Pictured: the BK4A-C and BK4A-HC variants
LiFePO4 battery
12.8 V / 320 Ah
AkuBox LiFePO₄ battery 12.8 V / 320 Ah / 4.0 kWh, 4× EVE MB31-D06-01, connectors on top. Bluetooth + CAN + HEAT heating. JK BMS with active balancer, hand-built in the Czech Republic, 4-year warranty on the cells.
- Energy
- 4 kWh
- Capacity
- 320 Ah
- Cycle life
- 8,000 cycles
- Cell warranty
- 4 years
Variants of this pack
Other voltage or capacity · AkuBox
What it's good for.
An enclosed 12 V battery built from EVE MB31 cells for motorhomes, caravans, boats and small PV systems. The plastic box protects it from damage and from curious hands.
A BAKOM battery pack with a nominal voltage of 12.8 V and a usable capacity of 320 Ah / 4 kWh in a rigid plastic AkuBox. The pack is made up of four prismatic LiFePO₄ (lithium iron phosphate) EVE MB31-D06-01 grade A cells in a 4S configuration. It is designed for PV systems, backup power supplies (UPS) and off-grid and mobile installations (cottages, caravans, motorhomes) where reliable, maintenance-free energy storage is required.
Safety and optimum operation are handled by an advanced JK BMS control unit, which continuously monitors all critical values — overvoltage (OVP), undervoltage (UVP), overcurrent (OCP), short circuit (SCP) and temperature — and intervenes immediately if the limits are exceeded. It includes an active balancer with a current of up to 2 A, which continuously equalises the voltage between the cells and extends their service life. All operating data is available wirelessly via Bluetooth in the BAKOM BMS app.
Why LiFePO₄: lithium iron phosphate chemistry is one of the safest lithium technologies — it resists thermal runaway, allows deep discharge and offers a much higher cycle count than lead-acid batteries. For a long service life we recommend using the capacity within the 10–100 % range and keeping the cells within the optimum temperature range (ideally 25 °C).
AkuBox design: a rigid plastic box protects the cells and the connection terminals, which makes the unit suitable for places where people may have access. On the side of the box there is an ON/OFF switch with an LED status indicator (on variants with an external LCD, ON/OFF is built into the display). The connection terminals come out through the top lid, while the communication and control elements are on the side as standard; in the “T” variant all elements are on the top lid, for installations with little space at the sides. Variants are available with CAN and RS485 communication for connection to inverters (Victron, Growatt, GoodWe, Deye and others), as well as HEAT variants with automatic heating (42–48 W), which allows safe charging even at sub-zero temperatures.
Installation must be carried out by a qualified person — correct polarity, appropriate fusing and correctly sized cabling are essential. The pack is covered by a warranty; any modification to the BMS configuration or the cabling voids the warranty.
This variant (BK4AT-HC): Communication: Bluetooth, CAN; cell heating (HEAT) for operation at low temperatures.
Technical specifications.
Values for the BK4AT-HC variant. The charge and discharge limits match the BMS settings the battery leaves the workshop with.
- Nominal voltage
- 12.8 V (4S)
- Capacity
- 320 Ah
- Energy
- 4 kWh
- Chemistry
- LiFePO₄ (lithium iron phosphate)
- Cells
- 4× EVE MB31-D06-01
- BMS
- JK B2A8S20P
- Balancer
- active, 2 A
- Continuous current (charge and discharge)
- 160 A
- Peak current
- 200 A / 20 s
- Cycle life
- 8,000 cycles to 70% capacity
- Charging — temperature
- +1 to +55 °C
- Discharging — temperature
- −22 to +55 °C
- Charging: absorption / float
- 14.1 V / 13.8 V
- Discharge cut-off (recommended)
- 12.0–12.4 V
- Communication
- Bluetooth, CAN
- Heating
- yes — HEAT
- LCD display
- optional
- Build
- AkuBox
- Terminals
- top (T version)
- Dimensions
- 36.5×19×25 cm
- Weight
- 25 kg
- Production
- handmade, Czech Republic
- Warranty
- 4 years on the cells
Energy = capacity × average discharge voltage (3.125 V per cell), i.e. the energy the battery delivers between the BMS limits. Cycle life is stated by the cell manufacturer for 25 °C; actual life depends on operating conditions. The 4-year warranty applies to the cells; the BMS and other electronics are covered as set out in the warranty certificate.
Ready to connect.
Each battery leaves the workshop with its BMS set up and after a final test. Every battery comes with a report of the measured cell capacity and a warranty certificate.
- Battery with the BMS configuredWe set the protections according to the battery type and the communication according to your inverter.
- Cell capacity reportMeasured capacity and internal resistance of each cell, and the result of the final test.
- Manual and warranty certificateWiring procedure, recommended inverter settings and warranty terms.
- Inverter cableIncluded with 48 and 51.2 V batteries with BMS+ according to the ordered configuration; for other batteries at extra cost.
- BAKOM BMS app and BAKOM CloudBattery status and cell voltages on your phone via Bluetooth, history and settings on the web. Free for BAKOM batteries.
What you ask us.
Didn't find your answer? Call or write to us — we'll help you choose and connect it.
When will I receive the battery?
We build batteries by hand to order and do not keep them in stock. After your inquiry we confirm the current lead time and put you in the order queue — the reservation is free and non-binding. We contact you before production starts.
Do I pay a deposit?
No. We build and test the battery, then send the invoice and dispatch the battery once payment has arrived. Smaller batteries go by PPL, heavier ones on a pallet; the shipping cost is stated in the quote. Collection in person is possible by arrangement near Klatovy or near Ostrava.
Will the battery communicate with my inverter?
CAN variants communicate with Victron, Deye, Growatt, GoodWe, MUST, Luxpower and other inverters, and via RS485 with, for example, Voltronic inverters. With a Victron system (Cerbo GX), it is the CAN variants that communicate. Our batteries are low-voltage — they do not work with high-voltage (HV) hybrid inverters. Send us your inverter type and we will check.
Can I charge the battery in winter?
Below +1 °C the BMS blocks charging to protect the cells and allows it again above +4 °C. Discharging is possible down to −22 °C. For unheated spaces there are variants with HEAT heating (suffix H), which warm the cells before charging.
What charging voltage should I set?
12.8 V: absorption 14.1 V, float 13.8 V · 25.6 V: 27.9 / 27.4 V · 51.2 V: 55.8 / 54.7 V · 48 V (15 cells): 52.3 / 51.3 V. The BMS protection voltage (3.56 V per cell) is not a charging target. For 15-cell batteries, do not use profiles for 51.2 V or for lead-acid batteries.
Is the inverter communication cable included?
For 48 V and 51.2 V batteries with BMS+ (RC variants), yes, depending on the configuration ordered. For 12.8 V and 25.6 V packs we supply it at extra cost or make one to measure.
Can I add another battery later?
Variants with BMS+ (BK8K-RC and the 48/51.2 V RC series) can be connected in parallel; up to 16 batteries with the same BMS version can be addressed. Each battery is connected separately to the DC busbar with cables of the same length and cross-section — daisy-chaining power cables from battery to battery is not permitted. For more than two batteries we go through the set-up with you in advance.
What is the difference between the AkuBox and a compression box?
The compression box keeps the cells clamped, which benefits their life especially under high load; it can stand horizontally or vertically. It is an open design, so it belongs in a lockable technical room. The AkuBox is a closed enclosure that protects the battery from damage and unauthorised tampering — made of plastic for 12.8 and 25.6 V. The metal AkuBox BK16A-RC also has a built-in display and an isolator switch.
How many cycles will the battery last?
Packs built from EVE LF280K and MB31 cells last 8,000 cycles until capacity drops to 70 %, 105 Ah packs 4,000 cycles to 80 % (cell manufacturer's data at 25 °C). Actual life depends on temperature, currents and depth of discharge.
How should I store the battery over winter?
If the battery will be out of use for more than a week, switch it off. Store it in a dry place, charged to roughly 40–80 %, and top it up every three months. Never leave it fully discharged.
How can I monitor the battery remotely?
The BAKOM BMS app connects to the battery via Bluetooth. The BAKOM Cloud web portal then keeps your batteries, measurement history and settings in one place — you add a battery to your account with the QR code on its label. More on the App page.
Am I allowed to change the BMS settings?
We set the protection parameters in the workshop according to the battery type. Normal user functions in the BAKOM BMS app do not void the warranty; changing the protection configuration, changing the administrator password or modifying the wiring does.
Interested in the BK4AT-HC?
Get in touch.
Add the quantity, the type of inverter or appliance and your timing. We check that the pack suits your system and send a quote with a delivery date.
- baterie@bakom.czInquiries, orders and technical questions
- Bronislava Baxová
- +420 737 344 853Orders, lead times, invoices and dispatch
- Petr Baxa
- +420 603 552 577Production, wiring of batteries and Deye inverters
- Michal Komenda
- +420 602 564 571Technical matters, off-grid systems and Victron, BAKOM BMS app
- Workshops
- Svrčovec near Klatovy and Krmelín near OstravaVisits and collection by appointment only