If your battery is not staying charged the problem is most likely one of three things. Ether There is a charging problem, a drain on the battery or simply a bad battery. The first step in isolating the problem is to test the charging voltage. With proper charging voltage at the battery, you can rule out a charging problem. The next step is to check for an excessive electrical draw on the battery. After ruling out a charging and draw problem there is only thing left. At this point it is safe to say you need a new battery.

Test #1Testing Charging Voltage


The fastest and easiest way to find out if you have a charging problem is with a voltmeter. Testing the voltage at the battery is very simple. Set your meter on a 20 volt DC scale. Connect the red lead to the positive side of the battery and the black lead to the negative side of the battery. Start the motor. If the charging system can maintain a voltage of 13.8 or higher at the battery terminals the battery should be charging. In this case move on to the draw test.

  If the voltage is low it is time to consider possible reasons.  A low but climbing voltage indicates the charging system is doing something. It is important that the voltage at the battery reaches at least 13.8 or the battery will not fully charge. On newer models with larger charging systems you can expect the voltage to jump right up. On older models with smaller charging systems the state of charge of the battery can effect system voltage.

  A low battery may be absorbing excessive amperage and dragging the voltage down.

It is a good idea to take a voltage reading on the battery before starting the motor. This will give you an indication of the batteries condition. It is important to do this before starting the motor to get a stabilized reading. Immediately after charging, the battery will have what is called a surface charge. This will give an abnormally high voltage reading. It can take an hour or two after charging for the surface charge to dissipate. Then you can get an accurate voltage reading. Set the meter for a 20-volt DC scale. Before starting the bike connect the voltmeter across the battery. Be sure to connect directly to the battery terminals and not the wire or bolt connected to the terminal. You may get a different reading due to a bad connection, which may cause a voltage drop. A voltage drop will only show up when current is flowing (For more on voltage drops see last months article.) Without the motor running a fully charged battery should read 12.7 volts at 72į F. Anything less indicates a battery that needs to be charged or has other problems. If the battery is low give it a complete charge. This may take 12 to 24 hours to do properly. If your battery has removable caps check the electrolyte level before charging. Add pure distilled water until the plates are just covered. As the battery charges the level of the acid will rise. Top it of to the high level after charging. Then give it a mix charge for another hour. This will mix the water with the acid.


  The motor must be running to test the charging voltage. If it is possible you should use a kick-starter. The electric starter draws a lot of amps and will discharge the battery. After the electric stator is used it may take some time for the battery to reach normal operating voltage. Since charging systems do not produce full power at lower RPMís, most motorcycles do not charge at an idle. If you must use the electric starter take a ride or allow the motor to run at a high idle to recharge the battery after starting. (Caution: when idling for extended periods the exhaust pipes can over heat which will blue the chrome. Use a fan when idling for extended periods.)

 The time it takes for the battery to reach normal operating voltage depends on the ampere output of the charging system compared to ampere usage of your bike. All of the electrical accessories that are running will be consuming power. The battery only gets what is left over. On generator models it can take up to 20 minuets of cruising for the voltage to come up. On alternator models the voltage should come up much faster. Models equipped with a 32 amps or larger alternator the voltage should come up within a minuet.

 After the battery recovers from starting, turn on all the accessories you would use in normal operation. I usually do not turn on the blinkers or horn because they are not used long enough to worry about. Since most motorcycles do not charge at an idle you may need to speed the motor up in order to get the voltage to come up. Bring the motor up to 2000 RPM and check the voltage at the battery. If you get between 13.8 and 14.8 VDC the charging system is keeping up at cruising speed. In this case move on to the draw test.


If you still get low voltage at the battery the charging system is not keeping up. Ether it failed or is too small to keep up with demand. I will cover this next month. You can find some charging system ampere out put tests on the Cycle Electric Inc web site, www.cycleelectricinc.com. Go to the technical section and scroll down until you find them.


Draw Test

The object of this test is to measure the milliamp draw from the battery when the ignition switch is off. Some electronic components such as security systems, radios and voltage regulators cause a small draw on the battery all the time. Too much draw will drain the battery in a short period of time.

 The amount of time it takes to discharge the battery to the point it will not start the motor depends on three factors. 1) The amount of milliamps drawn. 2) The ampere-hour rating of the battery. 3) The state of charge of the battery when parked. With a fully charged 16-ampere hour battery a 16-ampere draw will deplete the battery in 1 hour. With a .010-ampere (10 milliamp) draw it would take 1600 hours. 1600/24hours=66.67 days or about two month.

A completely depleted battery will not start the motorcycle. It is best to cut this amount of time in half. This must be added to the self-discharge rate of the battery. Many factors affect the self-discharge rate of a battery. Two of the main factors are the type of construction of the battery and temperature. For more information on batteries and self-discharge go to www.yusabatteries.com.

 This would be the acceptable draw for a new fully charged battery. Over time as the battery is discharged and charged again it gets used up. The number of times the battery can by discharged and charged depends on the design and quality of the battery. As the battery gets used up both cold cranking amps and ampere-hour rates go down

 To sum it up, the amount of draw on the battery that can be considered acceptable depends on the size of the battery, the self-discharge rate and how long the motorcycle will be parked. I would expect to see less then 10 milliamps.


Ampere meters

There are many kinds of ammeters. The two most popular styles are ether series or clamp on. With a series meter you must disconnect a wire and connect the meter in series so the current will flow through the meter. The clamp on style simply clamps around the wire.  Unfortunately most clamps on style amp meters do not have the resolution to measure small ampere draws. In this case we will use a series style meter. I will use a fluke 79. 

To complete this test you will need a DC ammeter capable of reading down to 1 milliamp or .001 ampere.

  Since I am using a series type ammeter, I will need to disconnect one of the battery terminals to connect the meter. You can use the positive or negative battery lead. It is safer to use the negative lead. That way if one of the meter leads accidentally touch a grounded surface it will not burn out the meter. Set up the meter to DC amps. Full current will flow through the meter. Since we donít know how many amperes will be flowing, it is a good idea to start with a higher scale to prevent damage to the meter. I usually start with a 10-amp scale and work my way down. Disconnect the negative battery cable. Connect the red (positive) lead from the meter to the end of the battery cable. Connect the black (negative) lead to the negative battery terminal. If you do not get a reading on the 10-ampere scale go to the milliamp scale. If the reading exceeds 10 milliamps (.010 ampere) tack down the cause.

The easiest way to find out what is drawing power is to disconnect different circuit until the draw goes away.

 Let the road you choose to ride bring you happiness.