Best way to reconect battery????

[Jerry May]

Could someone tell me the best way to reconect the battery on my C240 in a way I won't blow the rear SAM?... I thought years ago you always took the positive terminal off first, then the negitive.... then put the negitive terminal back on first so everything is earthed when the positive is replaced. My Mercedes Benz manual says do it the opposite way...
Jerry.

 

[television]

Could someone tell me the best way to reconect the battery on my C240 in a way I won't blow the rear SAM?... I thought years ago you always took the positive terminal off first, then the negitive.... then put the negitive terminal back on first so everything is earthed when the positive is replaced. My Mercedes Benz manual says do it the opposite way...
Jerry.

The reason why MB say do the Negative first is that should the spanner touch the chassis or any ground point there will be no danger in shorting the or blowing up the battery.

From an electrical point of veiw, i think that we will all argue till the cows come home as to what is right or wrong.

If you care to put up the first 6 vin numbers 202--- I will look for your specific car and any problems.

Malcolm

 

[Hibbo]

The reason why MB say do the Negative first is that should the spanner touch the chassis or any ground point there will be no danger in shorting the or blowing up the battery.

From an electrical point of veiw, i think that we will all argue till the cows come home as to what is right or wrong.

Malcolm

I don't mean to agrue , but it makes no difference at all. One terminal connected (+ or -) = no circuit, no current flow.
No difference whatsoever


Personally I would switch the ignition on and switch on all the heavy current consumers (full beam, demister etc) so that when the battery is reconnected, any voltage spike would be flattened out.

 

[Ultymate]

The downside of having lots of consumers switched on when you connect is you'll get a fat spark when connecting the last connector and chance igniting any hydrogen fumes which may be around particularly on a battery which is fresh from being charged if the hydrogen in the battery ignites you'll be flattened out

 

[television]

The downside of having lots of consumers switched on when you connect is you'll get a fat spark when connecting the last connector and chance igniting any hydrogen fumes which may be around particularly on a battery which is fresh from being charged if the hydrogen in the battery ignites you'll be flattened out

A friend of mine had a coach, with this huge battery,when he re fitted the thing his son was in the cab with his foot on the starter, we did not find much of it. The next day my friend had hundreds of little tiny holes in his clothes where the acid had eaten them. he was lucky.

Malcolm

 

[Hibbo]

Advice retracted!

 

[psmart]

Advice retracted!

Spoil Sport

It always suprises me, especially in this day and age, that each module doesnt have a simple high-current Zener or Zener-Power Transistor shunt circuit to protect against spikes, high voltage (from wayward chargers) etc. The idea that you cant put 20v onto the car without something blowing up just seems silly. You look at the lengths to which the designers have gone to protect output and input control circuits (take a peak inside an ECU for example and notice the extensive resistor/diode/capacitor circuits on each input)... why not the same on the voltage input?

 

[Jerry May]

Television (Malcolm)

Malcolm, my VIN no. starts WDB2030612F04----. thanks,
Jerry.

 

[television]

I have checked via your VIN and nothing shown or to abserve, so hopefully no problems.

Malcolm

 

[jonathanjhann]

you must take the neg off 1st, if you earth a spanner on the body it wont do any thing, there is already a good earth path. If you take the pos off 1st, you could short the battery between pos and the body and as the earth is still connected, you will create a dead short and a nice explosion followed by a refreshing acid shower!

 

[bibamus]

I was taught that you take off the neg strap first. When reconnecting, attach the neg strap first, then pos. Make sure nothing is turned on when you reconnect to reduce sparking.
I`ve always done it like that, but I suspect loads of people have always done it the other way.
There is probably a mathematical formula that will work out which way causes less of a surge through the system, any Maths professors out there?
Allan

 

[television]

.
There is probably a mathematical formula that will work out which way causes less of a surge through the system, any Maths professors out there?
Allan

Sadly there is no way of knowing, it is a sad situation for our cars that there is no protection.
As PSmart says, a big zener diode, the snag is that if they blow they always go short circuit, not a good situation with the high currents involved here.

One of the best ways would be to use very thin long jumpers when changing the battery, the snag here is that they are easily knocked off, and you cant connect up to a terminal post with a crocadile clip already on it.

A burglar alarm type battery joined into the sytem would work well during the changing process.

I have been working on a simple tool that would soft start the electronics and I am getting some where, there should be no problem getting someone to make it.

Malcolm

 

[eric242340]

best way to re connect

MB recommend the neg side because both mb and bmw are using a grounding system for their computers and modules, ie the computer is activated by neg and not by pos. However they realise there is still a risk. Now they are getting smart and using two batteries. On the 221 models they have a small battery for the engine and a big battery for the aux eqpt. So benzy owners when your rich enough to buy a 221, youll have two batteries to worr:cooly about and one of these affects the ECU. Have a nice day yall.

 

[television]

MB recommend the neg side because both mb and bmw are using a grounding system for their computers and modules, ie the computer is activated by neg and not by pos. However they realise there is still a risk. Now they are getting smart and using two batteries. On the 221 models they have a small battery for the engine and a big battery for the aux eqpt. So benzy owners when your rich enough to buy a 221, youll have two batteries to worr:cooly about and one of these affects the ECU. Have a nice day yall.

I have the same set up with two batteries, I can kill all of the ecu and SAMS by disconnect the rear battery only as they only link during starting when the front starter battery is low. Its OK Eric things can only get worse.

Malcolm

 

[wireman]

When I reconected the battery on my 201 the central locking pump ran and locked all the doors.
It was most fortunate that the key was retrived from the car before I did this.
Subsequent tests showed that this occurs every time you connect the battery and is afeature of the central locking system.
My MOT man did it to a Porche and it cost him £200 or so to get a man to help him into a customers car.

 

[television]

When I reconected the battery on my 201 the central locking pump ran and locked all the doors.
It was most fortunate that the key was retrived from the car before I did this.
Subsequent tests showed that this occurs every time you connect the battery and is afeature of the central locking system.
My MOT man did it to a Porche and it cost him £200 or so to get a man to help him into a customers car.

I think that they should bring back the starting handle and Magnito, there were no problems back then.

Malcolm

 

[CMR]

Battery Issues

Could someone tell me the best way to reconect the battery on my C240 in a way I won't blow the rear SAM?...

Hi Malcolm I notice in your reply to the above you ask for the VIN number as well as describing a reconnection method. Does this mean certain cars are prone to rear SAM damage and some are not depending on their VIN number? What are you able to tell from the VIN number out of interest?

Also quick question: I am going to charge my battery with a C-TEK XS3600 this weekend and probably do it without removing the battery hopefully so is it OK just to switch on the charger after connecting or should I have the car running before switching on? (as I read somewhere previous)

Many thanks for any replies

 

[eric242340]

Best way to reconect

I have checked via your VIN and nothing shown or to abserve, so hopefully no problems.

Malcolm

hi tv, thats observe and not abserve. Ps have you seen my reconect and reconnect?

 

[television]

Hi Malcolm I notice in your reply to the above you ask for the VIN number as well as describing a reconnection method. Does this mean certain cars are prone to rear SAM damage and some are not depending on their VIN number? What are you able to tell from the VIN number out of interest?

Also quick question: I am going to charge my battery with a C-TEK XS3600 this weekend and probably do it without removing the battery hopefully so is it OK just to switch on the charger after connecting or should I have the car running before switching on? (as I read somewhere previous)

Many thanks for any replies

Hello, I ask for the VIN to look up any specific rules that may apply to minimise the risk to ,as you say the SAM's.

One advantage of having the engine running is that the voltage is already then higher at 13.8 volts, then when you join the charger up there is no shock or sudden surge.

Chargers come in many forms, the best ones are the switchable output type, you can join up at trickle and then wind it up to full charge with no damage.


Malcolm

 

[eric242340]

best

Hi Malcolm I notice in your reply to the above you ask for the VIN number as well as describing a reconnection method. Does this mean certain cars are prone to rear SAM damage and some are not depending on their VIN number? What are you able to tell from the VIN number out of interest?

Also quick question: I am going to charge my battery with a C-TEK XS3600 this weekend and probably do it without removing the battery hopefully so is it OK just to switch on the charger after connecting or should I have the car running before switching on? (as I read somewhere previous)

Many thanks for any replies

all sams are suseptible to current fluctuations (signal aquasition module). and on the C class (wont specify which one) dont want to upset anyone the front left and right aquasition modules were defective to start with.:!: