Troubleshooting Your BMS: Why Your Battery Keeps Discharging and How to Fix It
Your battery management system (BMS) aims to protect your battery, but a constantly discharging battery can indicate issues related to your BMS. Whether the battery drain is due to protection mechanisms or a faulty BMS, it’s crucial to pinpoint the cause of unexpected discharging so you can address the root of the issue.
Here’s a guide on how to diagnose and fix what’s draining your power.
Top Reasons Your Battery Keeps Discharging
Your battery may be discharging for many reasons, but these five are the most common.
Age-Related Capacity Loss: As batteries age beyond the first three to five years, their capacity will gradually diminish. The BMS still reports using the initial specifications, so what may seem like 80% charged may only give you 60% of the expected runtime. Thus, your battery may appear to be discharging rapidly, but the truth is that it is just operating at a naturally reduced capacity.
Imbalanced Cell Voltage: The individual cells within a battery should be at the same voltage, but there’s a chance they get imbalanced. These slight (~0.1V difference) variations require more effort from the BMS to balance them. While you might not be actively using the battery, this balancing process consumes power in the background and can create spontaneous discharges.
Temperature Extremes: The BMS works within a specified temperature range, and when it falls below the minimum *(32ºF) or above the maximum (104ºF), it will automatically shut off to avoid damaging the battery’s lithium cells. It’s an important safety feature that can come across as mysterious battery drain if you don’t realize you’ve pushed beyond the temperature thresholds.
Parasitic Loads: If you have a device connected to the battery that is still drawing power, you can unsuspectingly lose battery life. These devices draw energy even when turned off, which makes unplugging crucial to protect the battery percentage. These are called “phantom loads, " making it seem like the BMS is malfunctioning.
BMS Miscalibration: When the BMS loses its reference points or is improperly calibrated, it may not read the state of charge correctly. The percentage shown may be higher than the actual charge, leading to unexpected shutdowns that appear to pinpoint a discharge issue.
How to Tell If the BMS Is Causing the Issue
Is it the BMS, or something else? Determining the cause of unexpected discharge can be tricky, but here are a few tips to help you determine if the BMS is the culprit when dealing with something like the EcoFlow DELTA Pro 3 Portable Power Station or a home solar system.
First, check your battery’s display or the EcoFlow Smartphone App. You may see alerts for temperature warnings, cell imbalance alerts, or overcurrent notifications. You could also use a multimeter to check the voltage readings of individual battery cells. If there are differences greater than 0.1V, it could indicate BMS-related balancing issues.
Next, use a 24-hour window to monitor and track your battery’s behavior. Don’t connect any loads; just observe. A healthy battery will lose about 5% charge daily, but if you see a loss of 10% or more within the window, it’s a good sign that the BMS is trying to address an underlying issue.
EcoFlow DELTA Pro 3 Portable Power Station
Steps to Fix or Reset a Discharging Battery
If your battery is discharging out of character, use these steps to reset your equipment and try to fix the issue.
Perform a Complete System Shutdown
First, disconnect all loads and charging sources. Turn off the main battery and wait at least 30 minutes for the BMS to power down. This total reset will clear any temporary error states in the battery and recalibrate the battery readings.
Clean All Connections
Inspect all of the battery's terminals and ports. Use a wire brush to remove any corrosion or debris. Check the tightness of all connection points, as looseness can create resistance that the BMS may perceive as system faults, triggering shutdowns for protection.
Mitigate Environmental Threats
Ensure the temperature and environment are appropriate for the battery. The temperature should be between 32ºF and 104ºF (0ºC and 40ºC). Move it out of extreme storage or operational conditions and place it in a moderate environment. Wait a few hours and then try using it again.
Test the Charge/Discharge Cycle
Perform a controlled charge and discharge cycle. Discharge it to 20% capacity, then begin a complete recharge cycle so the BMS can recalibrate its state-of-charge (SoC) calculations and resolve any present issues.
Update BMS Firmware
Check to see if there are any firmware updates to address known discharge issues. Wireless updates may be available to resolve bugs that impact the power management of SoC reporting.
Find an Alternate Charging Source
If issues persist, you may need to find alternative charging sources in the meantime. If you’re on the go, consider something like the EcoFlow 800W Alternator Charger, which can charge your battery while you drive using the car's power.
How to Prevent Battery Discharge Issues in the Future
If battery discharge issues are the culprit, there are a few things you can do to prevent similar problems in the future. Always operate and store your battery within the optimal temperature range, and check its capacity monthly to catch degradation as it happens.
Use app monitoring to stay aware of voltage imbalances and avoid deep discharges past 20% capacity to prevent unnecessary stress on the BMS and battery cells.
Check quarterly for potential firmware updates, and prioritize early issue detection to prevent discharge-related problems.
Frequently Asked Questions
Why Does My BMS Keep Shutting Off?
Your BMS may be shutting off to protect the battery from damage. Issues like overcurrent, extreme temperatures, imbalance voltages, or a low state of charge can all cause harm, and your BMS will shut down to safeguard the battery; it may not be a malfunction at all.
How Do I Tell if My BMS Is Bad?
Your BMS may be failing if it shows inconsistent or incorrect voltage readings, inaccurate state of charge readings, or fails to balance cells over extended periods. Use firmware updates and system reboots to reset calibrations and resolve issues. If problems persist, BMS replacement may be necessary.
Final Thoughts
A discharging battery for an unknown reason can cause frustration and confusion. Is it a faulty BMS, or is the BMS protecting you from other underlying issues? Knowing the potential culprits and the steps to resolve a discharging battery can help you pinpoint the root cause, fix present issues, and prevent more problems from arising in the future.
Use the helpful features of the BMS integrated in all EcoFlow products’ LifePo4 batteries, like the EcoFlow DELTA Pro 3, to find a solution.