PowerWalker LiFe Battery System 48-100 Mode D'emploi page 22

Notice
It's required to have RJ11 jumper connected to the single battery
module, or to the master battery module when working in parralel with
multiple modules for normal operation.
Step 2 (If multiple battery modules are in parallel):
Insert RJ11 cable to connect the extension port of the master battery
module. The other end connects to the extension port of the #2 battery
module. If there are more battery modules are connected in the system,
repeat this step to connect more battery modules.
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