How Long Can You Leave A Battery Maintainer On: Get The Best Out Of Your Harley-Davidson Batteries


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How Long Can You Leave A Battery Maintainer On

Do you often end up overcharging your Harley-Davidson motorcycle batteries? Do you go a long time without using your bike? Is it affecting the performance of the batteries? Then a battery maintainer is just what you need.

You can leave a battery maintainer on for as long as you want and it’ll monitor the charging. The goal of a battery maintainer is to maximize the lifespan of your Harley-Davidson batteries and keep the state of charge at 100%.

In this article, you’ll get to know all about a battery maintainer, how it benefits a Harley-Davidson bike, how long can you leave a battery maintainer on, and a lot more. Continue reading to know all the answers.

Is a battery maintainer the same as a battery charger?

Every Harley-Davidson motorcycle requires power to start the engine and function. The bike will derive that power through the battery. Just starting the motorcycle on a regular basis and riding it for a while is enough to keep the battery charged. It should come as no surprise that owners who rarely take out their bikes for drives tend to face battery discharge issues. Fortunately, this issue can be easily avoided by using battery maintainers. A battery maintainer will keep the battery at 100% at all times.

Many Harley-Davidson riders are never fully sure what a battery maintainer is. Most of them often confuse it with a battery charger. The big difference to remember is that a battery charger will send a constant charge to the battery. The charger doesn’t factor in whether the battery should be continuously charged. With battery chargers, it is highly likely that you might end up overcharging the battery. This will result in permanent damage to your bike’s battery.

A battery maintainer, on the other hand, will sense how much of a charge the battery needs. It will slowly send a trickle charge to it over a time period of several hours. It will automatically stop sending a charge once the bike’s battery is full. As a result, battery maintainers will not overcharge the battery the same way that a traditional charger will. This will help extend the overall battery life.

How long can you leave a battery maintainer on?

As surprising as it may sound, you can leave the battery maintainer on your bike at all times. In fact, it is recommended that you should plug in the battery maintainer and leave it. However, it is also recommended that you should check the maintainer once every couple of weeks.

The battery maintainer will be on float mode, which means you will not have to worry about the battery. Further, a battery maintainer will always slow charge the battery while also protecting it. Many people mistake a battery maintainer for a battery charger. While a battery charger and a trickle charger are similar, a battery maintainer is very different. Further, it’ll be more active than a trickle charger. A battery maintainer will provide the battery with its lost charge at a fixed voltage. If you’re able to keep the battery properly maintained, it’ll last for several years or even decades.

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The ultimate goal of a battery maintainer in the long term is to maximize its lifespan by keeping it at 100%. If you allow the battery to drop below 100%, the chemical reaction in the electrolyte will start to reverse. After that, the plates inside the battery will gradually start building a layer of sulfate. The longer you’ve left the battery under the 100% charge, the more the sulfate on the lead plates will crystallize. Once it has crystallized, it’ll start hindering the conductivity within the battery while also increasing internal resistance.

It’ll lead to decreased power and the battery will be at a higher chance of overheating during charging or discharging. The best way of keeping the battery at 100% charge is by using a battery maintainer. The best thing about it is that once it’s connected, it’ll essentially act as a mini-computer with a diagnostics system. It will perpetually monitor the state of charging in the battery and keep it at 100% precisely without overcharging. It will be safe to leave the battery maintainer connected to the battery once you’ve met these conditions –

  • You’ve tested the maintainer first while also monitoring for any abnormalities 
  • The water levels are good (in case it is a flooded battery)
  • The specific gravity is good (in case it is a flooded battery)

It is important to remember that battery maintainers are not the same thing as trickle chargers. Trickle chargers are an antiquated style of chargers. Moreover, a trickle charger lacks the microprocessor that perpetually monitors the state of charge in the battery.

A trickle charger will keep pumping current into the battery. It will continue doing so even after the bike’s battery has reached the 100% charge. Not able to process the residual electrical current into chemical stored energy, the battery will start releasing the energy. The energy will be released as heat and evaporation of the water within the electrolyte. If the battery loses enough water, the lead plates will get exposed. Once they get exposed to oxygen, there can be irreparable damage to your battery. Ultimately, the battery could lose all power and time, despite having a long lifespan originally.

What is the best time to use a battery maintainer?

The best time of using a battery maintainer is whenever your bike will remain idle for a long time. The biggest advantage of using a battery maintainer is that it will not overcharge your Harley-Davidson bike’s battery. It is perfect for keeping your Harley-Davidson batteries charged while it is not being used.

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After all, it isn’t possible to connect your motorcycle battery to a charger for days, let alone months. This will overcharge the battery and heavily damage it. However, leaving the battery connected to a battery maintainer is perfect, as the charging stops once the battery is 100%. This way, you will be able to ensure that your battery will remain fully charged, and your bike will be ready to function despite spending weeks or months in storage.

When should you not leave the battery maintainer connected to the battery?

If your Harley-Davidson bike has a damaged cell or battery, then you shouldn’t leave a battery maintainer connected. You should neither do this for the short-term nor for the long-term. This will do nothing but overcharge the battery. It will further ruin the other cells through sulfation once the lead plates get exposed to air.

Eventually, if you’ve left the battery charger connected long enough and the water has evaporated out, there would be a risk of fire or explosion if the charger is connected to a largely dry battery. Any battery maintainer will be able to recognize this problem. It’ll then turn off to prevent any incident from happening, but why take any risk in the first place? You shouldn’t let it come to this situation and prevent it before it happens.

Remember to supervise the battery maintainer before leaving it unattended

Before you leave the battery maintainer plugged into the battery for months without checking, you should first ensure that you use it to charge the battery first. Make sure that you monitor the charging for a while. This way, you’ll be able to get a feel of how the maintainer is working. Moreover, you will be able to detect any problems or abnormalities. Once you feel comfortable with it, you can go ahead and keep it connected for weeks or months. It is recommended that you should always get a battery maintainer from a reputed place for a safe, user-friendly experience.

Can a battery maintainer damage your Harley-Davidson motorcycle?

The simple answer is no. A battery maintainer will not harm your motorcycle’s battery under most circumstances. Technically, a battery maintainer is manufactured for turning off the charging once your motorcycle battery has reached the 100% mark. It automatically comes into action once the battery discharges. You will be able to utilize a battery maintainer on your bike’s battery for a long time period without any worry of it harming the battery.

You can easily keep the battery maintainer connected to the bike’s battery all through the winters or even during spring. However, you need to make sure that you test both the battery and the battery maintainer from time to time. By doing this, you’ll be able to know if the battery or battery maintainer has developed any faults.

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A battery maintainer is advised for people who sometimes go long periods without taking their Harley-Davidson bikes for a drive. It will also work well for people who are residing in a cold country. The battery tender will safely maintain the battery’s charging even if it isn’t being used. You must keep in mind that the batteries have to get warmed up during the winters. Plugging in a battery maintainer to the battery will greatly help. Moreover, an unused Harley-Davidson bike will lose its battery charge unless it has been connected to a battery maintainer. You will need to utilize a battery maintainer for keeping the battery well-charged and properly protected.

What to look for in a battery maintainer?

When you’re looking for a battery maintainer, you will want to ensure that it should meet a couple of demands. The unit you’re going for should have either a float or maintenance mode, while it should be microprocessor controlled. There are hundreds of options in the market. This is why you need to check for the best possible option, as you’ll be relying on it a lot. Go for a charger that will gently charge the batteries without overcharging them. It shouldn’t make the battery sound like it has been boiling. Moreover, the battery maintainer must give a “set it and forget” type of experience and leave you more than satisfied.

Battery maintainers come in 3, 4, and 5 amp models. These will work great for vehicle batteries. You could go with the 5-amp model. It is the fastest of the tree while not being high enough to possess any danger to the battery. For smaller batteries like a motorcycle, there will be a smaller 800mA maintainer available in the market (for 12V batteries). In case you have a battery like 6V, 8V, or 24V, there will be maintainers that work well. However, make sure that you verify the voltage before making the final purchase.


Thank you for reading. Hopefully, now you know a lot more about battery maintainers, how it affects the battery in your Harley-Davidson bikes, and how long can you leave a battery maintainer on. A battery maintainer is a great option for people who go a long period without using their bikes. It will keep the battery charged at 100% even if you don’t use your bike for weeks or months. It is recommended that you can leave the battery maintainer connected for months and get a 100% charge when you have to use your bike.

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