battery wiring

[davel]

Sorry not boat related, well only in as much as it gets us to and from the boat, but our Vauxhall Corsa seems to have the battery leads the wrong way round. The red (orange) lead goes to the neagative post and the Black lead to positive. It always starts but does need a bit of cranking. This morning I went to check to see if there was a charge getting to the glow plugs. First I checked the battery to see roughly what condition it was then checked from positive to Engine block -- nothing, then Matt noticed that the negative terminal had a positive symbol on it, so I tried from new proper positive to block and got a reading. Then I checked the heater plugs and they were on all the time and went off when the ignition was turned to the heater position. Has some Numpty wired it up wrong or am I a numpty and missing something?

[Nickhlx]

Sorry not boat related, well only in as much as it gets us to and from the boat, but our Vauxhall Corsa seems to have the battery leads the wrong way round. The red (orange) lead goes to the neagative post and the Black lead to positive. It always starts but does need a bit of cranking. This morning I went to check to see if there was a charge getting to the glow plugs. First I checked the battery to see roughly what condition it was then checked from positive to Engine block -- nothing, then Matt noticed that the negative terminal had a positive symbol on it, so I tried from new proper positive to block and got a reading. Then I checked the heater plugs and they were on all the time and went off when the ignition was turned to the heater position. Has some Numpty wired it up wrong or am I a numpty and missing something?

 

 

Which post is the thicker / larger ?

 

Nick

[DHutch]

Sounds like they have simply used somewhat misleading cable colours.

- Can you traced the orange cable, does it go to the block/chassis? If so, thats that story over.

 

 

Daniel

[Nickhlx]

I seem to recall that it is possible to use a battery "the wrong way round" and without "drama" if its flat when you "re-assign" the polarity, but whilst it will work, it will exhibit very low capacity and high self discharge...

 

The experts will be along soon though or when the sun goes down...

 

Nick

 

[matty40s]

I once had a lime green Fiat 1000, and it went round the corner for a local "mechanic" to do some work on it as the windscreen wipers had given up. He brought it back and next time I tried to start it, smoke came out from under the bonnet, lifted said bonnet and all the wires were smouldering. He had put the connections on muxed ip.

[Tony Brooks]

I seem to recall that it is possible to use a battery "the wrong way round" and without "drama" if its flat when you "re-assign" the polarity, but whilst it will work, it will exhibit very low capacity and high self discharge...

 

The experts will be along soon though or when the sun goes down...

 

Nick

 

 

 

Yes, correct about 45 years ago before alternators. If you try that now on a vehicle you will end up with a very expensive bill for all the electronics I expect.

 

If you fully discharge the battery and then recharged it the "wrong way round" OFF the vehicle it might work. I go with the odd coloured c able. The cables need tracing.

[Nickhlx]

Yes, correct about 45 years ago before alternators. If you try that now on a vehicle you will end up with a very expensive bill for all the electronics I expect.

 

If you fully discharge the battery and then recharged it the "wrong way round" OFF the vehicle it might work. I go with the odd coloured c able. The cables need tracing.

 

 

Tony,

 

The alternator will still present charge to the vehicle electrics at the correct polarity - it's only the battery that is subjected to the voltage the "wrong way round".... and as such performs very badly - presumably its "last ditch attempt" before it dies completely..

 

Nick

[Tony Brooks]

Tony,

 

The alternator will still present charge to the vehicle electrics at the correct polarity - it's only the battery that is subjected to the voltage the "wrong way round".... and as such performs very badly - presumably its "last ditch attempt" before it dies completely..

 

Nick

 

Connect a battery to a vehicle in reverse and the first thing that will happen is the alternator diodes will conduct and the uncontrolled current flow will burn them out. The car radio will also be damaged and if the ignition is turned on the the reverse polarity at the ECU will also have interesting results. All this is without running the engine.

 

If you can somehow get the battery charged in reverse initially and then fit the battery it will work as you suggest . I said you could do that off the vehicle, but any attempt to do it on the vehicle would most likely end up with fried electronics. Even an apparently flat battery could still provide sufficient current to damage an IC I would have thought.

 

In fact unless you have one of the very old transformer only chargers I doubt a modern one would even attempt to reverse charge a battery.

[MoominPapa]

... if the ignition is turned on the the reverse polarity at the ECU will also have interesting results.

 

Small point: most ECUs will be powered even when the ignition is off, so that wouldn't save you.

 

 

MP.

 

Edited to correct apostrophe crime.

Edited April 19, 2010 by MoominPapa

[Nickhlx]

Connect a battery to a vehicle in reverse and the first thing that will happen is the alternator diodes will conduct and the uncontrolled current flow will burn them out. The car radio will also be damaged and if the ignition is turned on the the reverse polarity at the ECU will also have interesting results. All this is without running the engine.

 

If you can somehow get the battery charged in reverse initially and then fit the battery it will work as you suggest . I said you could do that off the vehicle, but any attempt to do it on the vehicle would most likely end up with fried electronics. Even an apparently flat battery could still provide sufficient current to damage an IC I would have thought.

 

In fact unless you have one of the very old transformer only chargers I doubt a modern one would even attempt to reverse charge a battery.

 

I completely agree - my point was when the battery was completely flat ! " and without "drama" if its flat "

 

and then to use it in the reverse polarity to what it was intended. However I think we agree - it's a most unlikely scenario and would require some "careful fiddling" to get it into this situation deliberately, or some luck, which obviously would not have been intended...

 

On the other hand, it could have been completely flat and someone initially charged it up the wrong way, (whilst on the bench) and then it was fitted to the car - relatively easy to do if it has studs or the flat connectors...

 

Nick

[Gibbo]

Reread OP carefully.

 

The answer is in there for all to see.

 

Hint.

 

What will you measure from battery +ve to heater terminals with ignition off and on?

[Pretty Funked Up]

a bit but if it was wired back to front wouldnt it start copper plating the chassis???

[WotEver]

What will you measure from battery +ve to heater terminals with ignition off and on?

Exactly the same as you;d read to the headlights with them off or on...

 

Tony

 

a bit but if it was wired back to front wouldnt it start copper plating the chassis???

Not if he fitted anodes.

[RLWP]

Sorry not boat related, well only in as much as it gets us to and from the boat, but our Vauxhall Corsa seems to have the battery leads the wrong way round. The red (orange) lead goes to the neagative post and the Black lead to positive. It always starts but does need a bit of cranking. This morning I went to check to see if there was a charge getting to the glow plugs. First I checked the battery to see roughly what condition it was then checked from positive to Engine block -- nothing, then Matt noticed that the negative terminal had a positive symbol on it, so I tried from new proper positive to block and got a reading. Then I checked the heater plugs and they were on all the time and went off when the ignition was turned to the heater position. Has some Numpty wired it up wrong or am I a numpty and missing something?

 

"positive" to engine block - nothing means the "positive" is really the negative.

 

Richard

[davel]

--- or am I a numpty and missing something?

 

I am officially a Numpty, I should have checked more carefully ---

 

 

Which post is the thicker / larger ?

 

Nick

 

 

Sounds like they have simply used somewhat misleading cable colours.

- Can you traced the orange cable, does it go to the block/chassis? If so, thats that story over.

 

 

Daniel

 

--- the Black cable goes to the thicker post and the Orange goes from the smaller post to the block.

 

 

Reread OP carefully.

 

The answer is in there for all to see.

 

Hint.

 

What will you measure from battery +ve to heater terminals with ignition off and on?

 

As I said I am a Numpty and as such I have not a clue what I will measure, but thinking about it I guess that I was completing the circuit with the ignition off but why no reading with ignition on?

[Gibbo]

As I said I am a Numpty and as such I have not a clue what I will measure, but thinking about it I guess that I was completing the circuit with the ignition off but why no reading with ignition on?

 

Because when you turned the ignition switch to "heat" you connected the heater terminals to what you thought was battery negative (through the ignition switch) but this was actually positive and your other meter lead was connected to the same place (because you thought it was negative).