Will a Renogy Rover Li charge a lithium battery the BMS has shut off?
A LiFePO4 pack that reads zero volts at the terminals is usually not dead. The BMS has disconnected the output to protect the cells after an over-discharge, and it stays disconnected until it sees a charge voltage. The trap is that many charge controllers refuse to start into what looks like a 0V battery, so the pack and the controller sit waiting for each other.
The Rover Li is specified to operate with 0 volt batteries, sending a small current specifically to clear BMS protection. In practice that means a pack which has gone to sleep over winter storage can often be woken up with nothing more than sun on the array.
What to check before assuming the battery is finished
Measure at the battery terminals with a meter. A protected pack typically reads zero or close to it, while the cells inside are still at a usable voltage. A genuinely damaged pack will often read some low but non-zero voltage and refuse to hold a charge once it does accept one.
Leave the controller connected and give it time. Recovery current is deliberately small — the point is to nudge the BMS into reconnecting, not to bulk charge a flat bank — so this can take a while rather than happening the moment the sun hits.
When it will not work
If the pack went flat and then sat in the cold, the cells may have been damaged by the over-discharge itself, and clearing the protection just reveals a bank that has lost capacity. And if a cell has failed short, the BMS will re-trip immediately every time it reconnects. Neither is a controller problem.
How to avoid repeating it
Over-discharge in storage is nearly always a parasitic load — a propane detector, a radio memory, a tracker — draining a bank with no charge source. Either leave enough solar connected to cover the draw, or disconnect the bank at a switch before the rig is stored. A battery with Bluetooth monitoring makes this visible before it becomes a recovery job, since you can check the state of charge from your phone without opening the compartment.
What you need
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