We must all remember the purpose of this forum is to help one another as Brothers in Arms above all else, and generally that is what I have found on this “Gentlemans’ Forum” and long may it continue.

I am no expert on automotive battery charging issues I have to say and have merely reported others’ findings as impassively as possible above, however as a professional engineer of more than 40 years have researched battery technology extensively as a builder and user of ebikes. One possible caveat to the “charging from the other end” brigade is the possible effect on the BMS (Battery Monitoring System). JLR WM actually recommends “removing the battery from the vehicle” before charging. Yeah, right.
However, most of us know it’s proven to be OK to charge using a smart charger (CTEK or otherwise) connected to the underbonnet posts. Without knowing the logic of the BMS, it’s very difficult to say what might upset it, or cause damage if charging from the “other end” which may confuse /destroy the BMS, -I honestly don’t know, but is it worth taking the risk, or am I thinking BS?

So, until anyone can quote a “Scholarly Paper” explaining otherwise, I will not use the “recon” mode of my CTEK on my brand new and not inexpensive AGM battery.  “If it ain’t broke, don’t fix it” -where’s the fun in that?

I have been using the CTEK charger for over 18 months, with no issues. I use it to top up when I get the "start the engine message battery low" I use the extension lead and use the connections under the bonnet as well. I use the crocodile clips with no issues.
I did have the same set up on the DS but hard wired it direct to battery with a short lead that fitted to the extension lead, again no issues.

Its not often I need to use it (maybe every 3 months or so) my dash cam is a slight drain as it activates when raining or a leaf dropping (I really need to adjust the sensitivity ) and my rural journey dont really keep up with the slight loss over time. 2018 SE SDV8 4.4 Byron Blue

I charge my main battery by connecting directly to it in the boot, using both a Ctek and a solar charger. I’ve used this technique on 3 different L405’s (MY’s 15,16 & 19) for many years without problem.

This will probably give a few people on here a heart attack  MY23 D350 HSE
On my 7th RR plus various other JLR vehicles

Another aside!

Noting an early post about connecting live first,

On my grasscutter…. I connect the charging unit in any old order… so it’s 50/50 which gets connected first.

Does that matter? If so why?


Now I think about it , post covid, my wife’s car stood idle & again didn’t think about the order of connection. Filters are in fact so good that in certain circumstances, when the ambient air is already polluted, a diesel car will tend to extract more particles from the air than it emits. Emissions Analytics worked with........etc etc

He who dies with the most toys wins...

I connect positive first. Reasoning if you connect negative first then there is the chance of the positive, whilst disconnected, touching bodywork or engine parts causing a short circuit. That’s my reasoning. It shouldn’t happen if you don’t switch on power to the charger before everything is connected but no harm in being sure. lol John
2008 Stornoway Grey 3.6 Tdv8 Vogue - SOLD
2005 TD6 Java Black Vogue - Written off!!
GAP iiD BT-Sold

The reasoning behind +ve first connecting up, last when disconnecting stems from the possibilities of gas from the battery. In connecting up, +ve goes onto the battery post and the negative to metalwork away from the battery, if there's a spark it doesn't matter. When disconnecting the opposite, it true, negative first away from the battery etc. BMW i3 Electric Car
2012 Full Fat RR 4.4 TDV8 (now gone)
2006 VW Touareg 3.0 TDi V6

[quote= The reasoning behind +ve first connecting up, last when disconnecting stems from the possibilities of gas from the battery. In connecting up, +ve goes onto the battery post and the negative to metalwork away from the battery, if there's a spark it doesn't matter. When disconnecting the opposite, it true, negative first away from the battery etc./quote]

-This is the real reason, well said!  “If it ain’t broke, don’t fix it” -where’s the fun in that?

Blimey, could you call my missis tonight and tell her actually I was right  BMW i3 Electric Car
2012 Full Fat RR 4.4 TDV8 (now gone)
2006 VW Touareg 3.0 TDi V6

@AJGalaxy2012:

Call made. “If it ain’t broke, don’t fix it” -where’s the fun in that?

 “If it ain’t broke, don’t fix it” -where’s the fun in that?

Hopefully someone in here may have come across what I've experienced...
Back in winter I bought a CTEK charger and followed Gremlin500's exc advice and photo support..
I also have the CTEK socket down in the grille, and tucked away. I've been getting the famous 'Battery Low - Start Engine' message every time I've got in the car - It's never failed to start, but without the engine, sometimes the tailgate throws a strop. Although I do very little mileage (I'm due an MOT/Service this week and I've only done around 3500 miles..) I've not been worried too much about starting. On Saturday I CTEK charged the car via the modded bonnet posts, and the next morning saw that the charger was sitting happily at '7' - fully charged.
I hadn't been out in it at all since the charge - today I opened up the car to clean out the rubbish, and after 10 or so mins the 'Battery Low...' message popped up again.. !!
The battery is only about 2 years old, and so I'm thinking would the smaller second battery be causing this..?
TIA chaps.. MY17 VSE FF Corris

The socket can get corroded & wet in Winter especially, so need regular cleaning with switch cleaner and a liberal dose of SGB 200 contact grease, this is the downside of an external socket which you pay for the convenience. If there is poor contact or water in the socket, the CTEK will behave oddly. TBH, I have junked the CTEK plugs/sockets and switched to XT60 connectors which are far chunkier and easier to clean. “If it ain’t broke, don’t fix it” -where’s the fun in that?

Yes, thanks for that Gremlin500, although I wasn't too clear in my description.. Although I first chatted to you in the winter about the location of fitting, etc, I only recently ( a week ago) fitted the charger leads and extensions to the posts. They haven't been out in the cold and wet long enough to have corrosion..at least not to the point where they would start misconducting, or making the CTEK behave squiffy.
Of course I accept that's a downside of the quality of the connectors that I'm yet to come across.
Perhaps somebody from our well esteemed community will come out with 'You numpty - if you don't use the car that much, what do you expect?' , and that would be a completely fair comment.

I checked my receipts tonight and the battery is just a month over 2 years old, with a 5 yr guarantee...
Thanks all.. MY17 VSE FF Corris