Victron Inverter/Solar System with DIY LIFEPO4 Battery

[wireslv]

I finally finished up the Lithium/Solar/Inverter installation in my 375RES so I thought that I would share details in case it proves helpful for others.

We frequently dry camp and I wanted to run all outlets through the inverter without worrying about overloading if for example the microwave, air fryer, and coffee maker were used at the same time. I selected the Victron Quattro 5000w inverter since it could easily carry this load and still have headroom. The Quattro will also augment the AC input power with battery power, so I can plug into a 30A pedestal or generator and not trip it even when running several high-power loads. One air conditioner circuit is run through the inverter so that it can be part of the augmented loads.

I was initially leaning towards the 48 Volt Quattro, but after checking into overcurrent protection I would need to use exotic fuses and holders to get an adequate AIC rating. Lithium batteries can deliver an enormous amount of current and any fusing must be able to break that current without blowing up in an arc flash. As such I ended up using the 24 Volt model since fuses are readily available with adequate AIC ratings in an affordable form factor.

I personally am not comfortable running multiple Lithium batteries without a cell-level control link between the batteries and charging system. I am also not a fan of FET-based battery management systems like those typically used in drop-in Lifepo4 batteries. I looked at a few packaged communicating systems such as the Victron SmartLifepo4 batteries but the cost was prohibitive. This led to my decision to build my own LIFEPO4 system instead.

The battery system is 24V 400AH comprised of four strings of eight CALB CA100 cells monitored by a Batrium BMS. The battery pack is located in the front pass-thru compartment to provide a favorable ambient temperature. CALB brand cells are considered to be very reliable, and I opted to use their plastic cased cells instead of aluminum cased since they appear to be physically more durable. Each string has a 125A MRBF fuse at the positive battery terminal rated for 5,000 Amps interrupting current. These fuses protect the cables exiting the battery pack as well as protecting any single string from excessive current flow.

Each cell in the battery back has an attached Blockmon M8 which monitors temperature and voltage and acts as a balancer. The Blockmons are interconnected on a communication bus back to a Watchmon Core. The Watchmon is completely configurable for safety and operational limits as well as balancing. The Watchmon includes a CAN bus communication port which is compatible with Victron. A relay output on a Watchmon Expansion module is used to turn off the 24/12 DC-DC converter on low battery condition.

The Batrium BMS will monitor the pack operating conditions but requires an external device to disconnect the batteries. I wanted each battery string to be isolated from the others in a shutdown condition so I used a 4-pole circuit breaker with a shunt-trip accessory for this purpose. The breaker can be manually operated for basic on/off control when servicing the system, and the shunt-trip will trip the breaker when signaled from the BMS. The breakers are rated to interrupt 15,000 Amps DC.

After exiting the 4-pole breaker the battery leads are connected to a Victron PowerIn, Lynx Shunt, and Distributor. This provides a clean way to make the connections with no exposed terminals. The Distributor includes covered fuse holders, and the fuse status is communicated to the Cerbo GX. The Lynx shunt has a 500A fuse installed. Two 200A fuses feed the inverter, one 100A fuse feeds the solar charger, and one 125A fuse feeds a smaller SafetyHub fuse block. The SafetyHub feeds the 24V to 12V converter which keeps the house battery charged and also powers the BMS and Cerbo GX. Spare circuits are available for future 24V additions.

Since the house systems are all 12 Volt I installed an Orion-TR 24/12 70 Amp step down converter. The Orion provides a constant 13.4V output to keep the single house battery charged. The Orion could potentially power the entire 12V sytem without a battery, but I chose to have a battery present to handle inrush loads like the hydraulic pump and also to provide a backup for the electric/hydraulic brake actuator. I’m currently using the stock FLA battery, but when that eventually dies I’ll replace it with a small tractor or motorcycle AGM battery.

The 1600 Watt solar system was sized based on my previous experience with RV solar. The REC panels I’m using include extra support bars in the middle of the panel, hopefully helping them hold up to vibration and shock while driving. Solar alone should be enough to power everything (except air conditioning) when dry camping other than during a couple winter months. I didn’t use tilt mounts so winter production is much lower due to the low angle of the sun. Each panel is installed with four brackets and each bracket is lagged into the plywood roof deck using three lab bolts. The brackets were placed on butyl tape and a generous amount of Dicor sealant was used afterwards. Past experience with similar installations have held up well with no leaks. All panels are wired in parallel back to a combiner. I drilled adjacent to the plumbing vent and was able to run the solar cables behind the shower down to the basement. Each panel has its own 10 ga solar wiring back to the combiner, and panels are bonded together and to the frame using #8 ground wire. The Victron MPPT controller is oversized for my current system, but I wanted to leave extra capacity in case I add more panels, either to the roof or portable/ground mounted. I chose the VE.Can version so that it could communicate with the rest of the system.

The Cerbo GX is the heart of the system and includes three communication trunks. The inverter is connected to the VE.Bus port, the Lynx Shunt and solar controller are connected to the VE.Can port, and the Batrium BMS is connected to the CAN bus port. All connect using standard Ethernet CAT5E cables. The Cerbo GX system includes a touch-screen display to monitor and control the system. It also supports WiFi to allow remote monitoring and alarming.

The Cerbo synchronizes charging and discharging between all system components. The BMS enables charging or discharging rates through the CAN bus, providing a target Voltage and current setpoint. When the Batrium BMS allows charging it signals the maximum charge rate in Amps. The inverter and/or solar will charge while not exceeding the current limit. As the batteries near fully charged and begin balancing the BMS will signal the system to reduce charging to a low rate to prevent overvolting a cell or overheating the balancer. Once all cells have been topped off the BMS will signal the system to stop charging.
An important item to note is that the battery is being managed ‘per cell’. The charge rate is reduced once any cell reaches balancing voltage. When every cell is topped off the charging stops. If any cell voltage goes too far above the target setpoint charging is stopped. If any cell reaches a low voltage limit the inverter and DC-DC converter are turned off. And if any cell reaches a critical voltage level the shunt trip breaker cuts off the entire pack.

The user interface of the Cerbo provides a graphical display of the system and access to most of the system setpoints. I mounted the display in an empty section of the main control panel. I installed the Cerbo control unit under a cabinet near the display instead of near the Inverter and other equipment since the display cables are relatively short. Data is also sent via WiFi to a Victron server which provides web access to historical consumption and production data.
Initial configuration of the Quattro converter requires a USB-VE.BUS converter. The Solar charger is configurable via a Bluetooth phone app. The Cerbo and Lynx are configured using the Cerbo display or web page.

The line voltage wiring work for this installation was significant. I ran new 6/3 Romex cable from the side wall power inlet to the front compartment and terminated at a 14-50R range receptacle. I used a matching 50A range cord set to power the inverter. This allows me to plug in my surge protector and/or boost transformer in the front compartment instead of outside at the power pole. It also provides a disconnect at the inverter for servicing.

In order for the inverter to operate correctly, the neutral from the inverter can only be connected loads on its output. It can’t be connected to the same neutral that is serving the other line side of the split phase input. To accommodate this I used a Dremel tool to cut a piece out of my breaker box neutral bar effectively splitting it into two bars. I ran flexible ENT conduit between the inverter and breaker box containing two hots, two neutrals, and a ground conductor. The loads on one side of the 50A two pole breaker are connected to the inverter output, all sharing the same neutral bar that runs to the inverter output terminals. The other side of the 50A two pole breaker does not run through the inverter, and its loads are connected to the other neutral bar which doesn’t run through the inverter.
Overall, I am satisfied with how this project turned out. The amount of data available from the Cerbo and Batrium software allows me to monitor every aspect of the system. That way I can to sleep at night knowing there’s a giant lithium pack under my bed.

I did run into a few unexpected items along the way with the Quattro. It uses thread stud terminals for the electrical connections. This requires you to either use lugs or crimp terminals to attach your power wiring. If you use lugs, there isn’t much space between the lugs so you end up having the lugs uncomfortably close together. If you use crimp terminals, you’ll need quality terminals and a hydraulic crimper. Also, the Quattro VE.Bus communication port is located in the line-voltage compartment. This requires you to source a network patch cable with line voltage rated insulation instead of any generic cable.

I was also surprised to find out that I can’t use my solar panels to reduce the power being pulled from the pedestal (at least not in a code-compliant manner). With my previous Magnum MSH3012 system, any solar power not being used to charge the batteries would automatically be used to power inverter loads when the inverter was turned on. With the Quattro, there is no way to enable this without the possibility of back-feeding into the power cord. Think of those large prongs on your power cord being energized for a while when you unplug from the pedestal. Not good.

Another aspect of the Quattro that annoyed me was that that it includes separate Line 2 input and output terminals, but they are configured such that you can only use them as a grid/generator scenario. There is no way to use them for split phase.

From a system design standpoint the only thing that I might have changed was to use the Batrium shunt to monitor the system instead of the Lynx. This would have allowed me to gradually ramp down the charge rate as the batteries approach full charge instead of the single step I have now when balancing begins. The Batrium would have provided the state of charge to the Cerbo so it would still show up on the display.


Solar components:
(4) REC REC400AA-PURE 400 Watt panels
(4) S-5 VersaBracket-47
(48) ¼ x 1 Stainless Lab Bolts and Washers
(4) GBL4 DBT Solar Module Grounding Lug
(4) MNSR-1000 Strain Relief
(1) SmartSolar 150/85-Tr VE.Can
(1) 8x8x4 PVC Junction Box
(1) MidNite Solar MNPV6 Array Combiner
(4) MNEPV-15 15 Amp Breaker
(3) 100’ MC4 Extension Cable
(1) 50’ MC4 Extension Cable
(1) 25’ CAT5e Ethernet Cable
75’ #8 Bare Ground wire

Inverter/Power Components:
Quattro 24/5000/120-100/100 120V
Cerbo GX
GX Touch 50
VE.Bus to USB MK3-USB
Lynx Shunt VE.Can
Lynx Power In
Lynx Distributor
Orion 24/12-70A DC-DC Converter
Blue Sea SafetyHub 150 Fuse Block
CB185-100 100A Breaker
(1) 25’ CAT5e Ethernet Cable
2/0 Welding Cable
2 ga. Welding Cable

Battery Components:
(32) CALB CA-100 LIFEPO4 Cell
(32) Batrium Blockmon M8 Cell Balancer
(1) Batrium Watchmon Core
(1) Batrium Watchmon E3 Expansion Module
(4) Blue Sea MRBF Terminal Fuse Block w/ 125A Fuse
(4) C120N 125A DC Breakers
(1) MX Shunt Trip 12-24VDC
(1) HT-8 8-Way Breaker Box

Misc Components:
DIN Rail
Plastic Enclosure for BMS
Split Loom Tubing
Control Cable
Fuses
Wire Ties
5 Ohm Power Resistor (series current limiting resistor for shunt trip)
Dicor
Butyl Tape

[wireslv]

Adding a few more pics...

[TerryH]

Wow. Amazing write up and system. Thanks for posting.

[MoonShadow_1911]

Great work and write up! Thanks!

Sent from my SM-N986U using Tapatalk

[A.Texas.Yankee]

Did you balance all your cells? Or did you allow your cell balancer to do it naturally? I'll have 18 cells, but configured for 12v. On my current install I have 8 cells, and let the balancer do it, but it took weeks for it to finally balance.

Full Timing Family
2021 Momentum 395MS-R
2021 Ford F450 King Ranch

[Scott'n'Wendy]

Well...I guess that's a good start....

[Canyonlight]

I finally finished up the Lithium/Solar/Inverter installation in my 375RES so I thought that I would share details in case it proves helpful for others.

John - Double WOW !! This might be the most involved system anyone has shared on this forum since inception. You certainly seem to know your stuff. Curious, what is the investment $ committed to this ?

Dan

[wireslv]

Did you balance all your cells?

I didn't prebalance before putting together the pack since the voltage of each string was reasonably close. I have 1.5A of balance bypass current available per cell so when I did the first full charge of the pack I ran at a reduced charge rate for about 3-4 hours once the first cells reached balancing voltage while the others caught up. After that they only need a short time to balance for each charge.

Curious, what is the investment $ committed to this ?

Dan

About $12,500

[gabathey]

How many hours of research and actual labor?

[wireslv]

How many hours of research and actual labor?

Way too many hours of research, but I enjoy that side of it. The actual installation took me four weekends.