Negative battery terminal connection issue

[Blackberry66]

Hello. I have recently fitted a Bluetti Charger 1 into my 2016 T6 Caravelle. Both the Bluetti instructions and help on the Bluetti forum say to connect the cables to both the positive and negative terminal of the starter battery. Since doing this I have started to get issues with the van struggling starting and the battery going flat after a week. The battery is only a year old and this is happening despite the circuit breaker for the charger 1 being switched off once the van is parked up. I've seen a few posts on here saying that I should not connect anything to the negative terminal of the battery but not sure why and wondered if I should have connected the negative to a ground point instead. Can anyone offer any help and advice on this please?

 

[n10n]

You should not connect anything directly to the battery negative pole. Connect all negatives to the chassis / ground points instead.

The reason is the battery management - T6 calculates battery state of charge by measuring current through the negative lead, and adjusts alternator accordingly. If you connect any loads or chargers directly to the negative pole you bypass the measurement and the battery management will get confused.

 

[Blackberry66]

You should not connect anything directly to the battery negative pole. Connect all negatives to the chassis / ground points instead.

The reason is the battery management - T6 calculates battery state of charge by measuring current through the negative lead, and adjusts alternator accordingly. If you connect any loads or chargers directly to the negative pole you bypass the measurement and the battery management will get confused.

Great information thank you. I had a feeling this was the case but all the Bluetti people telling me its fine on their vehicles and that was the way I should do it.

 

[n10n]

There’s usually even this subtle hint on the cover of the negative pole

 

[Blackberry66]

There’s usually even this subtle hint on the cover of the negative pole

View attachment 268717

Unfortunately, I dont have this on mine

 

[t0mb0]

Despite not wanting people to use the battery terminal, VW completely fail to provide a very accessible ground point close to the battery on the T6…

 

[n10n]

Despite not wanting people to use the battery terminal, VW completely fail to provide a very accessible ground point close to the battery on the T6…

It’s crazy isn’t it?

Mrs n10n’s Q3 from 2015 has a mighty chassis connection point right next to the battery in plain sight for this very reason - so VAG group is not even consistent.

 

[Blackberry66]

Would you say my best option for a ground point near to the battery would be the headlight fixing bolt?

 

[t0mb0]

Would you say my best option for a ground point near to the battery would be the headlight fixing bolt?

Um, maybe! I know people do use that, but when I measured mine it had rather high resistance to ground so I don't know how reliable they are.

 

[n10n]

Would you say my best option for a ground point near to the battery would be the headlight fixing bolt?

The best option would be a proper ground point, there's one in scuttle bay behind the battery and couple low below the diesel filter. But they're quite hard to reach unfortunately.

Personally I've used the headlight fixing bolt, I cleaned little bit to ensure a good contact and measured the resistance to negative pole to be very low, about 0.002 ohm afair. I've had no problems charging through that.

 

[Blackberry66]

The best option would be a proper ground point, there's one in scuttle bay behind the battery and couple low below the diesel filter. But they're quite hard to reach unfortunately.

Personally I've used the headlight fixing bolt, I cleaned little bit to ensure a good contact and measured the resistance to negative pole to be very low, about 0.002 ohm afair. I've had no problems charging through that.

I will try the scuttle bay then thanks

 

[lance270]

Jumping on this thread, recently bought a Bluetti Charger 1 and can't figure where to attach it to the negative terminal either. Like you say, every instruction I've found online and from Bluetti says to attach to the negative terminal.

Can you provide an update when you've tried the headlight fixing bolt? Thanks

 

[Sasquatch]

I use the headlamp bolt for my chargers negative connection. Works perfectly.

 

[Dellmassive]

headlight bracket bolt - -scratch clean for good contact.

Battery Charging - Main Battery Chassis Point -

Battery Charging - Main Battery Earth Point - so weve all be told NOT to bridge out the battery monitor on the neg side of the battery when charging it. This is so the ECM can correctly gauge the SOC (state of charge) of the starter battery by monitoring the current flow in and out of the...

www.t6forum.com

 

[Vanderlust]

I use the headlight bracket also for connecting jump leads, noco charger etc and fitted a small bracket to make it easier, cleaned the thread and checked with multi meter to confirm good earth.

 

[Kind of Blue]

T6 Caravelle. For the negative attachment I tend to use the Ring lift on the top of the engine for things like higher power tyre pumps and the rare occasion that I have used a charger. It gives a good contact. The only problem is in the dark at night because the ring is a bit hidden under the engine cowl. In the dark I attach to the bonnet slam catch bolts The engine bay really could do with its own lighting, Why do manufacturers never fit them?! We have a number of things under the bonnet (hood) that need routine attention oils, for brakes, engine and so on, cooling and windscreen wash, Higher Amp electrical power and charging. I very nearly always carry a torch unless someone has removed it for charging changing battery etc but many do not. In any case its an absolute faff fiddling about with a torch when handling other bits and bob. The lack of proper negative -ve official bolt is unforgivable in any case. I remember during warranty the engine had a problem stalling and the starting. The chief VW Technician was advising me of where to stick the negative on the provided bolt and it was really funny watching him increasingly frantically looking for it. "they must of moved it somewhere else" He embarrassingly stated, still hunting. I put him out of his misery by showing him the lift ring.

So no proper -ve point and no engine bay lighting! What do others do and think?

 

[Chris1983]

Only scrolling and found this, educating self.

So I had need to use a battery charger on starter (should be a while, just replaced SB). I shouldn’t use the negative battery connection?and what about the battery monitor? Is this correct?

 

[Chris1983]

Missed an ‘if’ in that sentence

 

[Sasquatch]

Only scrolling and found this, educating self.

So I had need to use a battery charger on starter (should be a while, just replaced SB). I shouldn’t use the negative battery connection?View attachment 272075and what about the battery monitor? Is this correct?

That's fine for a monitor.

 

[Chris1983]

Thank you, what about if needed to charge the battery or jump start another vehicle (no plans to, again just expanding own knowledge)