CHARGING BATTERY ON CAR? - CORRECT WAY PLEASE

[6Channel]

My 2010 C5 Tourer has not run for a while - Lockdown etc and yesterday when I needed it, the battery was flat.
Lack of use, said AA man who got me started. The battery is in good shape apparently, just cold weather and no use..
He didnt connect directly to the battery and said I shouldn't use a home battery charger directly on it as I'd "blow the electronics"??!! What?!
What is the correct way to charge a low battery ON CAR please.

[GiveMeABreak]

There's a good reason why charging the battery on the car can be an expensive mistake - if you connect the terminals up incorrectly then you can damage the very sensitive ECUs on the vehicle and that can be very expensive. It may be obvious, but there have been quite a few examples of people doing this here accidentally and causing damage.

I rarely charged mine up on the vehicle because it is easy to get distracted and by then it's too late.

Some battery chargers have smart detection of the polarity.

But if you are going to charge the battery on the vehicle - always disconnect the battery terminals first (as that will prevent any damage to the ECUs whilst charging) and follow this guidance:

BSI Reset / Battery Disconnect / Reconnect Procedure

Follow the guidance from you battery charger as for connecting it up and when charging is completed, and you are reconnecting your car battery leads to the battery, always connect the negative lead to the car battery first.

[Hell Razor5543]

It MIGHT be worth checking out this charger, as it MAY have polarity checking.

https://www.aldi.co.uk/auto-xs-car-batt ... 9437763000

I have a smart charger from Lidl, and it DOES have polarity checking (it has FLIRT; Full Logic Intelligent Regulation Technology). If you have an Aldi nearby it could be worth popping in and taking a look at one of their chargers.

[wheeler]

The main reason for not connecting directly to the negative terminal is it can upset battery monitoring & smart charging systems. 'Blowing the electronics' is a bit dramatic. If you connect the charger with the correct polarity, connect the negative to the chasiss and are using a modern charger there is no problem charging the battery in situ.

[xu10t]

I have installed a fixed charging plug to the battery terminals so i can connect the charger without opening the bonnet. Every week I fully charge it because i don't drive very much at the moment. I will report here when I "blow the electronics".

[bobins]

I regularly top-up charge my C5 (and others in the fleet) with one of the Aldi/Lidl smart chargers without disconnecting the battery leads first. However, I WOULD disconnect the leads first if charging with one of my old fashioned 'non-smart' battery chargers.

[6Channel]

Thanks folks.
My charger is an old one with a light on it to show its ON. Lol.
The left hand terminal has what looks like a quick releease thing. If I disconnect that, can I then charge directly on the battery?
(You may gather I'm not technically minded. Lmao!)

[GiveMeABreak]

You want to ensure you isolate the vehicle electronics - especially as some of the ECUs are low voltage only and especially if you have an older non-smart charger - which is why I generally go on the safer side as we never know what kit people have.

I suspect your quick release lever is for the positive, if that's the case (and make sure). So just double check your connections and make sure you hook the charger up correctly. Make sure the quick release lever connector is not able to re-touch the battery terminal once you release it, so isolate it by putting something like a rag or a piece of cardboard between the lever and the battery terminal post.

[6Channel]

Thank you.
That is very useful information..