The tachometer DOES NOT have anything to do with charging the battery in a car at any time. The tachometer simply reads, and relays to the driver, how fast the crankshaft in the engine is turning. This is displayed in RPMs, short for "revolutions per minute" representing one complete revolution of the crankshaft. On some newer cars, the tachometer may share a signal from the crankshaft sensor with the ECU(the car's computer) as well.
The charging of the battery is handled by the alternator or generator which is most commonly belt driven and attached to the front of the engine. It may have gauges in the dash such as a Voltage gauge, Ammeter, or just simply a "dummy light" that illuminates and warns the driver of charging problems should they arise.
Your battery is weak, or your your alternator is not charging battery.
Be careful if you're charging the lithium battery with a generator connected through an isolator.
Stop driving until the charging system and battery have been checked for an overcharging condition.
Charging system problem. Normally this means there is a problem with the alternator.
About 2 days
It has to be a dead charging system.... usually a short internal in the alternator
The alternator may not be charging it enough. With the engine running at an idle check the voltage at the battery with a DC digital voltmeter. It should read from 13.5 to 15.5 Volts. Anymore, or any less, and the alternator is suspect. You might also have a defective battery.
battery light indication means a dead battery or a dead alternater/regulater or a fault in the charging/ignition system
It usually means that your alternator (or generator) is not charging the battery. At this point you need to check system voltage with a voltmeter when the engine is running. You should see at least 13.5 to 14.5 volts. If it is less than that, it is not charging. You can also have the charging checked at a repair shop if you don't have a voltmeter.
no it will not!
To check if your TomTom is being charged,connect the charger ,power on the unit , tap the bottom right of the Driving view to get to the route summary screen. If the battery is being charged, the word Charging is shown under the battery symbol on the right. If you don't see the word Charging, the battery is either fully charged (indicated by a completely filled battery symbol) or it isn't receiving external power.
If the battery, drive belt and wiring are okay then I would suspect the alternator is faulty. Your local auto parts store can test the charging system for you at no cost.