Discussion
I am changing some of the drive pulleys to better serve my s/charger, while I am at it I am going to refresh the alternator as the front bearing feels a little worn.
My question is what is the Max amperage anyone has used on an Ultima, the reason I ask is I feel I could do with a little more power so that I can run air con, fans, lights, ignition etc. without deficit to the battery.
I have sourced the correct size/fit alternator ranging from 80 to 200 amps.
I feel 200 may be a bit overkill and may fry my battery (though properly regulated I'd have thought it should be ok).
Any ideas?
My question is what is the Max amperage anyone has used on an Ultima, the reason I ask is I feel I could do with a little more power so that I can run air con, fans, lights, ignition etc. without deficit to the battery.
I have sourced the correct size/fit alternator ranging from 80 to 200 amps.
I feel 200 may be a bit overkill and may fry my battery (though properly regulated I'd have thought it should be ok).
Any ideas?
Edited by F.C. on Wednesday 14th May 12:54
So my rudimentary understanding is that the alternator will only provide what is required by the battery (the measured delivery being a function of the 'regulator') I'm in the process of fitting a 140amp unit (70amps at 960rpm) to cure a legacy charging issue on my car. Having done a bit of reading you probably should consider upgrading your cables to the battery to accommodate the kind of load the new alternator is capable of delivering.
Hope this helps.
Hope this helps.
Even with A/C etc, an Ultima has what would be considered by modern standards a low "power" consumption, because it has very few electrical systems!
If you have added EPAS, Heated seats/screens etc, then yes, you may need a few more amps to keep up.
Usually the issue is at idle, where the alternator cannot supply anything like it's full rated output. The cheat here is to simply set the idle a little fast (after all, fuel economy isn't exactly a priority ;-)
A "high current" alternator will not "fry" a battery, as they work in a voltage control loop. Eg, the alternator only generates enough current to raise the system voltage to between 13.7 & 14.3 volts. At that voltage, most of the alternators current output is being used by the consumers on the vehicle, and the battery itself will just be effectively trickle charging (unless it was depleted at start due to the car being unused for a while etc)
Most conventional LA/SLA batteries will never take more than about 20amps whilst charging, however flat they are.
The disadvantages to a "High current" alternator are really only in terms of cost and size/mass.
If you can get hold of a DC current clamp, you can measure your average alternator output at warm idle, which will only be in the order of ~20A for most cars (10A of fuel pumps, 5A of engine Ecu, 5A of instruments etc)
If you have added EPAS, Heated seats/screens etc, then yes, you may need a few more amps to keep up.
Usually the issue is at idle, where the alternator cannot supply anything like it's full rated output. The cheat here is to simply set the idle a little fast (after all, fuel economy isn't exactly a priority ;-)
A "high current" alternator will not "fry" a battery, as they work in a voltage control loop. Eg, the alternator only generates enough current to raise the system voltage to between 13.7 & 14.3 volts. At that voltage, most of the alternators current output is being used by the consumers on the vehicle, and the battery itself will just be effectively trickle charging (unless it was depleted at start due to the car being unused for a while etc)
Most conventional LA/SLA batteries will never take more than about 20amps whilst charging, however flat they are.
The disadvantages to a "High current" alternator are really only in terms of cost and size/mass.
If you can get hold of a DC current clamp, you can measure your average alternator output at warm idle, which will only be in the order of ~20A for most cars (10A of fuel pumps, 5A of engine Ecu, 5A of instruments etc)
Max_Torque said:
Even with A/C etc, an Ultima has what would be considered by modern standards a low "power" consumption, because it has very few electrical systems!
If you have added EPAS, Heated seats/screens etc, then yes, you may need a few more amps to keep up.
Usually the issue is at idle, where the alternator cannot supply anything like it's full rated output. The cheat here is to simply set the idle a little fast (after all, fuel economy isn't exactly a priority ;-)
A "high current" alternator will not "fry" a battery, as they work in a voltage control loop. Eg, the alternator only generates enough current to raise the system voltage to between 13.7 & 14.3 volts. At that voltage, most of the alternators current output is being used by the consumers on the vehicle, and the battery itself will just be effectively trickle charging (unless it was depleted at start due to the car being unused for a while etc)
Most conventional LA/SLA batteries will never take more than about 20amps whilst charging, however flat they are.
The disadvantages to a "High current" alternator are really only in terms of cost and size/mass.
If you can get hold of a DC current clamp, you can measure your average alternator output at warm idle, which will only be in the order of ~20A for most cars (10A of fuel pumps, 5A of engine Ecu, 5A of instruments etc)
I had initially thought about the current consumption of my car, but as you correctly mention it is the idle performance that may be my biggest problem, I do have EPAS and at idle it can be a little "laggy" (just when I need it for parking manoeuvres) and if the fans or ac run, then there is a notable change in engine rpm with the extra load.If you have added EPAS, Heated seats/screens etc, then yes, you may need a few more amps to keep up.
Usually the issue is at idle, where the alternator cannot supply anything like it's full rated output. The cheat here is to simply set the idle a little fast (after all, fuel economy isn't exactly a priority ;-)
A "high current" alternator will not "fry" a battery, as they work in a voltage control loop. Eg, the alternator only generates enough current to raise the system voltage to between 13.7 & 14.3 volts. At that voltage, most of the alternators current output is being used by the consumers on the vehicle, and the battery itself will just be effectively trickle charging (unless it was depleted at start due to the car being unused for a while etc)
Most conventional LA/SLA batteries will never take more than about 20amps whilst charging, however flat they are.
The disadvantages to a "High current" alternator are really only in terms of cost and size/mass.
If you can get hold of a DC current clamp, you can measure your average alternator output at warm idle, which will only be in the order of ~20A for most cars (10A of fuel pumps, 5A of engine Ecu, 5A of instruments etc)
I think there may be a "feature" within my ECU for this very event, i.e. when extra load is "detected" the idle speed is compensated for.
The size of the 200 amp alternator is identical to that of the 80 amp, I wonder if the parasitic loss/load is significantly greater the larger you go, say between a 120 and a 200 amp alternator?
ETS. It is a given that the extra mass within the bigger alternator will have greater effect on the ancillary drive and harmonics, my thought is could this bite me later on in terms of wear and tear on the drive train?
Edited by F.C. on Wednesday 14th May 18:42
I don't have EAPS but I did do a test yesterday with all electric components on (aircon - I have twin fans on my aircon, heater fans, lights full beam, heated screen, engine running (obviously) so all pumps) and the engine speed remained static.
Admittedly it does tick over at 900rpm but my engine tuner was very concerned that the car should not stall with aircon on when the revs drop.
I think my alternator is 90 amps so can't believe you would need 200amps.
Are you planning to leave the engine running and power your home with it????
Paul
Admittedly it does tick over at 900rpm but my engine tuner was very concerned that the car should not stall with aircon on when the revs drop.
I think my alternator is 90 amps so can't believe you would need 200amps.
Are you planning to leave the engine running and power your home with it????
Paul
spatz said:
the real problem in the ultima are the fans that if running can empty the battery very quickly. So if you look for a perfect solution find an alternator
that has a good charge when idling, since in traffic this is what will happen, fans on and only tick over !!!
I tend to agree with this, I will investigate further and see if there is an alternative alternator that has a good charge when idling, since in traffic this is what will happen, fans on and only tick over !!!
with such low speed characteristics (I somehow doubt) and if it exists see if it can be adapted to fit.I would think you need to be in the 120amp sort of range for an Alternator.
The V8's are quite low reving so make sure at max revs you have the alternator working at close to its maximum speed. This should give you good charging at lower RPM. Normally Alternators max RPM is around 14,000rpm some even more some less. The supplier of the alternator should be able to give a graph showing rpm/output but most reach max charge about 9000rpm. From this graph you can calculate the pulley sizes best for your application. I shouldn't be hard to add up the amps drawn by the various systems or if you want to get an exact reading put an amp meter on.
The V8's are quite low reving so make sure at max revs you have the alternator working at close to its maximum speed. This should give you good charging at lower RPM. Normally Alternators max RPM is around 14,000rpm some even more some less. The supplier of the alternator should be able to give a graph showing rpm/output but most reach max charge about 9000rpm. From this graph you can calculate the pulley sizes best for your application. I shouldn't be hard to add up the amps drawn by the various systems or if you want to get an exact reading put an amp meter on.
spatz said:
the real problem in the ultima are the fans that if running can empty the battery very quickly.
This is more of an issue with having a small lightweight battery rather than a small alternator! A pair of BIG fans only pulls 30A, which is not a problem for an alternator to produce assuming it is spinning fast enough. Most OEM based ES systems will jack up the idle speed if they detect a low system voltage and some aftermarket ones can also be set to do this, which means you can have your nice slow idle (quiet and good for low speed "creeping" in traffic with tall 1st gear!) most of the time ;-)ok I am using a yellow top optima which is the biggest that can fit in the ultima and last TUEV session with fans on while measuring exhaust gases, resulted in a flat battery which made it impossible to start the car again. So this is the reality with a motorsport alternator that has little charge in idling, so if you want to avoid this choose an alternator with good charge at low speeds. (e.g. the bigger the thing the more beef at idle, simple rules)
ok I am using a yellow top optima which is the biggest that can fit in the ultima and last TUEV session with fans on while measuring exhaust gases, resulted in a flat battery which made it impossible to start the car again. So this is the reality with a motorsport alternator that has little charge in idling, so if you want to avoid this choose an alternator with good charge at low speeds. (e.g. the bigger the thing the more beef at idle, simple rules)
spatz said:
ok I am using a yellow top optima which is the biggest that can fit in the ultima and last TUEV session with fans on while measuring exhaust gases, resulted in a flat battery which made it impossible to start the car again. So this is the reality with a motorsport alternator that has little charge in idling, so if you want to avoid this choose an alternator with good charge at low speeds. (e.g. the bigger the thing the more beef at idle, simple rules)
I don't think you will find an alternator that can produce the amps you are looking for at low rpm,(especially one to fit in the space available) the best bet as far as I can see is to use a smaller diameter pulley on the alternator, this will bring the alternator up to higher speed at idle and with a low revving (comparatively speaking) V8 it is unlikely to over speed the alternator at max engine RPM.I have scoured parts bins and specialist suppliers over the last few days and all said much the same thing; Change to a smaller diameter pulley).
F.C. said:
I don't think you will find an alternator that can produce the amps you are looking for at low rpm,(especially one to fit in the space available) the best bet as far as I can see is to use a smaller diameter pulley on the alternator, this will bring the alternator up to higher speed at idle and with a low revving (comparatively speaking) V8 it is unlikely to over speed the alternator at max engine RPM.
I have scoured parts bins and specialist suppliers over the last few days and all said much the same thing; Change to a smaller diameter pulley).
that I would say is the way to go, looking at my rev history car has not seen much beyond 5k rpm and if so not for a very long period.....I have scoured parts bins and specialist suppliers over the last few days and all said much the same thing; Change to a smaller diameter pulley).
F.C. said:
I don't think you will find an alternator that can produce the amps you are looking for at low rpm,(especially one to fit in the space available) the best bet as far as I can see is to use a smaller diameter pulley on the alternator, this will bring the alternator up to higher speed at idle and with a low revving (comparatively speaking) V8 it is unlikely to over speed the alternator at max engine RPM.
I have scoured parts bins and specialist suppliers over the last few days and all said much the same thing; Change to a smaller diameter pulley).
I did the same, worth checking the max rpm too. With one type of alternator I had issues with the fan disintegrating and throwing individual lugs into the winding. From what I could find out 15000rpm seemed to be an accepted maximum, depending on how long sustained etc.I have scoured parts bins and specialist suppliers over the last few days and all said much the same thing; Change to a smaller diameter pulley).
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