Learning how to check your motorcycle’s charging system is way simpler than you might think and at most takes about 1 to 2 minutes.
Learning how to diagnose a “no charging scenario” is where it tends to get a little trickier. Regardless of the case, I will be showing you how to quickly and effectively check your motorcycle’s charging system. I hope you are able to learn these important steps, as well as some important fundamentals to better understand exactly what it is you’re testing. In a hurry? Feel free to scroll down to skip right to the steps I have laid out to help guide you through checking your charging system.
WHY IS IT IMPORTANT TO CHECK YOUR CHARGING SYSTEM?
The Fundamentals
Your motorcycle functions either off of a 6-volt (early 60s-70s) or a 12-volt system. One common misconception people believe is that a 12-volt battery is actually a 12-volt battery. They are only called this to distinguish between other types of batteries. In fact, if your battery is checked at a “resting state” (meaning no charge or draw is being used and it reads 12.0- 12.01-volts), it’s pretty much considered a goner. At this state, the only useful energy left in the battery is at around 20-25%, that is unless it has been “Deep Cycled“, which can only be done a couple of times and is not typically used for motorcycles. Considering those facts, I personally have recharged multiple batteries at this reading for long charging intervals and was able to still use them for my daily rider. I’m not saying that they lasted another 5 years, but I was still able to get some use from them. The bottom line is that in order for this charging system check to be done effectively, the voltage from the battery should be above 12.4-volts in its resting state (12.6-12.78 is considered 100% charged and fully functional). So if it is below this reading, it’s a good time to put a charge on it for a couple of hours with a battery charger. Kinda makes you want to run out and test your battery right?
Also before you begin, keep in mind that on most motorcycles from 1990-2017, the charging system has NOTHING to do with a “no start” or ignition system problem. These two systems are separate altogether. Grounding wires that use charging system components can rear their ugly heads at anytime making it very hard to diagnose your problem. Also, it is very uncommon for a no charge problem to stem from parts like the pulse generator, regulator/rectifier, stator or alternator. On older motorcycles/ATV’s (before 1990) the charging system DOES play a role in the ignition system since the coil is energized by a component attached to or around the stator’s output signal. Got it? Good.
While you ride, your ignition system, head light, tail lights, signals, horn, blenders and disco balls require electricity to operate correctly. These are considered your bike’s electrical “LOADS”. They rob power continuously from your battery during use in order to stay operating with your bike, which in essence drains the battery. In order for your battery to stay at its peak operating output for the next time you start your bike, it has to have some way to have voltage/amperage return back. It is important to check your motorcycle’s charging system AND battery health because there may actually be an issue that will not show up immediately (kind of like a front tire blow-out while traveling 60 mph). Picture this: one morning you start your bike as usual and make a quick stop to fill up, but when you go to start your bike back up you suddenly realize that the bike will not turn over and all you hear is the discouraging CLICK coming from the starter solenoid. Now, I’m not saying that a charging system issue will be the only cause of this example, but it very well could be the culprit as to why it happened in the first place. That’s why you should check!
Before you go ripping your seat off in excitement, there is one tool that you must have on hand to make this check possible, a multi-meter. It does not need to be a top-end, fancy meter that is able to calculate the earth’s mass… a simple voltage reader will do.
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HOW THE HECK DO I READ THIS MULTI-METER?
Simple. You should see a symbol that looks like a V with a solid or dashed line above it OR it may even have VDC as your option. Don’t worry! They mean the same thing. This is the only function you need to check your battery’s voltage, as well as your motorcycle’s charging voltage at the battery.
This is the function for testing any circuit that uses VOLTS DC (aka volts direct current) to operate. Your battery is only able to charge with this type of current.
HOW TO CHECK YOUR MOTORCYCLE CHARGING SYSTEM
STEP 1.
You need to determine the current state of holding the voltage that your battery has to make sure your battery is up for the task. Using the information we’ve talked thus far, determine the health of your battery.
Go ahead and set the knob on your multi-meter to VDC (DC voltage).
Place your black wire lead from the meter to the (-) negative terminal of the battery (try to touch the actual battery terminal, not the cable attached to it). At the same time, hold your red wire lead to the (+) positive terminal of your battery. This is just a stationary check. Make sure your bike is not running or on in any way during this check.
What reading did you get? Above 12.4vdc? Great, continue to STEP 2.
Below 12.4vdc?
Maybe you get 12vdc, 11vdc, 9vdc, or even lower. Stop here and let’s evaluate.
If your battery is floating around 11-12vdc, there is still a chance that it is a usable battery but it will need to be charged. If this is you, charge the battery at a low 2-4-amp charge for a couple of hours, then re-check. In order to get a perfect diagnostic reading for your charging system, the battery must be charged at or above 12.4vdc (you can still do this check with a battery below this number, but 12.4vdc is the recommended peak operating voltage). If your battery is, in fact, lower than 11volts even after you charge it, it may be time to budget out some cash for a replacement. The possibility of this battery having some type of issue is much greater at this point. Once your battery sits in a drained state (below 12vdc) it will begin to eat itself and discharge at an increased rate. When a battery sits for a period of time, the battery’s life and ability to hold a charge will continue to drop until the point of no return. Your battery’s health is a CRUCIAL component when you are checking your motorcycle’s charging system because the readings you get can fluctuate, giving you false details on your charging system’s health.
STEP 2.
Now we will check the charging output to the battery. Go ahead and turn your key on to start your motorcycle and let it idle. Reconnect your positive and negative meter leads to the battery the same way as before. Now you SHOULD begin to see a change in voltage. Ideally, a charging system that is efficiently charging should read anywhere from 13.2volts to 13.8volts DC (or above) at idle.
STEP 3.
Now what you need to do is read the voltage output past idle by slowly twisting your throttle up to around 3,000 RPM and hold it there. You should see the voltage INCREASE on your meter even further up to around to 14.4volts (this will vary from bike to bike). If so, this is GOOD! Your charging system is putting out the necessary voltage to the battery during a running condition (past idle). Your motorcycle’s charging system check is complete!
Keep in mind that not all charging systems react in the same exact parameters that I’ve described. You may get 0.2volts (+ or -) during any one of these checks and that is OK! What you are looking for is the proper battery level and increase in charge once the bike has been started and given a little throttle. The charging system numbers should reach their peak at no more than 14.8volts and level out when you give the bike more and more throttle.
By doing this check you have learned that:
– Your stator has not failed (which would cause the voltage to never make it to the battery).
– Your regulator is working because it’s not allowing the voltage to exceed the threshold amount (past 14.8-15volts).
– Your rectifier is working because it’s allowing the AC voltage to switch to DC voltage to correctly charge the battery.
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