How many volts should a battery be while car is running?
As many volts as the voltage regulator is set to regulate to. It varies by manufacturer. As you have discovered, it also varies considerably based on how many accessories are drawing current. This is why an approximate general range of 13.5-14.5V is used. My ZX6R maintains a bee's pecker under 15V. It maintains this exact same voltage, even with a brand new regulator. This is only appropriate for a SLA type battery. Most cars that don't have a maintenance free battery fitted from factory will tend to sit lower to prevent the battery out-gassing electrolyte. If I saw the ranges you describe, I wouldn't be too alarmed personally. Voltage is one side of the coin, Current is the other. If you wanted an absolutely conclusive answer, have the alternator load tested. In my opinion, it's probably just fine. You were actually giving it a minor version of a load test by running the A/C and headlights. It doesn't catch fire and explode if it's 500mV off where it 'ideally' should be. There is no exact numerical specification for precisely this reason. The battery will test high if it has a 'surface' charge on it from the car and recently charging it. If you want an actual look at the battery voltage, leave the headlights on without running the engine for a couple of minutes, then allow the battery to recover for a couple of minutes. This will be it's actual voltage, minus the surface charge sitting on top of it. If your alternator was completely dead, you would see slightly under open circuit battery voltage, say around 11.9, it would slowly drop down until the battery became so exhausted it could no longer provide the energy to run the engine's critical systems. If the alternator wasn't completely dead (lets say one of the rectifier diodes or a Stator winding failed open for example), the output of the alternator would then be reduced by maybe 66.6%. What this would look like as a voltage could be, say 13.20V with every accessory turned off and your engine howling around 5,000rpm. If you let it idle, the battery voltage could drop to, say 12.55V and hover around there. Then when you load it up with headlights and A/C while idling, it would slap it down to below charged open circuit battery voltage, as your hypothetically defective alternator is only putting out 33.3% of it's normal capacity, it isn't able to keep up and the battery is being slowly discharged.
Inside an alternator the belt-driven rotor becomes an electromagnet when current is fed to it. As the rotor revolves it generates a higher current in the stator windings.References: How to Recondition a Car Battery at Home - MolditeIf the power came from an ordinary battery, it would soon run down. So a car has a rechargeable battery and a charging system to keep it topped up.Half of the plates are connected to each terminal. Electricity supplied to the battery causes a chemical reaction that deposits extra lead on one set of plates.The battery is charged by an alternator on modern cars, or by a dynamo on earlier ones. Both are types of generator, and are driven by a belt from the engine.The rotor is an electromagnet supplied with a small amount of electricity through carbon or copper-carbon brushes (contacts) touching two revolving metal slip rings on its shaft.The electricity is alternating current - its direction of flow changes back and forth every time the rotor turns. It has to be rectified - turned into a one-way flow, or direct current.Moving a magnet past a closed loop of wire makes an electric current flow in the wire. Imagine a loop of wire with a magnet inside it.The north pole of the magnet passes the top of the loop as the south pole passes the bottom of it. Both passes make current flow in one direction round the loop.In a dynamo the electromagnets are stationary, and are called the field coils. The current is produced in an armature - another set of coils wound on to a shaft and turning inside the field coils.The principle is the same as that of the alternator, but the current goes to a commutator - a metal ring split into segments that are touched by carbon brushes fitted in spring-loaded guides. Two segments touch a pair of brushes and feed current to them.
The battery in a car mainly have three basic function: starting, lighting and fuel ignition.After the car is running, the battery will take another two important function:1. To supply additional current when the charging system can’t keep up with electrical demand. A battery’s second function is to supply current when the charging system is overworked. This usually occurs (though not always) when the engine is being run at lower than normal operating speeds. Electrical components including: lights, fuel pump, ignition & fuel injection systems use most of the charging system’s capacity. If aftermarket electrical accessories have been added (heated clothing or extra lighting for example) the charging system may not keep up with the added electrical demand and the battery supplies the additional current to power these components.2. To act as a voltage stabilizer for the charging system.The third function of a battery is to act as a voltage stabilizer for the charging system. Vechicle charging systems need something to push against to keep from producing excessive voltage. In addition, high voltage spikes may be produced when turning on, or off certain electrical circuits. These fluctuations in voltage are partially absorbed by the battery, which protects solid-state components, including computers and ignitions systems from damage.Reference link: What's the function of a battery in a car?and [1]Footnotes[1] What's The Car Battery Function? - Western Electrical Corporation
You have a fundamental misunderstanding of what charging is.On the surface, its a bit like filling up a parking garage with cars or taking them out. But that’s a bad analogy, you can put in a 2 chevies and a chrysler and take out 2 fords and a toyota and they will pass each other on the entrance ramp.In practice, electrons are not different from each other, you do not have have them passing each other simultaneously.Basically electrons go into the battery and we call that charging or electrons leave the battery and we call that discharging.When you have three items, a battery, a charger, and a load, the current sums at the junction. The net load determines if the battery is charging or dischargingSay the Load takes 2A, the Charger pushes 3 A then I can determine that the Battery is getting the 1A difference. Thus it has a net charge, even though the load is being powered and the source is powering.If the Charger put out 2A and the load took 3 A then I can determine that the battery is furnishing or discharging 1 A Net. To really analyze this takes careful definition and attention to the sign of the current relating to its direction.There is no such thing as a component charging and discharging at the same time. Its a system solution.Therefore if a load and a charger were both connected you could either have a charging or discharging battery but it would be no worse than if you only had 2 components- either a battery and charger or a battery and a load.
Almost all cars can charge the battery at idle.There are some who remember the days before they could so there are still some who worry about that. Car electrical systems used to have several shortcomings. They used a 6V system with a generator instead of an alternator. An alternator can provide much more power to charge at slow speeds because of the adjustable armature voltage. All the electrical system parts improved, and the design improved, so now we don’t have to worry about the battery charge.There are still many motorcycles that are not able to charge the battery at idle. This is mostly due to the desire to keep the headlamp on, improving visibility. The start-charge system was designed well before this rule so the alternator is just sized too small for the task.Because the battery is being discharged at idle, the battery can drain completely in a slow moving parade, or a traffic jam. The easiest way out of this problems is to unplug the headlamp when in a parade and drive on the stripe in through a traffic jam.
How long does it take a car battery to not be charged on a undriven car?It depends. I have had car batteries run down in a few days. I have also started up a car after 6 months without recharging the battery.If you electrical system isn’t drawing power from the battery while it sits and the battery is in good condition, then you should be able to start your car 1 to 2 months out.It doesn’t always work that way. Most cars use some power when turned off. It isn’t much, normally, but it is some. A car can have a phantom power drain as well which can such power down fairly quickly - a matter of days, rather than weeks.If you are going to leave your car for an extended period of time, consider using a trickle charger on the battery. If that isn’t convenient, then take the negative wire off the battery while the car sits. You will have to reset your radio station presets, but the battery should remain charged.
Can i put a battery charger on a car battery while the battery is being used?
No - not unless they have a new charger I don't know anything about. You should not run anything while charging the car battery. Unless you have TWO car batteries depending on how much power the amp pulls may not last very long. Newer better Inverters protect a car battery from draining too much power so that a car will have enough juice to start. By doubling the batteries (must be same age and brand of battery if at all possible) you should get by and just charge it up at night. A Deep Cell boat battery is preferred for a long lasting power supply instead of two car batteries. The more batteries you have hooked up in either as parallel or series the longer you can go, the more you can run off it. Don't get crazy with it - all you really need is 3 to four if you run a fan, TV and stuff like that with the amplifier. LASTLY - Walmart has some nifty affordable computerized Battery Chargers that I recommend.
Use inverter while charging battery?
You could, providing your inverter doesn't draw more current than the charger is able to provide without overheating or turning itself off. Some chargers have a built in thermo protection device that will stop current flow if said current becomes excessive. The idea of a switch is a good one, but can cause a 1/4 to 1/2 of a second of interrupted power to your inverter. This can be cured by the use of a very large capacitor (used in car audio to keep the amplifier 'sagging' due to heavy bass notes). Connect the capacitor (2 farads) just like you would a battery. This will cure the problem. There will be some spark / arching action within the switch. This can be corrected by 1.: the use of a heavy duty high current 12 volt DC (coil) relay, or 2.: the use of 0.01 micro farad (uFD.) capacitors across each contact of the heavy duty switch. Me, I would use a big relay and wire it so it switches the battery and charger back and forth, with capacitors across all contacts to keep them from arching & pitting, causing premature failure. This can be expensive, so I would just stay with the heavy duty TPDT switch. This will only need 4 (four) 0.01 uFD. capacitors. The extra set of contacts is used to place the positive lead of the charger to the battery that is not in use. Remember, the BIG cap. connects directly to the input of the inverter, just as your battery would. The positive AND negative of the batteries are switched, if you ever need to service the unit durring operation. The negative side of the charger is common to both (neg.) battery terminals.
Sure; 2 ways:Towable generator/battery pack - This one isn’t guaranteed - the car might shut off the charger when it’s running down the road (one of the patents they picked up was using the motor as the “power inductor” for the charging system; you can still do that if it’s moving, but it requires some thought… but it’ll probably work unless the Tesla just says “gas cap open; I’m not gonna move until you unplug me.” Your genset / battery pack is gonna be awkward (for Supercharging, you can pump up to 120 KW to the car - that’s around 150HP and probably 200HP by the time you factor in the inefficiencies - your Coleman genset just ain’t gonna cut it).Regen Braking - Happens all the time, and will work. There’s nothing saying you can’t have a tow truck (or pusher) that’s shoving you while you’re sucking out the energy using regen — heck that’s a favorite charging technique for NEDRA / Electric Salt Flats, and other people because you can usually charge at 40–80 KW using regen (and that’s 50–100 HP, so a F250 can certainly provide — this was “the original supercharger”), as most electric chargers are limited to the 10KW range (50A / 220V)…. No idea how much “regen” is allowed by the car, but if you can come to a halt after going plaid without having to use the disc part of the brakes, it oughtta be impressive enough to give that F250 a hard time if you don’t link the throttles right.So, you wanna really do it “aircraft style” and have a pusher/puller link up without stopping and give you a supercharge boost? That sounds nifty — get self-driving cars involved (for some reason Tesla is pretty good at targeting other cars, so give the vision system some dots for where the attach points are), and you can have “mobile, on call supercharging” (and use regen… otherwise you end up having to fool with connectors plugs and other things that get annoying at highway speed).
Can I charge my car's battery just by leaving the engine on for few minutes.What does "rev the engine"mean?
My PU sits for about a week at a time in the cold with no starting problems. I drive it about 80 miles per week. The charging system is only designed to put a surface charge on the battery - more like a trickle charge. The battery measures 12.6vdc. When being charged, you'll measure about 14 vdc. That's only a 1.4 volts increase over the battery's nominal voltage - it's a trickle charge. I tell you this so that you'll understand that running the engine for 15 minutes won't appreciably recharge the battery. Most cars are driven about 1,000 miles per month. That is more thanenough to keep the battery charged. To "rev" the engine means to apply some gas to get the engine speed above idle. Normal driving is a better option. The electrolyte in a discharged battery will freeze if it is cold enough. Have the battery checked. It may be low on charge because 15 minutes isn't enough to replace the charge that starting the car took. Check your battery connections. Your battery can supply enough current to power the lights and radio even through a poor connection. But the starter needs much, much more current that the lights and radio, as much as 20x. A poor connection will hinder that current flow.