A question might arise in your mind about whether the alternator will charge your battery if the car is in neutral. Will you car battery charge while idling? Now… based on real world info gathered from readers of this site, the actual charging rate of a 220 amp alternator is closer to 100 amps. That leaves … A car alternator needs to be putting out at least 13-14 volts (ideally between 13.8 and 14.2 volts) to effectively charge a 12 volt car battery. Since ohms law predicts that as current drops internal resistance goes up. I am asking because I KNOW I need to maintain the charge in the secondary battery. This may cause important components like the car’s computer or the ignition to fail. 15 and 20 Amp Outlets. That's the whole purpose of the isolation relay and diode. Normal Output An alternator should put out between 13.5 and 15 volts of power. You mention using the top 20% of the battery in reference; well, at 25% discharge (or 75% charge remaining (or State of Charge (SOC))) your TYPICAL battery internal resistance is 1.3 ohms (TYPICALLY). The alternator will turn at idle but does not produce the maximum current. It is a give and take sort of relationship between the two. Battery vs. Alternator . The typical alternator on a motorhome or tow rig engine can charge batteries at from 40 amps to 100 amps. http://teres.info/BatteryReconditioningCourse/?51l... when is a car ready to go to the junk yard? Remember the time, when you got the car for yourself? So say with the fan on medium, lights, ignition, small charging current to a full battery, etc there is a draw of about 45 amps. The first thing that comes to mind to determine the internal resistance is to actually measure the current being drawn by a battery. The DC battery and alternator must supply the DC AMPS. Consequently, if the alternator doesn’t maintain rated charging voltage at lower engine speeds, the battery will discharge under heavy accessory loads. The photo that you uploaded is unavailable, is there any way you could re-upload it? Unlike a traditional charger, it will not overcharge your battery and you can plug it in and forget the rest. Wish I could post a picture of what I want to do. How long should I let my car idle to charge its battery? Having said that, it is highly possible for you to face a situation where you have kept the car idling to let the battery charge. All alternators have a voltage regulator which controls the alternator charging voltage and, in turn, the current produced by the alternator. You need to trickle charge the battery to replace the energy lost. This is my first attempt at uploading a photo. 12.8 volts is considered 100% charged. This is a fact known by most car owners. So, Larry, voltage aside, how many amps does the typical (I said TYPICAL) battery draw to charge? Glad you corrected your numbers. If I have, for example, a 200-amp-hour-rated battery that is fully charged at 12.6 volts, how many amp hours have been used when the battery is fully discharged at 11.0 volts? If you have an alternator that can produce 120 amps of current (max) and the the total current demand from the electrical accessories (including the battery) is only 20 amps, the alternator will only produce the necessary current (20 amps) to maintain the target voltage (which is determined by the alternator's internal voltage regulator). Yes, this is the best way to charge your battery. For those of you who must know, I'm thinking of putting a second battery on my truck. Thereof, how many amps do I need in my alternator? A voltage regulator will sense battery state of charge and prevent the alternator overcharging, (cooking the battery). You can see in the table above that the 300 Amp Hour battery can accept a charge at up to 750 Amps but the recommended continuous value is 150 Amps or less. A 120 amp alternator in a typical modern vehicle can safely deliver 70% of that current continuously (84 amps). Nevermind how many amps fairies must dance among while the mushrooms are in bloom, what will the second battery draw? The black lead should be connected with the negative end of the battery and the red end to the positive side. If your battery has crossed the threshold limit, you might need a replacement. Yes, your car battery will charge while it is idling and this is possible because of the alternator in the battery itself. If you have a volt/amp gauge, it will read the alternator output for you. This voltage will be enough to fully charge or maintain the battery on a trickle charge, but charging time will be very long at 13.8 volts. Same with 40A. For your specific example, it is totally fine to have a 20A b2b charger if your house battery can be charged up to 50A. Faulty fuse. Also if I have one of those small gasoline generators with an internal 12-volt DC 8-amp battery charger, would I have to run this generator for 12.5 hours to recharge 100-amp hours to the battery? NOT VOLTAGE, CURRENT? Since I don't know what the internal resistance would look like at 50%, I can't begin to guess at the internal resistance without doing a bunch of tests. An alternator that is putting out a reduced charge will eventually cause the engine to stall and not properly charge the battery, which can cause starting problems. Alternatively, the battery could be taken out and charged with a 12-volt battery charger inside your home. So, if we have a 220 amp alternator… that would mean the most amps we could see coming into our house battery bank is 154 amps. https://www.lifewire.com/understanding-alternator-output-ratings-534785 Different batteries will vary, so this is a typical number. If you know how to post pictures, let me know that too as that will help clear up any questions you might have regarding what I'm doing. As for voltage, I already know the typical battery voltages of a car battery at static rest (12.5 volts) and the float voltage (13.6 volts). Hopefully this will stop people from telling me how many amps my alternator needs to produce. Driving the care more will recharge the battery fully. However, since we've determined that at 75% you can expect a 7.4 amp draw (theoretically speaking) I would have to assume that a 30 amp diode and fuse BOTH should be MORE THAN enough to keep the second battery charged. So, if you are trying to pull out a high amount of power from the battery while the car is at idle, the input charge will be a deficit in regard to the charge which is being drained out from the battery. It will likely charge at 8-10 amps for at least 24 hours. I like the way you have the emergency jump switch connected to the battery with the full charge. Can A Bad Battery Cause A Check Engine Light To Come On. Only, I would advise installing a low voltage drop out circuit between the battery and the inverter. Your car can sit parked for a month before the battery goes dead. Basically the higher amps will allow you to charge a battery in a shorter period of time. If you bring your load up to 101 amp, then the voltage in the system will drop below 12.8V because the extra 1 amp that is needed and not coming from the alternator will have to be stolen from the vehicle's battery and hence the voltage will start dropping below the static battery level. so, the alternator produces 100A (amps,),and the battery has a capacity of 100Ah (amp hours.) There are 4 important parts are used in Alternator. Nice way to protect your circuit. More expensive two stage converter/charger ($300) have capacity to provide 30 amps of battery charging. Many cars will have a battery control module dedicated to power management. A battery can be hooked up to shore power with a home extension cord in the same way that it is hooked up with a 30 amp or 50 amp plug. at 75%, your voltage will be about 9.6 volts with an internal resistance of 1.3 ohms. Check the alternator gauge. but it is never that simple. When you start installing a bunch of aftermarket audio equipment, especially powerful amps, things can quickly get out of hand. Or , to keep in warranty? Around 60 amps or more. The fuse, diode and relay will bridge over a starter solenoid which may be occasionally used as a jump start circuit (the second battery can be introduced to the circuit in its FULL current capabilities but isolated from draining the main battery when the key is off). To maximize charging efficiency, a 180-amp rated alternator would be required. As for voltage, I already know the typical battery voltages of a car battery at static rest (12.8 volts) and the float voltage (13.6 volts). Different batteries will vary, so this is a typical number. When a battery charger says it is charging at 2 amps or 10 amps it is describing the number of amps it is delivering to the battery per hour. If the alternator is putting out too much voltage (15+ volts), it is likely your battery acid will boil over out of the battery. These alternators also typically come with a 10 to 15 … A 20A charger will draw 20A from the vehicle battery and charge your house battery with 20 amps per hour while driving. If I put a one amp diode on it - guess what will happen - - - the smoke will leak out and the diode won't work anymore (unless someone figures out a way to put the smoke back in). Now during the charge the voltage will change over time - from maybe 6 volts if the battery is stone dead to 14.4 during full bulk charge and then drop to 13.2 when in float. Well, the question which arises is how rarely do we use the car and how long before the battery flats out.eval(ez_write_tag([[468,60],'carcareportal_com-medrectangle-3','ezslot_4',109,'0','0'])); One month is a good amount of time. The battery in cars with more power might well be dead in two weeks, like a BMW or a Mercedes where the components of the car need the power to survive. Voltage is NOT my concern, I need to know how many amps this is going to draw - assuming I've drained the battery (typically at 80% the battery is considered dead). However, if there is an alternator installed, the battery should be disconnected. Voltage regulators were once a troublesome part of the alternator, most late model cars now control voltage using computerised control modules. It is also important for people to realize that cars are not meant to be kept idle. If i disconnect the battry cable on a 2010 Santa Fe Limited 3.5L will i have to reset anything after i connected it back? The engine must be running (even at idle, the engine runs). This can power an inverter that will deliver about 1,200 watts @ 120 VAC. You should be getting a reading of around 12.6 volts. I know my alternator is rated for 60 amps, but I'm sure that is to not only charge a battery from various states of discharge but also to maintain all other electrical needs of the car, so I don't think it's going to be 60 amps. So when I recharge it - how much current will it draw to recharge? Kudos' Larry for not paying enough attention to the question. How long to Charge a Car Battery at 4 Amps. Some alternator models may be damaged by the charging process. So when I recharge it - how much current will it draw to recharge? So when you are charging a battery at 2 amps then it takes 24 hours for the battery to receive 48 amps of charge. Double these times if the battery is fully discharged. Most factory alternators are rated at 65 to 100 amps and are capable of handling your vehicle's basic necessities, such as headlights, gauges, fuel pumps, A/C, etc. I just need to know how big the thing has to be. Good job, you're doing the proper engineering work. Does your car charge while driving? Otherwise, you can always take it around for a spin! The black is existing wiring, the blue is the proposed. I intend to hook it to the existing battery through a fuse (size to be determined), a diode (likely a 30 amp diode) and an isolation relay (likely to be a 40 amp rated contact). This is exactly what I want to do to my truck. But it is safe to keep a few pointers in your mind. Unfortunately, mounting a large-case alternator is not feasible in many vessels. The battery will be dedicated to running an inverter (size yet to be determined). at 75%, your voltage will be about 9.6 volts with an internal resistance of 1.3 ohms. A 10-amp charger will give you a quicker charge and is still relatively safe, though you should take care to remove the charger as soon as the battery is full. Repeated fast charging could overcharge your battery. Although many people assume that a car's battery powers all those things, the truth is that the battery only does one thing other than keeping the electronics on when the engine is off: It starts the engine. Dude. Run engine at 2,000 rpms for tests and turn on the blower fan for the AC or Heater, the headlamps, and any other accessories that put a strain on the alternator, and watch the gauge to see if it decreases voltage or amperage. And only for a limited time. From this, we can conclude that the battery gets charged slowly at idle and it would be the wiser decision to not place a high electrical drain when it is idling.eval(ez_write_tag([[336,280],'carcareportal_com-medrectangle-4','ezslot_10',110,'0','0'])); Yes, the alternator does charge the battery in your car but it must fulfill two criteria: The engine basically turns the serpentine belt which in turn moves the alternator. Once the engine fires, the alternator takes over and provides the juice. Main connection will be to positive charging battery terminal. Thanks Larry for listening. The alternator now puts a charge in the car battery. Around 60 amps or more. How to recognize if your battery is being charged? How loud do car tires screech (full throttle screech vs slamming on the brakes)? In fact, fast charging for this kind of battery is not recommended. If I put a one amp diode on it - guess what will happen - - - the smoke will leak out and the diode won't work anymore (unless someone figures out a way to put the smoke back in). A typical alternator may put out 100 amps for example. That would be catastrophic to it. Even though the belt turns faster when the car is in motion but the charge produced in the alternator is regulated by the ECU in the car and it produces the same voltage even when the car is in motion or it is idling. However, if you have a dead battery, pushing or switching on the solenoid you effectively add a whole new battery into the starter, giving you enough power to start. I only want to know how many amps the second battery will draw TO CHARGE. http://www.flickr.com/photos/85203140@N02/. The battery will demand a lot of current because of the fact that it has been discharged. Did Screech from Saved By The Bell make his vehicle's tires screech? Well, the answer is yes. 40 minutes is 0.66 hours. It is quite possible that you are in that stage of your life where you don’t really need to drive around anymore. To fully charge in reasonable times, alternator output must be 14.2 V to 14.5 V as measured right across the battery posts. it will take 1 hour to charge the battery. The average size alternator used in a vehicles' DC charging system is about 100 AMPS DC. That way you don't drain the second battery completely (100%). Many modern engines operate well under 2,000 rpm until they reach highway speeds of about 60 to 70 mph. Next you may select less or you battery may only accept the charge in amps it can handle. If your house bank consists of 400Ah capacity AGM batteries, the maximum available capacity would be 45 percent of 400, or roughly 180Ah. When you start a engine, at the same time Alternator rotates with the help of engine power. As long as the engine is on, the alternator will keep on charging the battery. For instance, installing a power amp that draws 70 or more amps in a car that shipped from the factory with a basic stereo, could cause huge problems if the alternator is only capable of putting out 60A to begin with. Without knowing what ratio that occurs at, one can only guess. Realistically speaking, a flat battery can be charged up to 80 percent in 2 hours. A 30 amp charger can only deliver 30 amps max. How to remove scratches from black plastic bumpers. Can cars with ABS screech when you slam on the brakes. Does your alternator charge your car battery at idle? A 4 amp charger can charge a 50% discharged small car battery (200-315 CCA or RC 40-60) in about 6 to 7 hours, a mid-sized battery (315-550 CCA or RC 60-85) in 7 to 9 hours, or a large car battery (550-1,000 CCA or RC 85-190) in 9 to 17 hours. the amps is not what you have to worry about,except on start up as long as your charging system is ok,,at least 13.5 volts,your fine on the run system,as far as hooking in a nother battery for an inverter,it still needs to receive a charge,or the inverter will run out of juice. We know that it is unlikely for someone to be sitting in their car while it is neutral but as long as the alternator and the engine are in good condition, the car will acquire charge at neutral. Charge Voltage As you can see in the table above the recommended charge voltage is 14.0 - 14.4 Volts Most alternators will not be able to get the battery to that voltage until the battery is nearly full. It is also important for people to realize that cars are not meant to be kept idle. Guessing you know ohms law, Voltage is equal to current times resistance. It is safe to leave the battery in the car while charging when it has a power point and about 3 to 4 amps in charge. 36 year mechanic, I'd not be taking any of my vehicles to you - you don't listen. Get your answers by asking now. How do you think about the answers? Many of us have moved to parts of a city, where we rarely need to use the car. Join Yahoo Answers and get 100 points today. It is often an … That cable that connects battery to power will be 3/0 or 4/0 AWG. 1. You can also turn on the vehicle and check the voltage at the battery terminals. Voltage is NOT my concern, I need to know how many amps this is going to draw - assuming I've drained the battery (typically at 80% the battery is considered dead). If it is around 14-15 volts, the alternator is working just fine and there is no need for your battery to be replaced. 20 amps are already fast charging. You would have never imagined that it would be lying around as this, did you? Well, you have deserved it, but what can you do about your car?eval(ez_write_tag([[468,60],'carcareportal_com-large-leaderboard-2','ezslot_2',113,'0','0'])); You can use a smart charger which gives your battery exactly the charge it wants. This increases the longevity of the battery by a considerable amount.eval(ez_write_tag([[250,250],'carcareportal_com-box-4','ezslot_7',111,'0','0'])); Even after considering the fact that your battery is dead, it will not take an eternity for your battery to charge. This is a slow charge. Which is connected to the alternator. 10 amps are the recommended current. Well if you don’t use your car regularly, it is highly possible that you have faced this before. However running this engine is not very efficient. Alternator is 220 amps. THEN when you release the button or shut off the switch the backup battery is isolated - except for being recharged through the diode and relay. The alternator will charge the car’s battery by providing it with electricity. Mounting Style Does any car actually require synthetic oil? Alternator or Generator : Alternator is directly connected with engine power through a drive belt. But to make this possible, the alternator has to manage 14 volts at the battery terminals, the whole time it is being charged. How long does it take to charge the battery at idle? Realistically speaking, a flat battery can be charged up to 80 percent in 2 hours. So basically the battery will only accept the amps it will accept at that time, where battery condition, selected rate of charge, battery temp and charger capactiy are all factors. A car alternator needs to be putting out at least 13-14 volts (ideally between 13.8 and 14.2 volts) to effectively charge a 12 volt car battery.If the alternator is putting out too much voltage (15+ volts), it is likely your battery acid will boil over out of the battery. Has your car battery ever gone dead? It just means the house battery while be charging slower than its capacity. 1 hour times 100 amps 100Amp/Hours. But my suggestion would be to take the car out for a spin now and then otherwise it is impossible for the battery to recharge fully. Is there a minimum height size to drive a car? This is a popular method of charging small pop up camper batteries. OK, consider that at 50% charge your battery is basically dead. Copyright © CarCarePortal.com All Rights Reserved. A 3000 watt inverter can only deliver 1,200 Watts @ 120 VAC using your vehicles existing DC charging system. But to make this possible, the alternator has to manage 14 volts at the battery terminals, the whole time it is being charged. So inversely, 9.6 volts divided by 1.3 ohms gives you an amperage (current) of roughly 7.4 amps. Emotional moment during Trump impeachment speech, NFL player helps raise $350K for girl injured in Reid crash, Geraldo Rivera insists Trump is 'guilty as charged', Why it might be a 'mistake' to file your 2020 taxes now, Claudia Conway set to appear on 'American Idol', CDC pleads with Americans to 'avoid travel', Grandfather sentenced in child's cruise ship death, Eli Lilly chief quits due to 'inappropriate' relationship, Mahomes will have surgery for turf toe injury, A few vaccine recipients get rare blood disorder, 'QAnon Shaman': I'm 'deeply disappointed' in Trump. Suppose the battery is cold stone dead - and I don't have facts or figures on the batteries internal resistance or I would be able to calculate it myself, so; what is the maximum amperage a TYPICAL car battery draw? You can sign in to vote the answer. The various components which draw power from the car’s battery work the best when the car is being driven around.