Alternator and battery tester

[ArunAlec]

My understanding is that you shouldnt connect the negative directly to the battery terminal but rather through the body earth? Maybe someone can confirm?

Again that’s my understanding but can’t find anything definitive.

 

[WelshGas]

My understanding is that you shouldnt connect the negative directly to the battery terminal but rather through the body earth? Maybe someone can confirm?

Again that’s my understanding but can’t find anything definitive.

Basically modern cars with Stop/Start and Regenerative Braking coupled with a Smart Alternator monitor the Engine Battery through a Sensor/Electronic circuit which is attached between the -tve pole of the Battery and the Earth/chassis/engine.
Connecting a Charger or Jump Starter directly to the -tve pole of the Battery bypasses this Sensor system.
The Sensor system monitors the Battery condition so that the Smart Alternator/Regenerative Braking works efficiently without damaging the battery. Connecting directly screws up this monitoring and gives the car electronics false information. Also, I'm not sure if you realise you shouldn't just swap out the engine battery. When a new battery is installed the vehicle has to be connected to the garage Diagnostic computer and told it has a new battery so that it can re-calibrate to the new battery so that the systems work efficiently. Failing to do so can shorten the battery life etc: by overcharging.

Gone are the days of a Lump hammer and an adjustable wrench to keep the car on the road. They are too clever by half.

 

[Neuon2003]

Connecting a Charger or Jump Starter directly to the -tve pole of the Battery bypasses this Sensor system.

Does this mean it is OK to use a Jump Starter with BMT technology if the starter -ve is grounded to earth? Or should a jump starter be avoided at all costs?

Edit: Found this post suggesting it is OK to use provided not connected to starter battery -ve.

 

[WelshGas]

Does this mean it is OK to use a Jump Starter with BMT technology if the starter -ve is grounded to earth? Or should a jump starter be avoided at all costs?

Edit: Found this post suggesting it is OK to use provided not connected to starter battery -ve.

Absolutely fine. Just put the -tve connector onto an earth point. Many modern vehicles with this technology normally have a convenient Earthing Point near the battery.

 

[Sp0_0k]

I suppose by "alternator or battery tester" it is meant a simple voltmeter.

The Sensor system monitors the Battery condition so that the Smart Alternator/Regenerative Braking works efficiently without damaging the battery. Connecting directly screws up this monitoring and gives the car electronics false information.

I very highly doubt that Sensor is tracking capacity flow both directions and cuts of charging based on that data. Even advanced lithium batteries which require serious monitoring don't do that.
So let's say charging it on terminals shouldn't influence the sensor, which is highly probable is only monitoring the voltage.
I suspect you can't overcharge the battery with properly functioning alternator which won't feed more than max 14,4 volts and the current flow will simply level.
The only reason for connecting negative last and on the body is known to prevent the sparks which can ignite the gasses from the battery.

 

[WelshGas]

I suppose by "alternator or battery tester" it is meant a simple voltmeter.

I very highly doubt that Sensor is tracking capacity flow both directions and cuts of charging based on that data. Even advanced lithium batteries which require serious monitoring don't do that.
So let's say charging it on terminals shouldn't influence the sensor, which is highly probable is only monitoring the voltage.
I suspect you can't overcharge the battery with properly functioning alternator which won't feed more than max 14,4 volts and the current flow will simply level.
The only reason for connecting negative last and on the body is known to prevent the sparks which can ignite the gasses from the battery.

I think not, I’m afraid.

 

[Loz]

I very highly doubt that Sensor is tracking capacity flow both directions

It does, it uses a resistive shunt and an algorithm to monitor capacity and that controls the charge profile. That is why you must adapt a new battery.

Edit: @WelshGas beat me to it..

 

[Loz2286]

I have added these to my shop. Ideal for checking leisure batteries or your alternator
Small compact and easy to use. Good for checking the leisure battery in the beach
http://www.vwcaliforniaclub.com/kevshop.html
Thanks for looking

Hi

The link doesn't work for me.

 

[Mr T]

I’m guessing that as that original post was 9 years ago a lot has changed since then. Certainly the Kevshop bit, which the link points to.