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Can someone give me a definative answer to this? Is it strictly necessary to remove any of the battery leads when attaching a home battery charger to the battery on a modern car? Years ago I remember when we had dynamos it wasn't necessary but with the advent of alternaters I think there is now a link (electronic or wire etc) with the alternater even tho' the ignition is 'off'. (First query)
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On modern cars all sorts of strange things can happen if you disconnect the battery. These range from the trivial such as the radio losing it's code to the rather important such as the engine mangement computer having to re-learn all it's parameters based on your driving style. Many garages connect a slave battery to the system if they have to replace a battery before disconnecting to keep all the settings.
With respect, if you find that you have to charge a battery on a modern car, then something has probably gone wrong or you've left the lights on! If you have accidently discharged the battery it's far better to get a jump start and let your car charge its battery itself. If the battery can't hold its charge then you really only have one option - buy another!
If you must charge the battery you really should disconnect the leads - many battery chargers have very poorly regulated outputs and could cause havoc with the electronics, especially if you accidently switch on the ignition while charging.
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Thanks for the advice. The battery is less than a year old but the car isn\'t used barring a long trip once a month and 2/3 short trips also. The charger is only a trickle one, 1 or 2 amp maxm. Thanks again.
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If you are going to salm 10 amps at it then no but if you are just going to float it with 3 or 4 amps athen it settles at less than an amp and the charger is of reasonable quality i.e. no £3.99 or 30 years old then no problem. Remenber that a charging battery gives off highly combustable gasses. Regards Peter
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Typo Salm = Slam and yes definitely no turning the ignition on. If you are unsure then once the battery has settled measure the terminal voltage it should not exceed 14.75 volts unless the battery is very old and has a high internal resistance in which case this battery should be changed. Regards Peter
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I have charged anything from BMW 3 series/Rover 800/Peugeot 106 with a 20 year old Woolies battery charger with no problems ever but I always connect the charger before switching it on at the mains and always switch it off before disconnection.. and of course never touch the cars lights/electricals/switches when running.
The major problems are caused by spikes: an electrical spark on connection/disconnection is bound to scramble something imo...
madf
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Follow madf's advice and you should be OK. There is no reason to disconnect the battery from the car to charge it, so long as an appropriate charger is used - after all, when running, the alternator is acting as a battery charger (as far as the battery is concerned) - and a much more powerful one than you usually buy to charge the battery from the mains.
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But an alternator only provides the output required by the battery/electrical system - it is very closely regulated. A battery charger, unless it's a very good one doesn't respond to anything like the extent an alternator system does. Despite the comments I would still be wary of using a battery charger on a modern car. Perhaps I'm just over cautious but fried electronics would cost a fortune to fix.
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If when your charger has been for a couple of hours the velotage settles at 13.75 to 14.25 and never rises to inexcess of 14.75 then is is fine. I recommend 13.75 for long periods, like you are away, or 14.00 if it is just overnight. If you are doing this all the time, i.e. every night then 13.5 to 13.25 if just fine. Regards Peter
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Hello all
So if i was to connect a battery charger to one of our cars with it all still connected it will charge the battery without having to remove all the cabbles and disturbing radio codes etc.
best regards
Martin W
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I bought an Accumate battery charger direct from their site a couple of weeks ago for the very same reason of not wanting to fry the electrics.
Excellent piece of kit and they state it can be left connected for months if required with no harm done.
Well worth reading all the technical jargon about charging directly from the site. tinyurl.com/26ouq
They are very sensitive to any current drawn and even opening a door (interior lights) changes the green fully charged light to orange charging light for about 20 seconds.
When I first put the Vectra which is used infrequently on charge it took around 20hours before it was fully charged. In contrast the wifes car was fully charged in a couple of hours.
Accunate also supply you with a special connector to attach to the battery terminals permanently. The other end of this lead is rubber waterproof socket to plug in the lead from the charger.
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