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A lithium bank without live BMS comms is a system running blind. This page is what “closed loop” means, how to recognise it on the display, and the pin facts behind it.

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Closed loop is mandatory for lithium

Closed-loop BMS: what the inverter must show — figure KNB-SVG-14

Closed loop = the inverter reads live data from the battery’s BMS over the comm cable — state of charge, limits, temperatures — and manages charging to what the pack reports. Open loop = the inverter only sees a DC voltage and estimates everything else.
  • On a Kent lithium installation, closed loop is the only acceptable state: the display must show the battery model and a live SOC % that updates. Voltage-only operation is reserved for lead-acid banks.
  • If SOC is missing, stuck, or reads 0 % while voltage looks normal, the comm link is down — go to Cable Checks before touching a single setting.
  • CAN is the lithium link on both Kent platforms. The Kent Lithium Battery talks CAN to the inverter’s BMS port.
  • RS485 exists as the alternative battery interface on the same RJ45 port for battery types that use it — it is not the Kent Lithium Battery’s link.
  • Lead-acid banks use no data link at all: the inverter manages them by voltage, with the PT1000 temperature sensor on the Kent M1 — see Kent M1 Battery Wiring.

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The pin facts (identical on both inverters)

Both Kent inverters define their BMS RJ45 port the same way (EIA/TIA 568B): CAN-H on pin 4, CAN-L on pin 5; the RS485 alternative sits on A = pin 6, B = pin 3. The Kent battery’s RJ45 is the mirror of that — CAN-L on pin 4, CAN-H on pin 5 — which is exactly why the labelled crossover comm cable exists. The full rule, the pin card and the field fallback live on Cable Checks.
Both source manuals carry the same instruction for pin-sequence mismatches: check the pin definitions on both ends before connecting, and if they differ, cut off the RJ45 at one end and re-terminate to match. On a Kent pairing that check always concludes: use the labelled Kent crossover cable.
  • Kent G3: CAN cable enters through COM1 or COM2 and lands on the BMS RJ45 — routing and glanding per Kent G3 Battery Wiring.
  • Kent M1: the BMS RJ45 sits on the comm interface — routing per Kent M1 Comms & Datalogger.
  • Multi-pack banks: packs parallel among themselves; one master pack’s CAN port carries the whole bank to the inverter.

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Common mistakes

  • Chasing menu settings for a comm fault that is the cable — cable first, always.
  • Reading “battery voltage visible” as “comms fine” — voltage is analog; comms is the SOC.
  • Plugging the battery link into the wrong RJ45 on a multi-port comm strip — label and trace.
  • Accepting a one-time SOC reading as a handshake — it must update.

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When to escalate