With the engine running you should read 13.5 to 15.5 Volts DC at the battery posts. A reading much higher than this indicates the voltage regulator in the alternator is defective.
Voltage Regulator?
Use a multimeter to measure the voltage.
Voltage regulator is defective. Have it replaced or this will ruin your battery.
Recharged or replaced
Only when you are Starting the car to turn the starter motor is the battery drawing current. Once the car starts, the alternator delivers the current and the voltage regulator regulates the voltage.
Voltage regulator or loose wire.
On Volvo S40 2004 onwards, when the remote key battery voltage is low a text message is displayed in driver's information message screen that the remote key battery voltage is low which means the remote key battery should be replaced. .ab.
Bad alternator not charging battery? Bad voltage regulator? Blown fusable link?
Nothing, as long as they're both the same voltage. The 18 Ah battery has just slightly more power. It will work perfectly.
The ground cable, on the battery may need to be tightened or cleaned. The alternator voltage regulator may need to be replaced.
all vehicles will drop a certain amount of voltage when accessories are turned on, you need to determine how much voltage is being drawn by using a volt meter, also check charging system and battery condition, if battery is weak or charging system isn't providing enough voltage back to the battery, that can cause your problem and last but not least make sure your battery cables and battery posts are cleanThe battery's charge is low or something is drawing from it.
battery produces voltage by