Battery charging with cables still connected
Discussion
Hi folks,
This morning after three weeks of not being used I tried to start my Honda Accord diesel and found a flat battery. I checked the voltage at 12.1 volts.
I called the main dealer to ask if it was safe to charge the battery on the car without disconnecting the car leads as I didn't want to lose my codes.
At first he said yes then a techie beside him asked if I had the sat nav model. When I said yes he then said it might not be safe to charge it with the leads connected! "We have had cars in with the ECU blown due to charging on the car"
I decided to jump start it from our Toyota. Alternator voltage then was 14.5. I ran the car for a few miles then checked the battery volts again. 12.7V
Odd that a drop of just 0.6 V could cause the battery to fail to start the car!
A chum with a Mercedes has his on trickle charge with car cables connected when he parks it for the winter and his dealer says that will cause no harm. Anyone know who is correct? On the car or with car cables disconnected?
This morning after three weeks of not being used I tried to start my Honda Accord diesel and found a flat battery. I checked the voltage at 12.1 volts.
I called the main dealer to ask if it was safe to charge the battery on the car without disconnecting the car leads as I didn't want to lose my codes.
At first he said yes then a techie beside him asked if I had the sat nav model. When I said yes he then said it might not be safe to charge it with the leads connected! "We have had cars in with the ECU blown due to charging on the car"
I decided to jump start it from our Toyota. Alternator voltage then was 14.5. I ran the car for a few miles then checked the battery volts again. 12.7V
Odd that a drop of just 0.6 V could cause the battery to fail to start the car!
A chum with a Mercedes has his on trickle charge with car cables connected when he parks it for the winter and his dealer says that will cause no harm. Anyone know who is correct? On the car or with car cables disconnected?
samuelellis said:
iirc the merc chargers are designed by a company called ctek - very cool very clever chargers - http://www.youtube.com/watch?v=qHSI_qHOI4U
that is why you can hook them up while the battery is still connected to the car as some chargers are more than a bit dumb and can damaged stuff
I asked the guy with the Mercedes if he was using an expensive charger with special protection and was surprised to learn he uses a cheapo one from Aldi!!that is why you can hook them up while the battery is still connected to the car as some chargers are more than a bit dumb and can damaged stuff
esselte said:
*Al* said:
I'd personally never charge a car battery insitu with the leads connected.Electronic 'spikes' can damage electrical circuits.
But wouldn't the circuits actually have to be connected to the battery for this to happen? If the ignition switch is off how many of these will there be?I don't see an issue with a good charger/conditioner like "AccuMate" etc...?I mentioned that years ago folks would leave their side lights on all night when parked in the street yet a mechanic told me that nowadays if they leave a car door open in the workshop overnight , it can flatten the battery.
Orb the Impaler said:
Charging batteries while leaving the car connected will be absolutely fine.
What you shouldn't do with a lot of modern cars (Mercedes are a good example) is jump start them with a booster pack, although normal jump starting is fine.
OP - your voltage is only part of the problem - it's the current that the battery can supply that's going to be the issue. Also have a look what voltage the battery is putting out when you crank the engine. Notalot I suspect.
Can you say what the voltage would be on a good battery when cranking? This Honda starts right away so I wonder how I would measure the cranking volts. Perhaps a check with a battery tester is called for.What you shouldn't do with a lot of modern cars (Mercedes are a good example) is jump start them with a booster pack, although normal jump starting is fine.
OP - your voltage is only part of the problem - it's the current that the battery can supply that's going to be the issue. Also have a look what voltage the battery is putting out when you crank the engine. Notalot I suspect.
miniman said:
mybrainhurts said:
Orb the Impaler said:
What you shouldn't do with a lot of modern cars (Mercedes are a good example) is jump start them with a booster pack,
Why, please...?Providing the negative lead is connected to a good earth point on the flat car rather than the battery negative terminal I can't see any reason why it would make a difference.
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