kirin

Hi, I am new to this forum and need your advise on changing alternator from original 90Amp to 120Amp if possible.
The reason is I have added a lot of electric consumable goods such as Car navigation, extra lights and so on.

The original altenator is Bosch and 90Amp and 120Amp is also the same maker and the same physical appearence.
My question is can I just change the alternator or should I change other related components like fuse and others?, I do not want to fry any of my electrical components.

My car is C280(W202), year 1996-1997.

Thank you in advance for your advise.

shandy2550

No problem in changing to a higher output alternator,it will still put out the same voltage so will not affect any other components.
Geo

kirin

Thank you Shady2550.

I am not sure if I understand you correct, it will still put out the same voltage so will not affect anu other components ?
Does this mean that there is no point in changing to an higher output alt?

Thank you again

shandy2550

Sorry if I confused you, the voltage output of an alternator is controlled by the voltage regulator and is the same regardless of the maximum output of the alternator. What you are interested in is the amperage rating which gives the maximum output of the alternator.
Watts = volts x amps (12v x 90amp = 1080watts);(12v x 120amp = 1440watts). So you have another 360watts load capacity available if you go for a higher capacity alternator.
The alternator gives out far more than 12volts when charging a low battery but that's another story.
Cheers, Geo.

kirin

shandy2550,
Thank you so much for your descriptive explanation. I understand as far as the amperage is concerned. So, it may be worth changing becasue I get extra 360Amp. Apart from this, I am bit curious to know about your last word.
Could you explain a bit about this far more than 12volts things in plain English ? or would it ddifficult to explain, then could you refer any web site ?

Thanks again!

shandy2550

Normal battery voltages are;( measured with a voltmeter across the battery terminals).
Fully charged but rested battery ;12.2-12.6v (engine stopped, no load).
Fully charged battery just off charge;just under 13v (engine stopped ,no load).
Engine running at around 2000rpm but no accessories switched on; 14.3-14.6v.
Engine running at around 2000rpm with head lights on main beam, heater blower on full and rear screen heater on; the voltage should be above 13.4v.

In your case, if you switch on all the extra load items you have installed and the voltage is maintained above 13.4v with engine at about 2000rpm, you should be ok with your 90amp alternator. If the voltage drops below this you should fit the higher output one.
Hope this explains it fully ,
Cheers, Geo.

kirin

shandy2550,

Again, you have explained so simple and I understand fully.
Thank you so much for your kindness.

Thanks again and Cheers