SOHC.co.uk Forums > CB750
Charging test
Johnwebley:
--- Quote from: El__burro on July 17, 2016, 10:23:46 PM ---
--- Quote from: K2-K6 on July 17, 2016, 09:24:29 PM ---If you have a voltmeter, then connect to battery, should show about 12.5 to 12.9 volts with bike turned off. Turn on and start, volts should now show about 13.5 to 13.95 volts as this is a normal charge rate for most systems. You may have to rev it to about 2000 rpm to see the max figure.
Most systems (apart from some of the newer stuff) will cut off at 14 volts max to avoid boiling the battery dry. If they can sustain anything above 13.5 then they should have the ability to keep the battery charged and at a healthy level
--- End quote ---
Not sure if I have got it right but I did exactly that yesterday, I attached the voltmeter to the battery and revved a bit, it went to about 15v, (I am surprised it didnt blow any lights off).
I will retry the test again tomorrow but.. can it be, also could this be the reason for a roasted battery?
Thanks
el__burro
--- End quote ---
could well be,what charging system,regulator/recifier are you using?
El__burro:
--- Quote from: Johnwebley on July 17, 2016, 10:46:03 PM ---
--- Quote from: El__burro on July 17, 2016, 10:23:46 PM ---
--- Quote from: K2-K6 on July 17, 2016, 09:24:29 PM ---If you have a voltmeter, then connect to battery, should show about 12.5 to 12.9 volts with bike turned off. Turn on and start, volts should now show about 13.5 to 13.95 volts as this is a normal charge rate for most systems. You may have to rev it to about 2000 rpm to see the max figure.
Most systems (apart from some of the newer stuff) will cut off at 14 volts max to avoid boiling the battery dry. If they can sustain anything above 13.5 then they should have the ability to keep the battery charged and at a healthy level
--- End quote ---
Not sure if I have got it right but I did exactly that yesterday, I attached the voltmeter to the battery and revved a bit, it went to about 15v, (I am surprised it didnt blow any lights off).
I will retry the test again tomorrow but.. can it be, also could this be the reason for a roasted battery?
Thanks
el__burro
--- End quote ---
could well be,what charging system,regulator/recifier are you using?
--- End quote ---
All stock, original K2
el__burro
K2-K6:
That would definitely compromise the battery If it's always charging at that rate.
Get a cross check of your meter by just measuring another car or bike which should give you a reasonable check to make sure your meter is not wrong.
Some of the newer cars and intelligent battery chargers run up to something around 16 volts but they have a strategy and measurement to ensure that a once fairly low battery gets quite a kick to bring it back toward normal range, then they back down the volts to avoid over heating the battery.
I'd say with reasonable confidence that continously charging at the rate you are seeing will screw the battery. Almost without exception you'd look to 14 volts as a general working maximum is what you should have in a normal system.
The lights would take probably more than 18 volts before they'd blow, so you won't necessarily see problems. Bright headlight though ;0
El__burro:
Did a car battery check with the multimeter, it reads 12,5v (engine off)
Then I did a check on the bike.
Battery level is 13v
turn the key, it drops to below 11v
kickstart and goes to 13.5v at low revvs
It reaches 15,5v at higher revvs.
I guess something is wrong but what?
el__burro
K2-K6:
The rectifier and regulator work on the output from the alternator.
AC current comes from the alternator and is converted by the rectifier to dc current suitable for the battery and bike electrics, but doesn't have any control as to the total output. The fact you can get too high a voltage confirms this area is ok.
Then the regulator has the function of controlling/limiting the DC voltage to the required maximum to run system within design limits, so it's this component that needs to be looked at.
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