Is it bad to leave a car charger plugged in – Overcharging an EV


It is scary to think that you might be damaging in your expensive high voltage electric car battery just because you are forgetting to unplug it.  You were away on a business trip and you had left it plugged in over 3-4 days.  What would happen?  We all know how expensive it can be to replace a damaged electric car battery. Do you need to be monitoring constantly the charge level so that as soon as they are fully charged, we unplug them?

Is it bad to leave an electric car charger plugged in? Fortunately, it is not bad to leave your electric car plugged in or charge for an extended period. With electric cars being more effective to run and operate more than fossil fuel, they have grown in popularity significantly and the battery charging systems are designed so that damage will not occur while charging.  They will trickle charge at the point where the charge is almost complete. 

As the number of electric cars increases in the market, most individuals tend to ask questions about maintaining their cars’ batteries’ functionality.  Therefore, in this article, I shall be answering some of these frequently asked questions. Such as, can just forget about my electric car and keep it plugged in whenever possible?

Can I leave my electric car charger plugged in all the time?

As stated earlier, leaving your electric car charger plugged in for an extended period is safe. Furthermore, it is standard practice, and the in-built battery management system significantly lowers the risk of overcharging.

The management system aids in lowering the down charging process once your car’s battery is near full charge. When it reaches 80-90% charged, the battery management system will trickle down the charging process.

Furthermore, electric cars will use up small amount of the battery charge in order to keep some electric functions run smoothly even when not in use.  Trickle charging an EV helps in restoring fuller battery charge until the charger is unplugged. This means that you will always find your car charged well-enough and not overcharged.

Is it okay to leave an electric vehicle plugged in charging over the weekend?

Overcharging an electric car is almost impossible, thanks to its in-built battery management system. This means that leaving your electric vehicle plugged in charging over the weekend will not negatively impact your car.

With a tesla, you can set the maximum charge level.  Once this level is reached the charging will stop even when the vehicle is still plugged in.  Most people set the limit to be 80 percent because at that level, they can easily reach a supercharger in case they are getting low on a charge after taking a trip that is close to home.

Some electric car manufacturing companies advise users to leave their cars plugged in while they are parked at home.  This is because electric cars have a maximum battery charge capacity it will allow, and when it is at this level, it will reduce the charging speed.

Also, if you have your car plugged in at home, you will still end up with an adequate travel range because your EV will not need to use up the battery charge to heat or to cool the inside of the car once you are ready to start your trip.

Plus, some on-board systems in electric cars run continually.  For instance, a subroutine may keep the car’s battery at a constant temperature.  This function will use a low amount of the battery charge while parked.

Can I leave my hybrid car plugged in overnight?

Just like an electric car, you can also leave your hybrid car plugged in overnight. In fact, leaving your hybrid car plugged in at night allows you to take advantage of the off-peak electrical hours; this means that you will be able to charge your car at a lower price.

In addition to that, hybrid cars are also fitted with an in-built battery management system. As a result, your car will not overcharge. Once your car reaches its capacity, it will stop charging automatically; therefore, your car’s battery will remain functional for an extended period.

Nevertheless, if you have fully charged it and then you try to top it off after a short voyage, the manual for the Outlander PHEV states that you should not do so.  A top-up uses yet another charging cycle and all electric car and hybrid car batteries have a limited number of charge cycles.  In other words, leave it plugged in when at home and try not to unplug it and plug it back in again too soon.  Use a good portion of the charge before you do so.

Is it okay to be charging a cell phone in an electric car with the engine off?

No, it is never okay to charge your cell phone in an electric car with the engine off. It turns out that charging your phone in an electric car does more harm than good. When you plug your phone into your electric car’s USB port, the phone will use up the charge in the 12v battery.  If you have a Tesla, you need a charge in the 12v battery to power on the touchscreen.

If you wish to charge two phones at once, I recommend that you use the Anker dual USB charger.  Click here to see the current pricing on Amazon. It can charge many devices in your car within 35 minutes to 100 percent.

If have read about owners that attach another 12v battery that can be used for the USB port, but that is extreme needing to charge your cell phone while your EV is parked and turned off.  A lot of people are so obsessed with cells that they will go to any length to keep their phones fully charged.

Is it okay to leave a flash drive plugged in an electric car all the time?

Is it okay to leave a flash drive within your electric car if data is not being written to it constantly?  If the security system is updating photos to it, there is a chance that you are going to wear it out overtime.  Each time that something is written to a flash drive, you are reducing its effectiveness.

However, if the flash drive only has data that is constant, leaving plugged in, is ok.  Your electric car will not be accessing it and its lifespan will remain intact.

If you have many USB devices, I suggest that you check out the BASENOR Tesla Model 3 USB Hub.  Click here for Amazon pricing.

With respect to the health of the electric car, leaving a flash drive plugged in is not going to do any harm.  Even though, you would drain the 12v battery if you were to read files that are on the flash drive if the engine is not running, the amount of power needed is small.

Most flash drives are not live all the time.  They are just accessories that store files and that need to be activated by another device to read the files.  Think of them as hard drives.  A hard drive in a computer that is turned off, does not draw power.

Here is a video explaining ways to keep your 12-v battery in your electric car healthy, even if you have devices such as flash drives connected:

Final verdict

As an electric car owner, taking care of your car’s battery is vital. Fortunately, electric cars are equipped with incredible technology that protects the cars’ batteries allowing them to be reliable and highly functional for an extended period. This means that you will not have to do much when it comes to taking care of your car’s battery. The length of time that you leave your car plugged in should not worry you.  Nevertheless, try not to complete small charges all the time.  Any battery has a finite number of times that it can be recharged.

The questions discussed above in this article, allows you to understand better how an electric car’s battery function and some of the dos and don’ts one should keep in mind as an electric car owner.

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