Reviving A Smart Fortwo Electric Drive Battery
- Hosea Embury
- Aug 19, 2025
- 4 min read
Updated: 1 day ago
Your Smart Fortwo Electric Drive Has HV battery Problems
Is your Electric Drive Smart car’s high-voltage battery officially "dead"?
If your car won't charge or start after sitting idle for a while—like after being in storage or tucked away for a long winter—you’re in the right place.
However, if you’ve noticed your driving range dropping significantly, or if issues keep popping up and "fixing themselves," the problem might be a bit deeper, such as moisture in the battery pack or a weak internal cell.
Understanding the Battery System
The third gen Smart Fortwo Electric Drive (ED3) uses a lithium-ion battery that powers the vehicle. The battery is made of (93) individual pouch style cells wired in series. These cells are divided into 3 modules of (31) each. Over time, factors such as age, temperature fluctuations, and long periods of inactivity can diminish the battery’s ability to hold a charge and the available range. This is normal; however, the ED3 battery is a very robust, German-made battery and has been known to last much longer than other batteries made around the same time. With proper care, these batteries can outlast the car and easily get you Smart to the 150,000-mile mark.
The Weakness: Battery Management System
The weakness lies in the very sensitive battery management system (BMS). The BMS in your Smart Fortwo closely monitors the battery’s health and performance. If the BMS senses that the battery charge is critically low, it may prevent the vehicle from starting to safeguard the battery from further damage. This feature helps prolong your battery's lifespan.
Occasional no start situations indicate a insulation fault commonly caused by moisture in the battery pack. The solution for this is to "dry" the pack and replace the desiccant.
In my humble opinion, there is a mis-programed function of the BMS is to deplete the charge from the HV battery if the low voltage (12V) battery has been removed, discharged, or in poor health for an extended period. This process is known as "Junkyard Mode." This "safety" feature prevents an electrocution situation if someone were to unknowingly tamper with a charged high voltage (HV) battery or HV wiring. To fix this irreversible program, also known as "bricking or locking", requires removal of the battery, cell revival, and possibly rewriting/re-flashing code in the BMS. This is the situation caused by inactivity. A locked BMS will have trouble code P18051C
Important: Make sure to keep the 12v battery in good repair and replace when necessary. A failing 12v battery will end up killing the HV battery.
Common Symptoms of a Dead HV Battery
Before diving into solutions, let’s identify some common signs that indicate your Smart Fortwo's HV battery might be dead or bricked. Look out for these symptoms:
Dashboard warning shows "Drive Sys. Engine off," "HV System Workshop," or "Malfunction, Service Required."
Your vehicle does not respond when you press the accelerator in "R" or "D."
The battery will not charge even when connected to a charger.
The right gauge pod on the dash surface (power meter) wont move from the "Off" position when attempting to start the car.
If you notice any of these issues, your battery likely needs some attention.
Troubleshoot First
Note: You will need a Scan tool capable of scanning every module.
Check the Charger and Connections First
Before concluding that the battery needs to be removed for repair, first ensure your charger is working properly. Inspect the charger for visible damage and ensure it is plugged into a functioning outlet. Also, check the connections between the charger and the vehicle. Loose or corroded connections can hinder the charging process and cause trouble codes that cause a HV system workshop warning. Scan the car, specifically the charging system module, with a scan tool to determine if there are any charging related trouble codes and clear them. If this does not change anything...
Scan the BMS.
Next scan the BMS and note the trouble codes. Look for codes (P1D799A) and (P18051C) The second code is the most undesired code that indicated a locked/bricked BMS. Clear any codes, wait 5 minutes and try charging again.
If still nothing works and you are still unable to start, move, or charge your Smart, you may need to book a battery repair service with Embury Automotive.
Alternatively I can guide you through the process if you feel comfortable tackling this procedure yourself.
Reviving the Battery
The revitalizing and repair process may take a few weeks to finish. This does not include the time to remove the HV battery pack from your Smart. Embury Automotive does not replace individual cells in the HV module. If there are individual cells that are damaged or weak, recovery may be impossible. Replacing individual cells is usually unsuccessful because the BMS closely monitors differences in each cell's internal resistance. BMS unlocking/re-flashing is currently outsourced, and is an additional cost.
Here is a DIY video: https://youtu.be/Mgh6KLAGYNU?si=PY6I9GJ9sgPgYGoC
Preventing Future Battery Issues
After repair, if successful, to avoid facing similar issues down the line, consider these preventive measures:
Regularly Drive Your Vehicle: If you don’t use your Smart Fortwo often, aim to drive it at least once a week to keep the battery active.
Maintain Battery Health: Check the 12v battery health every year and the terminals for corrosion occasionally and clean them if needed.
Store Properly: If you expect to store your vehicle for an extended duration, consider using a battery maintainer to keep the 12v battery charged.
Important: Make sure to keep the 12v battery in good repair and replace when necessary. A failing 12v battery will end up killing the HV battery again.
Get Your Smart Fortwo Back on the Road
Reviving your Smart Fortwo Electric Drive battery might seem challenging at first. But with the right approach, you can get back on the road.
By familiarizing yourself with the battery system, troubleshooting effectively, and taking preventive measures, you can ensure your vehicle remains reliable and ready for your next adventure. Don’t let a dead battery hinder your enjoyment of the unique driving experience that the Smart Fortwo provides.
Take action today and revive your battery! I am located in Myerstown Pennsylvania and you are responsible for transporting your car to me for repair. Give me a call for more info - 1(223)333-0880
Here is the 2016 Smart from the video link.
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