Go big or go home - 600ah @ 48v of battery + 4,000 watts of solar

[ependydad]

I'm in a 2022 Jayco Precept 36C class A. To get it out of the way, my CCC is about 4,200 pounds that I've verified by running to the CAT scale.

Now...

The Requirement/Inspiration

This whole project started because I wanted to be able to boondock but my wife and I always run the air conditioner overnight. When Wallydocking and some Harvest Hosts, it's fine to run the generator all night (yes, I get that's controversial, no I don't plan on debating it ). But when camping somewhere with generator hours or camping where etiquette deems it inappropriate to run the generator all night, we wanted an alternative.

 

[ependydad]

The Battery Bank

I started looking into DIY lithium cell buildouts and decided that I wanted to tackle it. A hot seller on the DIYSolarForums is Docan Technology. I priced out their various cells- from right about 200 ah to 304 ah cells and that's when Captain Overkill made his first appearance. Rather than settle on a 24v system with 8 cells, I decided to go nuts on a 48v system with 16 cells. Captain Overkill whispered in my ear with that Tim The Toolman Taylor grunt, "MORE POWER! YOU WANT MORE POWER!" So I doubled down and bought a total of 34 cells.

So here I'm sitting with a battery bank of 608 ah @ 48v (aka 29 kWh).

I opted for a Rec BMS to manage the cells in a 2 parallel/16 series (2P16S) configuration. Unsurprisingly, there's a lot of debate whether it should be 2P16S or 16S2P or, or, or. You makes your choices and you run with it.

All told, cells, wiring, battery containment, etc. come in around 400-450 pounds.

Currently the cells are installed under the bed, but I've been eyeing up a storage hatch that I opened up and think I can put them down there with a little bit of reinforcing. It'll also tremendously shorten my battery cables between the battery bank and the cells.

For reference, here's a detailed drawing of the Rec BMS + it's accoutrements.

 

[ependydad]

48 volts? But why? And... what about?

Why 48 volts? Well, given the grand intention to run high amperage through the system, the 48 volts gives me less amps at the same watts. Less amps = less heat = smaller wire sizes = supposedly is less cost.

But now that I've made the decision to go away from 12v, then I need to worry about powering the 12v system. I had 2 options here:

1, I could just keep a 12v battery and power some kind of DC-to-DC converter for charging it (heck, with my inverter plans that I'll talk about later, I could just as easily keep the stock converter).

2, ditch the batteries and plan on some kind of DC-to-DC step-down converters to power the 12v system directly. This runs the risk of not having enough cranking amps to start the generator.

As of right now where I'm mid-execution- I'm going with #1. I have the existing 12v system still living and I'm recharging the batteries from the existing 12v converter. Not super efficient, but I've got power to spare at the moment.

My plan is to install a pair of Victron Orion DC-DC 48|12 converters. This *should* give me enough juice to start the generator. If not, I should be able to use the battery boost button to combine the chassis battery with the house battery and then have enough. Worst case, I'll rewire the generator directly to the chassis battery.

I'm also planning on a 12 to 48 volt step-up converter for charging the battery bank from the inverter. For this, I've opted for the Sterling DC-to-DC charger.

I've got all of the pieces and even wires for the 12/48 converters (both) but haven't found time to wire them up yet. I need to do it soon.

 

[ependydad]

Inverters

I started this project planning on going for just a Victron Multiplus II 3000 inverter. It handles 50 amps of pass through at 50 amp split-phase. Super simple, super sweet. But that's 3000 kva which is only about 2400 running watts. Captain Overkill sauntered in and was like, "yo dawg, you got all of this battery power.. how fun would it be to run both air conditioners at night? You got kids in the front of the house that might appreciate that."

So, one thing led to another and I ended up with a pair of Victron Quattro 48/5000 inverters. These bad boys are heavy as all heck at 81 pounds each.

First, let me start with my wiring diagram showing all of this pulled together:

What I didn't quite realize coming into this is that my gas class A hatches are nothing more than thick plastic. My father-in-law and I worked through some ideas and basically used 1/4" thick x 4" wide x 11" tall pieces of aluminum to hang the inverters from the steel framework of the RV itself (same thing the hatch hangs from).

I wired up each inverter to a single leg of the 50amp power to the output of the automatic transfer switch (ATS). I take the output of the ATS and fed each leg into the input of the inverters; I then take the output of the inverters and fed it into the input of the breaker panel.

The inverters are then setup to communicate with each other and actually output split-phase power, out of sync at 180°.

Even when I'm on a garage plug in or 30 amp spot, I'm able to do some load supporting and it works really well.

I've had this setup for about a month now and it's been great. I'm able to set an input current limit and shouldn't ever trip a breaker again.

 

[ependydad]

Recharging: Generator + Solar

As of right now, my only means for recharging the batteries is by running the generator or plugging into shore power. This is all well and good, but when I'm plugged into a garage, the system is doing so much load supporting that I run at a deficit each day. In 85-90°, we ran out of excess power in about 3 1/2 days with 1/2 of my bank wired up at the time. I did fire up the generator and it was great for recharging.

But, that generator stinks and my goal has become to minimize it's use. So now it's time to start talking about solar on the roof.

My roof:

According to specs, it's a 38' 10" RV which surprisingly, I measured that it has 34' of usable roof space. I guess the other almost 5' is due to the nose cap, windshield, rear cap, and rear ladder. (shrug) On top of that, my wife has requested that I leave a few feet in the rear for us/the family to go up there and be able to sit. We just did it on July 4 as we watched fireworks in 270° around us at the Delaware shore and we go up at the Albuquerque Balloon Fiesta to watch the hot air balloons. So now I'm down to about 28'.

Captain Overkill chuckled when I started thinking about working around air conditioners and other roof obstructions and said, "you know, you know multiple people who have built a rack overtop of all of that. You're only 12' 10" now and your fifth wheels were all 13' 4" or so." If my buddy can put 1,700 watts onto a truck camper, so can I:

So first things first, I took the roof and panel measurements and started laying them out in a diagramming software:

This is the 2nd most efficient use of the space. The first is with going with 22 x 200 watt panels and that just felt like a lot of wiring, a lot of mounting, and a lot of work. Not that these 14 panels is a whole lot less.

Let's start with a total wiring diagram:

Now to figure out wiring of them. I am planning on 2 solar controllers. One for the 365 watt panels and one for the 200 watt panels. Each panel is going to be split down the middle for 2 parallel connections with each then wired in series (so, 365: 2 parallel sets of 4 panels in series; 200: 2 parallel sets of 3 panels in series). This all gets me down to under 30 amps so I can keep using MC4 connectors to a pair of combiner boxes and then dropping that down into the RV.

Here's what those panels look like wired up:

• Blue arrows are the panels' built-in MC4 connectors
• Purple arrows are the MC4 in-line fuses (20 amp on the 365w panels; 15 amp on the 200w panels)
• White arrows are MC4 connectors that need to be added

I've been working with a couple of the big names on solar quotes - AM Solar, Continuous Resources, and RV Solar Connections.

RV Solar Connections put me in contact with Chris Reed from Why Not RV? for some paid consultation time to do a technical review of the diagrams, wire sizes, and fusing requirements. He had some good input and I made a few changes based on his recommendations.

 

[ependydad]

Ok, all of the theory out of the way. How about some random installation pictures?

Here's how the inverters mount. You put a mounting bracket on the wall and the inverter essentially hangs from that. On the bottom of the inverter is a second set of screw holes to keep it from sliding sideways or jumping off.

Since our storage hatches are just heavy plastic, hanging them from the sides of them wasn't sufficient (each inverter is 81 pounds). Getting in/under/up close and personal, I found that the storage hatches are hung from 3" C channel across the top. My FIL suggested we just take 4" wide x 1/4" thick pieces of aluminum plate. Then he drilled + tapped mounting holes that correspond with the mounting plate.

This did mean we missed out on the center hole of the mounting bracket. I wanted to have a big "H" cut out of aluminum, but since I hadn't planned ahead, I couldn't find anyone to plasma cut it in as quickly enough of a time. Plus, 2 plates of 4" aluminum were WAY cheaper than a 18" square of aluminum.

For the bottom, we took 2" x 12" pieces and basically bolted through the storage side wall. This isn't really structural, its just to prevent the inverters from shifting laterally or lifting off of the upper mounting bracket.

On the outside of the storage hatch is the back-side of the mounted plate. This is just drilled with open holes, bolted, capped, and then loc-tited to keep it from falling off.

This isn't weight carrying, so going through the plastic is just fine.

Then it took some lever action with some random wood, some blocks, and whatnot to heft these heavy bastards up onto the brackets. And finally, installed!

 

[ependydad]

I had built the 16 batteries in series and configured the BMS at the house in my screen room. To keep things perfectly humble, I miswired the Rec BMS the first time I did it and instantly destroy the first one. That was a $500 mistake. YouTube tells me that I'm not alone and the manufacturer basically told me I was an idiot when I suggested a "#1" marking on the BMS to avoid others from the same fate. Ehh, it happens.

The bench build let me get the BMS together and the first Quattro built. I was able to run the small window air conditioner off of it. And then life got nuts and the whole project basically got put on hold as we tried getting out of the house for a 7+ month trip. The trip that this was all supposed to be done before we took off. Oh well, such is life...


Getting the batteries configured under the bed has been a fun challenge. My wife had planned on that area for some of her fancy dresses in vacuum bags and was none to pleased when I showed her my initial plan to take up 80-85% of that area with batteries, rendering it essentially unusable for her.

Here's one reconfiguration that we might go with:

The batteries will ultimately be wired where every 2 cells are wired in parallel (adds the storage together) and then each pair is wired in series with the next (adds the voltage together). This will give me 48 volts at the end of the 32 batteries.

There are also 2 spare cells in case any of them swell, as lithium is known to do.

I had significant more work here. I needed to raise the batteries up a smidge to give me more room working on the lower posts. I still need to add some kind of compression to the cells to extend their lives. And I need hold downs to make sure the cells don't jump on any particularly bad bumps (which would have to be a hell of a bump).

I also had to mount all of the BMS hardware and try to fit it into this area. For now, I've fallen back from this compact layout and moved all of the cells into 2 long lines of batteries with a mess of wires in the middle.

 

[ependydad]

The first thing with the inverters that I did was I started to wire up the 120v side of things. This involved running 4 cables of 6/2 between the bed and the storage hatch.

First up, drilling a new hole in the floor. Fortunately there was an existing hole into the water bay storage hatch. This gave me a reference point and I was able to drill a perfect pilot hole just behind that. Now, mind you- I thought it was going to be 3" from where it ended up, but happy mistakes are happy mistakes. I opened the hole with a jig saw and have a great accessway down into the chassis area.

Running the 4 cables was a whole lot of crawling around under the rig with my son on the top side feeding cable down, me down there cussing, getting scratched, and pulling. This took way more time than I anticipated and I basically lost an evening to just it. I cut a hole into the side of the compartment where the inverters to get them in.

I ran them 2 x 2 to try and make my life easier. I think it did. Or it was harder. I suck at pulling cable and have a ton of respect for those who do.

So now, I realized that I pulled these 4 cables and didn't actually mark them in some way. Since it matters as to what's input vs. output and L1 vs. L2, I needed to identify them. This turned into a quick little homeschool lesson for the kids on continuity. I showed them with the meter how if you touch 2 leads together, it'll make noise. I then have a couple hundred feet of silicone wire due to order mistakes, I spooled off about 40' of wire. I showed the kids that if we hold the wire to one probe and touch the other with the other end of the wire, it would make noise.

We labeled each of the top-side cables with a letter identifier (as shown above). With my daughter top-side, we taped one end of the wire to one probe. She was then going to put the other probe to the negative (white) of each 6/2. I then went down to the inverters/other end of the wire and we toned out + labeled each one. She was impressed, I was impressed. It was a good time.

With the wires ran and identified, it was time to start terminating them. Here's where I learned my first important lesson- always cut your wires shorter than your ground. You'll never have enough length to get that stupid ground to wherever you need it. I learned this way too late and it caused a lot of its own cussing.

To connect the 6 gauge wires to the inverter, it's setup for ring lugs. I crimped on a lug to the hot and neutral for each wire.

Then it was a matter of attaching each to the correct spots on the inverters. I ID's the rear inverter as L1 and the front inverter as L2. Right now, it's written in pencil but I'll have my wife make up a vinyl label. No pictures here because I was running out of time around dinner and thoroughly pissed off about the aforementioned short grounds. I made a not pleasant job way the hell harder than it needed to be.

Now, it's getting real. Up until here, everything has been fairly isolated. Dropping batteries in, hanging inverters, even wiring. But nothing has been connected, they don't DO anything. It's time to buck up and actually start integrating it into the RV's electrical system.

Step one, opening the ATS.

To be 100% honest, I cracked it open and my stomach sunk. There were so, so, so many wires. Nothing simply said, "L1 HERE, L2 THERE". I panicked a little and thought, "OH GOD, I'M IN OVER MY HEAD!" And then did the only logical thing for me, hit the Internet and looked for a manual for the ATS. The document I found wasn't overly helpful but it did calm my tits a little bit.

I did realize that I needed to identify which is L1 and which is L2 in a standard 50amp plug. I found a diagram that seemed to indicate that Red is L1's hot and Black is L2's hot. I don't think it so much matters which is which, so long as I'm consistent.

So once I got my wits about me, step 1 was just disconnecting the output of the ATS. Disassembly? I got this.

And then it was a matter of putting my C cable (output of ATS to input of inverter for L1) to where the Red and white were connected on the ATS. Next, the D cable (output of the ATS to input of inverter for L2) to where the Black was connected. The white had to be a little more creative but I found a spot (it is on the generator side which already had jumper cables over to the shore power side). And of course, both grounds. Now, I did learn my lesson from earlier- I cut my cables shorter than my grounds. Only minor cussing involved with this 6 gauge wire.

From here, I stopped and went and turned on shore power watching for the magic smoke. I was able to measure voltage at the ATS and down at the input for the inverter. I even kicked on the generator to ensure I didn't bust the ATS somehow. Things were coming together nicely!

 

[ependydad]

And now for the distribution panel. I cracked it open and saw what was expected - the 6/3 cable came in, red to L1, black to L2, neutral, and ground all accounted for.

Fortunately my nerves were much more calm and now I had a better idea of what to do with everything.

I pulled in my cables and started hooking up my A cable (output of inverter to L1 to the distribution panel). Short and sweet, honestly and then I moved onto the B cable (output of inverter to L2 to the distribution panel). Again, I had to deal with the extra neutral but it wasn't a big deal with all of the places for neutrals to go.

I turned off EVERY breaker- not just the 50 amp main, literally every breaker in my primary panel and my factory sub-panel. To say this part was about to be terrifying was an understatement!

Again, I went through a testing phase - turned on shore power and turned on the L1 inverter. I verified that power was coming in and power was coming out. About 124 volts with the inverter. Holy crap, this is working!

I turned on the L2 inverter and repeated the tests. I've got voltage as expected.

I moved inside and measured voltage at the double-breaker. As expected, I saw 120v at each leg and 240v across the 2 hots.

I turned on the 50amp main and a single breaker. Sure enough, I saw 120v there at that breaker.

Once everything looked good, I secured the wire stays (wire holder thingies) and closed everything up.

I shut it all down again, as it was now time to configure the inverters for 240v split phase (180° out of phase). Sitting in the dark outside at nearly 10pm, I followed the steps in this article:

https://shop.pkys.com/Setting-up-pa...Plus-and-Quattro-inverter-chargers_b_161.html

While it does say that you can use a different app for a simpler configuration, I hadn't downloaded it and have crappy internet (even with my Starlink). I followed their steps with the 2 legacy apps. They worked very well and short of shocking myself while plugging in a network cable, there's really nothing to write home about. The apps had me configure each of the inverters as L1 and L2.

Once that was configured, I kicked on campsite power, made sure the inverters were on, and headed inside for one final last set of meter readings as I turned on all of the breakers.

We're in business! I still don't have batteries hooked up, so the inverters are just passing power through. But this was my biggest fear, worry, and feelings of technical incompetence.

Now, I did have a minor surprise when I disconnected and fired up the generator for our travel day. Turns out, the system wouldn't pass through power to one of the legs when on a single-phase source (which is what my Onan generator is) unless there were batteries connected. You'll notice that in this particular post in this thread, I've only dealt with the AC side of the system. I did NOT do the DC side. I ultimately had to flip the inverters to parallel mode and then they worked fine off of a 120v source. Later in the implementation, I've been able to get the batteries installed and everything works like it should in split-phase configuration.

 

[ependydad]

Now, one last tricky wicket. I always knew I had a sub-panel in the RV. I posted about this in another thread.

But, I didn't really know how it was all hooked up or even why. I assumed it was hanging off of a breaker on the main panel. I had previously looked at the main panel and didn't see one, but I just assumed I didn't know what I was looking at:

Well, it isn't. It's literally wired directly to the ATS output.

It's hard to see, but do you see that orange wire on the left-side of this photo?

This means that it's on the input side of the inverter and I won't be powering it with how things are configured now.

Since I'm removing the stock converter, I'm going to put a 30amp breaker in its place and will then turn this secondary panel into an actual subpanel. What's even crazier is that I don't even have a 120v water heater (it's a propane only tankless). I literally have no idea where that breaker goes or what it feeds.

Now that the inverters are wired up with batteries, this secondary panel has reared its ugly head. The inverter senses how many amps are used and will use up the remaining amps with recharging the bank after we have times of deep discharge (i.e. drive ways where I run an air conditioner without running the generator). Which means, the inverter will take each leg up to 40+ amps and then we'll kick on the microwave or clothing machine and suddenly my Hughes Watchdog is cutting us off for over-current. I've actually had to limit the inverters to an input current limit of 30-35 amps so that I have that extra for the other stuff. So far so good, haven't tripped it. It's just really dumb, IMO.

 

[ependydad]

So now, with all of the wires ran (and being "done" on the 120v side of things), it was time to start wiring up the DC side.

This started at the table. I wanted to get everything mounted to a piece of plywood so I could take it and slide it into place.

I got things mounted and went to start doing cables but it was late (pushing midnight) and I had to go collect stuff. I turned in for the night.

Starting fresh after work the next day, I put the board into place and went about starting to make some cables:

This was going well until I realized I was going to run out of 5/16" 2/0 ring terminals. RAD. Fortunately with Amazon, I could have more in 2 days. Really wish I'd thought ahead on that one, but what's another delay? It's not like we weren't running air conditioner off of a garage outlet and tripping it about 3-6 times per day.. oh and now we can't run the generator to run the front A/C. Good times.

More ring terminals in hand and I was able to finish up the storage hatch side of things:

It's not the prettiest work. I'm especially disappointed in those 6/2 wires for the 120v side of things coming across the middle. I think I'm going to add a pair of 2-circuit breaker boxes so that I can easily disconnect power coming into and out of the inverters. This will give me enough extra wire to clean up the installation and be functional, too.

 

[ependydad]

And now, the moment of truth. It was time to start making the battery-side connections.

Before putting the false floor down in the bed, I mounted a positive busbar to the floor in there. I connected my 2 positive connections to the distribution system to it. I then mounted an on/off switch to the outside of the bed base so that I don't have to lift the mattress to turn off the system. This comes off of the busbar and that will feed into the battery/BMS connections.

It was pretty exciting to be able to put the false floor down and have the kids load in the batteries. For now, I'm still just focused on the 2 long lines of batteries and haven't yet worried about compression.

I mounted most of the rest of the hardware to a board, but my spacing here was pretty tight. I attached the catastrophic fuse, negative busbar, shunt, pre-charge controller from the BMS, and contactor (part of the pre-charge controller). I really need to get some pictures of this all and show the inter-connections. I set this into place under the bed where it'll go but hadn't secured it yet. I needed a placeholder for how long my battery cables needed to be.

So first, obligatory shot of the friend who came and sat with me while I did the work. He 100% was looking for the entertainment of me zapping myself. He was much disappointed.

Now, I apparently need to take a lot more pictures. But, what I did was- I took 16 of the batteries that I had previously top balanced and wired them in series. This gives me 304 ah at 48 volts. The negative comes off of one end and the positive off of the far end.

I double-checked the voltages in the BMS's cell voltage wires and came to find out that I had a battery upside down! Fortunately, no damage but it did mean that I had to tear down the whole pack, move batteries around, and build it back up. Fun times but fortunately I tested it before just blindly plugging it into the BMS.

And then it was time to start turning things on. This part was terrifying!

First up, the BMS. This was extra terrifying since I had previously burnt one up and know that they run $500 to replace. I surely didn't want to do that again. Simply plugging it in was hard on the heart. All went well- I had a moment of concern when the error light showed up, but this is its typical boot sequence.

I connected the laptop to the USB dongle and was able to verify that I was good. This is an older screenshot, but it looked exactly the same with some minor variance in the cell voltages:

Next, once that was all up and clean, I headed down into the hatch so that I could plug into the inverters and run Victron Connect so I could see what was going on.

I started with voltage at the busbar and it was showing a solid 50-something volts. Horray!

Loaded up Victron Connect and it wasn't showing the batteries. BOO! I shut them down, restarted them, did the classic IT things and had no change. Want to know what it was? I'm dumb, that's what it was- I have 2 battery disconnects for feeding power into the inverters and I had them OFF because I didn't want surprises as I was doing all of my wiring. DUH.

Turned them on and all looked pretty good!

I disconnected my shore power connection and the inverters hummed along nicely.

I tried the rear air conditioner and it roared to life!

I shut it down and tried the front air conditioner. After some brief reconfiguring of the inverters (I had been switching between parallel and split-phase during the troubleshooting with the generator), it roared to life, too!

I shut it back down and thought, OK- let's try this load assist feature. I went into VE. Bus System Configuration and enabled it and enabled the battery charger.

(Note, I've since updated the cutoff voltages for the load assist- though, that's a today job. Figure out the appropriate charging/discharging/cutoff voltages for the battery bank and get that configured in both VE. Bus and the BMS.)

I saved the settings and fired up the rear air conditioner- all excited for my new found load assist feature. And I tried the garage breaker. At nearly 11pm, well after my friends were asleep... well crap. Fortunately, they left the door unlocked for exactly this case. I sent my daughter in and I went about figuring out what was up.

Turns out, the battery charger portion was trying to pull too much power from the 15amp connection. If my math is right, it was:
2995.2 watts = 57.6 volts * 52 amps
2995.2 watts / 120 volts = 24.96 amps

Things get funny on a single-phase shore power connection with the dual inverters, so I don't think it was double that.

Once I dropped that 52 amps down to something like 8, everything hummed along nicely!

I was able to run both air conditions with the load assist supporting them on a 15 amp garage connection! And given that "funny" I mentioned, it was still trying to push some power back into the batteries.

 

[ependydad]

My first running was at my buddy's house. It's bloody incredible. Sitting at my buddy’s house and plugged into his garage. Before the inverter install was functional (I’m not done, but it’s connected to the AC and DC systems), we were tripping the 15 amp breaker 1-3 times per day. Tonight, for shiggles, we had 2 air conditioners and the microwave running.

And this is only with 1/2 my batteries.

I’ve successfully load assisted for about 3 1/2 days before the BMS started cutting me due to low voltage issues. I don’t have a good view of the battery’s state of charge outside of the voltage at the moment.

 

[ependydad]

Progress has slowed. Life and fun have been getting in the way of RV work and fun. I've been running the inverters. I intended to use them for an overnight at a Harvest Host location, but they offered a 50amp plug-in and I took it (forgetting that the listing said it was $20 for electric + water). I should have saved my money and really tested the system.

I then had a 2 1/2 hour drive and ran the main air conditioner the whole time + some other minor loads. Worked well. The inverters pushed about 100amps/hour back into the batteries; I didn't pay attention to how long it did that for.

But, I did come to realize that my concerns with the extra electrical panel circumventing the inverter/distribution panel did cause issues. Tried using the microwave and it ended up sending us up and over 50 amps on a leg. The Hughes Watchdog cut me off a few times before we started shutting the air conditioner off until the batteries were charged. Once they were charged, it hasn't been an issue. I do need to move that to be a subpanel to the main but need to do a little more research on the topic to make sure I don't do it wrong.

Continuing up the road, I took the Cape May/Lewes ferry with the air conditioner running with the engine + generator off.




We ran the RV air conditioner and a few other random loads from about 12:30 to 4:30. I get some stats from the Victron Remote Monitoring (VRM) that shows me how much historical use/battery voltages.



It shows that it took a little less than 4 hours to recover the battery charge from running the A/C on batteries.

I still haven't actually hooked up the proper battery monitor to the batteries. I need to run an extra cable into the inverter/hardware bay (which is kind of a pain in the butt!).

 

[ependydad]

And some more humble pie... I like to be completely honest about the good AND the bad. When I embarked on this journey, I knew it was a bit big for DIY and honestly for ME to embark on this upgrade, I was terrified. I had a huge reminder of why.

I wired the 2nd set of 16 cells in series and had disconnected the 1st set of cells. I was just starting to connect the negative battery cable. This area is tight, so my focus was largely on moving stuff around, squeezing my hand in small places, and for love of the all mighty, not touching the wrong things together! When I did just that...

I lost track of the other end of my negative battery cable. It hit the positive post on cell #10 (which is along about 30v or so). The pop was loud and the sparks it threw were massive (and stayed hot after they landed!). I'm pretty sure I yelped, peeds, and pooped myself all in the same instant.

The ring terminal meltage was impressive:

I really worried that I had ruined the cell when I saw the nut melted and scorch marks all over:

Fortunately, once I was able to collect myself, clean up the yellow + brown spots, and got a shower, I was able to start disassembling. The damage looked largely to not have gotten down to the threaded battery post:

The pair of busbars that I'm using did minorly fuse the corner together. I didn't like these anyway and have future plans for some flexible busbars:

So now, lessons learned...

1, I learned/was reminded of the importance of wearing safety goggles. I was not wearing them because, honestly, it felt silly wearing them. I will be from now on.

2, always manage the ends of your cables. Wrap them in tape, throw an extra 6” piece of shrink wrap over it. Always know where they are. A little paranoia is a good thing.

3, work towards the batteries. I started the second time around connecting my shunt/load side first to secure the end that had no power or ability to have anything flow through it.

 

[LCBoyer]

The Battery Bank

I started looking into DIY lithium cell buildouts and decided that I wanted to tackle it. A hot seller on the DIYSolarForums is Docan Technology. I priced out their various cells- from right about 200 ah to 304 ah cells and that's when Captain Overkill made his first appearance. Rather than settle on a 24v system with 8 cells, I decided to go nuts on a 48v system with 16 cells. Captain Overkill whispered in my ear with that Tim The Toolman Taylor grunt, "MORE POWER! YOU WANT MORE POWER!" So I doubled down and bought a total of 34 cells.

So here I'm sitting with a battery bank of 608 ah @ 48v (aka 29 kWh).

I opted for a Rec BMS to manage the cells in a 2 parallel/16 series (2P16S) configuration. Unsurprisingly, there's a lot of debate whether it should be 2P16S or 16S2P or, or, or. You makes your choices and you run with it.

All told, cells, wiring, battery containment, etc. come in around 400-450 pounds.

Currently the cells are installed under the bed, but I've been eyeing up a storage hatch that I opened up and think I can put them down there with a little bit of reinforcing. It'll also tremendously shorten my battery cables between the battery bank and the cells.

For reference, here's a detailed drawing of the Rec BMS + it's accoutrements.

WOW, JUST WOW! That is impressive

 

[ependydad]

So that's where I'm at.

My next steps are:

• Connect the BMS to the Cerbo
• Connect the Touch GX to the Cerbo + install it inside (though, the more I use the VRM- the more I'm thinking I might just go without the Touch GX
• Connect the 48/12 converters so I can do away with my AGM batteries
• Connect the 12/48 DC-to-DC charger so I can charge while driving
• Deep discharge the cells, recharge with the Quattros, and then top balance them all
• Reconfigure the 32 batteries:
  • Update their physical layout/final resting place
  • Connect them all together in 2 parallel/16 series configuration
  • Add compression
  • Reconfigure the BMS for individual cell voltages
• Buy + install all of the solar

I'm also debating adding an autotransformer so that my system sees split-phase coming out of the single-phase 110v generator and when I'm on 15/30amp 110v shore power connections. This isn't required, but it deals with some quirks of how the inverters respond when on 110v/single-phase.

 

[ependydad]

WOW, JUST WOW! That is impressive

It's coming together. Not bad for a computer geek who claims he isn't handy. I've learned a ton, though! My biggest benefit is that I obsessively learn about something before jumping in.

 

[ependydad]

Well, I'm officially started on the solar install. Even if it was the bare minimum last night.

I've gotten all of the solar panels (8 x 365 watts and 6 x 200 watts).

365 watt panels:

200 watt panels (there's only 5 here, I took the picture a few days prior and FedEx is dumb):

I’m using the box and packing material to lay out the panels on the roof and to ensure my plan will actually work.

365 watt panels perpendicular to the roof line and 200 watt panels going with it:

It overhangs the start of the roof radius just slightly. I’m going to have to be very careful that I don’t catch any tree limbs:

A look at the 200 watt panels vs the edge. They should end up extending 1/4 to 1/2 inch over the radiused portion but stay within the actual edges of the RV:

My riser/mounting plan. Each side will get a leg and I’ll cut a flange to tap into the side of the panel. Lock washers and lock tite to keep it all secure:

The full leg shown. It should work pretty well. They’ll all be hand cut but rather than prototyping with a hacksaw, I’ll break out some borrowed power tools. Let’s hope I end this project with 10 fingers!

 

[stinger608]

Wow, I just had to post for thread updates.

This is an insane build!!!!!! Amazing!!!!