battery - no amps
Moderator: RichardW
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battery - no amps
here's one for people who know about electricity. i've been told that the car isn't starting occasionally because the battery is showing 11.7v but no amps!! this is on a mercedes, i know it's not on that forum but more replies on this one - wonder why[;)]. any way the car will sometimes not start, turn key back and try again and car starts, three weeks ago car refused to start, green flag came out, checked voltage, said low jumped started and away it went. went to price and order new battery, checked by shop and voltage drop off was not severe- no bad cells, mercedes checked out immob, battery and ignition and stated batt at fault - low volts and no amps. car still starts every time no matter how cold, with the very occasional no start until key turned back and fires on second attempt. so is it possible to start a car with no amps in the battery? forgot to say car is '98 e240 don't know age of battery but more than 3 years
I think you got the term "battery with no amps" a bit wrong here.
The problem with a low battery voltage - and then no-start - is in fact ohm's law :
Low voltage x constant ohms in starter motor = too low starter umph to crank the engine.
(badly simplified I admit)
The battery may have a dodgy cell which shorts out now & then. If this happens while the battery is charged - then the remaining 5 good battery cells are in fact overcharged. But they will instantly loose their overcharge when loaded by a starter motor.
The battery voltage should be checked at least 1 hour after engine (and thus the charging alternator) has stopped. This will tell the correct voltage condition of the battery.
A good battery will then show some 12.7 - 12.8 volts.
The problem with a low battery voltage - and then no-start - is in fact ohm's law :
Low voltage x constant ohms in starter motor = too low starter umph to crank the engine.
(badly simplified I admit)
The battery may have a dodgy cell which shorts out now & then. If this happens while the battery is charged - then the remaining 5 good battery cells are in fact overcharged. But they will instantly loose their overcharge when loaded by a starter motor.
The battery voltage should be checked at least 1 hour after engine (and thus the charging alternator) has stopped. This will tell the correct voltage condition of the battery.
A good battery will then show some 12.7 - 12.8 volts.
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- Posts: 41
- Joined: 05 Feb 2005, 01:05
- Location: United Kingdom
- My Cars:
-
- Posts: 1635
- Joined: 03 Oct 2003, 00:50
- Location: United Kingdom
- My Cars:
- x 1