The electrical system of your truck could be overloaded. A timely reassessment can help improve productivity and save you a bundle on repairs of damaged internal components.
Have you ever stopped to wonder how healthy the heart of your electrical system is? Many of us are guilty of ignoring the need to calculate the total power usage of our vehicles and make sure we have the right alternator.
The electrical system of your vehicle finely balances energy demands with energy production and when this balance is disturbed, subsequent failures may occur in various components causing expensive downtime and mechanical repair. This electrical balance is often disturbed by the addition of driving lights, marker lights, cooling systems, refrigerators, microwaves, etc. These products draw additional current, placing more load on a system. The outcome can present itself in premature battery failure, damage to starter motors or the alternator itself.
PACCAR Parts senior product manager Rekha Mohan shares some key points with us to help us better understand the need to assess the vehicle’s electrical demands and how the next generation of alternators can reduce the risk of system failures.
A truck’s electrical system is a basic one that uses the alternator to convert mechanical energy into electrical energy. This supports the primary electrical loads of the vehicle and also maintains a healthy battery. If your electrical system is underperforming then chances are your current alternator may not match your vehicle’s demands. Please be mindful that variables such as temperature, cable condition and battery condition can impact the charging system.
A typical prime mover requires 65–75 amps to cover the bare minimum electrical load of the vehicle’s systems. This includes engine management, internal and external lighting, heater and air conditioning fans, gauges, UHF and radio. When you install extra accessories to your prime mover such as driving lights, additional trailers requiring marker and rear lights, fridges, electrical cab cooling systems and so forth, the total electrical load can exceed well over 100 amps.
Table 1 lists the electrical requirement of some common accessories fitted to a truck.
If a truck had all of these installed, the current requirements to cover these electrical loads are:
- Electrical accessories: 80A
- Engine control system: 65–75A
- Total current requirement: 145–155A
Any alternator’s advertised output rating is at a stabilised 24°C (SAE J56 standard). The alternator output achieved at the normal under bonnet operating temperature of the truck (~125°C) will be considerably less than the advertised rating. It is important to ensure the output of the alternator at operating temperature will exceed the combined electrical loads of the truck and the electrical accessories that are installed.
Using an example of a road train departing at 6pm from Townsville to Mount Isa, let’s assume the electrical accessories listed in Table 1 are working for the majority of the 10-hour trip. The electrical requirement at this stage is approximately 155A. When the truck stops at a set of traffic lights or a rest area, the alternator output is about 70 amps at idle, which implies that the batteries are discharging to assist the alternator in providing power to the system.
Upon arriving at Mt Isa, the battery may be further discharged, at times to less than 10.5 volts. A deeply discharged battery (below 11.9 volts) may not start a truck or potentially may even damage the starter motor because the starter motor does not get the required voltage to engage or disengage correctly.
The costs to maintain an adequately rated electrical system are minor when compared to downtime, loss of contracts, penalties and component replacement.
To ensure the correct alternator is fitted to the application:
- assess the electrical accessories on your truck (refer to Table 1)
- ensure the alternator output (amps) at operating temperature is able to cover all the electrical loads of the vehicle. The type and the rating of the alternator you need will depend on the nature of your transport application and the amount of time your engine idles
- it is important to note that ensuring the alternator will provide high output at low rpm is critical to exceeding the electrical load requirements found in modern vehicles fitted with aftermarket accessories and options.
PACCAR Parts recently added the new Prestolite IdlePro range of alternators to its distribution network.
“We are seeing a number of new and older vehicles that have higher electrical loads due to the nature of their application upgrading to these high-quality alternators,” Mohan says.
“The IdlePro alternators deliver industry-best output at low engine speeds (63 per cent efficiency at idle) thus reducing loads placed on the batteries and also reducing wear and tear on starter motors. We want to educate more operators on upgrading the electrical systems, to ensure a balanced and reliable charging system.”
Figures 1 and 2 compare the performance curve of various alternators at 650rpm and 1,450rpm. This output is measured at normal under bonnet operating temperature.
The IdlePro series alternators support electrical systems and engine performance through their various features that help extend battery life and increase vehicle uptime. They are available in 170, 190, 210 and 240 amp ratings with both J180 hinge mount and pad mount. They come with a warranty of two years/500,000km (conditions apply).
IdlePro alternators can be purchased at 57 PACCAR Parts and TRP dealerships across Australia and New Zealand. Supported by skilled technical product assistance staff, the PACCAR Parts dealership network will support customers promptly and efficiently.
Look out for a price promotion on the IdlePro alternators in the PACCAR Parts July-August catalogue. For more information or to enquire on stock availability, please contact your local dealer or visit www.paccarparts.com.au/find-a-dealer.
PACCAR Parts would like to thank Prestolite Electric and Century Yuasa for their technical advice and contribution to this article.