993 Battery Charger - Positive or Negative earthed ?

[ByronBayChris]

Just me and my basic questions again.....I am hooking up a trickle charger  and have used them before on my other cars.  However, I am not 100% certain if the battery is negatively earthed.    I cannot tell if the cable from the negative terminal runs to the chassis.

 

Is it a 100% certain answer either YES or NO - or do I need to remove the battery just to be sure.

 

Thanks in advance as always.

 

BBC

[ByronBayChris]

Ok. I'm getting positive earthed.

So what is the best place to attach the lead from the charger to the chassis? Do I use the hood release mechanism?

[wasserkuhl]

That should work.

 

If in doubt just remove the battery to be sure.

 

I just connect the charger to the relative terminals on my C3 and that is positive earthed, works fine!

[ByronBayChris]

Sfeve

Connecting leads to both terminals....... Isn't that a BAD thing to do - or is that an old wives tale?

[randall]

Can't think of any reasons why you would not connect your charger directly to battery terminals.

[Russ]

attach it straight to the battery.

 

I thought positive earth was something for 'special' English cars?

 

I think the only reason you earth to the chassis when jump starting is to try and minimise any possible ECU damage

[Peter M]

....the only reason you earth to the chassis when jump starting is to try and minimise any possible ECU damage

The last connection to earth when jump starting a car is done away from the battery itself to minimise the risk of the spark igniting any hydrogen gas that the battery has generated.

So I guess you could say it is to minimise the risk to the ECU in a sort of indirect way!

As for using a battery charger, I agree, connect straight to the terminals and then turn it on at the wall.

[OZ930]

Positive has a big terminal and a + symbol adjacent to it in most cases, usually a red colour or tag over (new) or around it.

 

The wet cell battery produces hydrogen, which is flammable, so the practice was to connect the earth last anywhere on the engine or chassis (metal parts) away from the battery, so if there was a spark then you avoid the chance of the battery exploding.

 

+ve earth ?  I think I would check again.

 

OOPs, beat me to it 

[ByronBayChris]

aaah - get it now.

 

Connecting to both terminals directly is BAD when JUMP STARTING.

 

Connection to both terminals directly is OK when charging.

 

I think I might make a small bracket with a set of leads from the battery to make it a simpler job each time - rather than having to unload the luggage area each time.

 

Thanks for your help guys.

 

BBC

[ByronBayChris]

All good - just threw it on the terminals and the CHARGE light on the trickle charger came on (and no sparks or fire = good)

 

Thx

[pocketscience]

I've had one of those fancy "smart" chargers for a while. It came with a plug to wire directly to the battery, then you only have to connect the plug to the unit to start charging. Installed that and the plug is hidden under the carpet near the battery. Super simple to charge now when I'm away for extended periods of time (work = mostly overseas travel unfortunately).

 

G.

[Simonoz]

Chris

Just a thought re batteries.

On all my 911's over the years, and anything else collectable thats not driven daily, I have had my mechanic fit a manual kill switch near the battery.

I just turn the battery off when I park the car.

No drain on the battery, and more importantly, no fire risk.

It hasnt affected the elctronic brain on my cars at all, never had an issue.

The fire risk was the reason I started doing this, and competition cars have to have them anyway, so it added up.

It also makes them hard to steal if you take the red key with you.

Rgds

[pocketscience]

Yup, I put one in my 924, but it was a PITA for 2 reasons 1) the clock was never right, 2) the radio stations defaulted back to rubbish.

[cyberpunky]

The main reason you attach negative lead to engine/chassis when jump starting is to avoid resistance(voltage drop caused by poor connections in wiring) and to avoid creating a spark at the battery, not to protect ecu. Often when cars need a jump, it is partially due to poor grounds in electrical system(which means more current is needed and therefore making car harder to start if battery is in poor condition too). By fitting neg lead either direct to motor or chassis, it minimises the chance of a poor ground pushing load higher, as it bypasses all potential poor connections between battery and starter.