By Dave Miller · off-grid sparky · 22 years wiring solar, batteries and sheds in central QLD

“After a $4,000 cell mismatch in a 20kWh bank nearly burned my shed in 2019, I now balance every cell manually before wiring a 32kWh build.”

Huge 32Kwh Lifepo4 Diy Battery Build — Essential knowledge for Australian off-grid living

Huge 32kWh LiFePO4 DIY Battery Build

Why Go This Big?

I've spent 22 years wiring solar, batteries and sheds in central QLD, and most DIY builds use 280Ah or 304Ah cells to make 14 to 15 kWh packs, which is a solid foundation for a small off-grid home. But some applications demand significantly more storage.

• Whole-house off-grid systems in areas with extended cloudy periods (southern Australia in winter, for example)
• EV charging from solar: a single EV charge session can draw 10 to 15 kWh. With a 32 kWh battery, you can charge your car and still have reserves for the house.
• Workshop and farm loads: welders, compressors and heavy tools draw substantial energy
• Reducing generator runtime: more storage means fewer generator starts during prolonged bad weather

The Build Process

Despite the enormity of the job, the build follows the same steps as a smaller pack. We're using prismatic LiFePO4 cells wired 16S for a nominal 48V system.

Cell Preparation

The 628Ah cells are physically large and extremely heavy. Each cell weighs approximately 17 kg. The complete pack with BMS, cabling, and enclosure exceeds 270 kg. Will chose to build the battery on a pallet so it could be moved with a pallet jack.

1. Arrange cells in alternating polarity: negative, positive, negative, positive.
2. Insert cells into the enclosure. The fit was described as "tight" with these massive cells. Take care not to short terminals against the enclosure walls.
3. Install bus bars. These cells use screw-type bus bar connections rather than bolt-through terminals, which Will noted makes tightening significantly easier.
4. Connect bottom cells to top cells with a bridging bus bar to complete the series string.
5. Attach BMS sensing wires and power cables.

Capacity Testing: The Full Procedure

Will runs a rigorous two-stage capacity test on every battery he builds. Here is the protocol:

Stage 1: Full Charge

• Charge at 100A (approximately 5 kW) until all cells reach the absorption voltage set in the BMS.
• At 100A, a 628Ah pack takes roughly 6 hours to fully charge from empty. That is 5,000W sustained for six hours.
• Configure the BMS capacity setting to match your cells. The default password on many BMS units is 1234 or 123456.

Stage 2: Full Discharge

Here is where things get creative. Moving 32kWh of energy isn't trivial. Running that through resistive heat loads would literally overheat the workshop. Will's solution was to use an EV charger as the load, effectively pushing the energy back into a Tesla.

• Discharge via a NEMA 14-50 outlet at 240V through a Level 2 EV charger.
• This provided a true high-rate discharge test at approximately 6,000W (117A at 48V).
• The result: 672.91 Ah delivered, confirming 107% of rated capacity.

Real-World Performance: EV Charging

After testing, Will mounted the battery on a heavy-duty cart to create a mobile EV charging station. The results:

Safety: This Is Not a Small Battery

Will is refreshingly honest about the safety risks with batteries this size. During the video shoot, he dropped a 45 kg server rack battery on his foot and ended up with serious soft tissue damage. He was on crutches for days.

Handling Heavy Batteries Safely

• Use proper lifting equipment. Will purchased a forklift for his workshop specifically because of this incident. For home builders, an engine hoist or at minimum a sturdy trolley with rated capacity is essential.
• Never lift heavy batteries with ropes attached low. Will noted the lifting straps bent under the weight. Attach lifting points as high on the object as possible.
• Build in place when possible. For a stationary installation, assemble the battery where it will live permanently. Moving 270 kg across a workshop floor is dangerous.
• Wear steel-cap boots. Not negotiable when handling anything over 20 kg.
• Work with a partner. 300 kg is manageable with several people and proper equipment. 600+ kg is forklift territory.

Choosing Your Inverter for Large Battery Banks

A 32 kWh battery paired with a small inverter wastes its potential. Will recommends the EG4 12000XP (or SRNE equivalent) for large battery banks. Key considerations:

• Continuous output: Match inverter output to your peak expected load. A 12 kW inverter maxes out at 48V x 250A = 12,000W.
• Battery current rating: Your BMS must handle the sustained current the inverter draws. A 200A BMS on a 48V system limits you to about 9.6 kW of continuous output.
• Ease of setup: Will specifically noted hating the settings on the 18KPV and preferring the 12000XP for its simpler configuration.

Use the off-grid master calculator to match your battery bank size with appropriate inverter and solar panel configurations.

Is a 32kWh Build Right for You?

This is not a beginner project. It is best suited to builders who have already completed at least one smaller battery pack and are comfortable with:

• Working with voltages above 50V DC
• Handling extremely heavy components safely
• Configuring BMS settings via app or interface
• Electrical system design for high-current applications

For most Aussie off-grid sheds here in central QLD, I'd stick to two 280Ah 48V packs using lighter cells, hitting 28 kWh total. It gives you the same capacity but handles way better, plus you get redundancy with two separate systems. If one BMS guts it, the other pack keeps the house running.

Max Output Load Test

Will finished the video by running the 32 kWh pack through its maximum continuous discharge test. Connected to a 12,000W inverter pulling 201A from the battery:

• Zero BMS disconnects throughout the entire test
• All cables were warm to the touch but within safe limits
• The battery ran from fully charged to 0% state of charge without incident
• The BMS app confirmed 88 miles of range added to the Tesla during the run

This is a well-designed, robust battery. The cells, BMS and connections all held up under sustained maximum load: the gold standard test for any DIY build.

When to Call a Professional

While many off-grid projects are achievable as DIY, certain situations require licensed professionals:

• Electrical work beyond basic 12V DC additions — requires a licensed electrician
• Structural modifications to buildings or load-bearing elements
• Gas line installation or modification
• Solar array installations above safe voltage thresholds
• Any work that affects the structural integrity of your property

Always check local regulations and obtain necessary permits before commencing work.