48V or 51.2V rack battery: which one matches your inverter?

Direct answer: Match the battery’s voltage window to the inverter’s battery settings and its approved-battery list. The 48V module charges to 54.75V and cuts off at 37.5V; the 51.2V module charges to 58.4V and cuts off at 40V. Both are LiFePO4 and both are “48V class”, so the right answer depends on the inverter, not on the name.

The numbers from the product pages. The PM-LV48100-3U lists 48V nominal, 100Ah, 4.8 kWh, 54.75V maximum charge and 37.5V cut-off. The PM-LV51100-3U lists 51.2V nominal, 100Ah, 5.12 kWh, 58.4V maximum charge and 40V cut-off. The PM-LV48200-5U is the 48V class at 200Ah and 9.6 kWh. All three list 100A maximum continuous charge and discharge, RS485 and CAN bus communication, and more than 8,000 cycles at 80% DOD and 0.5C on the 3U pages.

Our arithmetic, not stated on the pages: dividing the voltages by 3.65V per cell gives 15 cells in series for 54.75V and 16 for 58.4V. That is consistent with a 15-cell “48V” pack and a 16-cell “51.2V” pack. The point is that the two modules are not interchangeable and should not be mixed on one bus.

On the inverter side, find three things in its manual or settings: the battery voltage range it accepts, the charge voltage it will apply to a lithium battery, and how it selects a battery profile (a named protocol, or user-defined voltages). The inverter’s maximum charge voltage setting and DC input range must include the pack’s values (54.75V or 58.4V). If the inverter can only be set to a narrower window, check whether that still allows the pack to be used safely.

The pages list compatible inverter brands, such as Growatt, Victron, Deye and SMA, among many others. A brand list is not a model-level approval. It does not state firmware versions, protocol versions or the settings to use. Ask Redway for confirmation that names your inverter model and firmware, and which protocol and DIP-switch address to use.

Before the first charge, set the battery profile on the inverter, confirm voltages and current limits against the product page, and watch the first full cycle on the inverter’s battery screen. Inverter profile selection is specific to each inverter, and Redway’s page does not publish a per-model list, so confirm both with Redway engineering first.