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A 4S DIY battery kit for pack builders: steel or ABS case, smart BMS and the full accessory set for 280Ah-class prismatic LiFePO4 cells — supplied as a kit, assembled by you, branded by you.
A Kit, Specified Like a Component — Not a Finished Battery
This page is for assemblers, RV and marine outfitters, and distributors who build their own 12.8V packs: you source the cells, we coordinate the case, BMS and hardware around them. Four 3.2V prismatic cells in series give a nominal 12.8V pack; with 280Ah cells that is about 3.6 kWh — the size that has largely replaced paired lead-acid banks in motorhomes, boats and small off-grid systems. What this kit is not is a finished battery: no cells are inside unless you order the tier that includes them, and nothing on this page should be read as a ready-to-install product.
The kit is supplied in three tiers. The market uses loose words like “complete kit” for all three, so we define each tier by what is physically in the box:
| Tier | What is in the box | What you supply |
|---|---|---|
| 1 — Case-only kit | Case plus accessory set: series busbars, sampling board or balance harness, insulation set, main terminals, protection hardware, fasteners | Your cells and your own BMS |
| 2 — Case + BMS kit (standard offer) | Everything in Tier 1, plus a fitted 4S smart BMS. This is the configuration meant when a listing says “Battery Case + BMS + Accessories (Cells Not Included)” | Your cells |
| 3 — Complete kit with cells | Everything in Tier 2, plus 4 matched Grade A cells of the model confirmed in your order | Assembly only |
If you only need the protection board itself, see our standalone smart BMS boards. If you would rather not assemble at all, finished units are in our 12V LiFePO4 battery range and surveyed in the 12V LiFePO4 battery series guide.
Reference Standard Configuration
The table below is the reference build most buyers start from. It is a starting point for a written specification, not a locked catalogue item — the next section lists what can be changed.
| Item | Reference configuration | Basis |
|---|---|---|
| Pack format | 4S (4 × 3.2V cells), 12.8V nominal; ≈3.6 kWh with 280Ah cells | Fixed by the kit design |
| Case format | Powder-coated steel case; sealed ABS waterproof case as the light-duty option | Option — see matrix below |
| Case size, reference range | ≈ 342–402 × 185–230 × 247–273 mm across mainstream market cases of this class | Reference range — exact drawing confirmed per order |
| Cell layout | Single row of 4 cells (row ≈ 288 mm thick at the cell faces), with compression plates | Fixed by the kit design |
| BMS (Tier 2/3) | 4S smart BMS, 200A continuous class for 280Ah builds, Bluetooth monitoring; 100A class for lighter-duty builds | Brand family and model confirmed per order |
| Main protection | Fuse or breaker sized to the BMS class | Rating and type per kit — confirmed per configuration |
| Display | LCD or touch display on some with-BMS configurations; not included in the case-only tier | Per kit — confirmed per order |
| Main terminals | P+ / P− terminal pair sized to the current class | Confirmed per configuration |
Two case routes exist at this size and they suit different buyers. Steel cases (the format most established kit makers sell) take compression hardware properly, stack and mount rigidly, and are what we recommend for anything vehicle- or vessel-mounted. Sealed ABS cases are cheaper and lighter and are a legitimate choice for stationary indoor builds — but check the internal dimensions, not just the shell: a published ABS shell of 342 × 185 × 247 mm measures about 330 × 178 × 215 mm inside, and that inner space is what your cells actually have to fit.
Configuration Options — Nothing Is Locked
| Dimension | Options | Notes |
|---|---|---|
| Supply tier | Case-only / Case + BMS / Case + BMS + cells | See tier table above |
| Case format | Steel case; sealed ABS waterproof case; custom dimensions for volume programmes | Custom sizes are an OEM item, confirmed per project |
| Cells fitted (Tier 3) | EVE LF280K / LF280K V3, CATL 280Ah, Hithium 280Ah, REPT 280Ah | Terminal form confirmed against the physical batch |
| 314Ah upgrade path | The same case family also accepts 314Ah-class cells | See the dedicated 12.8V 314Ah kit page and the compatibility section |
| BMS family | JK (active balancing, Bluetooth built in) / JBD (passive balancing, Bluetooth module, RS485 and heating options) / Daly (classic passive lines, or the active-balance line) | Category options — the brand and model in your kit are confirmed in writing per order, never assumed |
| BMS continuous current | 100A / 120A / 150A / 200A class | Size from your inverter and load profile — a 280Ah pack on a 2 kW inverter wants the 200A class |
| Balancing | Active 1A or 2A, or passive balancing depending on BMS family | Active balancing earns its cost on large 280Ah cells |
| Communication | Bluetooth app monitoring as the norm; RS485 as an option module; CAN is a custom item at 4S, not a standard fit | Say so in the enquiry if a system controller needs a wired link |
| Display | LCD / small touch display / none | “None” applies to the case-only tier |
| Heating pads | Optional add-on | Not standard fit. Add them if the pack will charge below 0 °C; this is separate from BMS low-temperature charge protection |
| OEM appearance | Case colour, your logo and labels, rating plate, manual and packaging | See the OEM / ODM section |
Cell Compatibility: The 280Ah-Class Footprint
The kit is built around one cell footprint family. 280Ah and 314Ah prismatic cells from the major makers share it — roughly 174 mm long, up to 72 mm thick, and up to about 207.5 mm tall including terminals:
| Cell | Capacity | Size (L × T × H, mm) | Terminals |
|---|---|---|---|
| EVE LF280K / LF280K V3 | 280Ah | 173.7 × 72.0 × 207.5 (incl. terminals) | Welded M6 stud, single or double-hole versions |
| CATL 280Ah | 280Ah | 173.9 × 71.7 × 207.2 | M6 laser-welded stud |
| Hithium 280Ah | 280Ah | 174.7 × 71.65 × 207.11 | M6 stud (DIY-market version) |
| REPT 280Ah | 280Ah | 173.93 × 71.55 × 207.23 | Published sources conflict (M4 vs M6) — confirmed against the physical batch before busbars are drilled |
| EVE MB31 / CATL 314Ah / Hithium 314Ah | 314Ah | Same footprint family (173.7–174.3 × ≈71.7 × ≈207.2) | M6 stud versions |
The compatibility rule is mechanical, not commercial: a cell fits if its footprint falls inside the family above and its terminal form matches the busbar drilling. Capacity class alone is not a mechanical standard — cells sold as “280Ah” can differ by several millimetres between makers. Send the exact cell model with your enquiry and the match is confirmed in writing. If you are still choosing cells, our guide on choosing LiFePO4 cells for pack assembly and the 280Ah / 314Ah prismatic cell range are the right starting points; cells are also listed on our cell wholesale page.
What Is in the Accessory Set
- 3 copper series busbars — a 4S pack needs one link per cell junction, i.e. series count minus one; the count follows the format, not a marketing bundle
- BMS connection busbar set — the main-path links between cell block, BMS and terminals (a separate set from the series links)
- Sampling board, or a balance-wire harness — the two market forms of the same job: routing the 5 sense taps (B0–B4) to the BMS in order
- P+ / P− main terminals, sized to the current class
- Fuse or breaker for the main path, rating per kit configuration
- Display where the confirmed kit includes one
- Insulation set — epoxy / fibre sheets between cells and case, EVA pads between cells
- Fastener pack — terminal bolts, case and lid screws
Exact counts of insulation pieces and fasteners follow the bill of materials of the case in your order and are listed in the order confirmation — makers vary these counts widely, and we would rather confirm ours in writing than copy a competitor’s packing list.
Assembly: Four Cells Into a Working 12.8V Pack
- Check the cells before anything is bolted. Compare resting voltage and internal resistance across all 4 cells, and bring them to a common state of charge. A spread you ignore here becomes the imbalance you chase for the life of the pack.
- Insulate first. Epoxy or fibre sheets between the cell block and the case, separators between cells. In a steel case especially, prismatic cell cans must never rely on the cell’s own film alone.
- Set the row under even compression. Fit the end plates snugly and evenly — prismatic LFP cells want moderate, uniform compression, not maximum force. Torque values come from the cell maker’s manual for your exact cell model and are stated in the kit documentation; there is no universal number, and anyone who gives you one without naming the cell is guessing.
- Land the sampling connections before the power path. Fit the sampling board or balance harness from B0 upward and verify every tap reads in sequence before any busbar carries current.
- Bolt the series busbars in order — 3 links, polarity checked twice. Work cell 1 negative to cell 2 positive and onward, checking polarity at every step with a meter, not by eye.
- Wire the BMS main path and protection. B− to the first cell’s negative, P− out to the load terminal, fuse or breaker in the main line, then the P+ terminal. Confirm the BMS wakes and reads all 4 cell voltages before the lid goes on.
- Supervise the first full cycle. Watch per-cell voltages on the app or display through the first charge. A cell that runs away on cycle one is cheap to fix on the bench and expensive to find in a customer’s motorhome.
- Close up and record the build. Note the cell batch, BMS model and settings on the build sheet. That record is what makes warranty discussions and repeat orders simple.
A necessary word on who should do this: a 12.8V 280Ah pack can deliver very high fault currents despite its modest voltage. Assembly belongs with trained technicians using insulated tools. If your operation does not have them, buy the finished battery instead — it is the honest recommendation.
Where a 3.6 kWh DIY Pack Earns Its Keep
- RV and camper conversions — the classic 12V 280Ah use case: one pack replacing a lead-acid bank under a seat or in a locker, built under the outfitter’s own label; see our RV power page
- Marine house banks — sailing and workboat house power where local assembly and serviceability matter; see marine power
- Small off-grid and cabin systems — 12V-native lighting, refrigeration and communications loads; see off-grid power
- Assembler production — workshops turning imported cells into own-brand 12V packs for regional RV, marine and solar retailers
OEM / ODM: Your Brand, Your Specification
The kit format exists for buyers who sell under their own name. OEM options cover case colour, logo and rating labels, manuals and packaging; configuration options cover the BMS family and current class, terminal arrangement, display, and — on Tier 3 — the cell model the kit is built around. For volume programmes, case dimensions can be produced to a project specification rather than taken from the standard range.
Our role in that process is coordination: requirements are confirmed in a written specification, matched against manufacturing partners’ production, and the agreed checkpoints and documents are handled on the export side. The specification confirmed in your order document is what binds the shipment — not this web page, which is why every variable item above is marked “confirmed per order”. Start from our OEM & ODM coordination page or the OEM / ODM RFQ checklist if you want the full document list.
What to Send Us for a Quotation
- Tier — case-only, case + BMS, or complete with cells
- Cell model — the exact cells you will fit (or ask us to supply them under Tier 3)
- BMS current class and main loads — inverter size and surge loads, so the current class is confirmed against your real use, not the cell label
- Case format — steel or ABS, and any dimensional constraint of the locker, rack or compartment it must fit
- Quantity and destination — a sample kit for evaluation, or your expected regular volume, plus the destination port
One logistics advantage worth planning around: Tiers 1 and 2 contain no cells, so they ship as general cargo — no lithium-battery dangerous-goods freight. Many buyers ship kits by standard freight and source cells on a separate, optimised route; Tier 3 ships as regulated lithium cargo like any cell shipment. Exact packing dimensions and weights for your configuration are stated in the quotation.
Related reading before you enquire: the BMS selection guide for sizing the board, and the rest of this series below.
Frequently Asked Questions
Steel or ABS case — which should I choose?
Steel, for anything that moves. Vehicle and vessel installations vibrate, and a steel case holds compression hardware, mounting points and terminals rigidly over years of it. A sealed ABS case is a reasonable budget option for stationary indoor builds, but verify the internal dimensions before ordering cells — published ABS shell sizes are external, and the usable inner space is several millimetres smaller in every direction.
Can I build it with 314Ah cells instead?
Yes — 314Ah cells share this footprint family, and cases in this class are commonly rated for 280–314Ah. That is exactly what the dedicated 12.8V 314Ah kit page covers. Confirm the exact 314Ah model when you enquire, because terminal form, not capacity, is what the busbars are drilled for.
How big a BMS does a 280Ah pack need?
The BMS is sized to the load, not the capacity. A 280Ah pack behind a 2,000 W inverter can be asked for 170A or more, so the 200A class is the common choice for this size; a lighting-and-refrigeration build may never pass 80A and can use the 100A class. Tell us the inverter size and surge loads and the class is confirmed in the specification.
Can I parallel two of these packs?
Parallel operation is a system design decision, not a kit feature: each pack keeps its own BMS, the packs must be built from matched cells at a matched state of charge, and the interconnect and protection must be sized for the combined fault current. If your product plan calls for parallel packs, raise it in the enquiry — case and terminal arrangements for parallel builds are confirmed per project rather than assumed.
Do I have to buy the BMS from you?
No. Tier 1 is case-only precisely for buyers with their own BMS platform. What we would ask is which board you plan to fit: the case’s BMS mounting position and display cut-out are arranged around a board class, and it is cheaper to confirm that fit on paper than to discover it on the bench.
Is a heating pad included?
No — heating pads are an optional add-on, confirmed per order, and we say so plainly because some listings imply otherwise. Add them if the finished pack will be charged below 0 °C — a real consideration for RV and marine packs wintering outdoors. They are a different thing from the BMS’s low-temperature charge cut-off, which is a protection setting on the board itself.
The DIY Kit Series
This page is the 12.8V 280Ah model in an eight-model DIY kit series: 12.8V 100Ah / 280Ah / 314Ah (4S), 25.6V 280Ah / 314Ah (8S), and 51.2V 100Ah / 280Ah / 314Ah (16S). Each model gets its own page because the cases, cell families and assembly details genuinely differ. The other seven models in the series: the 12.8V 314Ah DIY kit, the 12.8V 100Ah DIY kit, the 25.6V 280Ah DIY kit, the 25.6V 314Ah DIY kit, the 51.2V 280Ah DIY kit, the 51.2V 314Ah DIY kit and the 51.2V 100Ah DIY kit. The full product range is on Products.
Request a quotation for this kit: Start a DIY-Kit-12V280 inquiry · WhatsApp: +86 159 8945 0735
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