Under bonnet charging point?

[Andymharrison]

Over in the XC90 2015> sub-forum there is a thread about the best place to connect a CTEK charger and the consensus seems to be to use the under bonnet point as then both main and support batteries charge and the battery monitor knows whats going on.

Which got me thinking, does anyone use the jump start point in the older single battery XC90s for charging?

I was always told, many years ago when cars were cars rather than mobile computers, you shouldn't charge a battery while connected so I've always pulled up the boot floor and disconnected first.

I'll most likely continue doing that but was curious what others do?

[Harley Dave]

When required, I charge by connecting to the under-bonnet points. (too much faff to disconnect the battery)

Electrically, they are the same as connecting direct to the battery.

The charging current involved is quite low, so you can discount the small volt drop you will get due to the length of cable between battery and under-bonnet points.

I sometimes use a small solar panel (resting on the roof) which I connect to the rear cargo area 12v socket.

Both methods have been problem-free for years.

Cheers

Dave

[Andymharrison]

Thanks Dave, I'll try it next time I need to charge, what do you use for the negative, engine lift point?

I have a small solar panel ready to go as I'm about to park mine up for a few months so glad to hear that works for you.

[Harley Dave]

For the Negative connection, I clamp on to the 3 or 4 bolt heads on the right side wing, looking from outside the front of the car (UK Passenger side)

Cheers

Dave

[ommony]

I have had a CTEK plug wired permanently in under the bonnet for many years and regularly use it without any issues.

[Moose Test]

Originally Posted by ommony

I have had a CTEK plug wired permanently in under the bonnet

Whilst I've yet to get around to doing it myself, I think this is the 'real' answer, for long term best results.

The voltage drop in loom cables back to the battery isn't likely to be that high for the purposes of charging but the quality of the connection between croc clips and painted/corroded/dirty studs isn't great and probably does have some effect. That said, I've been using it too and it seems to work ok for charging. Jump starting is a whole other matter; I've failed to start the vehicle with a completely/highly discharged battery without going direct to the battery terminals. Here, contact and cable resistance are important for the current levels involved.

In reference to the OP's original comments, I think something to be aware of is that if you're using a 'smart' charger with a repair mode, some manufacturers of such devices do recommend disconnecting the battery from the vehicle due to the higher charging voltage and patterns involved, if you are operating in such a mode.

[Andymharrison]

Originally Posted by Moose Test

Whilst I've yet to get around to doing it myself, I think this is the 'real' answer, for long term best results.

The voltage drop in loom cables back to the battery isn't likely to be that high for the purposes of charging but the quality of the connection between croc clips and painted/corroded/dirty studs isn't great and probably does have some effect. That said, I've been using it too and it seems to work ok for charging. Jump starting is a whole other matter; I've failed to start the vehicle with a completely/highly discharged battery without going direct to the battery terminals. Here, contact and cable resistance are important for the current levels involved.

In reference to the OP's original comments, I think something to be aware of is that if you're using a 'smart' charger with a repair mode, some manufacturers of such devices do recommend disconnecting the battery from the vehicle due to the higher charging voltage and patterns involved, if you are operating in such a mode.

I've just got one of the ctek mx5 chargers to replace my aging one which isn't that smart and screams like a banshee for some reason. I also got the cigarette lighter adapter which I'm using to trickle charge via the rear socket when the car is unused near power and a small solar panel to do the same when it isn't.

For bulk charging or reconditioning I'll contine to remove the battery as i always have, not doing so just seems to be inviting the electrical gremlins to come out to play.

[Moose Test]

If anyone is interested in the broader details of lead acid battery electrochemistry and it's practical implications for charging and battery life, I find this site to be a useful resource: https://batteryuniversity.com/articles