W124 Alternator

[Niks]

I need a bigger alternator for my car to cope with a bigger sound system setup with a few amplifiers. I might also go down the route of having a second yellow top battery running via a split charge system, but this will put a lot of load on the alternator.

Does anyone have any recommendations?

 

[brigadier]

what engine? and which alternator you have now?

 

[Niks]

I have a M104 2.8L, I have no idea which alternator it has...

 

[grober]

W124 batteries were either 70A 4cylinder cars or 90A six cylinder models 100Ah battery is about the biggest that will fit in the battery tray. The 4 cylinder M102 engined models around that time were sometimes fitted with 120A alternators-- my guess the special taxi versions or perhaps for overseas markets. Option on engine nos M102.94, M102.99

addendum:- HELLA make one 8EL 737 007-001 120A for the long wheelbase version of your car W124.029 / ENGINE M104.924 ---just don't know if it will fit your car but pretty likely?

 

[Niks]

I'll have a look into that, cheers Grober. Would an alternator from an S-Class work? or could I use a dual alternator setup?

Im looking to get out another 50-60A (I think thats correct) to drive 3 amplifiers in total with one of them inline with a capacitor.

 

[grober]

I'll have a look into that, cheers Grober. Would an alternator from an S-Class work? or could I use a dual alternator setup?

Im looking to get out another 50-60A (I think thats correct) to drive 3 amplifiers in total with one of them inline with a capacitor.

Depends on the mounting lugs I guess as to whether the pulley would line up but if it was off a M104 engined car almost certainly yes- however I would check the alternator output carefully - even the big V8's didn't have that big an alternator.

 

[Number_Cruncher]

I'll have a look into that, cheers Grober. Would an alternator from an S-Class work? or could I use a dual alternator setup?

Im looking to get out another 50-60A (I think thats correct) to drive 3 amplifiers in total with one of them inline with a capacitor.

I would be interested to see how you have calculated your power requirements, and how you have translated that into a specification.

It's worth considering that the alternator doesn't need to supply the peak power requirement, only the average, which is usually quite low when compared with the peak figures which suppliers of in car systems tend to quote.

 

[Niks]

I would be interested to see how you have calculated your power requirements, and how you have translated that into a specification.

It's worth considering that the alternator doesn't need to supply the peak power requirement, only the average, which is usually quite low when compared with the peak figures which suppliers of in car systems tend to quote.

Well im guessing that my current alternator only gives an output of around 70A, which is enough to feed all the electrical systems in the car. It probably has an extra head room of 10-20A worth as apparently alternators dont produce as much electricity in the heat compared to when its cold.

So the way I have calculated it is, one amp to power the front 3 way speaker system which is rated at 200W x 12V = 16.7A, a second amp of the same to power the rear 2-way setup at 200W x 12V = 16.7A, and a monoblock amp to power the sub at 750W x 12V = 90A (thereabouts) . So total system power Amperes required is 114A (as a guide) altogether. I know im not going to be listening to it at those crazy levels all day long, but its better to have more in reserve than less and strain the electrical charge system/battery.

A dedicated second battery will provide an extra 55A and using 0 gauge earthing cables will give full grounding.

I know a lot of people go ahead and install big systems to cars without considering the cars electrical system and what it was originally designed for. I'd rather be safe than sorry, plus it eliminates any problems down the line.

 

[bh13coupe]

I am interested to see the end result NIKS, are you changing all the smaller speakers and replacing with different sized replacements? Are we looking at lots of cutting into door cards etc etc?
i am not meaning to change the direction of the thread feel free to pm me any details.

thanks

 

[Niks]

Hi Paul, yeah im going for a major upgrade on the speakers and installation. Up front, the dashmount speakers are way too small to produce any mid-bass whatsoever, although the acoustic imaging is very good. Im going for a 3-way setup at the front using the Jennhert door cards with JL Audio component sets (2x 6.5", 1x 4" and 1x tweeter per side). Tweeters will go in custom fabricated fibreglass pods where the wing mirrors are to match up with the 4" mid bass speakers.

The rears will have 2-way JL Audio component speakers but im still undecided to go custom fabricated fibreglass pods or get a whole MDF shelf instead.

I already made a MDF board for my amp which powers the sub, thats sitting right behind the petrol tank and i'll use this to mount the other 2 JL Audio amps on. Im in the process of making a MDF box to house the second battery in the spare wheel compartment.

Possibly toying with the idea of getting rear screens in the headrests as my Pioneer head unit has the facility for this, great for watching DVD's on a long journey. I could also hook up a forward facing small camera above the rear view mirror so rear passengers can see thats going on in front!

Before any of this happens, I need to gut out the whole interior of the car and lay Dynamat sound deadening on the floor, door panels, boot and wherever else I can to reduce road noise, rattles and so on. Then i'll need to redo all the cabling running from the front to the back, stick it all down and make sure the earthing is all done properly.

It'll be a big project and will take time, but it'll sound amazing once its all done. Im not going for huge SPL, more for sound quality as I really love my sounds, especially coming from a recording studio background.

 

[Number_Cruncher]

Well im guessing that my current alternator only gives an output of around 70A, which is enough to feed all the electrical systems in the car. It probably has an extra head room of 10-20A worth as apparently alternators dont produce as much electricity in the heat compared to when its cold.

So the way I have calculated it is, one amp to power the front 3 way speaker system which is rated at 200W x 12V = 16.7A, a second amp of the same to power the rear 2-way setup at 200W x 12V = 16.7A, and a monoblock amp to power the sub at 750W x 12V = 90A (thereabouts) . So total system power Amperes required is 114A (as a guide) altogether. I know im not going to be listening to it at those crazy levels all day long, but its better to have more in reserve than less and strain the electrical charge system/battery.

A dedicated second battery will provide an extra 55A and using 0 gauge earthing cables will give full grounding.

I know a lot of people go ahead and install big systems to cars without considering the cars electrical system and what it was originally designed for. I'd rather be safe than sorry, plus it eliminates any problems down the line.

The alternator is usually sized to provide for the constant, or near constant vehicle electrical loads at very low, near idle, engine speeds. Consumers which are used intermittently are given a factor, and the total load must be balanced, again at low engine speeds, typically 2000 - 2500 rpm.

When the engine is running, the system runs at 14 volts - use this to calculate the required currents, not 12v.

Take some measurements of your amplifiers, and find what the mean current is - if you size for peak currents, you will be significantly over-sizing your system.

I wouldn't worry too much about heat and cold with respect to alternator output - let the alternator's regulator sort that out.

In your shoes, I would either check the real current requirements and design accordingly, or, install the system, and monitor the battery for a while after fitting the system before making modifications.

The main thing I would like to emphasise is the importance of making sure that any wiring modifications you make are appropriately fused, and the wiring safely routed. It's shockingly easy to set fire to a car electrically.

 

[Niks]

Oh yeah I totally forgot about the 14V thing, its actual output is 13.8V whilst the engine is running. Also, I got the x mixed up for /. The formula is:

Watts (RMS) / Volts = Amperes

200W / 13.8V = 14.5A (front)
200W / 13.8V = 14.5A (rear)
750W / 13.8V = 54.34 (Sub)

Total current pull = 83.34 Amps (including music peaks)
41.67 will be my average pull (at half system volume)

Will this alternator work with my car?

SB019 MERCEDES 300SE SL280 SL320 93-98 120A Alternator | eBay UK

Absolutely, I'll have all the sufficient fuses put in place where needed, electricity safety always comes first in any ICE install!

 

[Number_Cruncher]

You may need to check each amplifier's efficiency - they won't be 100%, that's certain!

Electrically, the alternator looks like a good solution; I don't know whether or not it will physically fit your car.

Some MBs have very little clearance between the rear of the alternator and the crossmember.

 

[bh13coupe]

Hi Paul, yeah im going for a major upgrade on the speakers and installation. Up front, the dashmount speakers are way too small to produce any mid-bass whatsoever, although the acoustic imaging is very good. Im going for a 3-way setup at the front using the Jennhert door cards with JL Audio component sets (2x 6.5", 1x 4" and 1x tweeter per side). Tweeters will go in custom fabricated fibreglass pods where the wing mirrors are to match up with the 4" mid bass speakers.

The rears will have 2-way JL Audio component speakers but im still undecided to go custom fabricated fibreglass pods or get a whole MDF shelf instead.

I already made a MDF board for my amp which powers the sub, thats sitting right behind the petrol tank and i'll use this to mount the other 2 JL Audio amps on. Im in the process of making a MDF box to house the second battery in the spare wheel compartment.

Possibly toying with the idea of getting rear screens in the headrests as my Pioneer head unit has the facility for this, great for watching DVD's on a long journey. I could also hook up a forward facing small camera above the rear view mirror so rear passengers can see thats going on in front!

Before any of this happens, I need to gut out the whole interior of the car and lay Dynamat sound deadening on the floor, door panels, boot and wherever else I can to reduce road noise, rattles and so on. Then i'll need to redo all the cabling running from the front to the back, stick it all down and make sure the earthing is all done properly.

It'll be a big project and will take time, but it'll sound amazing once its all done. Im not going for huge SPL, more for sound quality as I really love my sounds, especially coming from a recording studio background.

Just small upgrade then

sounds awesome, no pun intended. Looking forward to a thread documenting the build

 

[Indyz12]

Apparently the saab 9000 alternator will fit as long as you change the pulley.
They are 120A and are dirt cheap compared to the S class alternators.....