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Alternator FAQ

What size alternator should I choose?
Choose an output that is at least 10%  more than the maximum amps demand from all of your electrical consuming ancillaries when added together. You cannot have too much output, the Alternator self regulates to only give enough output to satisfy demand.

Higher output units are generally heavier and bigger in diameter with the exception of 'uprated' types. If you need a high output at very low engine speeds, there is no substitute for a bigger diameter, and heavier Alternator.
Does an alternator amps rating stay the same at all engine speeds?
No - the output of all Alternators increases with rotor speed / engine speed, a graph of output against speed shows a rapidly rising curve from 'cut-in' speed to stabilised maximum.

Standard specification alternators have a low speed 'cut-in' and reach their maximum output at a relatively low engine speed, about 3000 RPM depending on pulley drive ratio. Uprated Alternators do not stabilise at this speed but continue to rise in output up to about 6000 RPM.

What voltage should an alternator give?
The charging voltage is dependent on the amount of amps being demanded by the vehicle electrical system, if the Alternator is giving near its maximum amps output the voltage is likely to be about 12.9v, if the amps output is low, the charging voltage will rise to about 13.9v - 14.1v. A voltage of more than 15.0v could indicate a failure of the voltage regulator. If charging voltage drops below 12.0v, either the Alternator could have failed or the amps demand from the vehicles electrical system is too high for the alternator to supply at that particular engine speed.
Will an alternator with high output damage my cars electrical system?
No - an Alternator self regulates by referencing the Battery Voltage and increasing or decreasing it's charging voltage within set limits. The voltage regulator is the component that is responsible for this, it will vary the field current it supplies to the electromagnetic coil in the rotor thereby controlling the charging voltage.
What is an 'uprated' alternator?
Brise 'S' series Uprated Alternators are modified to achieve higher outputs in the smallest size and weight possible. The internal components, Stator, Rectifier, Regulator, brushes, bearings, etc. are hand built for Motorsport applications to the highest quality. Output of a standard Alternator can be doubled in this way however, heat management is very important with Uprated Alternators due to the extra heat produced by the higher electrical power produced. It is very important to have the correct pulley drive ratio for Uprated Alternators because at low engine / rotor speeds the output may be lower than a standard Alternator.
What speed should the alternator run at?
The maximum advisable rotor speed for Brise Alternators is 18000 RPM, therefore for an engine with maximum RPM of 9000 RPM, an crankshaft pulley to Alternator pulley ration of 2:1 would be allowable.

Running your Alternator at slower speeds can give benefits in lower inertia and fan losses but must take into account the Amps output graph for any given Alternator.
How do I connect the alternator into my  vehicles electrical system?
Brise Alternators can generally be supplied with what we term as 'one wire'  or 'three wire' connection systems. The one wire regulator that is available for certain DENSO type alternators only requires a connection to the main Battery output post with no connections to the voltage regulator. This type does not have the option of a warning light control terminal.  

Three wire systems require the same battery output post to be connected but also need an ignition switched 12v power supply to the 'IG' terminal of the regulator.  The 'IG' terminal provides the power for the regulator to operate, and needs to be switched on and off with the ignition to avoid power drain when the engine is not running.  

If the regulator connector includes an 'S' battery voltage sense terminal, it must be connected to a +12v supply.  It is not necessary for this to be switched as it is only a sensing wire and does not consume any current.  It is advisable for the connection to the 'S' terminal to be made as directly to the battery post as possible to eliminate voltage drop in cables however the alternator will work properly even if the 'IG' and 'S' terminals are linked together.

The 'L' terminal controls the dashboard warning light and in most cases is an optional connection.  This terminal is effectively the same as battery negative or earth when the alternator is not charging, hence connecting your warning light wire to it will illuminate the bulb. When the alternator is charging, this terminal becomes the same as battery positive which will extinguish the warning light bulb.

The Alternator is earthed through it's body therefore it is important to check that the mounting bracket gives a good earth and there is no paint or aluminium anodising treatment that could degrade the connection.

Be sure to use cables that are rated to carry adequate current.  If the cables are too small in cross section then there will be a high resistance causing voltage drop and overheating.

What can potentially harm my alternator in Motorsport environments?
Heat, Vibration and electrical 'spikes' are the main causes of failure.  The twin internal fans that cool most Brise Alternators draw cooling air through the rear cover and from the pulley end, this air then exits through the radial slots in the case. The most sensitive components are housed underneath the rear cover therefore it is important to ensure a good supply of cooling air at this point, especially in the case of Uprated 'S' type Alternators.  If piped cooling air is provided, it should not point directly at the outer radial slots because this would oppose the outgoing heated air.

Vibration issues are normally associated with inadequate mounting design. Mounts should be as solid as possible without any flexing, if anti-vibration bushes are used they should be of a suitably hard material to avoid movement.  Tensioning arms, if used, should be designed to aid rigidity of the Alternator, avoid using spherical ball joints if possible as they are only rigid in one plane.

Electrical transient spikes are caused by bad or intermittent connections, this can damage the voltage regulator electronics.  spikes can also be produced if the engine is stopped with the battery master switch rather than the ignition switch.

What alternator pulley should I choose?
Choose a pulley that matches the crankshaft pulley width and belt design, Brise Alternators can be supplied with either single 'V' belt type in A or B width, or multi-v types in 3-8pk width. The diameter should be chosen to ensure that the maximum rotor speed of 18000 RPM is not exceeded.  Brise Alternators are usually supplied with a steel pulley, however various uprated 'S' type Brise alternators are supplied with an aluminium pulley. If you require a different pulley to what is supplied with the product, you can purchase one from the Pulleys section of our website.

What are the main components of an alternator?
The main components of an Alternator are the Stator Winding including the steel laminations,  the rotor, rectifier, brush box, voltage regulator, body castings or brackets and bearings.

What is an alternator?
An alternator is a three phase AC generator with rectified DC output. Alternators are used in modern automobiles to charge the battery and to power the electrical system when its engine is running. Until the 1960s, automobiles used DC dynamo generators with commutators. With the availability of affordable silicon diode rectifiers, alternators were used instead.


Starter Motor FAQs

What is the difference between pre-engaged and inertia starter motors?
A pre-engaged starter motor fully engages the pinion gear with the ring gear before using full power to crank the engine.  this is achieved by the solenoid, which when energised, pushes the pinion gear into the ring gear.  Only when the solenoid has reached its pre-determined position will the electrical contacts that power the motor  close.  An inertia starter motor starts under full power as soon as it is energised and uses the inertia of the heavy bendix assembly to throw itself along the shaft helix and into engagement with the ring gear.  

Pre-engaged starters are preferred due to their more reliable and softer engagement mechanism that causes less damage to the ring gear and less chance of disengagement during cranking.

My car was fitted with a Lucas Inertia type starter, can I use the same wiring?
An inertia starter utilises a remote solenoid to switch the motor,  this solenoid has only an electrical switch function. In the case of a pre-engaged starter there is a built-in solenoid that not only switches the motor once it is engaged but also has the job of mechanically moving the pinion gear into position. changing from an Inertia Starter wiring system to a pre-engaged type involves removing the remote solenoid and re-wiring the main battery and starter switch cables direct to the starter.  

It is possible to leave the remote solenoid and it's cables in place and use a link lead between the pre-engaged Starter's main battery connection and it's solenoid switch connection. this will enable the Starter to work but is not recommended as there would be two solenoids, with their attendant volt drops, doing the job of one.

What is an 'Axial' starter motor?
An 'Axial' Starter Motor is a particular design that incorporates the solenoid at the back and in-line with, the motor.  The solenoid actuated directly through the centre of the motor shaft thereby eliminating the need for levers and a separate housing that are necessary with an externally mounted solenoid.  The Axial design is more compact and suitable for applications where space and weight is at a premium.  The suffix "AXG" after the part number refers to Axial with Gearbox, this describes the Axial type of starter that also has a planetary gearbox in it's drivetrain. The planetary gearbox gives the starter higher torque capability with lower weight. The axial design also has interchangeable pi on gears on a splined shaft and a removable mounting bracket that can be rotated to achieve the optimum position for the electrical connector block. You can view our range of base model Axial Starter Motors here.
What is a 'PGR' starter motor?
A PGR Starter is a more conventional pre-engaged design that has an externally mounted solenoid, suffix PGR refers to permanent magnet gear reduction, the type of gear reduction system can be either planetary or spur gear type.  Brise PGR starters have removable mounting plates that can be rotated so that the solenoid can be placed in the most suitable position to avoid clashes with engine of chassis parts.

What power of starter motor do I need?
The power required to crank an engine to it's required starting RPM is obviously determined by many factors, the number of cylinders, compression ratio and gear train efficiency. A Starter Motor does not have a synchronous speed, it's speed is determined by the mechanical load placed upon it, therefore the more powerful the starter the faster it will crank the engine. A high torque Starter with gear reduction will crank faster than a direct drive Starter without gear reduction due to the increased torque available. Gear reduction will be in the order of 6:1 therefore the starter armature is able to turn 6 times in order to make one revolution of the pinion gear, this allows operation at the motor’s  most efficient speed.
How fast will a starter motor crank my engine?
The cranking speed is determined by mechanical load placed on the Starter Motor and also by the ratio of the pinion gear to the flywheel ring gear. Small diameter clutches and flywheels will increase the torque requirement and may result in slower cranking speed. Battery voltage applied is critical to Starter speed.
How does battery voltage affect starter motor power?
Starter Motor power is proportional to applied voltage and is therefore crucial to Starter Motor performance, whilst cranking hundreds of amps may be drawn from the Battery and it's ability to maintain a good voltage is determined by its CCA (cold cranking amps) rating. You can expect to see the measured battery voltage drop to as low as 9 Volts during cranking.
Why is a gear reduction starter better than a direct drive starter motor?
A high torque Starter with gear reduction will crank faster than a direct drive Starter without gear reduction due to the increased torque available. Gear reduction will be in the order of 6:1 therefore the starter armature is able to turn 6 times in order to make one revolution of the pinion gear, this allows operation at the motor’s  most efficient speed.
What different types of pinion gear are commonly used?
Starter Motor pinion gears may vary by their diameter and number of teeth.  Gear types are classified in either DP ( diametrical pitch) or module. DP is an imperial measurement of gear pitch whereas Module number is a metric measurement. Typical pitches for automotive use are DP10 equivalent to mod. 2.54. and  DP12 - equivalent to mod. 2.116. 

The module measurement can be determined by dividing the pitch circle diameter of the gear by the number of teeth. Note: the pitch circle diameter is not the same as the overall diameter, it is approximately half way down the tooth depth. It is essential that the gear pitches of both pinion gear and flywheel ring gear are identical to avoid meshing problems, incompatible gears will easily in damage, noise, and cranking power loss.
My starter motor just 'Clicks' when I turn the key, what is the problem?
The problem could be either mechanical or electrical, if the pinion gear is not located the recommended distance from the ring gear when it is at rest, then the pre-engagement mechanism may not operate correctly causing the pinion gear to 'stall' against the ring gear face. If the gears are not compatible or the gear backlash is incorrect  i.e.  too tight in engagement, then the gear may not be able to find a tooth gap in which to insert itself.

If all mechanical mounting requirements are correct then the problem could be electrical, the solenoid requires a certain minimum voltage to operate correctly, if repeated clicks are heard it could be caused by a collapse in battery voltage when the starter operates. Check voltage applied at the solenoid terminal, it should be no lower than 9.6V when the starter is energised.  The solenoid may be affected by excess heat, check to see if the problem persists when cold.  Check that the solenoid energising wire is of adequate size for the solenoid amps draw required, if too small, an excessive volt drop will occur. 
How long can I crank my engine before the starter will overheat?
You should avoid continuous cranking of more than 10 seconds, after long duration cranking a delay of at least 3 minutes should be allowed for Motor temperatures to stabilise. Overheating can cause damage to armature brushes and commutator.
How many amps does a starter motor use when cranking?
When cranking at at normal speed the Amps draw should be in the order of 300A, if the starter is locked in stall position with power applied the Amps draw may go up to 600A.

A graph of starter motor performance is available from Brise on request.
What voltage should I expect to measure during cranking?
The voltage during cranking depends on mechanical load applied, Amps drawn and CCA rating of the Battery, if the voltage drops below 9.6v the Starter may not operate correctly.


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