Applicable Systems
BYD Battery Management System
Symptoms
The BYD BMS reports alarm BY005, indicating low insulation resistance. The insulation resistance between the battery pack and the chassis or enclosure has dropped below the safety threshold, risking electric shock or ground fault.
Possible Causes
- Moisture has entered the battery enclosure, reducing the insulation resistance between the pack and the chassis
- Cable insulation has been damaged by abrasion or a rodent, creating a partial ground path
- Cell module potting or insulation sheet has degraded, allowing a leakage path from the cells to the enclosure
Troubleshooting Steps
- Step 1: Measure the insulation resistance between the pack positive and the chassis with a megohmmeter at 500V DC
Insulation resistance is above 100 ohm per volt, which is 500k ohm or more for a 500V pack - Step 2: Inspect the battery enclosure for water ingress or condensation
Enclosure is dry with no water or condensation visible inside - Step 3: Check all cable insulation and cell module potting for damage or degradation
All cable insulation is intact and the cell module potting shows no cracks or degradation
How to Reset
To reset: 1) Dry the enclosure and seal any water ingress points. 2) Repair or replace damaged cable insulation. 3) Re-pot or replace degraded cell modules. 4) Restart BMS and verify insulation resistance is above threshold.
Source: BYD Battery Management System Manual, BYD Company Limited
Category: Battery