right is a battery shows 12.5 volts its been on charge for a few hrs batters 6-8 month old ish , now when the cars on tick over it shows about same , but when headlights are on it drops just under 12 , and if fans are on its arround 11.4 would this suggest the alternators nackard
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car voltages
- Thread starter biojo
- Start date
Carrera 4S. Clio 172. M5
A wet plate car battery has a nominal voltage of 13.8 volts when fully charged. Each of the 6 cells that go to make it up produces 2.2 volts.
Your batteries inability to hold a full charge could be attributed to age. Although you say this one is less than a year old. Check the electrolyte if its not a fully sealed type.
A car battery will last for 3-4 years under normal conditions depending on the amount of daily use. But if you are doing a lot of short trips with lights, heater, screen heater and hammering it with a big sound system, this will drop dramatically.
Simply measuring the voltage across the terminals will tell you very little, you need to have a drop test done or get a specialist to check it on a battery diagnostic tool.
Don’t use Halfords, they usually haven’t got a clue, go to LSUK (used to be Lucas) they are proper auto-electricians.
If your alternator is managing to put any charge into the battery, chances are it is working correctly. It is unusual, but not unheard of, for an alternators performance to drop off, they normally work or they don’t.
Give it a good charge (12 hours) and see if things improve or If you have access to another car, swap the batteries for a couple of days and see what happens.
You may have to bite the bullet and replace it, (or take it back under warranty) but it’s worth checking it first before you go looking for an expensive alternator.
Your batteries inability to hold a full charge could be attributed to age. Although you say this one is less than a year old. Check the electrolyte if its not a fully sealed type.
A car battery will last for 3-4 years under normal conditions depending on the amount of daily use. But if you are doing a lot of short trips with lights, heater, screen heater and hammering it with a big sound system, this will drop dramatically.
Simply measuring the voltage across the terminals will tell you very little, you need to have a drop test done or get a specialist to check it on a battery diagnostic tool.
Don’t use Halfords, they usually haven’t got a clue, go to LSUK (used to be Lucas) they are proper auto-electricians.
If your alternator is managing to put any charge into the battery, chances are it is working correctly. It is unusual, but not unheard of, for an alternators performance to drop off, they normally work or they don’t.
Give it a good charge (12 hours) and see if things improve or If you have access to another car, swap the batteries for a couple of days and see what happens.
You may have to bite the bullet and replace it, (or take it back under warranty) but it’s worth checking it first before you go looking for an expensive alternator.
Carrera 4S. Clio 172. M5
Yes, it will if all the cells are good and the plates are not buckled.
Once you remove it from charge the terminal voltage will drop quickly to 13.2v and then slowly to 12.6v. If it drops any lower then get the battery checked.
If you run the engine the same numbers will apply ie: 13.8v under charge.
You should also check that you don’t have something draining it when the cars not in use.
Alarms, clock etc. don’t draw enough to discharge a good battery, but will help kill a poor one. An amp that’s not switching off or a boot light that’s staying on will kill it overnight.
