Most motorcycle riders, at least in the USA, use their bikes for leisure rather than primary transport. As a result, our bikes are often sitting without the battery being exercised or charged by the alternator while riding. With parasitic draw increasing on modern bikes from various electronic elements, keeping your battery charged while parked is critical for motorcycles. But what is the correct motorcycle battery charger for your bike?
We’ll cover the major types of chargers available for motorcycles and some thoughts on specific models we have experience with. We’ll also discuss the connectors that can be used to charge the battery and some specialized chargers for specific bikes that have features you may find helpful.
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Align your charger to your battery
Motorcycle batteries typically are in one of a few chemistries: lead acid, AGM, or Lithium. While ancient bikes may use Lead Acid, the vast majority of bikes use AGM & in most cases, an AGM battery can replace an older lead acid one in your motorcycle.
AGM & Lead Acid
Technically, AGM is still a lead-acid battery, but it differs from what most people think of as a typical lead-acid battery in some important ways.
A conventional lead-acid battery is sometimes called a wet-cell battery. You need to monitor the electrolyte level and top it off with distilled water. As a result, there are ports where you can add fluid to the battery, and you will feel the fluid splashing around if you shake the battery. Most lead-acid batteries are 12 volts, but some older bikes may use a 6V design that requires a special charger to support it.
AGM batteries, on the other hand, are often called a sealed design. A fiberglass mat is placed between lead plates and is soaked in electrolyte. The design eliminates the need to refill the electrolyte, so they are sometimes called no-maintenance batteries. They require a specialized charging approach different than conventional lead acid batteries. Almost all AGM batteries are 12V, typically for more modern bikes. You might find some 6V AGM batteries intended to replace a conventional lead-acid battery on an older bike. Some other variants of AGM batteries are called GEL, which uses a gel as the electrolyte to keep it from splashing around.
Lithium
Most phones and laptops available today use a battery chemistry called Lithium Ion. Some variants include LiPo (Lithium Polymer), which uses a gel as the electrolyte. These batteries have some benefits over the older lead acid battery designs, including a higher energy density, longer cycle life, and calendar life. That means a lithium battery can be physically smaller and have the same capacity as an older lead acid design. This often results in a lighter battery, so modern sport bikes usually use these as the OEM chemistry to keep overall weight as low as possible. You can also switch your older battery to Lithium to save some weight on your bike, but you must ensure the capacity and charging levels work with your bike’s alternator.
The biggest downside to lithium batteries is that they are more likely to catch fire than lead-acid batteries. This often happens due to overcharging or charging too high of a current. Because of this, special chargers are required to avoid damaging the battery and causing a fire.
Review the battery on your bike before buying
Because batteries have different charging needs, you must review the battery in your bike to understand its chemistry and capacity before buying a charger. In the following sections, we’ll look at chargers for each chemistry to see which might be right for you.
If your bike is modern and has a DIN plug, like most BMWs, you might be able to charge through that connector. Review your owner’s manual to see if this is possible, and look at the section on specialized chargers for more details.
AGM Chargers
The most popular chargers available today are AGM chargers. These can work with most bikes produced within the last 20 years. Most AGM chargers can also charge conventional lead-acid batteries, so there is no need to buy a separate charger for the older batteries.
Check your battery before buying one of these chargers to confirm two necessary specifications:
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Chemistry: It should say AGM or Absorbent Glass Mat. They will often say sealed or no maintenance on the battery. In some cases, they use a GEL battery, which has a slightly different design but is also compatible with charging. Many chargers can also support conventional flooded lead-acid batteries.
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Capacity: The energy stored in the battery is typically listed in aH or amp hours.
Battery Tender Brand
Battery Tender is the “Kleenex” of chargers. It has been around for so long and ubiquitous that people say they “throw the bike on a tender” even if the charger is from a different brand. The big difference is compared to earlier chargers, which were meant to charge a dead or low battery; Battery Tenders could maintain a battery and leave the charger connected indefinitely. This was a massive boon to motorcyclists who may park their bikes for days or weeks during the riding season and for a few months in the winter. They are thus the originators of this type of charger, even though others have followed in recent years.
The first charger I got for my motorcycle was a Battery Tender brand & they are a good option for many motorcyclists. They have a broad range of chargers to fit any budget and size of bike, so you can find one that works for you.
This tiny charger is perfect for a bike with a lower-capacity battery. It can automatically switch charging modes after charging the battery to go into maintenance mode. I suggest this only for bikes with smaller-capacity batteries because the maximum charge rate is 750ma. I use one of these with my Vespa, which has just a 10aH battery. This is a brick-style charger, so you need to ensure you have space on your outlet so it does not cover other plugs. If you need one without the brick or with more charging current, look at one of their other offerings.
This is probably the most popular Battery Tender option. It offers up to 1.25A of charging current, making it a good option for most motorcycle batteries. As the charge circuit is in the main body, the cord to go to your outlet is smaller and won’t block other ports like a brick charger. Like the Junior, this charger is fully automated to switch between charging modes.
If you have an older bike with a 6V system, this is the charger for you. It can switch between 12V and 6V charging, enabling you to work with an old classic bike or a modern one. It’s otherwise similar to the Battery Tender Plus charger above.
Optimate Brand chargers
TecMate’s Optimate chargers are a newer brand than the Battery Tender. Optimate’s maintenance program is a bit more advanced than that of Battery Tender, so it can help extend the lifetime of your battery. I’ve been slowly switching over all my old Battery Tender chargers to Optimates.
This is similar to the Battery Tender Junior but has the added benefit of supporting lithium batteries. It has a slightly lower charge current of 600mA, so it can take a while to charge batteries. I suggest using this only on smaller-capacity batteries. Unlike the Battery Tender Junior, this is not a brick design, so it is easier to use on a power strip.
This charger’s significant advantage is the increased charge current, offering up to 2A of charging, making it ideal for larger-capacity batteries. It’s the primary competitor to the Battery Tender Plus charger.
The benefit of the Optimate 3 over the Optimate 2 is that it can recover a dead battery. If you’ve ever had an alternator failure or added an accessory to your bike that drained more power than the alternator could provide, you may have deep-discharged your battery. The Optimate 3 can often recover these batteries, so it’s a good option for a few dollars more than the Optimate 2. I think this is the sweet spot charger that is probably the best option for most riders.
Lithium Chargers
Lithium chargers are the newest type of charger for motorcycles. While most bikes still use AGM batteries, more bikes are coming with Lithium batteries as the OEM choice. If your battery is Lithium, you MUST use a lithium charger. An AGM or lead-acid charger could be dangerous and cause a fire.
Most modern lithium batteries have an internal balancing circuit to ensure the charge of each “cell” is at the same level. Some of the earliest lithium batteries, like those from Shorai, required the charger to have a balancing circuit. If that is the case, you’d need a specialized charger from the battery manufacturer and multiple connectors.
Battery Tender Lithium Chargers
While Battery Tender has always been known for its lead-acid/AGM/Gel chargers, it has recently added some options to charge lithium batteries to its catalog.
Like the original Junior, this is a small brick-style charger limited to about 800mA. It’s best used with batteries of smaller capacity. Unlike the original Junior, this has a switch to change the charge programs between lead-acid and lithium ones. With a similar price to the AGM-only Junior, it is probably worth getting this one instead if you add Lithium in the future.
This charger tries to give you everything you might want in a charger. Two variants are available, one that allows charging up to 3A and the other up to 4A. This increased charge current makes them perfect for larger-capacity batteries. It can also switch between 12V or 6V, which is ideal for those with classic bikes. But it can also support lead-acid or lithium. This is an excellent option if you want one charger for all the bikes in your garage.
Optimate Lithium Chargers
Optimate, a newer brand, was quicker to support Lithium batteries than other manufacturers.
This charger is only for Lithium batteries. If your needs are only Lithium, it can be a good option, but I think spending a few bucks more for the next charger is the better buy.
Optimate 4 Quad Program Charger <$110
Purchase from Amazon
This is the ultimate charger from Optimate. Offering 1.25A of charge current, it will work with batteries up to 15AH in capacity. It can recover dead batteries with a low-voltage recovery program and innovative desulphation programs. Additionally, it can support both Lead-Acid and lithium batteries. If you have a BMW with a DIN plug that is usable for CANBUS charging, this charger also supports that. If you can spring for it, this is the best value across all the chargers listed.
Connectors
Batteries have two terminals, one positive and the other negative. They are connected to your bike through cables, typically using black for negative and red for positive. Most chargers come with one of a few connectors to put on the battery to charge it, and these cables often have matching colors to ensure correct hookup.
Alligator clips
The simplest and most widely available is the alligator clip. These spring-loaded clips can be opened and placed on the battery’s appropriate pole. They are intended for temporary connection only. You can use them with the battery still on the bike, but you often need to remove the seat or some panels to get to the terminals to access the battery. You need to ensure the clip is securely connected to the terminal so it doesn’t pop off and then touch the bike’s frame or some other metal that can cause a short circuit. Be sure to match the polarity as well when connecting the clips.
SAE pigtails
An SAE pigtail has advantages over alligator clips in providing a more permanent connection to the battery. The cables on the opposite side of the SAE plug usually have ring connectors, allowing them to be bolted onto the terminal just like the motorcycle’s cables. This secure connection means the pigtail can be left on the bike permanently, as it won’t pop up while riding like an alligator clip. Installation involves loosening the original bolts holding the battery terminal to the bike’s cables, adding the correct ring (matching the colors and polarity) to each terminal, and retightening the bolts.
The SAE plug’s design allows it to be connected only in one way, ensuring the correct polarity. As long as the ring connectors are hooked up correctly, the SAE plug will also be connected correctly. The contacts on the pigtail are exposed a bit, so some brands offer covers to seal this up to avoid water ingress while riding or cleaning the bike.
DIN Plug
On some bikes, there is an accessory power socket that looks like a miniature version of the cigarette lighter found in cars. This can power various accessories like heated gear, USB chargers, and more. On some bikes, it can also be used in the reverse direction to charge the bike. This requires special CANBUS circuitry in the charger to “wake up” the port to allow charging. Generally, this is limited to BMW motorcycles. We’ll cover that in the specialized chargers section below.
Specialized chargers
If you have a few bikes with different types of batteries or a bike that supports DIN port charging, it might be worth investing in a more specialized charger.
Multi chemistry chargers
Recognizing that consumers wanted to easily transition across different battery chemistries, manufacturers have been producing chargers that can work with a few different chemistries selectable through a switch and sometimes automatically. These are great if one bike has AGM batteries and one bike has lithium batteries. You can use the same charger for both bikes (not at the same time).
See the Battery Tender Junior Selectable charger, Battery Tender 12v/6v Lead Acid/Lithium charger, and the Optimate 4 Quad Program Chargers from the lithium section above. Each of these chargers works on both lead acid and lithium batteries.
CANBUS chargers
If you have a BMW or Triumph motorcycle that supports charging through the DIN port, a charger that supports CANBUS charging and includes the DIN adapter from the SAE plug makes a great option. I use one of these with my BMW R18 Classic. The battery compartment on the R18 is quite tight, so adding another pigtail connector can be challenging. The R18 has a DIN plug on the left side of the bike, meaning I didn’t need to add a pigtail to the battery. Instead, I connect the charger directly to the DIN plug, which wakes the circuit up to begin charging.
If you want to support lithium batteries, see the Optimate 4 Quad Program Charger above.
Optimate 4 Dual Program Battery Charger <$90
Purchase at Revzilla
If you don’t need Lithium support, the Optimate 4 Dual Program Battery Charger is cheaper but doesn’t include the DIN plug adapter. With the adapter running about $22, the Optimate 4 Quad Program Charger is the better buy.
Multi-port chargers
If you have more than one bike, you might want to consider a charger with multiple banks. A single charger could manage a few bikes, which can often be more cost-effective than a dedicated charger per bike. It can also work if you have limited power outlets in your garage. However, there are a few limitations to these chargers. Often, the charge power per circuit is limited to just 800ma, so charging time can be increased if your battery is low.
In most cases, the charge lead from the charger to the SAE plug is just 6 feet, so you need to park your bikes close together. While I can see this working for two bikes, practically a four-port charger might be challenging to get all four bikes charging ports within 6 feet of the charger and still have them easy to pull out of the garage. They are often better for when you take the batteries out of the bike so that long-term storage could be helpful. With five bikes that I ride year-round, I have a dedicated charger per bike as I prioritize the ease of getting the bikes out of the garage vs. saving some money on the chargers.
This unit has four 1.25-amp chargers, which can still work with higher-capacity batteries. It only supports lead-acid and AGM/gel batteries, so it won’t work with Lithium batteries. The charge leads are only 6 feet long, though, so it might be tough to reach four bikes from the charger while keeping each bike easy to pull out. But you save some cash over buying four regular chargers.
This charger has the same charge program benefits as the Optimate 3, meaning it can recover some dead batteries. But, unlike the Battery Tender version, it is limited to 800mA per port. It also has the same 6-foot charge lead limitation as the Battery Tender, so your parking options are limited if you don’t remove the batteries from the bike for charging.
Conclusion
No matter which battery you have in your bike, there is a charger to keep it topped up and in the best condition, no matter what. While I have owned Battery Tender brand chargers for over 20 years, I’ve been switching my chargers over to the Optimate chargers. They could recover deep discharge batteries, and the option to support CANBUS charging through the DIN port was a big draw. In most cases, I would recommend an Optimate over the equivalent Battery Tender charger. They are priced similarly, and the added benefit of recovery does benefit Optimate. However, Battery Tender is the best option if you need a charger for an older 6V bike. Some dealers sell battery tender chargers and may even include them with bikes, so they are still prevalent. They aren’t bad chargers at all, but I prefer the Optimate & continue slowly replacing my older Battery Tenders with the Optimate chargers.
