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Found the following at Yuasa's web site -


The MOST IMPORTANT thing to remember about charging a new battery is to actually do it!

How many times have you seen somebody ready to throw a new battery into a bike and ride off - without charging. "The bike will charge it," they figure.

Wrong. The battery will be damaged for life.

A battery out of the box, with the electrolyte added but uncharged, is at 80% capacity tops. If it's installed and used that way - without an initial booster charge first - it'll never hold more than that 80% charge. The bike won't charge it higher. Neither will pulling the battery off later and trying to charge it to full capacity. The battery's capacity has been immediately and permanently cut by 20%, and there's nothing you can do about it. Insist on that booster charge.

The rule of thumb is to charge a new battery for three to five hours at a rate equal to 1/10 of its rated capacity. But there are a lot of exceptions to that rule, as this table shows:

If you're careful about monitoring and you're using a digital voltmeter (or multimeter), it's possible to bring that new battery to more than a full charge. This is what you do: periodically pull the battery off the charger and give it time to stabilize. Then check the voltage. The voltage will continue to climb and then will start to drop. When it does that, you've reached max.

Quick Charges
What about quick charging? The quick answer is don't. We don't recommend it, and here's why: only the surface area of the battery plates can be quick charged. A lower current charges the battery more uniformly. That means better performance. Also, charging rates above 2 or 2.5 amperes increase the chance of overheating, which can mean battery damage.

Two of the biggest battery killers - sulfation and freezing - aren't a problem if the battery is properly maintained and water level is kept where it should be.

This happens because of 1) continuous discharging, or 2) low electrolyte levels.

Let's back up just a minute: we said earlier that discharge turns the lead plates into lead sulfate. This lead sulfate is actually a crystal. If the discharge continues uninterrupted, the sulfate crystals grow and blossom into sulfation - and a problem.

Much the same happens if the fluid level is too low, which exposes the plates to air. Then the active lead material oxidizes and sulfates, and it doesn't take long before it won't hold a charge. (Low electrolyte levels cause another problem, too: acid in the electrolyte becomes more concentrated, causing material to corrode and fall to the bottom. In sufficient quantity, it will short out the battery.)

Keeping a battery charged, pulling the battery cable during storage, and keeping electrolyte levels up eliminate the problem. For added protection, YUASA's YuMicron, YuMicron CX and GRT batteries are treated with a special chemical formula called "Sulfate Stop." This dramatically reduces sulfate crystal buildup on plates. The result: longer battery life.

How good is Sulfate Stop?

We simulated a constant discharge condition on two batteries with a 10-watt bulb. Even after being totally drained for a week, the battery with Sulfate Stop made a 90% recovery.

The untreated battery: useless.

It shouldn't bother you - unless a battery is inadequately charged. Looking one more time at the discharge process, remember that electrolyte acid becomes water as discharge occurs. Now, it takes Arctic temperatures to freeze acid. But we all know, freezing starts at 32° F. A sign of this is mossing - little red lines on the plates - but it's tough to see unless you've got great eyes. Freezing can also crack the case and buckle the plates, which means the battery is shot.

A fully-charged battery can be stored at sub-freezing temperatures with no damage. As the chart shows, it takes - 75° F to freeze electrolyte in a charged battery. But as just a couple degrees below freezing, at +27° F, a discharged battery's electrolyte turns to ice. That's a difference of more than 100° F between the low temperatures a charged and discharged battery can stand.

At temperatures such as these, incidentally, the self-discharge rate of a battery is so low that a recharge usually isn't needed for months. But to stay on the safe side, test.

 Electrolyte Freezing Points

 Specific Gravity of Electrolyte

(degrees F)


-75 F


-35 F


-17 F


+5 F


+18 F


+27 F

Perform Monthly Maintenance

A battery only requires a little monthly maintenance to perform perfectly. Keep the battery charged to 100%, recharging when the lights dim, the starter sounds weak, or the battery hasn't been used in more than two weeks. Other than that, follow this simple check list every month:

Check the electrolyte level
Keep the top free of grime
Check cables, clamps, and case for obvious damage or loose connections
Clean terminals and connectors as necessary
Check inside for excessive sediment, sulfation or mossing
Make sure the exhaust tube is free of kinks and clogs
Replace caps firmly
Finish up by testing the battery with either a hydrometer or voltmeter. If you make monthly maintenance on your battery part of your routine, your battery is guaranteed to live a long life.

Storing Your Battery

If the vehicle is in storage or used infrequently, disconnect the battery cable to eliminate drain from electrical equipment. Charge the battery every two weeks.

For extended storage, remove the battery from the vehicle and charge to 100%. Charge the battery every month if stored at temperatures below 60° F. If stored in a warm area (above 60° F), charge every two weeks. Make sure batteries are stored out of reach of children.

Self-discharge goes on all the time. It's a battery fact of life that they get weaker from "just sitting". How rapidly a battery self-discharges depends on battery type. A lead-calcium battery discharges at a much slower rate than a conventional battery. Lead calcium discharges at 1/300 volt per day. Conventional lead-antimony batteries discharge at 1/100 volt per day.

What Adds To Rate of Self-Discharge?

As outside temperature rises, so does the rate of discharge. A battery stored at 95° F will discharge twice as fast as a battery stored at 75° F, and a temperature of 130° F is deadly to a battery. In some parts of the country, garages and storage building easily reach that temperature in the summer.

Accessories like clocks and computer memory will discharge the battery even when the ignition is off. And remember that the battery is self-discharging on its own at the same time the accessories are drawing on the battery.

Short trips (under 15 or 20 miles) will also add to the drain on your battery because the charging system doesn't have time to make up for losses from normal starting and self-discharging.

Some people believe that letting the battery sit on concrete causes it to discharge faster. This is absolutely not true. The battery discharges at the same rate whether it is on concrete, stones, macadam, sand, or dirt.

Article By: David J. Morrow

August 2001

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