Where This Guide Comes From
Every step in this article comes from one source video — Solar Supply House’s build log DIY LiFePo4 Battery Build. 280AH 12V Drop in battery made easy., a 6-minute assembly walkthrough that has been watched more than 33,000 times. The build takes four 280 Ah EVE prismatic cells and turns them into a 12V drop-in battery inside an ABS box, supervised by a Daly smart BMS. It is the cleanest four-cell build we have seen for a camper, trolling-motor or small off-grid setup, and the video is embedded right here if you want to follow along:
What You Need for a 280Ah 12V Drop-In
The parts list for this build is short, which is exactly why four-cell drop-ins are the most popular DIY format. You need four 280 Ah EVE prismatic cells (the video notes you can also use 271–280 Ah Lishen or CATL cells), an ABS battery box sized for them, and a Daly smart BMS — the builder says he has used Daly units successfully on many builds. The box is made to fit these cells perfectly, with room left over for most BMS units, so there is none of the foam-shaving that bigger packs usually need.
The tool list is deliberately modest: 10mm and 13mm sockets, a 10mm combination wrench, a razor knife and a voltmeter. You will also want some 4-inch gaffer tape, electrical tape and a few cable ties. Three bus bars come with the cells, and a hardware kit adds 3M double-sided tape, blue Loctite, M4×8mm stainless flange bolts for the box top and bottom, M6×20mm stainless grub screws, M6 stainless flange nuts, a 3mm hex key, and a custom-made 12-inch 2AWG jumper with 5/16-inch and 1/4-inch heavy-duty ring terminals.
Placing the Cells: Orientation Matters
Before anything gets bolted down, the builder labels the cells one through four for organization, then places them in a specific alternating pattern. Cell 4 goes in first with the positive terminal on the right, cell 3 with positive on the left, cell 2 with positive on the right, and cell 1 with positive on the left. This alternation is what creates the series path with the three bus bars: cell 1 positive to cell 2 negative, cell 2 positive to cell 3 negative, and cell 3 positive to cell 4 negative.
A tiny but important detail from the video: the grub screws are pre-assembled with Loctite before the build. Pre-applying thread-locker is a time-saver on camera, but it is also the right habit — stainless grub screws against aluminum terminals need all the thread-holding help they can get under vibration.
Mounting the BMS and Temperature Sensor
The Daly BMS arrives in a foam cutout that the builder trims to fit the box. He takes the BMS temperature sensor, pushes it slightly down the right side of the pack, and secures it with a piece of electrical tape. Then the 3mm foam square goes on the back of the Bluetooth module, adhered to the center of cell 4, with the Bluetooth lead routed up the center of all the cells. Keeping the sensor close to the cells and the Bluetooth module free of shorts is the kind of detail that separates a tidy build from a noisy one.
Sense Wires and the Sequence That Keeps You Sane
Wiring order in a 4S build is easy to get wrong, and the video’s sequence is worth copying exactly. The number-one black sense wire goes to cell 1 negative, secured loosely with a flange nut. Positive sense one goes to cell 1 positive, then cell 2 positive, then cell 3 positive. Cell 4 gets the 2AWG jumper using the 1/4-inch ring on top of its terminal, followed by the last positive sense wire and a flange nut.
Before tightening the flange nut, the builder wraps the 2AWG jumper roughly down the center of the pack. Doing this lets the upside-down 5/16-inch terminal align with the top of the battery box positive terminal. The direction of the 2AWG lead matters too — it sits at a specific angle so the box lid fits accurately. Finally, the BMS B- negative wire is installed to cell 1 negative with the black sense ring terminal on top. Daly’s highly flexible silicone wires make it easy to adjust where they sit in the space allowed.
Torque by Feel — and the Stainless-Aluminum Warning
The builder admits he has no torque specification for these terminals — he has been tightening by feel for years, and the target is simply “tight enough that the BMS B- lead does not move under good pressure.” That is a reasonable standard for a hobby build, but the video carries a warning that deserves emphasis: the grub screws and nuts are stainless steel, while the battery terminal is aluminum. Excessive torque can strip out the aluminum terminal.
One subtle point worth knowing before you copy this build: some newer EVE cells ship with welded studs that are no longer aluminum — the video’s comment section confirms the newer cells use a steel alloy against the stainless hardware, which removes most of the galvanic and stripping concern. Check your own cells before choosing torque and anti-seize strategy.
Voltmeter Check, BMS Activation and Dressing the Wires
With every terminal tightened to a good firmness, the builder checks the pack with a voltmeter to confirm the pack voltage is correct. Only then does he attach the BMS 5-pin connector and activate the BMS. The order here is deliberate: verify the series string before the BMS’s protection logic is even in the loop.
After activation, the wires are dressed with cable ties and two layers of gaffer tape go over everything as a safety measure. That tape layer does real work: it holds the sense wires flat against the pack so nothing shifts, and it keeps stray conductive material off the BMS board and terminals.
Closing the Lid: the Trickiest Step
The final assembly step is the one most builds get wrong: installing the eight M4×8mm bolts that came with the hardware kit to the top of the inside of the box lid. This step is tricky because you may have to adjust the position of the BMS B- negative, the 2AWG positive lead and where it hits the battery terminal. Once everything lines up, torque each bolt down tightly and put the lid on the box. A final voltage check and the drop-in is done.
That is the whole build — a 12V 280Ah drop-in battery, ready to slide into the same space as a lead-acid group-size battery, with roughly 3.4 kWh of usable storage. If your vehicle or system already has a charging profile for lead-acid, remember LiFePO4 charges at the same absorption voltage of about 14.2–14.6V but prefers a slightly lower float, and many drop-in installations simply let the existing alternator or solar controller do the job. For a deeper dive on matching a battery to your RV or camper, our buying guides cover it; and for a ready-made version of exactly this build, see the drop-in replacement battery line at our product center.
Six Batteries in Parallel: How Big Can You Go?
One of the most useful exchanges in the comment section answers a question every drop-in owner eventually asks: how many batteries can you parallel? The builder’s own answer — quoted in full in the Q&A section below — is that he runs six 100A BMS units on six batteries in parallel and has never needed more, even at his largest loads. The practical ceiling is usually set by the charge source and cable sizing rather than by the batteries themselves.
The same thread carries an update that matters if you are buying parts today: the builder no longer recommends Daly BMS units. His shop switched to JBD because the firmware is “far superior and they run cool.” BMS choice is genuinely a moving target — JBD and Daly both work for four-cell packs, but the firmware quality gap is real, so check current recommendations before you order.
Compression: the Question Everyone Asks
Drop-in builds get asked about cell compression constantly, and this comment section has the cleanest field report we have seen: the builder’s own 280Ah cells have sat in the box without anything to compress them for two and a half years, with no expansion. A commenter challenges the no-compression approach, arguing cells will expand and press the BMS; the counterpoint is that LiFePO4 prismatic cells in a protected box with room to breathe typically show minimal swelling, and the builder’s long-term field data backs that up.
The honest summary is that compression matters far more in high-cycle commercial applications where every fraction of cycle life counts than in a hobby or RV pack cycled gently. Charge habits matter more: the builder charges to 94% and never discharges below 30%, which he says leaves the pack “no different than new.” LiFePO4 genuinely likes a shallow duty cycle.
And if you would rather not build it yourself — a drop-in 12V battery at 100, 200 or 280Ah, ready to bolt in with the same footprint as lead-acid — that is what we do. Dajiu Energy is a Chinese manufacturer building LiFePO4 batteries for RVs, homes, golf carts and portable applications since 2017. Our product range covers LiFePO4 drop-in replacement batteries, EV and golf cart batteries, wall-mounted home storage, portable power stations, commercial energy storage and battery swap cabinets — explore the full lineup in our product center, or browse more buying guides. Tell us your voltage, capacity and size, and we’ll engineer the pack to hit it.
What Viewers Are Asking (Top Comments on the Video)
These are the most useful of the video’s top comments, with our practical answers. Where the creator replied, we quote his response; where he did not, we give our own answer written the way we would answer a customer on the shop floor. Thanks-only comments were left out on purpose; these are the ones with actual information in them.
Source video: Solar Supply House — "DIY LiFePo4 Battery Build. 280AH 12V Drop in battery made easy." (youtube.com/watch?v=VgtZ0L4uLgs). Comment excerpts are quoted verbatim from the video’s top comments; creator replies are marked as the builder’s reply. Build steps are transcribed from the video’s captions.