Can you parallel PM-LV rack batteries of different ages or capacities?

Direct answer: Not as a casual mix. Keep parallel groups matched in voltage class, capacity, and preferably age/firmware. The PM-LV51200-5U offers 51.2V 200Ah (~10.24 kWh) with long cycle-life messaging; pair like with like, or expand as separate groups per Redway parallel guidance.

Operators expanding a rack ESS sometimes want to parallel a new PM-LV51200-5U 51.2V 200Ah module with older PM-LV48100-3U 48V 100Ah modules. Mixed-age and mixed-capacity paralleling is a common request—and a common source of imbalance if done casually.

What the product pages support: the PM-LV51200-5U is a 51.2V 200Ah LiFePO4 rack battery with about 10.24 kWh class energy messaging, operation called out from about −20°C to 60°C, and longevity messaging over 8000 cycles at 80% DoD at 0.5C on that page. The PM-LV48100-3U is positioned as a 48V 100Ah server rack battery for uptime-focused storage. Both are modular rack form factors intended for scalable energy storage, but “modular” does not automatically mean any ages and capacities can share one DC bus without following the manufacturer’s parallel rules.

Best practice for paralleling: keep identical nominal voltage classes, prefer identical capacity and firmware generation on a parallel group, and bring modules to a similar state of charge before closing parallel contactors. Mixed capacities (100Ah beside 200Ah) can work in some architectures with proper BMS master/slave or inverter configuration, but current sharing will not split perfectly—wiring resistance and BMS limits matter. Mixed calendar age increases the risk that weaker modules hit voltage limits first, shrinking usable pack capacity.

If you must expand an older string, safer patterns include: adding a new parallel group on a separate inverter MPPT/battery port, or replacing a whole parallel set together. Always follow Redway’s current parallel wiring guide for the PM-LV series (communication cables, addressing, and maximum modules per group). Do not invent series strings across different firmware without documentation.

Direct answer: avoid casually paralleling mixed-age, mixed-capacity PM-LV modules on one bus. Prefer matched modules; if expansion is required, isolate groups or refresh the set so BMS current sharing stays within published design intent.

Commissioning checks should include verifying each module’s reported voltage and temperature before enabling high charge rates, confirming that the inverter’s battery profile matches 51.2V LiFePO4, and documenting module serial numbers by rack position. When a single module in a parallel group repeatedly shows higher internal resistance or earlier current limiting, plan a targeted replacement rather than forcing higher charge voltage to “keep up.” That habit overstresses healthier modules and shortens the string’s useful life even if nameplate cycle life remains high on paper.