Complete Newbie - Please help with battery polarity & ribbon cable

[Leolion2177]

Afternoon folks.

Can anyone please help a total newbie.

Opened a piece of equipment that we own that needed a replacement 12 volt battery put in.

The cables from the battery are connected to the circuit board via a flat ribbon cable. The cable is light grey in colour with the top "stripe" in red. As the cables in the equipment are red and black I assumed the red cable was positive.

I connected the red first and then when I attempted to connect the black , got a large spark and burning smell. Chickened out and went no further as I was afraid of damaging the pcb (which I maybe already have???)

There are no markings anywhere to advise on + or -. Any advice on whether the sparking is normal? or anyway I can check if I have the polarity wrong????

Thanks in advance.

Leo

 

[alfa88]

Advice

Here's what I'd do to verify polarity. With no battery connected and the power switch off measure resistance from each of the connectors that go to the battery to the screw tops or the chassis. The one that has zero ohms is the negative terminal. This works in almost every case.

 

[davenn]

Afternoon folks.

Can anyone please help a total newbie.
Opened a piece of equipment that we own that needed a replacement 12 volt battery put in.
The cables from the battery are connected to the circuit board via a flat ribbon cable. The cable is light grey in colour with the top "stripe" in red. As the cables in the equipment are red and black I assumed the red cable was positive.
connected the red first and then when I attempted to connect the black , got a large spark and burning smell. Chickened out and went no further as I was afraid of damaging the pcb (which I maybe already have???)
There are no markings anywhere to advise on + or -. Any advice on whether the sparking is normal? or anyway I can check if I have the polarity wrong????
Thanks in advnce.
Leo

HI Leo,
no the sparking is NOT normal are you totally sure you connected the red striped one to the positive of the battery ? as laid out in you photo ?
if you look closley you will see that they have doubled up the wires
1st and 3rd (1st = red stripe) = positive and the 2nd and 4th = negative
nice and easy, tho a little unconventional

I would be very suprised if they used the red strip for the negative
a really good reason to ALWAYS note how wired are connected before removing them off a bit of gear
I will often make some notes on paper as sometimes it can be a day or 2 before reassembling something

That looks like a regulator chip, with 5 pins, to the left of the connector ( not the vertically mounted one below of the connector) google the part number on that and see which pin is the positive input and trace that back to the connector and out to the end of the cable

Dave

 

[davenn]

Afternoon folks.

Can anyone please help a total newbie.
Opened a piece of equipment that we own that needed a replacement 12 volt battery put in.
The cables from the battery are connected to the circuit board via a flat ribbon cable. The cable is light grey in colour with the top "stripe" in red. As the cables in the equipment are red and black I assumed the red cable was positive.
connected the red first and then when I attempted to connect the black , got a large spark and burning smell. Chickened out and went no further as I was afraid of damaging the pcb (which I maybe already have???)
There are no markings anywhere to advise on + or -. Any advice on whether the sparking is normal? or anyway I can check if I have the polarity wrong????
Thanks in advnce.
Leo

HI Leo,
if you look closley you will see that they have doubled up the wires
1st and 3rd (1st = red stripe) = positive and the 2nd and 4th = negative

nice and easy, tho a little unconventional

Dave

 

[Resqueline]

Put a 12V 23W bulb in series with one of the battery terminals for fairly safe testing. The lamp will light fully if there's something wrong, and dim or no light if it's ok.

 

[duke37]

I thought that the striped wire went to pin 1 of the plugs. The polarity could be anything.

 

[Resqueline]

I thought that the striped wire went to pin 1 of the plugs. The polarity could be anything.

Yes, that's right, wire # 1, going to pin # 1. Any sane engineer would use any opportunity to use a red stripe as positive, but then some ribbon makes have a blue stripe - so...