My Interstate Lithium Battery Adventures

[amirm]

Originally Posted by FlyFishinRVr

I think I'll just use the genny. That's what it's designed for......

In my system, that puts out 60 amps through the charger. Using stock Magnum 1KW inverter, max is 50 amps. That means double the run time of the main engine for similar charge. That little lawnmower engine in the generator is not going to last long relative to the main engine, costing money to replace/repair down the road. To say nothing of the racket it makes.

In our case, we use our AI to drive around a lot anyway so idle is only if we are staying put which is not often. But if I have to idle it, I do so without guilt. The machine is there to be used. If it costs money later, it will be worth it in all the enjoyment it has provided up to that point.

[InterBlog]

Originally Posted by amirm

...But in ours there was a half space lower cabinet that all it had in it was this stupid subwoofer. I say stupid because it took a ton of space and pumped its output into a closed enclosure! ...

Oh my word, is Airstream still doing that?! Same thing in our 2007 T1N. I looked at ours and marveled at the fact that someone would even consider that to make sense.

Originally Posted by amirm

I am going on a business trip this week but when I come back I will document and post pictures for more.

I'm looking forward to it!

Incidentally regarding battery placement, we have a potential consideration that you do not, on account of your geography (but if MCRIDER ever decides to take the lithium plunge, this is something for him to contemplate also).

I was a bit disturbed by Technomadia's report on temperature degradation, from which I've excerpted the following quote:

"This means at 33C (91F) usable battery life will be cut in half, and presumably to a quarter at 43C (109F). This is VERY substantial."

Here in the subtropics, we go for months at a time when our rig never falls below 91 F (due to the thermal inertia in our storage unit), and it routinely hits 107 F for short periods when taken into the open in the summer (we don't travel in such conditions, but I take it over here to our stick and brick house to work on).

The issue got me thinking... is there a way we could incorporate a quick disconnect for the batteries? A physical disconnect, not just a conventional electrical disconnect?

This might sound absurd, but I could spend $120 on a dormitory refrigerator that, when set on minimal cooling, would keep about $2,000 worth of lithium batteries at an optimal temperature, if only I could pop them out of there easily, and shift them ten feet into the fridge that I could run in the storage unit next to our rig, because we do have electrical service in there. And then when we get ready to travel, pop them back in. IF they could be made to be poppable.

Conversely, might there be a way to place a 110 V device in or near the battery storage chamber, or run a line from an external device, such that it could provide a measure of in situ cooling? A few of the Airstream trailer folks who park for long periods do run temporary ducted a/c to their rigs from external sources.

Anyway, no decisions on that point, but it's something to weigh as we design going forward in the immediate future.

[73shark]

Originally Posted by FlyFishinRVr

I've read everything from early death of EGR valves to leaking oil seals as a result of idling, but the amount of time seems to be highly variable before these things can happen.

One common comment seems to be if you must idle, then a high idle is best for the health and longevity of the engine.....but then the definition of what exactly constitutes "high" idle is also debated. Sigh....

I think I'll just use the genny. That's what it's designed for......

The MB Sprinter has a high idle option but I can't remember what the rpm was for it but suspect it's probably between 1500 and 2000 rpm.

[73shark]

Originally Posted by InterBlog

Conversely, might there be a way to place a 110 V device in or near the battery storage chamber, or run a line from an external device, such that it could provide a measure of in situ cooling? A few of the Airstream trailer folks who park for long periods do run temporary ducted a/c to their rigs from external sources.

Anyway, no decisions on that point, but it's something to weigh as we design going forward in the immediate future.

Might check out thermionic plates to put in the battery compartment.

[amirm]

Originally Posted by InterBlog

Incidentally regarding battery placement, we have a potential consideration that you do not, on account of your geography (but if MCRIDER ever decides to take the lithium plunge, this is something for him to contemplate also).

I was a bit disturbed by Technomadia's report on temperature degradation, from which I've excerpted the following quote:

"This means at 33C (91F) usable battery life will be cut in half, and presumably to a quarter at 43C (109F). This is VERY substantial."

Here in the subtropics, we go for months at a time when our rig never falls below 91 F (due to the thermal inertia in our storage unit), and it routinely hits 107 F for short periods when taken into the open in the summer (we don't travel in such conditions, but I take it over here to our stick and brick house to work on).

I have not studied this in detail but my understanding is that cycle reduction at high-temp includes high current usage. Plain storage, or light usage will not cause the same issue. Other than inverter to power microwave or inverter, these batteries will cruise with so little consumption. On my installation, current consumption is around 6 to 7 amps per hour. The total capacity of the cells is 300 amps which would put this at "0.02C." Life cycle testing is often done at 1C to 3C. That data would not at all represent what happens in our light duty consumption.

FYI my BMS has a built-in profile for my batteries that calls for reduction of current discharge above 45 degree C. For every degree above that, it drops the discharge rate by 30 amps or so. In that sense, it follows the above notion of not stressing the battery when it is at elevated temps.

To the extent you use the microwave/AC, and you place the batteries in living quarters, high temps should not be a concerned.

But let's put all of this aside and look at this philosophically. In my view, batteries are consumable part of the RV. Just like gas and DEF that you buy, you should assume the batteries will degrade and at some point you will buy fresh. My total cost for the batteries including shipping was about $1,500. If I get usable capacity for five years out of it, that is just $300/year. Cost of gas alone will dwarf that.

Micro analysis of battery performance when it comes to LifePO4 just cannot be done anyway. These are produced by Chinese companies and who knows what recipe they use now versus last year. The science of them is very lightly studied since they are one of the least desirable types of Lithium batteries from market potential point of view. Use them until they die and buy new.

[FlyFishinRVr]

Originally Posted by 73shark

The MB Sprinter has a high idle option but I can't remember what the rpm was for it but suspect it's probably between 1500 and 2000 rpm.

I've read that there are two options offered but not sure if they can be retrofitted. One is a fixed rpm high idle and the other is adjustable. In either case even if they are available as a retrofit, I think the least expensive of the two options is $650. I think if someone planned to do this a lot the expense would make sense, otherwise the "stick" method might be a good option......

http://www.tooldiscounter.com/ItemDi...zA4aAtz18P8HAQ

[LB_3]

Interblog is overthinking the life cycle reductions from elevated temperatures. We're not retired so we're only going to put a few dozen cycles on the batteries per year. The lithium choice wasn't driven by lifecycle costs but by energy density and charge rates. If we only get a quarter of the rated cycles, these batteries may last us the better part of a decade.

Our T1N has the coach battery under the passenger seat so there is no room for additional capacity in that location. Additionally, that location is nearly impossible to fish a really fat cable so adding an inverter to run the microwave is not an option. That means that in order to increase capacity we must relocate our battery somewhere else in the coach and that is where the deeper discharges and higher energy densities of lithium batteries will earn their keep. My hope is that the higher charging rates for lithium means more effective charging on the road. If true, we may offset some of the volume displaced by the new battery bank by not installing a charger.

[LB_3]

Edit for double post.

[amirm]

With engine and AC charger going, I have pumped nearly 130 amps into my bank and they don't even blink! Done the same with generator powering the AC charger and main engine. I call it "turbo charging."

How much capacity did you end up with LB?

[InterBlog]

I'll continue to over-think the system, too, because everything about it has been under-thought to date, from Airstream's initial design (which failed repeatedly on our 2016 Canada trip) to that lousy electrical converter that failed catastrophically earlier this year due to the manufacturer's self-admitted defect which almost burned down our rig, to the fact that the converter retrofit doesn't even charge how it was supposed to charge stage-wise, which is the reason why we spent the money to replace it to begin with.

Engaging in over-thinking doesn't mean that every resulting idea has to be adopted. It just means that someone is putting some effort into evaluating all the ancillary possibilities on any given project. If I hadn't over-thought the cab roof while we were installing the rear and side cameras and front monitor, then we'd have no Dynamat and radiant barrier up there today, and those things were a big improvement.

[LB_3]

We purchased 300Ah of batteries. I'm pretty excited about seeing more than 6-7 charging amps getting pushed to the batteries but if they can take over 100A, well I may want to install a bigger alternator.

Amirm, when you get some time can you post a schematic of how you integrated your BMS, chargers, inverter, etc....

IB, we're a great team because your continuous scope creep gets us things like overflow valves on our grey water tanks :-) And for anyone confused by this conversation, I'm working nights this week so this back and forth isn't me antagonizing IB in public so much as us leaving breadcrumbs for each other to find when the other is asleep or at work.

[amirm]

On track to do that next week LB. I am on a trip this week through Sunday so no time.

[InterBlog]

This is what I accomplished yesterday as my husband spent the day with 106,248 of his closest friends watching A&M struggle almost endlessly against Tennessee. If you were ever curious about what's beneath the closet floor of a T1N Interstate, here's your answer.

The bad news is that it's a dog's breakfast. The good news is that it's going to make a helluva "before and after" presentation, with this mess being the "before".


Also good news is that it will be extremely easy to convert this closet floor into removable form for future lithium battery system access. You can already see that it basically just rests on two rails (plus there was an aluminum L-bracket along the back wall to secure it there). All we need to do is trim down the corner that is typically covered by the wooden shroud that hides the vent / wire rise, and the aft side, maybe expanding that aft rail so that the resulting floor can be small enough to easily clear the door frame during removal.

Why we didn't make that mod well before now is a mystery to me. All that solar apparatus went in - somehow - without ever removing this floor. But it is what it is, and it's getting done now.

It is frustrating to me that Airstream put the water lines and valves for the outdoor utility shower literally in physical contact with important electrical components. I looked at this and asked myself... why?! To the best of my ability to speculate, it's because the city water inlet is located just to the right of the edge of the photo, and so they had a cold line coming there anyway, and it was easy to junction it off there and run it to the shower for close supply.

The resulting morass has inspired my first item of scope creep on this lithium project. We are going to have to modify those lines no matter what, because they intrude too far into the space. We can't really remove the shower entirely, because we do use it and value it, and also because it would leave a gaping hole in the body (however, if in the future we decide that we need the resulting lithium chamber to be externally ventilated - presto - a Sprinter body cut is already right there in that exact location). We hope to keep the shower but we only need those lines to be pressurized on those occasions when we use it, so I'm advocating for safety valves to be installed upstream so that it's only pressurized when we activate it, rather than being pressurized automatically along with the rest of the water system, as it is right now. It's just too much of an unnecessary risk to have water lines running straight through the heart of the electrical system like that. We have already had one of those PEX connections spring a leak, that being on the opposite side of the vehicle (and what a mess it made). If the same thing happens in this location, the results could be disastrous.

Anyway, ^^ there are some thoughts on this small portion of the project.

[Mcrid]

Originally Posted by InterBlog

(but if MCRIDER ever decides to take the lithium plunge, this is something for him to contemplate also).

I

I'm following with great interest. We just returned from TN where the temps were fabulous. Our Solar and battery set up are working great even with that cheap Atkinson Controller. I'm considering the Morningstar Sunsaver MPPT, but not sure I want to take on that task at the moment.

The rig will be a year-old later this month and we just rolled over 19.3K miles.

[InterBlog]

Originally Posted by amirm

...

You may be relieved to know that I sleep right on top of mine with no fire stop! ...
....

Today in the theme of, "I've done just enough additional research to be even more dangerous", I note that, in the category of DIY battery bunkers for fire stop purposes, the two most common construction methods appear to be gypsum wallboard and HardieBacker.

We in Houston are generally very fond of the Hardie line of fiber-cement sheets and planks because they liberated us from cellulose-based products of yesteryear, which were the source of who knows how many class-action lawsuits (natural fiber exterior cladding products do not have a history of standing up to subtropical humidity). The exterior portions of our stick-and-brick that are not actually brick are mostly HardiePlank.

So HardieBacker is appealing to me greatly as a material source for this application. The space is not large so a HardieBacker liner would not add much weight, and it would not be as potentially subject to crumbling due to road vibrations as wallboard might be.

Model airplane people are a sobering lot - they regard Lipo battery fires as a foregone conclusion. The only questions are which cell and when will the fire start. My husband has explained that RV systems (DIY and commercially-produced) have additional tech integrated that is designed to prevent the precursor conditions from arising that may give rise to certain kinds of fires. And obviously those design elements are absolutely essential, but tech has a way of failing at times, hence the relevance of redundant measures.

[73shark]

And the US Navy doesn't allow Li on their subs.

[FlyFishinRVr]

Originally Posted by InterBlog

Today in the theme of, "I've done just enough additional research to be even more dangerous", I note that, in the category of DIY battery bunkers for fire stop purposes, the two most common construction methods appear to be gypsum wallboard and HardieBacker.



We in Houston are generally very fond of the Hardie line of fiber-cement sheets and planks because they liberated us from cellulose-based products of yesteryear, which were the source of who knows how many class-action lawsuits (natural fiber exterior cladding products do not have a history of standing up to subtropical humidity). The exterior portions of our stick-and-brick that are not actually brick are mostly HardiePlank.



So HardieBacker is appealing to me greatly as a material source for this application. The space is not large so a HardieBacker liner would not add much weight, and it would not be as potentially subject to crumbling due to road vibrations as wallboard might be.



Model airplane people are a sobering lot - they regard Lipo battery fires as a foregone conclusion. The only questions are which cell and when will the fire start. My husband has explained that RV systems (DIY and commercially-produced) have additional tech integrated that is designed to prevent the precursor conditions from arising that may give rise to certain kinds of fires. And obviously those design elements are absolutely essential, but tech has a way of failing at times, hence the relevance of redundant measures.

I've been keeping my eye on the battery industry and I think in the not-too-distant future they will completely solve this with a different design and/or chemistry (and increase energy density at the same time). As a result, by doing what you're doing now, you'll have the "bones" in place to take immediate advantage of the new tech when it becomes available. Sure, you'll likely need to swap out charge controllers and depending on your setup, inverter/chargers, but in the mean time you will be able to enjoy this new era of propane and generator freedom. Once the new tech is available, I'll certainly be moving to it! [emoji3]

[73shark]

If only Samsung had used a Hardibacker board case for their new Note 7 phone.

[amirm]

Originally Posted by 73shark

And the US Navy doesn't allow Li on their subs.

They are not having to camp overnight with no power source in middle of nowhere.

Seriously, what is the source of this statement? I just did a search and the first hit was this document which stipulates how to use Lithium battery in all naval facilities including subs and boats: http://www.public.navy.mil/navsafece...3FList%3D8006e

"LITHIUM CELLS AND BATTERIES. The use of lithium cells and batteries in Navy systems and equipment offers the advantage of increased voltage and longer life, when compared to other power sources. Lithium batteries can provide increased energy density, extremely high currents, and can discharge very rapidly when short-circuited. Although these characteristics are useful in applications requiring sustained high current, a too-rapid discharge of a lithium battery can result in overheating of the battery, rupture, and even explosion. Because of these risks, lithium batteries shall be considered hazardous at all times. The Department of the Navy has adopted a Lithium Battery Safety Program to minimize hazards associated with their use"

I have not read the rest of the doc but does not at all admonish their use.

[InterBlog]

Originally Posted by 73shark

If only Samsung had used a Hardibacker board case for their new Note 7 phone.

Samsung is one of my case-study darlings that I use to argue against just taking on faith that nothing can go wrong with these things. Stuff keeps going wrong and the best minds in the business can't always figure out why.

Airlines are in a similar groove. E.g. this news story published yesterday that describes how they are now adding the equivalent of a fire stop mechanism to commercial aircraft just in case they are forced to isolate a flaming phone battery at 36,000 feet. I'm also looking at those materials, which I think are probably more fabric-y / Nomex-like. I'm not done with that part of the research.