By Stu Oltman

Most motorists who purchase a battery charger do so for one main reason, to recharge a dead battery. Automobiles are driven daily, so their batteries don’t get much chance to self-discharge. However, a loose alternator belt, faulty alternator, or a dome light left on overnight could result in a discharged battery. In cases like these, the typical automotive charger is useful for quickly getting your car back on the road.
Most motorcycles aren’t used daily, and disuse and/or seasonal storage present problems not encountered by the automobile owner. The relatively small size of most motorcycle batteries and alternators creates other problems as well. Let’s discuss the problems specific to motorcycles and their batteries and see how these battery maintainers address them.

The Power Grab
In 1976, daytime headlamp laws became universally mandated in the United States. Starting with 1976 models, all new street bikes had their headlight switches eliminated, leaving only the high beam selector for controlling the always-on headlamp. Many street bikes of the day had alternators barely able to keep up with the bike’s electrical demands, even during daytime use. The always-on requirement, with no increase in electrical output capacity, caused the batteries on these bikes to be in a constant state of partial discharge. We know, from our six-part electrical series in previous issues of Wing World, that discharge creates sulfate crystals on the battery plates. If the battery isn’t returned to a state of full charge, the crystals will harden, become permanent, and will shortly render the battery useless.
So, how far have motorcycle electrics progressed since then? In some cases, quite far. The GL1800’s alternator has the capacity to keep its battery from discharging at all engine speeds. Other bikes with ABS or fuel injection also have improved electrical output potential because the computers for these devices must never be starved for voltage. Sadly, many other bikes of recent or current manufacture, including the GL1500, are no more capable in the electron department, especially during slow riding, than those models of the mid to late ’70s. Keeping these machines plugged into a battery maintainer when not in use is one cure for the electrical deficit spending. Another cure is to ride the machine often and at high enough revs to ensure thorough battery charging.
Seasonal storage of batteries is a challenge to many new motorcyclists. Many riders simply ignore the issue and buy a new battery in the spring. Most batteries that become useless over the winter suffer at the hands of well-intended owners who simply forget how long ago it was that they last shoveled their way out to the garage to monitor their battery charger. However, since a battery maintainer can be left connected to a battery indefinitely (with precautions described later), a single hookup in late fall should insure a good battery come springtime.


Battery Maintainers Versus Battery Chargers
Most automotive-type battery chargers can attain an output voltage of more than 17 volts if left connected too long, and this will cook the electrolyte out of a battery. Likewise, trickle chargers put out a constant charge regardless of battery voltage and can seriously overcharge if left unattended for extended periods. The smaller the battery, the quicker the damage will occur.
A battery maintainer has several functions to address the special requirements of batteries in infrequent or seasonal use. First, it must be able to charge a battery until the majority of the sulfate is back in solution, and this requires attaining a voltage of around 14.2 volts; slightly higher is preferable. To be useful in charging depleted batteries, the unit should also have the ability to hold its output current high until the battery reaches gassing voltage. Secondly, since many bike batteries have been in a state of partial discharge prior to charging, the maintainer should have the capability of breaking up slightly hardened sulfate crystals and discouraging their formation. Lastly, the maintainer should be able to hold the battery at a post-charge voltage that will neither cook out its contents nor allow it to self-discharge. During this last “float” mode, it’s desirable to incorporate a method of discouraging sulfation. A battery supplied with a constant current and held at an unwavering voltage that’s less than the gassing voltage will begin to sulfate after 60 days or so. A pulsing current or some method of exercising the battery is desirable during float maintenance.
You’ll note pulsation in the current waveforms displayed in this article. The ones that occur in the float mode of the Yuasa 900 are intentional. All others, though the simple result of unfiltered AC ripple, will nevertheless have some beneficial effect on sulfate accumulation. Speaking of AC ripple, it should be obvious from these current waveforms that use of a battery charger to power DC devices is likely to damage them. For bench testing electronics, use a regulated power supply.
In this article, keep in mind that we tested these products on batteries the size and capacity of those owned by most Wing World readers. A product that doesn’t quite make the grade here may be more than adequate on smaller batteries, while more powerful units may be required to do a quick and thorough job on large automobile batteries.

The Products
We didn’t attempt to test every single product on the market billed as a battery maintainer. Instead, we sampled five of the most popular and readily available products, believing these most likely to be purchased by our readers. These included the Battery Tender Plus by Deltran, the AccuMate sold by Westco, the new Schumacher 1.5 amp Battery Companion, Yuasa’s 1.5 amp unit, and Yuasa’s 900 milliamp product. All of these products are sold as multi-stage battery maintainers. That is, they bulk charge the battery at their highest output capacity until the battery reaches some pre-programmed voltage level just below the gassing voltage (14.2 volts). Then the units are supposed to switch to what’s called an absorption mode in which the battery can soak up the last bit of charge at a natural absorption rate that won’t result in excess gassing or heat. Finally, upon reaching some programmed end point, they stop charging. As the battery’s voltage decays to the unit’s float set point, a small, continuous current is then delivered to hold the battery at that voltage. Manufacturers often disagree as to what the optimal float voltage is, but it’s generally 13.2 volts to 13.6 volts, depending on temperature and battery type.

Testing Methods And Equipment
To eliminate variables, we used a single battery for testing all of the products. Our 19 amp-hour battery was fully charged between each test using the same charger/maintainer each time. It was then allowed to rest for 30 minutes before being drained at a rate of 4 amps for 10 minutes. This sucked 0.67 amp-hours from the battery prior to testing each maintainer. If you recall our articles on electricity in recent months, you’ll remember that about 0.8 amp-hours will be required to fully recharge this battery (.067 x 1.2).
To view the performance of these units while charging, we used a digital storage oscilloscope sampling at five million samples per second and capable of displaying “events” as short as two millionths of a second in duration. The current was picked up using an inductive probe that did not alter the circuit or current in any way. Voltage was monitored across the battery terminals on a voltmeter with ten megohms input impedance; again, negligible effect on the circuit was the goal. Ambient temperature during the testing was held fairly close to 70 degrees Fahrenheit.
When viewing the current waveforms in this article, the reader will notice evenly spaced downward spikes. These result from electromagnetic interference due to the 60Hz, 120VAC electricity coursing through the building’s wiring. Ignore them.

AccuMate Power-Charge System
First up was the AccuMate. This is a dual voltage unit (6 and 12 volt). Its manufacturer claims it will charge at 1.2 amps constant current until the battery reaches 14.3 volts. The voltage is then maintained at 14.3 while the battery absorbs charge at its own natural rate. When this rate decays below 200 milliamps (.200 amps), the unit is supposed to supply only the current necessary to maintain a float voltage of 13.8 volts. Should the battery begin drawing more than 200 milliamps at any time afterward, the maintainer will re-start its main charging program. The product comes complete with a pigtail lead for permanent attachment to the battery as well as a set of alligator clips for on-the-bench work.
As can be seen on the graph, the AccuMate applies a pulsing current in charge and float modes to help get rid of sulfation. Current pulses peaked at 4.4 amps during charge and ranged from zero to 2.2 amps during float. The maximum average charge current noted was 1.25 amps, so the output exceeded the manufacturer’s claims in that regard. Maximum voltage during charge was 14.4 volts. The current tapered at 14.3 volts, and this was accomplished by reducing the pulse heights while retaining their shapes. Float voltage was 13.47, below the maker’s claim of 13.8. Current supplied during float was .038 amps. However, that’s somewhat immaterial, as the current required to “float” a battery at a particular voltage will vary with the size and capacity of the battery and any parasitic loads present. The unit did indeed switch back into charge mode when a load was applied to the battery.

Schumacher 1.5 Amp Battery Companion
The Schumacher is a fairly new entry into this market. We first noticed it at an automotive product show in Las Vegas and were sent a sample for testing.
Like the AccuMate, the Schumacher features 6 or 12 volt capability. The instructions indicate only that the amber charge light remains on until the battery reaches about 14.4 volts and the charge current has decreased to 0.5 amps. Though maximum output is claimed to be 1.5 amps, there’s no indication at what voltage the current will begin to drop off. This is important, because a charger that tapers the current too early in the charge cycle will take longer to accomplish a full charge, if it ever does accomplish a full charge. More on that later. The manufacturer warns not to leave the unit hooked to a battery while it’s unplugged from AC power. The 12 milli-amp parasitic current draw will slowly discharge the battery if this advice is not heeded. A permanent-mount pigtail and alligator clips are both included.
When the Schumacher was first turned on, it began charging the battery at 1.65 amps, exceeding its rated maximum. The charge tapered to 1.45 amps at 13.5 volts, and the unit maintained this charge rate to 14.3 volts. At that time, the charge current pulses quickly flattened away while charging continued to 14.44 volts. Float voltage was 13.23 at 20 milliamps, and the float current contained no pulsation. As with the AccuMate, placing a load on the battery activated the charge cycle once again. Looking at the shape of the current pulses, it can be seen that they are not as abrupt or as great in amplitude as with the AccuMate. These gently rising and falling 2.4 amp pulses may discourage sulfation, but perhaps not to the degree of the more abrupt 4.4 amp pulses delivered by the AccuMate unit. Then again, as we stated earlier, the pulsing was not designed for any particular purpose. It’s simply the result of the chosen method of rectification and filtering. We feel that the Schumacher acquitted itself nicely.


Yuasa 1.5 Amp Automatic
The larger of the two Yuasa maintainers is unique within this group. It’s billed as a five-stage charger/maintainer. When first connected and plugged in, it flashes lights to signify correct polarity and the presence of AC power. The unit then applies a series of pulsing currents while monitoring the rate of voltage increase and decay. The electronics within the charger use the resulting information to determine whether the battery is serviceable. Assuming the answer is affirmative, the charger then applies a 1.5 amp pulsing current to bring the battery to near gassing voltage. The current at 14.0 volts was still up at 1.4 amps, but 14.1 volts triggered the device into absorption mode.
At 14.1 volts, the big Yuasa switched to a 0.9 amp pulsed charge rate while maintaining the abrupt pulse shape. It tapered the charge rate as the battery approached 14.3 volts, finally holding the battery at 14.3 while the absorption rate dropped to 0.3 amps. The switching from 1.4 amp constant current charge to a tapering current constant voltage charge of significant duration clearly indicated that this product does indeed employ a multi-mode charging process.
During float, the Yuasa 1.5 maintained a 10-milliamp current and kept the battery at 13.29 volts. Applying a 4-amp load to the battery caused the charger to immediately go back into charge mode. As a fifth and final stage, this unit claims to shut down, then re-start the charging process every 28 days. This final stage of operation exercises the battery, providing additional protection from sulfation damage for batteries stored for extended periods.

Yuasa 1.5 Amp

Yuasa 900 Milli-amp Wall Plug Charger
The smaller of the two Yuasa products is designed with the AC electrical plug built right onto the cabinet of the device. Like its larger sibling, it has multi-colored LEDs that indicate power, polarity, and charge. Unlike the larger Yuasa, this charger didn’t exhibit a clear transition from bulk charge to absorption. It began charging at 0.9 amps with the battery voltage at 12.5 volts and slowly tapered the charge rate as the battery voltage increased. At 14.0 volts, the charge rate was down to 0.425 amps, but the unit did manage to charge the battery to a terminal voltage of 14.48 volts. It then dropped the 0.3 amp pulsing charge that it was delivering at that point and waited for the voltage to decay to 13.24 volts.
The unit then kicked back in with a 0.665 amp current containing 2.25 amp spikes, and it applied this charge until the battery reached 13.56 volts. This on again, off again float cycle repeated each time the battery dropped to 13.24 volts. A 4-amp load across the battery terminals instantly caused the start of a new charge cycle. While the maximum voltage attained was very good, the tapering current caused the charger to take more time to replenish the battery than if it had held its maximum output until gassing voltage was reached. The float cycle is interesting in that it has features that discourage sulfation and exercise the battery as well.

Yuasa 900 Milliamp

Battery Tender Plus by Deltran
The Battery Tender Plus, like the others in this comparison, is claimed to be a three–stage charger/maintainer. That being the case, the bulk charge mode should hold a current at or close to the unit’s maximum output until the battery voltage is at or near gassing voltage. That didn’t happen with the first example we tested. When the Tender was first turned on with battery voltage at 12.5, the unit began charging at 1.34 amps.
The current waveform taken at 12.75 battery volts showed the current still slightly above manufacturer specs, though it had dropped noticeably in a very short time. By the time the battery had reached 13.4 volts, the charge rate was down to 0.9 amps. The charge rate continued to drop dramatically, and the rate of voltage rise slowed just as dramatically.
The battery eventually reached 13.88 volts and went no higher. After about six hours in the absorption mode, the unit stopped charging. It then went into float mode at 12.90 volts.
Suspecting a defective unit, we obtained two others and tested them in the same manner. Both of these additional units held maximum current output (1.25 amps) up to 13.75 volts, then began a tapering, constant voltage charge commensurate with the battery’s natural absorption rate and the unit’s temperature compensation scheme. One achieved 14.1 volts before “floating.” The other went to 14.4 volts, but both required significantly longer than the other products to reach that level. That’s not an issue if storage was your reason for attaching the Tender. But if you’ve accidentally left your key on, don’t plan to go anywhere for a while if you want to completely recharge your battery. Deltran states that the battery may be returned to service at around the 80 percent state of charge. But based on the existing loads and charge output of the average Gold Wing, we’d prefer to completely recharge the battery before riding off.
We had been told by one informed source that the Tender was programmed to charge to 14.4 volts, then hold the battery there for around six hours for a thorough charge. That seemed to be the case until we hooked the Tender to a battery that had just been charged with one of the competitors in this test. In that particular case, the absorption mode lasted only ten minutes before the voltage rose to 14.4, and the steady green “charged” light came on. We therefore conclude that like the other units in this test, the absorption mode terminates when the battery’s current acceptance rate falls below a certain level.
When a 4-amp load was placed on the battery, the Tender didn’t respond as the other units had. The green “charged” light remained on. The charger ramped up its output until the load was removed. It then cut back its output and gradually brought the battery back up to float voltage. All of the other brands tested here, after being subjected to a 4-amp load, completed a charge to around 14.4 volts before reverting to float. In the float (maintenance) mode, of the three Battery Tender examples tested, one simply allowed the battery to slowly discharge to around 12.4 volts. A second unit allowed the battery voltage to drift between 12.75 and 12.95 volts. The third unit, newly purchased, held the voltage at 13.15 for two days before allowing it to drift down to 12.89.

Battery Tender Plus

Conclusions And Recommendations
We chose to test the units at room temperature to verify their manufacturer’s claimed performance, and relative to one another rather than to some industry standard for motorcycle battery chargers (if such a standard exists).
For quickly charging a depleted battery, the Yuasa 1.5 amp, the AccuMate Power Charge, and the Schumacher Battery Companion are equals in our opinion. If a thorough charge and long term float maintenance are of equal consideration, without the occasional need to manually “exercise” the battery, we’d substitute the Yuasa 900 into this group in place of the Schumacher. Though the original Battery Tender was the first commonly available inexpensive charger of this type—a unit that can be left connected without fear of overcharging—competition in this market has grown considerably. New or different technology has resulted in many competing products, and the four others examined here exhibit charge and maintenance qualities that we prefer over those we noted in the three Battery Tender Plus examples that we tested.
The Yuasa 1.5, the AccuMate, and the Schumacher all performed very well in these tests. They were observed to perform extremely close to their manufacturer’s specifications. They all achieved gassing voltage and then some. They all maintained charging current near their maximum output capacity until reaching 14 volts, quickly replacing the amp hours we’d removed with our timed load. They all held the battery during float at what most books we’ve read on the subject consider to be proper at the test temperature. The Yuasa 1.5, the AccuMate, and the Schumacher all operate in float mode by supplying the current necessary to maintain their advertised float voltage. Should the units be required to supply more than a designed maximum current while in float (like if the ignition key is turned on), they all trigger into a new charge cycle. We give a very slight edge to the Yuasa 1.5 for its 28-day battery exercise cycle, but all of these units are excellent performers. Suggested retail price for either the Yuasa or Westco’s AccuMate unit is $59.95. Order the Westco on-line. The Yuasa can be purchased on-line at Yuasa’s website, through many certified Yuasa battery dealers, and through Member Services at GWRRA.
The Schumacher Battery Companion may be purchased directly from Schumacher for $42.99 or from Auto Zone, Ace Hardware, and Tru-Serv Hardware. Prices from sources other than Schumacher range between $24.59 and $34.99. Sears will be adding the product to their line this fall under the Die Hard banner (model 71220) for $29.99.
The smaller of the two Yuasa products performed surprisingly well. It required a bit more time than its big brother, the Schumacher, and the AccuMate to replenish the charge we’d sucked from the battery. This was partly due to the maximum output being less than the others, and partly because the charge current began tapering well before gassing voltage was reached. For that last reason, we don’t consider the Yuasa 900 to be a true three-stage charger. However, at no time did the charge rate drop below 300 milliamps, and the little 900 managed the highest charge voltage of any of the units tested. As can be seen on the accompanying graph, the pulsating float current is applied at 13.24 volts and discontinued as the voltage rises to 13.56. This repeating cycle varies from the float method employed by the other tested units, but should be effective nonetheless. As a matter of fact, our two-year experience with this unit, as used on a common lead antimony battery, has proven its float scheme highly effective. Suggested price for the Yuasa 900 is $41.95. Availability is through Yuasa via their website or through certified Yuasa dealers.
The Battery Companion from Schumacher is a very cost-effective way to charge a motorcycle battery and hold it in float for periods of 60 days or less. The Companion held near its maximum output current until the battery reached 14.3 volts. For this reason, it equaled the Yuasa 1.5 and the Westco in ability to recharge a depleted battery quickly.
Because the float current neither exercises the battery nor has any pulsation to discourage sulfation, we recommend disconnecting this product from the stored battery for 24 hours every 60 days or so. Reconnecting the unit will then provide battery exercise. Had we not felt the need for this caveat, the Battery Companion would have ranked above the smaller Yuasa product. As with the Westco and both Yuasa products, this charger will provide the current necessary, up to some maximum of around 200 milliamps, to keep a battery at the designed float voltage. Above that amount, the unit begins actual charging again.
Though we attempted to be as consistent in our testing as humanly possible, given our lack of laboratory grade equipment, we readily admit that the number of amp hours drained from the battery before each product test was not identical in each instance. Still, the Battery Tender Plus from Deltran Corporation was surprising to us in its inability to recharge a depleted battery with the speed of the other products in this group. Had products with similar operating characteristics varied wildly in the time they required to return the battery to 14.4 volts, we’d have suspected our own inaccuracy. However, even the smaller Yuasa 900 required only about 30 minutes more than the other chargers (except the Battery Tender) to return the battery to gassing voltage. The Tender kept charging hours longer than the others before attaining 14.4 volts across the battery terminals.
While Deltran claims that the charge and float voltage is a function of the temperature compensation feature of the product, we believe that 13.2 to 13.4 volts would be a more appropriate float voltage for the 70-degree temperatures at test time. Further, we firmly believe that any temperature compensation scheme should be based ideally on the electrolyte temperature inside the battery. Ambient air temperature at the battery case might be a reasonable substitute, but we noted no external sensors on the device. We have no way of knowing the algorithm used, but a program which caused the unit to assume a certain temperature differential based on its own internal temperature would be the highest level of sophistication we’d expect to see at this price level.
The Battery Tender Plus is available at most motorcycle dealerships and accessory shops and at Batteries Plus outlets at a suggested retail price of $59.95.

Yuasa Battery, Inc.

WestCo Battery Systems

Schumacher Electric Corp.

Deltran Corporation