Battery Charging

Is it good practice to leave a battery connected to the charger even if the battery has fully charged?

Depends on the charger, if the charger is a maintaining charger then yes it is fine, and most are. We use the Noco chargers and they will allow the battery voltage to drain some then bring in back up as to not over charge.

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If you have a ‘smart’ charger, then it’s generally okay. As Bmongar said, most of them are like this and will automatically keep the battery at a healthy charge. If your charger is old or it doesn’t have this sort of auto management feature (or it’s not very reliable), then you have to be more careful.

With batteries it’s poor practice to overcharge them. You can’t “shove” more power into a full battery, and the excess heat just leads to risk of the battery bursting/igniting, and it’s just generally unhealthy because it speeds up the rate of corrosion in the intermal metal things. If you (or someone you know) had a hoverboard that was left plugged in overnight and you woke up to the pleasant surprise of a now on-fire and/or covered in acid hoverboard, that’s exactly why you don’t overcharge batteries.

Batteries won’t ignite just because you left them plugged in.


I was being general, but as you try to add more energy into the battery it all has to go somewhere. Since the working energy storage is full, it builds up as heat which causes pressure. With enough heat and pressure, it’ll eventually burst and whatever leaks out can cause fires. That’s a pretty extreme case though, in general overcharging batteries just causes the metals inside it to corrode and store energy less efficiently.

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“No, it is not recommended to leave a battery on the charger after it has finished charging. Overcharging can cause the battery to overheat and release potentially dangerous gases, and can also reduce the battery’s overall lifespan.” This is the common answer to this question, but most modern SLA battery chargers have built-in overcharge protection that prevents the battery from overcharging, but it is still a good idea to remove the battery from the charger once it has finished charging. This will help to ensure the safety and longevity of the battery. It won’t hurt to leave it on as the FRC chargers from AndyMark have the overcharging protection but we normally unplug overnight if we aren’t there for extended periods of time.

Exert from the AndyMark chargers

This charger is a great tool for competition robotics teams and hobbyists using Lead Acid batteries. Dual Pro chargers charge batteries to 100% specific gravity every charge, and are able to adjust current in the absorption and finish stages based on the battery’s communication with the charger

There are 3 unique charging banks included in this charger, meaning that you can charge three batteries at a time. Each bank has a capacity of 6 AMPs. This charger supplies a safe amperage level to quickly charge 12V lead acid batteries. The charger is engineered for occasions which need a charging system that may require the battery to be left on the charger for days at a time.

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Thank you!

You are welcome! Good luck this season!

We use the Andymark chargers and are happy with them. But this is marketing. It uses a voltage profile to charge the battery just like many other smart chargers. I actual have a specific gravity gauge floating use to measure charge in slosh batteries. Anyway continuing to attempt to charge a lead acid battery after it has reached full charge will start turning water into oxygen and hydrogen gas. Not good for the SLA batteries that you cannot replace the water. Smart chargers have the ability to drop back to a maintenance voltage and don’t do this so they are safe to leave on the baattery.

Frank I fully agree with you that this is marketing as far as making the charger seem far superior for others, I was just mainly pulling the description provided by AndyMark themselves.

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