what the heck keeps a motorcycle battery charged

[ledzep12184]

I think my battery is dead after riding around with the high beam on all the time, now I'm faced with the daunting task of finding a place to buy a motorcycle battery. What in the mechanical structure of a motorcycle is supposed to keep the battery charge. There is a heavy pull on mine, because I have an electronic fuel pump and I leave my high beam on all the time.

[Sev]

The alternator. Should be three yellow wires coming out of the left side engine case.

From there they go into the rectifier which converts the generated AC into DC, and then through the regulator which will dump excess charge to ground into the battery.

If you have a multimeter, or want to buy one I can walk you through all the tests to make sure that your charging system is working correctly.

[Erg0n]

isn t the only time the battery gets used is when you are turning on the motorbike? Eveything else runs off the alternator, Unless you leave your highbeams on while the car isn't running

[ledzep12184]

The alternator. Should be three yellow wires coming out of the left side engine case.

From there they go into the rectifier which converts the generated AC into DC, and then through the regulator which will dump excess charge to ground into the battery.

If you have a multimeter, or want to buy one I can walk you through all the tests to make sure that your charging system is working correctly.

Yes, I do have a multimeter and a little help would be great. That electrical system on that bike is screwy.

[Sev]

isn t the only time the battery gets used is when you are turning on the motorbike? Eveything else runs off the alternator, Unless you leave your highbeams on while the car isn't running

Everything gets run by the alternator across the battery. If the alternator isn't working correctly then it'll run until the battery dies. And then you're borked.

Yes, I do have a multimeter and a little help would be great. That electrical system on that bike is screwy.

Mmmkay,

Start with the simple stuff, charge the battery using a trickle charger and allow it to sit half an hour afterwards. Check the voltage DC using the mulitmeter, it should read at least 12.8 volts. If not you'll need to replace the battery.

Install the battery in the bike, making sure that all of the connections are tight. A loose connection means your bike won't start.

Start the bike and check the voltage DC across the battery, depending on your bike and the year it might be slightly more or slightly less then 12.8 volts. Have someone rev the bike up to aprox 4000-5000 rpm while you check the voltage. It should be reading in the range of 14.0 to 15.0 volts depending on the type and age of bike. If it is then your charging system is fine. If not we've got to figure out what part is bad.

Trace those three yellow wires coming out of the alternator (left side engine case when you're sitting on the bike). Find where they're plugged in and disconnect them. You're now running on battery power. Set the multimeter to volts AC.

What you'll have in the plug that you disconnected is three different spots where the wires come out. Call them A, B and C. You need to check the volts AC across each combination - AB, BC, CA at aprox 4000-5000 rpm (you'll need an assistant). You should be getting in the range of 60-80 volts AC off each combination. If one is substantially lower, or doesn't work at all then you've got a bad coil in the alternator. If they all read way low you may need to replace the stator or the magnets.

Shut the bike off and set your multimeter to resistance (ohms). Stick the positive tester into one of the spots (ABC) and touch the negative to the frame or engine block. It should read infinite resistance. Repeat for the other three tests. If you find there is continuity - a resistance other then infinite, then you need to replace the stator (coils of wire).

If all of that checks out, then you need to check the wiring too the rectifier (which converts AC to DC). Just check for shorts or continuity problems using the methods described above.

There are specific methods for testing the rectifier... but those are. Well you need the manual, and you need to know exactly what bike you're doing it for. I couldn't tell you how to test yours correctly. Besides, most rectifiers come with a built in regulator, which makes it even tougher to test.

The regulator dumps excess current to ground - because you didn't say your battery had boiled over and exploded I will tell you right now the regulator... if it is a separate unit from the rectifier is fine.

Yikes! That's WAY too much typing, but you get the idea.



Having said all of that... the problem is rarely the alternator/charging system. It's usually a short to ground, or pinched wire, or a loose connection somewhere. People tend to say, "it's the alternator" because that's the easy way out. Then again without checking, what do I know?

[mydlyfkryzis]

What model/year motorcycle is it.

The charging systems on the older motorcycles used a zener diode to dump excess charge to ground. Newer bikes use a regulated alternator.

Knowing the model and year helps with giving the right information

[Sev]

Only real difference is that on modern bikes the zener diode is built into the rectifier. When the battery is charged it'll dump excess power to ground.

Unless the bike uses electromagnets. In which case the ecu with regulate how much power is sent to the electromagnets, and it will regulate itself to produce power equal to consumption.

[telefunkin]

isn t the only time the battery gets used is when you are turning on the motorbike? Eveything else runs off the alternator, Unless you leave your highbeams on while the car isn't running

Everything gets run by the alternator across the battery. If the alternator isn't working correctly then it'll run until the battery dies. And then you're borked.

So, if you have a kick start, you could have a fully funtional bike without needing a battery?

[Sev]

Yes, you can run basically everything on a bike on AC off the alternator.

The only real purpose of a battery is to store energy to crank the starter - if you don't have a starter you don't technically need a battery. But it's good to have for the simple fact that the alternator might not be up to the full power use your bike is using at any given moment.

EG - if you've got high beam, low beam, ignition, turn signal, brake light, and horn all going at once for some reason you're technically running on battery power. Especially on a FI bike. If you didn't have that battery it's possible you'd kill the bike and have to restart it.

[beardking]

If you do end up needing a battery, give these guys a call, they'll either have it in stock, or can probably get it for you in just a couple of days. Great place, you'll get to know them well, I believe.

http://www.bates2.net/