My Interstate Lithium Battery Adventures

[LB_3]

This is the obsolete DVD player that was in that location:


And this is the prototype panel freshly delivered from BigBlueSaw.com:

I highly recommend their service. The black acrylic panel was laser cut for $32 + S&H and arrived on my door 4 days after uploading the file. Water jetting the aluminum panel will be nearly 3x as much which is why I opted for the test panel.

There are some interference issues with this panel since I initially didn't plan on illuminated switches. I was also thinking of using a hinge to access behind the panel but all the hidden hinges I considered weren't terribly space efficient so I'm going to hold the aluminum panel in place with magnets.

The two volt meters will be used to measure the voltage loss to and from the inverter to help me spot any loose cables before I burn up the van pushing 200+ Amps to the inverter.

Unfortunately, the postal service thinks the mud slides in California last week may have washed my 4/0 cable away so I may not get it powered up for another week.

[InterBlog]

USPS really does suspect that our cable washed away. I stood in the counter line for half an hour yesterday with a tracking number to find this out.

Thought experiment: How would you have handled this scenario if you'd encountered it in your less-maneuverable Interstate?

https://www.youtube.com/watch?v=48LEIlQUkS8

[FlyFishinRVr]

Originally Posted by InterBlog

Thought experiment: How would you have handled this scenario if you'd encountered it in your less-maneuverable Interstate?

I would have driven in reverse at least 2x as fast as that driver and gone straight to the nearest Walmart to replace my soiled clothing. Holy crow that driver was lucky.

Re. your test panel, might I ask about the (assumed) vent fan? What is generating the heat, and how quiet is the fan?

Really clean and professional looking work you two.

[LB_3]

The fan is the quietest computer fan on the market and is rated at less than 8 dB (which is quieter than breathing) so it should be inaudible when in use. I plan to put it on a thermostat so it may not even run all the time.

As for heat sources, the battery management system will handle all DC loads (except for the inverter) and has an overall resistance of .001 Ohms. The charging circuit is .0024 Ohms. Pretty low resistance values but if I have the alternator hooked up, it could dissipate as much as 12 watts.
8.6 watts from the alternator(60A), 1.4 watts from the solar (24A), and 1.6 watts from the house loads (40A).

I also plan to have 5 dc/dc converters, and audio amplifier, an AppleTV, and a WeBoost in that and the adjacent compartment.

[InterBlog]

Also on a more general note, living in the subtropics, one can never be too careful about heat build-up and air circulation. Even if the fan is overkill in almost every conceivable scenario, I don't think it can hurt in ours. We're talking about a van that routinely hits 105 degrees in the summer months - and that's with every other protective shielding and ventilation measure in place. I get the heebee jeebees if I see unventilated electronic components.

[InterBlog]

Originally Posted by LB_3

The fan is the quietest computer fan on the market and is rated at less than 8 dB (which is quieter than breathing) ...

BTW, the search for that ultra-quiet computer fan was inspired by my experience with our internal surge suppressor for shore power, which we retrofitted a while back.

In most use scenarios, the electronic hum that it makes is not an issue. But if one happens to be in a remote park with all the silence that it entails, all of a sudden it becomes louder than heck in comparison to the rest of the environment.

I've had instances where, because of the heat, I've had to hook up during the day, but then I turned off the coach a/c after the sun went down and it cooled off. But I also have to pull the shore cord at the same time, because the hum is just too loud if I leave the rig connected.

Moral of the story is that what is not noticeable in most scenarios can quickly turn into a quality-of-life issue under remote conditions. Silence is one of the explicit goals of remote camping. The electronics fan can't jeopardize that.

[Troutboy]

Why don't you put the fan on a switch where you can turn it off if noisy?

[amirm]

Originally Posted by InterBlog

Dry fit of the prototype control center for the lithium system. The final panel will be made of aluminum - LB_3 ordered this black plastic trial version to ensure fit in the cabinet (which has a slightly irregular shape) and placement of the components.

Previously in the RS model of T1N Interstate, the front of this space consisted of a vertical wooden panel that held a DVD player only, and there were miscellaneous wire guts in back of that, for the phone jack, TV cable, a 12 V port, etc. that hung from the underside of this cabinet near where his hand is located.

Looking good!

Is that fan pulling in or pushing out? If it is exhaust then the hot air blowing over the two external thermostats and smoke detectors may be problematic.

[FlyFishinRVr]

Originally Posted by LB_3

I also plan to have 5 dc/dc converters, and audio amplifier, an AppleTV, and a WeBoost in that and the adjacent compartment.

Ah, ok. Those devices alone would warrant the airflow.

[LB_3]

That fan is exceptionally quiet. I've held it in my hands while it's running in my office and I can't hear it at a distance of more than 5 or 6 inches. At it's lowest setting it's half the sound pressure as breathing.

For fun I just measured the sound pressure in my office at 34.9 dBA and locking myself in our master closet I got a reading of 29.8 dBA. I'm sure that fan is audible in an anechoic chamber but it would likely only be heard between breaths. I've been in some RF anechoic chambers and I can't help but try to hold my breath to keep from hearing myself.

Getting back on track. I removed the charger since I don't plan to ever use shore power to charge the batteries. To do this, I'm planning to put all the parasitic loads on switches, with the thermostat being one at 100m.

[LB_3]

Sorry about they typos. The thermostat uses 100 miliAmps. That seems terribly inefficient to me given that the charge controller only uses 25 mA and has a small microprocessor running in it.

[InterBlog]

T1N Interstate owners (at least the mid-bath owners) will recognize this white rectangular panel as being the same size as the existing blank wooden bulkhead at the top of the closet. There's a shelf about four-fifths of the way toward the ceiling, and it's the panel inserted at the back of that, that I have re-interpreted here.

I did all the work on this one but I can't say whether I'm proud of the design because it hasn't passed operational muster yet. For better or for worse, this is what I came up with as a way to fit the Blue Sea Systems fuse panel securely in the space. I used scrap thin plywood and leftover paint from our recent overhead cabinet expansion (blog post here). The purpose of the hinges is so that this side of the panel can be opened up easily if access is needed (there will be a catch added to hold it in place when closed). Enough slack will be left in the wires to pivot it on the hinges. All the hardware, including hinge hardware, is nut-and-bolt rather than wood screws so that there will be no sharp points sticking out anywhere on the back side of the panel where vulnerable wires are located (chalk that up to yet another in an infinite number of unscheduled trips to Lowes).

My design was inspired by one of my husband's prime annoyances, and that is the fact that things get whacked inside the Interstate. It's just so small that nothing can be left in a fragile state because it's only a matter of time before it gets bumped, yanked, squashed, or kicked accidentally. The closet shelf has to do double, if not triple, duty - it's where I prefer to store the dog food because she can't get at it up there. So I'm building this assembly to withstand being clobbered by a five pound sack of kibble on a rough road. It already has a protective cover (clear plastic with yellow latch shown in photo) but I might even add a little metal mesh cage over top of the entire works for an extra measure of robustness.

Incidentally, those are the aforesaid cheap manual crimpers in the photo foreground. They remind me substantially of the breast enhancement gizmos that snake oil salesmen used to peddle in the 1970's ("We must, we must, we must increase the bust!"). They get the job done (crimping, not bustline), but they require patience.

[FlyFishinRVr]

Originally Posted by InterBlog

There's a shelf about four-fifths of the way toward the ceiling, and it's the panel inserted at the back of that, that I have re-interpreted here.

Can I assume you're going to use some sort of grommet in each hole to protect the wire from chafing? I realize the material it's passing through is wood, but as you said, this needs to survive endless bumps and the constant vibration of a moving vehicle. Over time, even a drop of water will wear through stone....

[InterBlog]

Originally Posted by FlyFishinRVr

Can I assume you're going to use some sort of grommet in each hole to protect the wire from chafing? I realize the material it's passing through is wood, but as you said, this needs to survive endless bumps and the constant vibration of a moving vehicle. Over time, even a drop of water will wear through stone....

It's a good observation and it's something that I will keep an eye on to see if any issue develops. The edges and interiors of the holes were rat-tail filed down and painted with two coats of oil-based enamel, so they are not sharp. I was more concerned about wires hanging only semi-supported and therefore constantly flexing at the stud rings (think metal fatigue) than I was concerned about them contacting the wood. That's why I chose to try individual holes rather than creating a single heavy bundle that might have passed them through a common side slit.

It always a judgment call as to how far to take any given sub-project before the point of diminishing returns is passed. So far we've been lucky and everything we have built has proven to be stronger than a brick outhouse. The good news in this process is that, if one builds it oneself, one knows what to look for in terms of incipient problems, should any develop.

[LB_3]

I was going to put the fuse panel behind the closet closeout panel but IB didn't like needing a screwdriver to access the fuses. I'm success oriented but even I can see the logic of being able to access the fuses. I was more concerned with losing space on an already small shelf but IB pointed out that the closeout panel could be pushed back several inches to make up for the lost volume.

That wire has silicone insulation so while it is quite flexible and can handle 200 degrees C, it may not have the highest abrasion resistance. It's eye level in the closet so we'll have our eyes on it frequently and since wood is a half decent insulator and it's only 12 volts, I don't think it will create any hazards before we can catch them. I'm quite pleased with how this turned out particularly since I had no involvement in building it and it freed me up to build the rack holding the inverter.

More on that this weekend but I was able to shoe horn the inverter in the bottom of the closet without having to raise the floor as I origionally thought. I still don't have locations for the bus bars, relay, fuse, or shunt picked out yet but I think they will fit.

[InterBlog]

To re-emphasize the underlying issue because I think it's globally important in all DIY work - FlyFishinRVr's comment really asks the larger question of where do you draw the line on any given decision?

It's the most valid question of all. If you're developing van systems, you're probably doing things that no human has ever attempted (or at least no human known to you or your forum group). How do you know when something is safe enough? Strong enough? Secure enough? Time and money are not infinite, so judgment calls must be made.

Most of the time, even when we can quantitatively estimate the expected strength of some component, confidence in that estimation remains low. That's why engineers calculate the strength needed for a bridge to carry car traffic but then build it 3x as strong. They know that there might be variables that remain outside of their awareness and thus unaccounted for, so they overbuild in compensation for those unseen factors.

Overbuilding is one approach to tackling this predicament. Iteration is the other. When LB_3 and I re-designed the van's gray water system (blog posts here), we were essentially iterating on the mess that Airstream had initially created. We didn't know if our design was going to be optimal, but we did know that it was going to be better. In a similar vein, I may also have to iterate on the fuse panel assembly - I knew that when I put it together. But doing it like I did to start with was necessary to move the project forward.

Yeah, I was not up for having a concealed fuse panel. Interstates tend to blow fuses for reasons that nobody understands. Even if they don't blow, they still need to be checked (e.g., our experiences this past summer when we kept intermittently losing coach power for no apparent reason). I was sick of having to ball up on the floor of the Interstate in a child's pose (yoga) in order to view the fuses that were mounted on the front of the previous electrical converter. The new panel had to be accessible, and mounted somewhere near to eye level.

[InterBlog]

State of project:

The shallow white rectangular box represents the lower of the two levels, sitting on the closet floor. I'm neurotic about water leaks, so I cut a scrap rubber left over from the wet bath floor mat (blog post on that here) and used it to underlay this battery tray. It raises the batteries off the floor and will also provide some cushioning against road shocks. Given that wood dimensions are nominal, 3+0.5=3 in this context. A box built out of a three-inch piece of pine strapping overlain on a half-inch rubber restaurant mat fragment equals three inches total height, which is precisely the height of the corner braces that I picked out to secure this thing to the floor - hence I didn't need to trim any metal for this sub-project, yay. (I actually stood in BORG and cogitated that assembly out specifically to avoid metal cuts). The corner braces can be screwed to the floor right through the rubber mat, given that it already has holes in it. Tie downs will also be added once everything is installed. I'm not sure that we will keep that simple assembly indefinitely (I still have fantasies about building a Hardiboard battery box), but it will do for now.

The white assembly shown with the inverter dry-fit will float beneath the existing closet floor but above this battery array. The wooden shelf inset to the right of the inverter will hold additional components such as a buss bar and a master fuse and probably some other stuff. The floating shelf was intentionally not built exactly on square due to the existing configuration under the floor of the closet. Easier to adapt the shelf to off-square than to change the van. BTW, I no longer want to remember life before we owned a Miller welder - jobs like this become insurmountable without one.

[LB_3]

Van should be semi functional sometime tomorrow but the 120v wiring will not be complete, nor the inverter installed, nor any of the fancy stuff like the water sensor activating the cutoff switch, etc...

Here's where I called it quits for tonight.

[Troutboy]

Nice work, did you have to make the bus bars for the batteries? Also, what is the total amp hour of that install?


Thanks,
Troutboy

[LB_3]

The battery is 'only' 300AH but it's usable capacity is about 5x what we started with. I purchased BlueSea bus bars.