The Manager30 Battery Management System supports adding extra batteries to increase off-grid power, but all batteries must match in chemistry, capacity, and brand to avoid uneven charging and premature wear.
Batteries should be wired in parallel, not in series, with positive and negative connections made diagonally opposite across the bank to balance current flow. Correct cabling and terminal connections are critical to prevent voltage drop, overheating, or faults.
Using REDARC’s recommended parallel wiring method ensures all batteries charge and discharge evenly, improving efficiency and extending battery life.
REDARC recommends seeking the support of a qualified auto electrician or technician.
Important
For your safety, REDARC recommends installation by a qualified auto electrician or technician. Our trusted REDNetwork is made up of professional auto electrical businesses certified by REDARC to install the complete of REDARC solutions. Find Your Local Installer
This information is applicable to the following products:
- Manager30 Battery Management System (BMS12030S3, BMS12030S3-xx)
Adding an additional battery to a Manager30 Battery Management System increases available power for off-grid use. To maintain safe operation and system performance, it’s important to use the correct battery type and follow best wiring practices.
Battery compatibility requirements
When adding a second or third battery to your Manager30 setup, ensure all batteries share the same characteristics:
- Battery Chemistry: Match lithium, AGM, or lead-acid chemistry types.
- Battery Size (Ah): Use batteries of the same amp-hour capacity.
- Battery Brand: Keep all batteries from the same manufacturer for consistent performance.
Using unmatched batteries can lead to unequal charging, premature battery wear and system faults.
Correct parallel battery wiring method
Batteries must be connected in parallel, not in series. Parallel setup means voltage remains the same while capacity (Ah) increases.
To ensure that all batteries are equally charged, loads and The Manager30 should be connected with ground and 12V power connected diagonally opposite across all batteries.
The Ah rating needs to be setup when prompted on first start up (Refer Section 3.3), these settings can also be modified in the “Advanced Settings” menu.
To calculate Ah rating of batteries in parallel simply add the rating of each battery in the bank together. For example, 3 batteries with an Ah rating of 100Ah each will yield a total of 3 x 100Ah or 300Ah.
Recommended wiring practice
- Positive connection: Connect to one end of the battery bank.
- Negative connection: Connect to the opposite end of the battery bank.
The diagram below shows parallel wiring method and recommended wiring practice.
This technique helps ensure equal charge and discharge rates across all batteries by compensating for voltage drops along cabling.
Connecting battery terminals
- Positive Linking Cable: Required between the positive terminals of all batteries.
- Negative Linking Cable: Required between the negative terminals.
- Auxiliary Loads and Charging Positive: Connect these to the battery furthest from the BNEG (Battery Negative) shunt.
- Negative/Return Cables: Ensure proper connection to the BNEG shunt or system ground.
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Cable sizing and installation tips
- Cable Size Matters: Use appropriately sized cables for both battery connections and system wiring to avoid voltage drop.
- Avoid Undersized Cables: Undersized wiring can cause overheating, charging issues, or system errors.
- Correct Terminal Connections: Confirm that positive and negative connections are properly assigned to avoid reverse polarity or system faults.
- Professional Installation Recommended: Batteries should be installed by a qualified technician familiar with REDARC systems and battery management standards.
Why parallel wiring matters for charging efficiency
Traditional wiring methods often result in the first battery receiving most of the charge, leaving additional batteries undercharged and unevenly discharged. With REDARC’s recommended wiring method, resistance in the positive and negative wiring paths is balanced, ensuring each battery receives an equal share of current.
This approach extends battery life and maximises charging efficiency.