Off-Grid Upgrade Minimal Design – Victron Multiplus-II and 600AH Epoch LiFePO4

[jd1923]

I got a lot done this week! 🤣
In introduction, our 2016 Hull #113 has roof-mounted 340W Zamp solar, and had a 2KW Xantrex inverter (only with separate PD4000 converter) and 450AH 6V lead-acid batteries renewed in 2021. Given a recent price reduction and a 10% off sale with free shipping, we were motivated to purchase two Epoch 300AH LiFePO4 batteries for a total of 600AH and it made sense to upgrade to the Victron Multiplus II inverter/charger at the same time. Everything described to follow came to $3200 total investment including all small parts and the costs of many on-hand shop materials. Just two years ago, the cost of the LiFePO4 batteries alone would be nearly double!

First, all the old had to be removed. Demolition is always fun first step in a project! I removed the lead-acid batteries (sold them on Craigs in just a few days) and all the cables, the Inverter, the ATS and junction box. It’s crazy how OTT wired shore power to inverter power, using wire nuts in this junction box, real backyard mechanic stuff (correct design would be to use a dual-bus power panel). Everything in these pics has been removed (anybody need a 2kW Xantrex system or spare parts)? The second crazy thing is where they installed the main DC fuse (see pic). No way would I have known it's up there until I removed the cables! To access this fuse, you have to sit low reaching through the rear dinette seat.

[jd1923]

Simplicity in design is something I live by, so the goal is, beyond new batteries and inverter, to reuse everything else possible and not add any unnecessary cables, switches, buses, display screens or the like. Every additional connection adds resistance and possible points of failure. Mine is a minimum viable design (KISS).

Getting the batteries positioned was my first task, since their purchase was the start of this project! The Epoch 300AH LiFePO4 batteries at 13 ½” long fit nicely sideways in the 14x21” battery tray. They are 7.3” wide, so there is a lot of space that I’ve filled with some 2x3” stock and rubber toolbox liner, both items I had on-hand. Given the snug fit, I do not believe they need a tie-down strap. They’re not going anywhere!

Originally, I thought I would have a breaker and shunt in the battery bay and later decided all could be installed in the interior. I reused the 4/0 cables that OTT had installed but drilled a new hole for the B- cable to go directly rear to the new inverter location under the streetside bed. The B+ cable will be routed to the original Blue Seas ANL mount. I made a new 4/0 cable about 4’ long to get from the fuse assembly to the rear-mounted inverter. I was thinking Class-T fuse but decided to save the money and just buy the Victron specified 400A ANL fuse mounted in the OEM housing. Kept the original 250A fuse as a backup that would work for everything but running the A/C.

I've cut battery weight near in half, and they sit further in as well. Don’t these batteries look great and there is nothing that can go wrong here. I’ll check them once or twice and then hope to keep this bay locked for years to come without worry!

[jd1923]

I had just installed a Beech Lane dual cooling fan for the fridge cavity and thought the same fan would be great to vent the basement area under the streetside bed. A 3KVA inverter produces a great amount of heat when inverting and charging large amperage. I was waiting on delivery of the Victron Multiplus II inverter anyway and it makes sense to install this before the large inverter is in the way. This fan is a dual 5” fan. I had a 4” hole saw available and thought that was enough of an opening to clear the hot air in this small basement space.

I ended up using a jigsaw to cut a straight line opening above and below (not pictured). Notice the L-bracket top-right in pictures, necessary since this wallboard is only connected to the floor and outer wall. Then I hung the fan inside, added a wire loom. I used the grill that I removed from the furnace return when I added a filter there. Yes, the control and grill are hung upside down. I could have wired it the other way, but the wires would have to loop below. I keep a duffle bag there, so I pointed the vent up to blow over it.

Edited Sunday at 07:51 AM by jd1923

[jd1923]

Next task was to build a platform for the MP2 to lay on it’s side and strapped to the wall. I purchased 4x4 post mounts and other Simpsom ties until it all came together.

Notice the open area in the center of the first picture, rubber mat floor 4x4" in size. The area further back where the second mount would be would not take a 4x4 mount, closer to 3” width. The 4x4 in front just fit with one base tab cut off and the rear mount had to be inserted in the two parts pictured and bolted together in position. The rear mount as assembled was about 3/8” lower, so I added another layer of 3/8” HDPE board and the main board is 6x24” which you can see leveled in the last picture. I bolted strapping material to both bases prior to taping the shelf in place. Neither mount is bolted down since I did not want to penetrate the outer hull. Everything fits snuggly and the 42 LB weight of the MP2 (later) strapped above should hold it nicely.

 

 

Edited Sunday at 08:03 AM by jd1923

[jd1923]

I wired everything prior to strapping the MP2 in place. The dual DC terminals allowed for the 4/0 battery cables and other +/- connections to the B+ and B- buses. These terminals made it so no additional +/- buses were required. Notice the SmartShunt (battery monitor) is wired directly to the ground at the MP2 vs. at the batteries, yet it is still first inline as it must be.

I had 10-2 AWG direct burial cable from when I added the 30A RV outlet to our shed. I wired two runs, from the EMS and back to the 30A panel main breaker. One picture shows the old short round cable that was removed. The next picture under the rear dinette seat shows the new 120VAC wiring the MK3-USB-C interface needed to configure the MP2 inverter/charger. While I was in there, I disconnected the PD4000 controller and used that breaker to separate the microwave (now our Emeril Air Fryer) from the other 110V outlets.

I will keep it there for if/when any major changes are met. Normal operation (OFF, ON, Inverter only, Charger only) and to set incoming amperage (15, 20, 30, or 50 (N/A)) can be set via the VictronConnect App via Bluetooth from VE.Bus interface. Both devices connect using any ethernet cable (have a box full)! No panels or screens must be installed cutting into walls, unless wanted. I must find a decorative patch for the Xantrex on/off switch I removed.

[jd1923]

Time to strap down the MP2. I used ¼”x20 Plus-Nuts that I learned of on a thread that @Frank C wrote on replacing the bathroom vanity cover. There is a heavy-duty interior lip that allows for this without exposing screws to the interior. I knew of this HD lip from last year, when the curbside I mounted brackets for our motorized ball valves for the plumbing system. Not easy to get these started without the special tool but I was not going to spend that money for two bolts! A long-bolt-nut concoction and needle-nose Vise-Grip did the trick. Doubled some rubber tape for a tight fit. I got sloppy on the rear-side strap allowing the drill bit to catch and it pulled the strap in a spiral. Had to straighten it out the best I could because replacing it would be a pain.

I’ll add to this post soon to explain programming, both configuring the MP2 and updating the Blue Sky SC for LiFePO4 batteries and more usage data. Ran our old LOUD-dog Dometic Penguin II for 4 hours today while strapping down and finishing up. The inverter was supplying ~1600W and the SC about 200 (cloudy day) for 1800W total. The batteries were close to full and read 37% when done, but 100% SOC is not yet set so these may be off. Finally, thanks to Mike @rideadeuce for leading the way on Epoch batteries and the MP2 installation.

[jd1923]

Another item on the mechanical installation. I used some rubber to cushion the inverter on the bottom and backsides. The thin rubber was cut to 6x24" the size of the HDPE board and I used carpet tape to keep it in position. The thick rubber cushion was cut from a truck rear floor mat, just laid in position and the strapping should hold it nicely in place.

[jd1923]

Besides the MP2 inverter, you need to purchase two devices. The VE.Bus Smart Dongle is used in place of a control screen. It's required to read MP2 status and for some basic functions like setting the shore power amperage and as an ON/OFF switch: VE.Bus Smart dongle - Victron Energy

This device does not allow for configuration of the setup menus, so you will need the MK3-USB interface. I purchased the MK3-USB-C version since USB-C is faster and the newer style: Amazon.com: Victron Energy Interface MK3-USB-C (VE.Bus to USB-C) : Electronics (The picture shown is the USB but I purchased this item, and the title was correct as the MK3-USB-C and it was $8 less).

The MP2 can be configured when attached to either 12VDC or 120VAC. I thought it would be smart to start the configuration and see the MP2 operate as a bench test prior to loading the 42 LB monster into the Oliver basement. I had a power cord I had saved from some device I had trashed. Pretty cool and everything working! Setup menus for 

[jd1923]

On the rare chance that you would be upgrading to LiFePO4 batteries and have the Blue Sky with IPN ProRemote, Ryan Gurin, Product Support Engineer at SUNFORGE LLC is amazing, responsive, friendly and helpful. All you need is this link he supplied and it's rather a straightforward configuration as soon as you get a handle on all the button clicks without missing! (Watch the video to learn this.) How to program BSE charge controllers for LiFePO4 batteries – Sunforge LLC

Edited Sunday at 07:55 PM by jd1923

[jd1923]

Epoch batteries come with Bluetooth and their App interface. You can see battery status and status of each of the 4 cells in the 2 batteries I installed. These pics were taken earlier and after a good discharge and full recharge the VOLDIFF between cells was only 0.01V, reading 0.0V in the top summary. Nice!

Edited Sunday at 07:56 PM by jd1923

[jd1923]

This inverter is a beast! When I first field tested it, I disconnected shore power and ran the A/C off of inverter only. It was reading over 3500W and I didn't understand. This is not a 3KW inverter, but a 3KVA rated at 2400W continuous. How was it able to run at 3500W+ for 1-2 minutes until I realized it and turned off the A/C? When I did the inverter was still pulling over 1500W. I thought that nothing else was on, so I started tripping the 120VAC breakers. The last one did it and I found out we had the HWH AC switch on! Whoa, won't do that again. Then it ran A/C for the next 4 hours. I turned it down to 72 degrees and the compressor was running about 2.5 of the four hours. This old Dometic PII takes +/- 1800W or 150A DC inverted. IT dropped down for 37% SOC. Given 63% of 600AH used is 378AH and if you divide that by 150A for the A/C it comes to 2 1/2 hours running the PII full on compressor running. As @rideadeuce has shown the Atmos A/C takes half this amperage, so with a future A/C upgrade, we should be able to run all the A/C we need for the hot day now and then. Here's the internals of the MP2 Beast!

[MAX Burner]

Very clean install JD!  Thanks for the awesome step by step chronicle of your upgrade - definitely on our radar for a future project!