External charger connection for the 12v battery

[Red_Corolla]

I put my Battery on charge today because it was down to 12.1v. Knowing that this is something of an achilles heel and combined with the fact that my car often sits for a few days between uses, I'm thinking about situating a connection point somewhere underneath so that I can easily connect my charger whilst leaving the car secured, with no faffing around routing cables so that they don't get trapped or damage the weatherseals etc.

Anyone done this and have a good idea for the installation? I have a 2.0 estate with tow bar, so my Battery is in the boot and I could potentially tie a CTEK connector behind the socket for the towing electrics. Alternative is to hook up to the main fusebox terminal under the bonnet and have it somewhere at the front end. What I want to avoid is making any new holes.

BTW, I learned to be mindful of the keyless system when using a smart charger, because the mere proximity of the key fob is enough to make the car turn on the interior lights and then the induced volt drop sets the charger off again. So, every approach to check the charger with key in pocket will result in finding the charging not finished lol.

[Woofwoof]

It doesn’t really matter rid the charging restarts as long as it keeps the Battery with adequate charge

[Gray86]

2.0 estate here, and just charged mine with my CTEK MXS 5.0 charger. I used the ‘live’ connection to the 12v under the bonnet in the fuse box (red flap), and use an earth on the strut tower. Done it this way numerous times, and it’s fine. 
 

I noticed interior lights are a bit brighter as a result - must have needed the charge! 

[Red_Corolla]

4 hours ago, Gray86 said:

2.0 estate here, and just charged mine with my CTEK MXS 5.0 charger. I used the ‘live’ connection to the 12v under the bonnet in the fuse box (red flap), and use an earth on the strut tower. Done it this way numerous times, and it’s fine. 
 

I noticed interior lights are a bit brighter as a result - must have needed the charge! 

Thanks Graeme, I did the same although I didn't notice the red terminal that you mentioned. I used the main connection to the passenger side fusebox, which is black on my car and accessed by removing the fusebox lid. There's an earth point just in front and slightly below.

What I'm after is a good place to install a connecting lead so that I can just hook up underneath the car without having to faff with opening the car up and arranging the cables under the bonnet etc. For safety, I will be including a fuse at the end that connects to the car. Just need a good place to position the plug that will be accessible without being too exposed.

[Red_Corolla]

5 hours ago, Woofwoof said:

It doesn’t really matter rid the charging restarts as long as it keeps the battery with adequate charge

I know, I just like to see it finished and on the green light once so that I know it got there. With the charger on the windscreen and me approaching from behind, I would never have witnessed that without leaving the key fob behind when I went to check it, because the interior lights would make the charger restart before I could get eyes on it. It was just a heads-up for others to be aware that simply walking past the car can wake up both the car and the charger.

The newer Cteks have more indicator lights to tell you what stage the charging is at, so you can always see when it's nearly full. I only have that on my 0.8A motorcycle charger. My car charger is an older model that shows either 'charging' or 'charged' with nothing between.

[Corollanutter]

9 hours ago, Red_Corolla said:

I know, I just like to see it finished and on the green light once so that I know it got there. With the charger on the windscreen and me approaching from behind, I would never have witnessed that without leaving the key fob behind when I went to check it, because the interior lights would make the charger restart before I could get eyes on it. It was just a heads-up for others to be aware that simply walking past the car can wake up both the car and the charger.

Don’t forget that you can easily temporarily turn off the auto unlocking / lights on feature on the fob by button presses. It reactivates the next time you press a button on the fob. Hold down the Lock button and at the same time press the unlock button twice. The red light on the fob will flash 4 times and mean your fob is now switched off. 

[forkingabout]

Any permanently mounted socket would need to be waterproof & fused.

Also there wont be any safety interlock for accidently driving away with the socket connected. 

As there's already a tow bar fitted, could the tow bar electric socket be used either through its existing wiring OR adding an extra 12+ wire in to the socket to charge the 12 volt Battery?

[loz8]

first lockdown and 2 flat Battery callouts,off went the interior lights,and life's been good.

only checked Battery state once using car system and never been able to repeat it.going into yr.7

Edited December 3, 2021 by loz8
more clarity

[Red_Corolla]

5 hours ago, forkingabout said:

Any permanently mounted socket would need to be waterproof & fused.

Also there wont be any safety interlock for accidently driving away with the socket connected. 

As there's already a tow bar fitted, could the tow bar electric socket be used either through its existing wiring OR adding an extra 12+ wire in to the socket to charge the 12 volt battery?

Already thought of that one, but the +12v pin powers down when the car is off. Or should I say, the potential is still there and can be measured with a high impedance multimeter, but it pulls to 0 if you try to apply any load. Must be controlled by a MOSFET. No good for charging, in any case.

I do think that behind the towbar socket is going to be best bet, though, if I can find an existing grommet to pass a wire through the boot floor. If not, I'll probably settle for a Ctek connector installed inside the boot and just leave the tailgate down but not closed.