Alternators produce amps, and starters use amps. There should be a balance between the amps put in the battery and amps drawn out of the battery. The alternator balances the amps used by the starter and other electronic devices in the truck. If the alternator fails, the battery makes up for the difference but may later fail and die.
As a truck driver, you need to ask yourself, how many amps my alternator has to be? You don’t want a situation where your battery doesn’t recharge, and your engine fails to crank due to less or no battery charge. The alternator amps range about 60 or 70 amps up to 150 amps for the latest model vehicles. Some other high-output alternators may also produce up to 200 amps. The amperage of your alternator will depend on the truck’s consumption rate of the amps.
What Determines the Alternator Amps Rating?
Amp’s load varies depending on the battery’s state of charge, the electrical devices you’re using in the truck, and the power they consume. For instance, cranking an engine on a chilly morning may draw up to 200 amps or more from the battery. An extended cranking can drain the battery quickly, lead to overheating and even damage the starter. The battery only recharges when the engine starts.
Other additional amp loads that you have to offset include;
- Starter (when cranking): Up to 250 Amps (depends on your engine size)
- Electric defrosters 20-25 amps
- Heated seat 5-7amps
- Wipers -6 amps
- A/C 15-20 amps
- Sound system 10-40 amps
- A reserve to recharge the battery and keep it topped up even under full load
Most on idle loads (excludes the starter) are about to exceed 100 amps, you should have an alternator that exceeds 100 amps to ensure that you’re not always running your electronics off your car battery when driving at low speeds.
Check this too: How Long Does an Alternator Last
A typical factory alternator rated at 65 to 100 amps may handle the truck’s basics like the headlights, gauges, pumps, etc. But with more power consumption, like having a stereo system that draws 60 amp, you may consider an after-market alternator for your truck.
The most accurate way on how to size a car alternator is using an ammeter. With your engine off and battery charged, connect the ammeter with the battery ground’s system. Switch on each electrical device and record the amps draw, and have the total. Your alternator should be 50% greater than the figure.
Another way is through estimation by checking the accessory fuses. The amp ratings may be higher than the peak draw of each accessory, but it will help you have a clear idea of the electrical load. Sum up all the fuse ratings to know the total electrical truck’s load. It’s best to verify the numbers with the part manufacturer for you to choose the appropriate alternator.
To get an alternator size calculation, divide the number of watts you use by the number of volts you are pulling. For instance, if you require 3000 watts and have a voltage reading of 14.4, divide 2000/14.4 to get 139 amps. Therefore, you require at least 139 amps and other extras like lights, A/C, etc. But remember, sometimes it’s impossible to get an alternator that provides the highest amperage that we need; we may require a backup of two batteries.
Check this too: How Long Does It Take To Charge A Car Battery While Driving?
Conclusion
The amperage of an alternator depends on the total amount of amps that your truck requires; stereo system, lights, ignition, A/C, and all electrical components in the vehicle. To choose the best size of the alternator you need, follow the tips explained above.