How Long Does It Take To Charge Car Battery With Alternator?

Disclosure: This page contains affiliate links, As an Amazon Associate, I earn from qualifying purchases (at no extra cost to you). Learn More

You are required to charge your car battery whenever its power is so depleted that it can no longer run your engine. You need an alternator to do this, either all by yourself at home or with the help of accredited service centers employing skilled technicians and other professionals. (Read Also: Can You Start A Car Without A Battery?)

If you run your engine at high RPM, the alternator charges your battery faster. The question, however, is, ‘How long does it take to charge your car battery using an alternator?’ To answer this question satisfactorily demands due consideration to certain battery conditions such as how much your battery has run down, the capacity of the battery you wish to charge, and the condition of your alternator. (Read Also: Can I Charge A Car Battery With UPS? Find Out Now)

All these factors can affect how long it will take you to charge your battery. Additionally, even the conditions of the road on which you usually drive have a bearing on the length of time it is likely going to take for complete battery charging. (Read Also: How To Charge Car Battery With DC Power Supply)

For instance, it takes longer to charge a car battery that has been used on city roads than that which is used on the highway. All in all, it takes an average of about thirty minutes to re-charge a battery that has been used on the highway and an average of one hour to charge a battery used in the city.

Generally speaking, when the engine runs on an RPM of about 2000, the battery is bound to charge well regardless of the battery’s extent of power depletion or its capacity, as long as it does not have any defects or is in any state of disrepair.(Read Also:Does Bluetooth Headphones Drain A battery?)

Table Of Contents

How Does The Alternator Charge Battery?

It is known that mechanical energy turns the rotor of the alternator which eventually makes the electron pixies in the alternator very excited and begin to both dance and jump. The faster the alternator turns, the higher and faster the electron pixies jump. The car battery also has electron pixies that jump too up to a certain height caused by the chemistry within the battery.

Read Also: Does Revving The Engine Help Jump Start A Car? Find Out

A thick copper wire which is connected between the alternator and the battery causes a net migration of the pixies from the alternator to the battery when the alternator pixies jump higher than those of the battery. These pixies move into the battery and thus make a home for themselves until there is only very little spare space left for them.

The regulator of the alternator detects this and calms its own pixies down a little bit which will finally disallow any more electron pixies to move into the battery. Charging can be both instantaneous or via stored energy if the pixie flow is either measured in Amps or integrated over a period of time respectively.

Though the alternator’s main function is to recharge the battery, it can also supply all the pixies needed to operate the vehicle’s lighting, passenger comfort, entertainment, safety, communications, and even vehicular management systems. (Read Also: How To Charge A 12Volt Battery From A 24Volt System)

Does The Alternator Charge The Battery While Idling?

The alternator is a superior charging device compared to other means used previously that utilized a generator. However, the generator has to rotate very fast before it can start generating valuable power. For this reason, most generators do not produce enough power to charge the battery at idle modes, but an alternator generates enough power even when it is idling and hence the engine can idle indefinitely without the risk of running out of battery power.

However, where you have more added need for energy on the idle mode, then you may require to upgrade to a higher alternator. All vehicles that need to idle for long periods such as police or other emergency vehicles that run sirens, flashing lights, computers, and radios,  should be equipped with very big alternators that can cater for their excessive need for power. (Read Also: Can You Charge A Marine Battery With Your Car? Find Out Now)

Ordinarily, you can have the engine idling while the alternator will keep the battery fully charged. Note that you should never idle a cold engine and hence, on a cold start, give the engine about ten seconds of idle time before you begin to drive normally. To answer the topic question, you should note that the alternator will only keep the battery from losing power despite any prolonged idling, under normal circumstances.

How Many Batteries Can A Car Alternator Charge?

Generally speaking, an alternator is quite capable of charging up to two car batteries but you ought to take great care in making sure that you correctly connect the two batteries together especially where one is charged while the other is not. Since there is no current limiting in the circuit, you could easily exceed the manufacturer’s maximum charging current of the flat battery. (Read Also: Can I Start A Car With A Battery Charger Connected? Find Out)

You should in addition be careful not to leave the spare battery connected while starting because it can draw a large current which may burn out the wires particularly if they are not capable of carrying the current in them. Essentially, there are two things to keep in mind; if it happens both the two batteries are low on a charge which may be more than one alternator can contend with. (Read Also:Can You Spray An Alternator With WD40?)

Secondly,  where only one battery is low, the alternator may be able to cope quite well. In addition, linking the two batteries may cause problems if you run the inverter from the battery in the back which may eventually run them from both. Cranking the engine from the front battery will also crank the engine from both batteries and also when you trickle charge the back battery,  you are essentially trickle charging both batteries.

How Does An Alternator Know When To Stop Charging?

There is always a system that alerts drivers when their attention is needed such as when something is wrong or when the alternator has completed its work. This system can be either a dashboard-mounted ammeter or voltmeter or even a lamp labeled as ‘Gen‘, ‘Bat‘, and ‘Alt‘.(Read Also:How Much Voltage Is Too Much From An Alternator?)

These various mechanisms are meant to notify you when your attention is needed. In order to wire a warning light to these indicators, just remove the terminal plug cover and connect the R or left terminal from the back of the alternator to the warning light wire.

For any alternator to charge properly, it must be grounded to the engine block. This warning or alert light, which is mostly mounted on the dash, will always tell you when charging is effectively completed and the alternator will automatically stop,  in order to avoid overcharging the battery.

At What RPM Does An Alternator Charge?

In a car or motorcycle, the alternator is connected to the engine crankshaft via pulleys or belts. Though the procedure may differ slightly in cars and motorcycles. The minimum RPM needed for an alternator to charge depends on the capacity or specifications of the alternator.

Nevertheless, a standard alternator will produce a charging current of over 2000 rpm. In a nutshell, an economy car will idle at about 750 rpm, a sports car about 1250 rpm, and a race car up to 2000 rpm. The pulley between the crankshaft and the alternator should be kept at about 3:1 for an economy vehicle, 2:1 for a sports car, and 1:1 for a normal race car. (Read Also:How Long Will Boat Battery Last Without Alternator?)

Conclusively, therefore, an rpm of anything from 2000 will certainly send current. Note that the rpm for a car alternator is usually equivalent to the idle speed of that car.(Read Also: Can Jumper Cables Get Wet?)

Alternators are selected based on their load rating of both the electrical and electronics of the entire system in any particular car. The minimum speed range for the rpm of an alternator is anywhere between 750 to 900 rpm because alternator pulleys are smaller than crank pulleys.

How Do I Wire An Alternator To Charge A Battery?

To wire an alternator for the purpose of charging any battery, you should start by:

  • Opening the hood or bonnet of the car and removing the black battery cable from its terminal with a wrench. Thereafter, locate the voltage regulator and also the multi-wired harness beside the alternator and voltage regulator.
  • Proceed to insert the plug into the socket on the voltage regulator. Alternatively, you can simply run a direct cable from the battery to the alternator. The wires in the alternator are the battery positive wire, the voltage sensing wire, and the ignition input wire.
  • The battery’s positive wire connects to the starter while the voltage sensing wire is connected to the battery and the ignition wire connected to the key switch. The two wires connected to the alternator are the positive and negative cables, but be sure to use a fuse as insurance against any undue damage to the wires and other components.(Read Also:Can You Clean An Alternator With Brake Cleaner?)

What Is A Voltage Regulator?

A voltage regulator is a piece of equipment that maintains the charging voltage which the alternator produces and hence keeps it low in the range of 13.5 to 24.5 volts to make sure that your electrical components are adequately protected from damage. This gadget is also provided with a warning system that notifies you whenever something is not right and is mounted on the dashboard of your car.

It can also be an ammeter, voltmeter, or even a lamp. The instant this warning lamp of the regulator comes on, you should know that something is definitely wrong with the charging system or even when an alternator has stopped functioning entirely. (Read Also: How Many Times Can You Start A Car Without An Alternator?)

The most common cause that stops an alternator from working is a broken alternator drive belt. The alternator has a belt that is activated when the engine runs and it goes around a pulley connected to the crankshaft of the engine. This belt also runs the water pump, power steering, and the vehicle air conditioner compressor.

Recommended Products

Alternators just like vehicle tires and other products which we use daily are produced with different features, specifications, and qualities. In order to get the satisfaction we crave, there is the need to have a good knowledge of what we want and where to get them at the best possible prices and supplied on customer-friendly terms.

For these reasons, we shall introduce to you some products that are among the best you can get anywhere which are related to the topic of our discussion. Below are some of them that you would be glad to have that will give you value for money spent:

  • DB Electrical ADR0215 Alternator: This item is sold at the most friendly prices and is compatible with most vehicle brands with a lengthy warranty agreement for customer protection at all times.
  • NEW DB Electrical Alternator: This alternator is built to meet all OEM specifications and is covered with one year warranty after purchase. It is guaranteed to meet the requirements of most types of vehicles.
  • Interstate Batteries 12V 35AH Sealed Lead Acid(SLA) AGM Deep Cycle Battery: This battery is a perfect fit for most vehicles, is rechargeable and spill-proof too. It is of the highest quality available on the market and hence excessively durable as well as very resistant to corrosion.

How Long Does It Take To Charge Car Battery With Alternator – Conclusion

There is just no way any driver can do without batteries and as such, we ought to acquaint ourselves with every information pertaining to how we can benefit from them maximally, starting from buying the correct ones, their proper maintenance as well as how we can recharge quickly should they run down. To effectively charge car batteries, we need alternators.

The best alternators for this purpose have been introduced to you and you have also been informed on how to detect signs of malfunction from your alternators before they can overwhelm your vehicle. In addition, you have been taken through the process of connecting these alternators correctly to your batteries.

The frustration associated with battery disappointments to all drivers will be a thing of the past should hearken to the advice and resourceful information in this article. Wish you a pleasant motoring monsieur.

Leave a Reply