forward voltage of each diode, but depending on how the lights are designed it might not make any visible difference. Ok, even with that, it would be a hack. Schottky diodes would be less drop.

I'm sure that there are ways that this could be done easily for an electrical engineer, and maybe one day I'll do those. But for now, this is good enough.

 

[Spring Ford]

Polarity insensitive LEDs seem to be a thing. Not sure which bulbs are available.

Google [car leds no polarity]

Recently ran into this on a 12V DC boat. Replaced about 20 overhead G4 lights with LED and all worked first time. Clearly no polarity involved. A while later got some festoon and an instrument bulb. Suddenly polarity rears it's ugly head. Festoon is easy but the map light will need to be rewired

G4

 

[Albany Tom]

I'm sure that there are ways that this could be done easily for an electrical engineer, and maybe one day I'll do those. But for now, this is good enough.

Yep, understood. It's pretty simple, though:



Taken from the following site found at random: https://electricalworkbook.com/full-wave-bridge-rectifier/

It just makes a DC power circuit insensitive of input polarity, at the expense of voltage drop of a couple of diodes. Typically used as the input stage of either a switched or linear DC power supply that is powered by line voltage. But it can be used to make a dc circuit that will work powered either way too.

 

[Ted]

The issue isn’t just an LED bulb, but the fact that the LEDs are built into the housings. So a setup like what @Albany Tom described would be required, and I don’t feel like doing that… at least right now.

 

[Albany Tom]

Not trying to change you mind...it's your bus and I think you're doing a fantastic job of improving it. If you do go the diode route, I'd use something like this:

https://www.digikey.com/en/products...conductor-diodes-division/SB560-E3-54/1023528

That's Vishay's version of an industry standard part, 60V 5A Schottky diode, about $.60 each. 60V is the reverse rating. To me 50V is minimum in a 12V automotive environment that may see surges, 60V adds a little more safety factor. 5A is continuous current with a perfect heat sink. It will easily handle 1A full time and stay cool w/o any heat sink. By the numbers, 3A, no heat sink at 100F ambient would work. I'd go with a bigger part for more than 2A. (You can't parallel diodes to improve current rating, because they won't share the load equally.)