Illustrative photo of the open-frame assembly
LiFePO4 battery
12.8 V / 320 Ah
Open-frame LiFePO₄ battery 12.8 V / 320 Ah / 4.0 kWh, 4× EVE MB31-D06-01. Bluetooth + RS485 + CAN. JK BMS active balancer, handmade in the Czech Republic, 4-year warranty on cells.
- Energy
- 4 kWh
- Capacity
- 320 Ah
- Cycle life
- 8,000 cycles
- Cell warranty
- 4 years
Variants of this pack
Other voltage or capacity · Open
What it's good for.
An assembly without a cover, made from EVE MB31 cells, for building into a dedicated space. It is a few centimetres smaller than the AkuBox in every direction.
The BAKOM 12.8 V / 320 Ah / 4 kWh battery assembly is a lithium iron phosphate (LiFePO₄) storage unit in an open-frame design — four prismatic EVE MB31-D06-01 grade A cells held together with straps, with terminals protected by plastic caps and no plastic AkuBox. It is intended for PV systems, backup and off-grid installations and for mobile use (motorhomes and caravans) where compact dimensions and lower weight count.
Compared with the AkuBox version, the open-frame assembly is a few centimetres smaller in every direction (dimensions 31.5 × 23 × 18 cm, weight approx. 23 kg), so it also fits into tight spaces such as a double floor. As it has no protective housing, it is only suitable for dedicated spaces with no access for unauthorised persons and requires professional installation.
Every assembly includes an advanced BMS control unit that continuously monitors all operating values — it protects against overvoltage, undervoltage (deep discharge), overcurrent, short circuit and temperature extremes, continuously balances the cells and estimates the state of charge (SOC). Operating data is available in the BAKOM BMS mobile app via Bluetooth. A heated variant (HEAT) is not available for the open-frame version — for charging in freezing temperatures, the AkuBox version is the one to choose.
LiFePO₄ chemistry offers high operational safety and resistance to thermal runaway, a long service life of thousands of cycles and the option of regular deep discharge. To keep the battery in good condition, we recommend using the capacity in the 10–100 % range and topping it up to 100 % roughly once a month so that the state of charge is recalculated correctly.
This variant (BK4-RC): Communication: Bluetooth, RS485, CAN; LCD display optional.
Technical specifications.
Values for the BK4-RC 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, RS485, CAN
- LCD display
- optional
- Build
- Open
- Dimensions
- 31.5×23×18 cm
- Weight
- 23 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 BK4-RC?
Write to us.
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