Battery or alternator?
Discussion
My Honda is having issues starting.
Will start fine for a week or so, then suddenly it will fail to turn over. So today, wife drove from home to sports club (roughly 25 mins drive), club to friend's house (15 mins) and then the car wouldn't start. Will start instantly if given a boost off another car.
Recharge battery and it will be OK for a few more days but will then fail to start again.
If it is the alternator i'd have thought it would go flat quicker than that - currently seem to get around 15-or-so starts out of it.
But if it is the battery, i wouldn't expect it to hold a charge for a couple of days and then start...
Will start fine for a week or so, then suddenly it will fail to turn over. So today, wife drove from home to sports club (roughly 25 mins drive), club to friend's house (15 mins) and then the car wouldn't start. Will start instantly if given a boost off another car.
Recharge battery and it will be OK for a few more days but will then fail to start again.
If it is the alternator i'd have thought it would go flat quicker than that - currently seem to get around 15-or-so starts out of it.
But if it is the battery, i wouldn't expect it to hold a charge for a couple of days and then start...
Simple test: get a multimeter and see what voltage the battery is at rest with nothing turned on. It should be about 11v ish. If it’s below then prob battery replace. Batteries often do not last 5 yrs now.
The other test is start car and now test voltage, it should be around 14v… if it’s below then good chance the alternator is faulty.
The other test is start car and now test voltage, it should be around 14v… if it’s below then good chance the alternator is faulty.
Caddyshack said:
Simple test: get a multimeter and see what voltage the battery is at rest with nothing turned on. It should be about 11v ish. If it’s below then prob battery replace. Batteries often do not last 5 yrs now.
The other test is start car and now test voltage, it should be around 14v… if it’s below then good chance the alternator is faulty.
Agree with the tests but NOT the first reading.The other test is start car and now test voltage, it should be around 14v… if it’s below then good chance the alternator is faulty.
If it is 11v the battery is flatter than a flat thing that has been sat on by an Elephant & run over by a herd of Wildebeest.
A good battery fully charged is around 12.6 volts, for every 0.1 volt below that it has lost around 15% of its charge.
OP.
Get a multimeter & test as above & see what you find.
However as what you are describing sounds like it is intermittent I would suggest the likely cause is a poor/loose/dirty connection on the main supply cables between the battery/alternator/chassis/main fuses/starter.
The only way to sort them out is to take them all off one at a time, clean & refit making sure they are tight & taking care not to short out 12v to chassis anywhere along the way.
Jump started car last night and drove it home (approx 30 minutes) and checked battery voltage - showing 12.6V on my multimeter.
Put it on charge overnight and checked again this morning and it was 12.75V.
Alternator is obviously providing at least some charge as the headlights didn't fade over the 30 minute journey, and the car restarted once it was home.
Will check voltage at the battery with car running tonight when i get home
Put it on charge overnight and checked again this morning and it was 12.75V.
Alternator is obviously providing at least some charge as the headlights didn't fade over the 30 minute journey, and the car restarted once it was home.
Will check voltage at the battery with car running tonight when i get home
boyse7en said:
Jump started car last night and drove it home (approx 30 minutes) and checked battery voltage - showing 12.6V on my multimeter.
Put it on charge overnight and checked again this morning and it was 12.75V.
You need to use the car or charge the battery and then leave it to stand overnight. Check the voltage next morning to get a genuine reading.Put it on charge overnight and checked again this morning and it was 12.75V.
Those voltages seem encouraging at face value but unless the battery has been left several hours to settle they won't be reliable. When a battery has just come off an alternator or charger it is still carrying some of that ritzy charging voltage as opposed to its own steady state voltage.
Panamax said:
boyse7en said:
Jump started car last night and drove it home (approx 30 minutes) and checked battery voltage - showing 12.6V on my multimeter.
Put it on charge overnight and checked again this morning and it was 12.75V.
You need to use the car or charge the battery and then leave it to stand overnight. Check the voltage next morning to get a genuine reading.Put it on charge overnight and checked again this morning and it was 12.75V.
Those voltages seem encouraging at face value but unless the battery has been left several hours to settle they won't be reliable. When a battery has just come off an alternator or charger it is still carrying some of that ritzy charging voltage as opposed to its own steady state voltage.
annodomini2 said:
tr7v8 said:
Had this on both my Granada & my Jeep. The battery is knackered, it may NOT show on a discharge test. Or possibly a starter issue with a dead spot..
If the battery was toast, recharge wouldn't fix it.boyse7en said:
If it was a parasitic draw problem, wouldn't it be worse after the car had been sat overnight?
It seems to start ok in the morning after sitting for 12+ hours, it fails after 3-4 starts during the day when it has only been sat for an hour or two
That would suggest a failing battery, short journeys I assume?It seems to start ok in the morning after sitting for 12+ hours, it fails after 3-4 starts during the day when it has only been sat for an hour or two
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