This guide is for projects using multiple independent lithium battery packs in parallel. It shows what must be checked before selecting the BMS for each pack and the complete parallel system.
Start by Defining What Is Being Connected in Parallel
This guide covers systems built from multiple independent lithium battery packs whose outputs are connected to a common DC bus. It does not cover cells connected in parallel inside one battery pack.
Does Each Independent Pack Need Its Own BMS?
For a system built from multiple independent lithium battery packs, each pack normally needs its own BMS to monitor and protect that pack. The complete system must then be checked for safe parallel operation.
Before connection, confirm the pack chemistry, series count, voltage, capacity, state of charge, condition and operating temperature. These differences can affect current sharing between packs.
Do Not Divide Total System Current by Pack Quantity
If a 300A system uses three packs, 300A ÷ 3 does not prove that each pack will always carry exactly 100A. Current sharing can change with pack resistance, state of charge, temperature, cable resistance, connection resistance and wiring layout.
For each pack, confirm the expected continuous battery-side current, the highest peak current, how long the peak lasts, how often it repeats, and the thermal conditions around the BMS.
Verify Parallel-Pack Capability as a Separate Requirement
A BMS with the correct voltage and current rating is not automatically suitable for a multi-pack parallel system. Packs connected at different voltages can exchange current when the connection is made, so the intended parallel function must be verified for the selected BMS.
DALY Mini-Red Smart BMS: What Is Verified
DALY's current A-Series Smart BMS current ladder is AH 40A/60A, AK 80A/100A, AM 150A/200A and AS 250A/300A/400A. The number of packs does not determine which current rating to choose; the current requirement of each pack must be confirmed first.
Source: DALY A-Series current tiers
DALY also publishes a current Mini-Red application example stating that the built-in parallel module can support up to 10 packs in parallel. Treat that as a product capability to verify against the exact project configuration rather than as permission to connect any 10 packs without checking pack compatibility.
Source: DALY 16S/48V, 8S/24V and 4S/12V pack-spec article
Confirm Communication Separately
CAN, RS485 and UART are communication interfaces. An interface does not by itself prove that several BMS units will coordinate current, operate as master/slave devices, or communicate with a specific inverter or controller. Confirm the required protocol for the project.
What to Send DALY for Selection
| Project input | What to provide |
|---|---|
| Battery | Chemistry, exact S count, nominal voltage, capacity per pack |
| Parallel system | Number of packs and intended connection method |
| Current | Continuous current per pack; peak current, duration and frequency |
| Equipment | Charger, inverter, controller or load information |
| Communication | Required interface and protocol |
| Commercial | Sample/pilot/production quantity |
Send these parameters to DALY. The engineering team can recommend the suitable BMS current rating, confirm whether the proposed parallel-pack configuration is supported, and provide the corresponding datasheet and quotation.
Q1Can any two BMS-protected lithium batteries be connected in parallel?
No. The packs and the BMS configuration must be checked for the intended parallel system before connection.
Q2How should I size BMS current for parallel packs?
Use the expected continuous and peak current of each pack and consider current sharing and operating conditions. Do not rely only on total current divided by pack quantity.
Post time: Aug-06-2026
