Battery charging

[Tub Thumper]

Evening all. Is it best to disconnect the battery before charging, or is it OK to just connect the charger up in situ?

I think the last time I charged a battery was on my old Mini where the most high tech piece of kit was the cassette player

Cheers.

[Georgeandkira]

A smart person would let a smarter person answer that question definitively.....but I ain't that smart.

I've always just thrown small chargers (trickle chargers or common "6 amp" chargers) onto an installed battery without thinking about it. Never had a problem.

If I had a larger charger than 6 amps I'd disconnect or remove the battery.

a) Many have written "charge the battery out of the car".

b) You can then go at it (thoroughly washing and rinsing the battery itself and its tray, both top and bottom of the clamps and its niche) with baking soda and water easily. Lots of times a battery which needs charging involves older, possibly neglected vehicles so delivering a little TLC wont hurt.

c) Removing the battery before clamping on a 50 amp charger is insurance in the event you absent mindedly get the polarity wrong. You can say "whoops" and correct it but a car's precious electronics mightn't be as forgiving of a backwards zap.

Others will be along.

[barrybritcher]

take it out, if it ****es down with rain the extension lead on the floor isnt going to like it either

[MWMan]

I have always charged the battery while its connected to the car. I have used a wide range of battery chargers over a wide range of cars and have never had a problem. I used to hear a lot about diodes being stressed by doing this. If they are, its not something that has shown up on my cars, and I tend to keep them for a long time.

[Dippydog]

Never having had the access to charge the battery while it was still attached to the car I've always[had to] remove it.However given that you can get "smart"chargers/battery conditioners that operate with the battery connected I see no other reason why you can't leave it in place.

[340man]

I must admit to charging with an external charger whilst battery is still in the car and connected.

However, in my view it's better to disconnect the battery from the car before charging. If connected, any quiescent or parasitic draw that the car takes from the battery may stop the charger from reaching it's maximum voltage and any over voltage may? damage electronics on the car.

Another point, after charging the car battery with an external charger, either wait a few hours for the excess surface charge voltage to die down before connecting the car to the battery, or, briefly connect a something drawing say at least 0.5 A to remove this surface charge.

[BobS]

Hi,

It's always safer to disconnect the battery when charging.

Depending on the charger and condition of the battery the risks range from negligible to quite likely. The problem is the voltage peaks.

A trickle charger charging a good battery will not raise the battery voltage much above the 14.2v. This should be relatively safe.

But a high boost charger is a different matter. The voltage peaks needed to fast charge the battery can stress some components in the car electronics and if the battery has a failing cell this voltage will be even higher. Some good quality (re Expensive) fast chargers have a voltage clipping circuit to help with this problem. But not all have it.

But on the other side of the coin. Reconnecting the battery also has a very small risk too. That's why Volvo have a procedure to reconnect the battery (ignition in position II).

The only helpful tip I can give is always connect the charger before switching it on.

Bob