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A.C. ripple percentages


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The question has been raised as to what an acceptable ripple percentage is. Depemding on who you talk to you get everything from .1v all the way up to 2.0v

and from where I'm standing even .1v ripple is enough to upset a computer that likes 5vdc for operations. so this post is going to be kind of dualistic 1 I'm asking for members to post what thy are reading from theyre trucks and 2 anyone that hgas a specification for an alternator to post them here. the following are the parameters to follow

1 of course is automatic as you post your id

2 the year make model and mileage of the tested vehicle

 type of life it has if you commute on weekdays and mud on weekends I need to know or if you don't shut it off for 3 days straight from runnin3000 miles I want to know you get the idea

3 type age and shape of your batteries as well as specs and don't say square shape duhhhh I mean are they pristine or do they look like a pair of double a batts found in a ten year old flashlight in a swamp

4 and this is important please follow exactly or your results will be suspect. you wi be taking readings in a scientific manner which is extremely important for correlation later

   information necessary at start of test

   the meter must be a digital variety with good leads set to vac in a lower range so that any ripple will be recorded take your time and double check your readings before recording them please and use the right hand battery Driverside for grounding don't worry about ground loss as the purpose is to get a good ripple cross section

   A. temeperature in farrenheit at time of test.recorded both at start and conclusion

   B. the truck needs to be warmed up for a sufficient time so as to attain normal operating temperature for your truck

   C. you will be taking two separate readings at  different rpms with and without device loading

   D. unloaded test no accessories of any kind not fired up via the key run cycle

   E. loaded test to include full headlights in hibeam mode, heater set on high heat/highfan/ through the vent

   test point A is at the stud of the alternator output not.... I REPEAT NOT the nut the cable or any other point . I will dissertate on this subject in a later article please just take it as gospel

   test point B will be at the stud of the power distribution box again this is important for continuity in the study

   est point C will be at the tow connector at back of vehicle youll be testing the run light circuit which on a four pole flat will be the only one with juice on a seven pole the aux power the             center will also work but please specify which one you took

   F. you will be testing at each of these points at the following rpm ranges

       range 1  idle and record your rpms via tach

       range 2 1800 rpm or nominal cruise speed youll need someone to hold it right there for each point

       range 3 2200 rpm hi output limit though most will start to fall off a touch at this point

   G. one last thing is a loss test this is to be conducted at idle and its the control portion you will attach the black probe to ground with the meter set to dc and the engine at idle

        take the following readings at the exact points  A at the alternator output stud

                                                                                   B at the nut on the output stud

                                                                                   c at the furthest point on the cable connector to the alternator output

                                                                                   D at the furthest point on the connector to the power distribution block( make sure its the alternator feed )

                                                                                   E at the nut of the power distribution block

                                                                                   F at the stud of the power distribution block

record all dat and report it in the following format


Outlaw 7

2001 dodge 3500 series 6 c&c

354,627 miles used primarily for hotshotting until 5 years ago at 334k then a daily driver average 500 miles per month if driven

original alternator, old batteries lh (pass side ) 750cca deep cycle Walmart rh 800cca deep cycle Duracell both in good shape clean ends oem cabling new clamps

temp 56 degrees F


rpm              idle750      1800       2200

point a           .09vac    .14vac      .13vac

point b           .08vac    .13vac      .12vac

point c           .05vac    .1vac         .09vac



point a          13.5vdc

point b          13.4vdc

point c           13.4vdc

point d           13.2vdc

point e           13.2 vdc

point f            13.1vdc


all my data is fake as my dually issans ecm and pcm till next week some time ill post my actuals then


remember this is volunteer only please and thank you but if your going to take the time to do this do it right and accurately and take pride in knowing you are benifiting the greater good of the cause you never know helpers might just get rewarded as well in the end thank you again guys I look forward to seeing your posts this is outlaw7 over n out......

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ok I bit the bullet yesterday and order a cheaper hankok ???? 8ch usb oscilloscope which apparently ships from china as it wont be in until 2nd week of February if I'm lucky but it claims some seriously awesome capabilities including can buss diagnosis etc so well see... I mainly wanted it for my r&d on the ripple filter project but I can think of like a thousand other things ill use it for ill start a thread on it once I get it and put it to use

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for those of you that are curious about the last portion of the test , this article should clear up any questions


I'm creating a form that you can print out to make this easier itll be up soon


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