Building the LiFePO4 battery

Finally, my battery cells arrived. It took much longer than expected due to customs delays. The seller shipped my cells by train from China and did send me a tracking. The cells would enter Europe through the Warsaw train terminal, and once arrived and released by the Polish customs, UPS would ship them from Poland to the Netherlands.
Unfortunately, this took a very long time, but once the UPS tracking was (finally) working I’ve received the cells within a few days.

But this was to be expected. You do save money, but have to order it yourself, have access to the required payment methods, you have to find a reputable seller (some sell refurbished cells), and you need to have the proper tools and knowledge to balance them.

Since I did order bare cells, I had to top-balance them myself in order to get the best performance. The cells can have different SOC levels (State-Of-Charge) and once in series, the cell with the lowest SOC would trigger the BMS to shutdown. By balancing the cells you’re equalizing all cells to be as equally close as possible, thus allowing you to use the most of its capacity. I’d opted for a top-balance, which is the most recommended way of balancing for RV usage.

Basicly: connect all cells in parallel, charge them to 3.65V till the current is (almost) zero and you’re done.
However, this can take a long time, especially if you have big/many cells and/or they are at a low SOC. It all depends on your power supply. Since mine could only deliver 5A.. and each cell is 280Ah, you can do the math: 4×280 / 5 = 224 hours if they were completely flat.
Also, I didn’t want to leave the cells charging unsupervised during top balance, so that wasn’t really an option, even if the cells were at 50% SOC it still would take 100+ hours.

So I connected all cells in series, and hooked up my BMS. I’ve set the high-voltage disconnect to 3.65V and connected my regular 24A charger. Using this method, I could charge much faster (11.6 hours if completely flat). But mine came pretty full, I think somewhere around 75% SOC. So after only a few hours of charge the BMS did shutdown as it should, since 1 cell reached 3.65. Once that was done, the cells were near full.

I rewired the cells in parrallel to do a full top balance. Since the cells were now either full or very close to, it only take a few more hours with my 5A power supply (set to 3.65V) to full charge all cells.

Once that was done, topbalancing was finished and I could start assembling the final battery.

I used concrete forming plywood for the case. Since the cells are aluminium I checked if they were connected to any of the poles, and yes, the outer case was +. Although the cells are covered in a thin foil, I wasn’t very happy to clamp them together, since the protective layer isn’t very thick. To reduce the chance of a short I’ve added some 2mm PVC between the cells (Which I had as leftover from my build).

The cells are clamped using M8 threaded rods, with a big washer and a locking nut on both sides. On the inside, I’ve covered the rods with plastic tubing, used for air pumps in a aquarium.
On one side I have left some space to mount the BMS. I also added a CF8 fuse to the positive terminal and added a main switch on the outside

For the negative pole, it’s connected to the shunt of my Victron BMV. From the shunt, there are 2 wires: 1 thick 50mm2 (0AWG) to my inverter, and a 5AWG to the BMS.

The output of the BMS is connected to my main fuse box, so everything is ran trough the BMS (loads, charger, DC-DC, solar and so on). Only the inverter is bypassing the BMS.
If there is an error, the BMS will shutdown and protect the cells.
I will add a relay to the switch of the inverter, so the relay is released once the BMS shuts down, thus shutting down the inverter as well, without having me to run the huge currents of the inverter through the BMS.
Altough my BMS is capable of handling 120A, I didn’t want to run the inverter, since it requires cooling and generally isn’t really recommended to run a BMS on or near its maximum rating.

The cells came with double busbars and M6 screws, but I’ve seen reports of people stripping the threads in the cells since that’s aluminium, so easy to overtighten.
To prevent this, and have maximum thread available, I’ve cut a M6 threaded rod into small (2.5cm / 1″) pieces and screwed them down to the bottom, making sure all available thread is used. Using lock nuts I connected everything on top. This gave me also plenty of length to work with (the included screws are too short anyway if you want to used double busbars, decent cable lugs and spring washers).
Using a torque wrench, I’ve thightend everything to 7nm, as stated in the datasheet so I should be ok.

Finally, it was time to add the cover. I’ve installed an aluminium air vent in it, and cut a hole to connect the wire from my shunt.
The box is securely fixed to the van using steel angle brackets, so even in case of a crash, it won’t come flying through my van (It does weigh approx 30kg (66lb) or so, so that’s something you need to avoid.

Finally, I had to adjust all chargers to the optimum settings for LiFePO4, so I’ve changed the solar controller, DC-DC charger and regular charger, and it was time to test.
Connected the normal charger to the mains, works. Started the van: DC-DC charger also started working, so I was able to charge 60A in that case (40A DC-DC, 24A mains charger, but I did have lights on so that was about 4A load)

Wiring Head-unit, rearview camera and DC charger

Now it was time to do some modifications in the main cabin. I still had to connect the wire from my DC to DC charger to power it on, and had to connect my rearview camera.

Initially, I planned to keep my existing headunit, a simple JVC radio with bluetooth, and use the provided monitor to use with my rearview camera.
However, this monitor was supposed to be mounted on the existing rearview mirror, but my van didn’t have one.. And even if it had, I wasn’t very happy to mount a ‘big’ screen: It would block my vision partially.
Also, I couldn’t find a nice place to mount it on my dash, without compromising my view, and I didn’t like having a ‘unit’ sticking out.

So plans were changed: I needed to get a simple in-dash monitor. Since i’m using my phone for navigation, which works fine for me, I didn’t need a satnav in the dash. Android auto or Apple Carplay was nice to have, but I wasn’t willing to pay for it ;).
That means I only had a few requirements: Bluetooth (I’m using it mainly for streaming, especially when in another country), FM radio (although if reception was poor, I still could use the bluetooth) and an input for the camera.

I found a cheap chinese radio at Banggood: The iMars 7023B “7 inch 2 DIN car MP5 player stereo radio FM USB AUX HD bluetooth touch screen support rear view camera”
Did fit my needs, and it was cheap: 28 eur (Approx 33 USD) including shipping. Nothing fancy, just some cheap Chinese thing. Arrived in only a few days.
Very lightweight, and small. Definitely within its price range: Cheap plastic..

I also had to get the appropriate mounting brackets: 2 pieces were required: A 2-din frame to support the radio, and a matching faceplate to fit it in a Ducato.
Found those on Amazon for 27 euro in total (Generic 2DIN frame and a CARAV 40-205 frame for the Ducato). Almost as expensive as the radio 😉

Installing it was pretty straightforward, however I had to do some cutting (Had to remove a piece of plastic seperating the existing 1U and the tray above). Also the generic frame wasn’t a very close fit, had to do some adjustents and remove some plastic from the outer frame to fit the tuner, but with some patience and carefull cutting with a knife it wasn’t a major issue.

Wiring was the next challenge.
I did run the wire from the dashcam through the passenger side to the radio. I only had to find a swithed power line to power the cam. Also, the radio required a 12V to automaticly switch the reversing camera. I didn’t run a wire from the back (reversing lights) so I had to find a wire somewhere in the cable loom underneath the dash which was only active when reverse was engaged.
In Fiat E-Learn (the digital documentation of the whole van, including engine and wiring diagrams), I found there is a wire from the reverse switch on the manual transmission to the main wiring cabinet under the dash. (Pin 8 on the E connector of the B002 unit below the drivers side).

From E-Learn:
The reversing lights switch I020 is supplied by the INT line protected by fuse F35 of the junction unit under the dashboard B002.
When reverse gear is engaged, the switch closes and sends a power supply to the reversing light in the right rear light cluster F031 (pin 4) via pin 8 of connector E of the junction unit under the dashboard B002.

So I spliced that wire, and ran an wire to the headunit This wire supplies the reversing signal to the headunit and powers the rearview camera. (So it isn’t powered on always, only when reverse is engaged).
I used the connector which came with the radio to act as a donor for a wire: The original connector of the Ducato didn’t have all pins connected, so I had to add 1 connection for the reverse switching line.

Once the radio was fitted, and the wiring looms and fuse panels were exposed anyway, I was up to the second job: The wire for the DC-DC charger.

I could just connect it to a switched 12V, but that would mean it will charge always when the ignition is on, even without having the engine runnning.
I however wanted to have it only active when the engine is running (so it would draw power from the alternator, instead of draining the starter battery if you’re for example having a small stop without the engine running, but with the key in ignition.

So again, Fiat E-Learn to the resque:
The connection between connector B (D+) of the A010 alternator and pin 25 of connector A of the M001 Body Computer allows the performance of the alternator itself to be diagnosed (in the event of an insufficient recharging level).

Found this wire (it was Green/Brown unlike White/Pink as stated in Elearn, but anyway), so I spliced this wire also, and connected the DC-DC charger and put some heatshrink on. And yes, it was working fine: DC charger only powered on when the engine was running and switched off when I stopped the engine.