Motorcycle Battery Care

Sound RIDER! logo


Yamaha Motorcycles Street Event - Adventure Motorsports


Motorcycle battery care

Part 1

By David L. Hough

Dave & Cycletron 01

I normally plug my machines into automatic chargers when they aren't being ridden. Each machine normally stays on the charger until I take it out for a ride—sometimes months later. I haven't been very critical about my chargers. I just picked up different ones over the years, without much research.

But at the end of the riding season I had a brain fart and forgot to plug a charger into Sparky's battery. After two months the Cycletron Plus was flatter than a pancake, and none of my chargers would bring it back to life. A quick trip to the dealer determined the charging system was fine and the Cycletron battery was OK, just severely discharged.

The experience was another reminder of the need to keep my motorcycle batteries charged. But the big eye-opener was that none of my automatic chargers could bring a discharged AGM battery back to life.

If you're a battery guru, you can skip the rest of this. But if you're a rider like me—who hasn't been paying much attention to battery and charger technology, perhaps you're ready for a jolt of reality. First, for those who aren't "gearheads", let's do a little battery review. There are two basic types of lead/acid motorcycle batteries on the market, "flooded" and "sealed".

Flooded batteries

The old flooded lead acid battery (FLA) has lead plates suspended in liquid battery acid. A 12 Volt battery has six separate 2V cells, wired together. The flooded battery has removable caps on the cells to allow checking the electrolyte and topping up when needed. Flooded motorcycle batteries usually have a small vent tube plugged into the top chamber, extending down underneath the bike to allow any acid droplets to bypass any delicate motorcycle parts. One advantage of an FLA battery is that you can top up the electrolyte as needed, with distilled water. FLA batteries also have a slightly lower resting voltage.

Sealed batteries

The most common battery today is "sealed lead/acid" (SLA) that seals the acid electrolyte inside the case, which is a huge advantage for reducing corrosion. Since the acid is sealed inside, an SLA battery can be shipped through the mail, and installed in any position. You can even lay the bike on its side, without fear of battery acid dribbling out. The best news is that SLA batteries can hold a charge for long periods of time—assuming no parasitic loads such as a clock or security alarm. The downside of an SLA is that there is no way to replace the electrolyte as it slowly evaporates.

Batteries tend to heat up and generate gas when being charged, and that creates pressure inside a sealed battery case. To prevent a nasty explosion, there are tiny relief valves in the case. That's why sealed batteries are sometimes called "valve regulated lead acid" (VRLA).

The most common type of SLA battery is Absorbed Glass Mat (AGM), in which the battery acid is entirely absorbed into dense fiberglass mats, so it can't leak out. AGMs typically have a higher resting voltage than other types. Another type of sealed battery is "gel", where the battery acid is chemically treated to make it about the consistency of pudding.

Did you ignore the hoopla, too?

Now, I admit that I pretty much ignored the hoopla when AGM and Gel batteries came out about 20 years ago. There were all sorts of rumors about AGMs and Gels needing special battery chargers, but, like most riders, I naively assumed that 12 volts is 12 volts, and any suggestions about buying pricey special chargers was just sales hype.

My little experience with Sparky demonstrated that it's a bit more complex than that. First, although we might call a battery a "12-Volt", different types of 12V batteries prefer slightly different charging voltages, maybe 12.9V or 13.7V. Why does this matter? Well, if a battery isn't fully charged, it loses some life. My old FLA batteries liked to rest at about 12.5V. My fleet now uses various AGM batteries, which if disconnected will "rest" somewhere between 12.7V and 13.1V.

What's more, SLAs have different chemistry that responds differently to charging rates. The old way of charging a flooded motorcycle battery was to wire up a trickle charger (say, 1.5 or 2 Amps) for several hours, and then disconnect it when the battery acid started to bubble and boil.

Yeah, but doesn't the bike charge the battery?

Of course, the battery is recharged when the engine is running. And, after a ride, the battery will be at whatever voltage the bike's voltage regulator has been supplying. The important point here is that if you install a new AGM battery in an old machine that was originally designed for a flooded battery, the charging system could be working perfectly, but never keeping the AGM battery fully charged. And if the battery isn't fully charged, it loses some life. If you run the bike every week or two you'll keep the battery alive, but not necessarily fully charged. Contemporary machines regulate at a slightly higher voltage—more in line with SLA batteries.

The problem comes when you let the bike sit for a month or two without running—as I did. Today's machines have various parasitic loads, such as clocks and security systems that slowly draw down the battery even when the key is off. When Sparky's Cycletron battery went flat, I tried all my old chargers, but none would bring it back to life. One charger flashed a light indicating a bad battery. The reality was that none of my chargers were capable of bringing a discharged AGM battery back to life. What I needed was not only a smarter charger to make up for my less powerful memory, but a more powerful charger with the amperage capacity to wake the dead, and a charging sequence (algorithm) suitable for an AGM battery.

The Odyssey battery site recommended an ACI smart charger, and I got the model 1214CC with a capacity of 7 Amps. And, at the recommendation of several battery gurus, I obtained a 0.8A Optimate 4 for my other machines. With the new chargers in hand, I excitedly hooked them up and tested the voltages with a new Radio Shack digital voltmeter, comparing the new chargers against the old ones in my garage.

Photo, ACI 1214CC

Photo, Optimate 4 02

Photo, Battery Companion 01

span style="font-size: 10.0pt; line-height: 150%; color: blue">The Schumacher Battery Companion can automatically charge either 6 or 12 volt batteries. The only indications are lights indicating charging or charged. But it has up to 1.5 Amps, it's very reasonably priced, and it comes with a huge selection of different connectors.

Photo, Battery Doc Port 01

span style="font-size: 10.0pt; line-height: 150%; color: blue">The 1.25A Battery Doc Portable is small enough to carry on a bike, has a detachable power cord, and has a column of lights to show more about what its doing. In my tests, the Doc cranked out just enough voltage to keep an AGM charged. There's also a sealed version that's waterproof, if you don't mind the extra weight. The downside is that I had to make up my own adapter to connect the BD output plug to a standard SAE plug.

The Hough test

My batteries included a Panasonic AGM, a Westco AGM, an Odyssey AGM, and the Interstate Cycletron Plus AGM. To see how my different batteries would respond to the different chargers, I connected each charger to each battery for a minimum of 12 hours, then checked the voltage, which after that time should have reached the float mode. Then I disconnected the chargers, allowed the batteries to rest for a minimum of 12 hours, and measured the "resting" voltages. I rotated the chargers and batteries over several days, with the garage maintained at 65F.

ACI 1214CC

Panasonic       Odyssey         Westco                       Cycletron

13.76V          13.76V                       13.72V                       13.74V

Optimate 4   

Panasonic       Odyssey         Westco                       Cycletron

13.55V                       13.47V                       13.54V                       13.57V

Battery Doc Sealed after 12 hrs.

Panasonic       Odyssey         Westco                       Cycletron

13.34V                       13.59V                       13.58V                       13.58V

Panasonic       Odyssey         Westco                       Cycletron

13.34V                       13.34V                       13.35V                       13.35V

Schumacher Battery Companion

Panasonic       Odyssey         Westco                       Cycletron

13.23V                       13.24V                       13.24V                       13.24V

Battery Tender Plus

Panasonic       Odyssey         Westco                       Cycletron

12.89V                       13.09V                       12.90V                       13.08V

Resting voltage 12 hrs after disconnecting charger (average)

Panasonic       Odyssey         Westco                       Cycletron

12.91V                       13.01V                       13.06V                       12.93V


Note that this wasn't a comprehensive test of all the latest chargers on the market. I just wanted to see whether the various chargers in my garage seemed to be working acceptably. It's clear that my battered old Battery Tender Plus wasn't adequate for my AGM batteries. I also measured a pair of brand new Battery Tender Juniors, which produced lower float voltages than the Plus version. I tossed the BT in the trash, and gave away the BTJs to someone who lives in a warmer climate.

If a charger can't produce float voltage that's higher than the resting voltage of a battery, it can't charge until the battery voltage drops to the output of the charger. For example, my old Battery Tender didn't produce enough voltage for the Panasonic. So, a cheap charger might maintain a battery at 60% or 70% of full charge - keeping the battery from completely discharging, but shortening the battery's life by a year or two. That's why the manufacturer of a battery charger can state "charges all batteries". They don't say their charger will keep all batteries charged to 100% of capacity in all climates.

All my AGM batteries seem to "rest" at right around 13V, which means my other chargers are adequate for maintaining them. The ACI 1214CC settled on float voltages averaging 0.77V above the typical "resting" voltage. The Optimate 4 charged an average of 0.56V above resting voltage. I was pleased that the Battery Doc smart chargers I've been using are in the ball park.

However, the two high-zoot smart chargers, the ACI 1214CC and the Optimate 4 are capable of handling more complex issues, such as reducing plate sulfation, and bringing a discharged AGM battery back to life. The Optimate 4 has a panel of colorful lights that wink and blink to show what it's doing, and a handbook to help you decipher what they mean. Of course you don't Have to read the lights, since it's all automatic. The ACI does its job with just a single indicator light, but it cranks out 13.74V at up to 7 amps. My flat Cycletron battery snapped to attention after a few hours hooked up to the ACI.


My point in all this is not to diss any brands, or convince you to buy what I use. But I strongly suggest laying your hands on one of the new smart chargers, and keeping it hooked up to your battery whenever the bike is parked. That's really important if you park the bike outside in sub-freezing weather, or park it for months at a time.

And, if you've been using a charger, but your battery always seems to be a little flat, I suggest taking a few voltage measurements with a reliable digital voltmeter to see how your charger measures up. With the key off, and the charger connected for 12 hours or so, a "flooded" battery should settle to a float of around 12.5 – 12.6V, indicating 90% to 100% of full charge. An AGM would prefer at least 12.7V, and maybe 13.6V depending on temperature.


Battery Doc chargers: online store. Tel (206) 329-7808

Optimate 4 automatic 0.8A charger:

ACI 1214CC automatic 7A charger: tel strong>(888) 379-2555

strong>Schumacher 1.5A Battery Companion: Wall Mart stores  

For additional information on batteries:


We've worked hard to upgrade this site. Click here to notify us of any problems we need to correct.


Subscription has its privileges - Each month Sound RIDER! publishes new features on rides, clubs, dealers and events. Don't miss out on these informative stories.

Sign up today for your FREE subscription and you'll get notification each month when the new issue comes on line. You'll also be the first to find out about special Sound RIDER! events. From time to time, we also provide valuable coupons that can save you hundreds of dollars on motorcycle services. What are you waiting for? Click here to sign up now!