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Re: charging system problems
The battery is 12 volts. Anything under that will result in battery being discharged and ultimatly your bike will cutout. You should have between 13.00v and 14.50 max even with lights on. If you have less than this, you need to have your charging system checked.
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So you had the battery tested? Possibly the alternator or charging system is not up to par? Before you assume there is a drain, first make sure both battery and charging system are working good.
Best to buy a cheap voltmeter (or multifunction meter) to do any testing. Put a voltmeter on the battery, with key off, volt reading should be at least 12.4 volts-any less, like below 12 volts, then battery is not taking full charge OR the charging system is at fault. Now start the car and put voltmeter on the battery again: the reading should be at least 13.5 volts- somewhere between 13.5 and 14.5 volts. If it is, then charging system is good. If both battery and charging system check out, then you start looking for an unintended drain. YouTube has lots of videos on how to find an unintended drain.
quick check is to remove a battery cable while the motor's running. If the motor stays running when you pull off the battery cable, the charging system is functioning properly, if it dies then there is a problem with the charging system. Don't leave it off long, as this test is stressful to the circuit. You can test the voltage regulator by putting a volt meter across the battery posts to verify voltage. A fully charged 12 Volt battery should show slightly above 12 volts DC. With the engine running and the volt meter hooked to the battery, the charging system should be showing around 13.8 volts DC.
unfortunately the alternator is only a part of the charging system and it should be tested by an auto electrician not a parts shop
replace the alternator and then take the vehicle to an accredited auto electrician for a charging system check charge rate should be 14.5-14.8 volts DC at around 1500rpm
they can check the alternator out put , voltage regulator or if the regulator is part of the ECM they will be able to test that as well especially when the system is hot as that is when the problem occurs
I would check the charging system on the bike. With the battery at full charge, start the bike and measure the voltage at the battery. Use a DVOM (digital volt ohm meter) and put the red probe on the positive terminal and the black probe on the negative terminal of the battery. Put the meter in DC volts 50 volt range. When you rev the engine a bit, you should read 14.5 - 15.0 volts. If you're reading under 13 volts with the engine running, your charging system had gone out.
This used to be a common problem back in the days of generators but I've not heard of this since Harley went to the alternator systems in 1970. It is unusual to say the least.
The first thing I'd do is have my battery tested. This is simply good procedure anytime you are experiencing a charging system problem.
Next, check the output of your alternator. To do this, you'll need a DVOM, digital volt ohm meter. Unplug the voltage regular at the front of your engine case close to the oil filter. Now, put your DVOM into "Voltage", "AC", Range 50 volts or better. Now, with the engine running, put one lead from the meter to one of the pins in the plug in the engine case. Put the other lead in the other pin. Rev the engine up to about 2000-2500 RPM. You should read at least 30 Volts AC. You must have the meter in the AC positon because an alternator puts out alternating current. Your regulator converts it to Direct Current voltage for the charging the battery and reduces the voltage. If you are reading thirty volts or better, I would suspect the Voltage Regulator is your problem.
Sounds like either you're drawing too much current in the brake light system or your alternator is not charging the battery fully.
On the brake light system, have you added additional lights or changed the type of bulbs in the lights. If so, you may have exceed the output of your charging system. I've seen people put so many lights on the back of their bikes that they've burned up alternator stators on a regular basis.
To check your charging system, put a battery charger on your battery and bring it to full charge. Then connect a digital multimeter to your battery, red lead to positive, black to negative, 50 volt scale. Start the engine and bring the idle speed up just a bit. After about a minute or so, the meter should read about 14.5 volts to 15.5 volts. Any higher or lower could indicate problems. If you find this, repost with that problem and I'll tell you how to check the alternator with your meter.
A 12 volt battery is actually 13.2 volts fully charged. If you are reading 16 volts, you are probably getting extranious voltage from the system somewhere, especially if the vehicle is running when you check the voltage. The alternator will put out about 15-18 volts to charge the battery normally, and yours may put out 28-32 volts to charge them in series, but the batteries, when disconnected, should never read more than about 13.2 volts each. Typically, it will read about 12 1/2 volts when disconnected. COMPLETELY DISCONNECT BOTH OF THE BATTERIES. If you still read 16 volts when it is disconnected, you must have a bad meter because the battery can't produce that much voltage, no matter what. (Six 2.2 volt cells connected in series inside the case.) Put the meter on a known good battery on another car that is not running and see if you get the same reading. It sounds like the other battery is almost dead, regardless, and it sounds like your series/parallel switch may be malfunctioning. (That is the switch that puts the battery in series to run the 24 volt starter, then puts the batteries in parallel to run the remainder of the vehicle on 12 volts. This is all assuming that you have a diesel vehicle with a 24 volt starter and that is why you have two batteries.