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Discussion Starter #1 (Edited)
I see the quick release is on the positive. General consensus when disconnecting the battery for whatever reason is negative first. Is the negative first rule purely because of safety reasons, i.e. if you did have to use a wrench to undo the positive & accidentally touch the chassis with the wrench while doing it.

Are there any purely electrical reasons why you should undo the negative first. If so, why is the quick release on the positive ? Is it in case of a fire & not for maintenance ?

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Are you sure there isn't a quik release on the megative side?

Eve peugeot I've had has quick release on both terminals - it's just the negative side is a real pain to get to and usually requires taking the battery cover off.
As for which one to remove first, as far as I'm aware, it was the best procedure to remove the ground terminal first back when you needed tools to disconnect the battery terminals to prevent a short if the spanner contacted the body when removing the none grounded terminal.
 

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Discussion Starter #4
Yes its on the positive only. Peugeot must have it there for a reason.

I understand the physical safety reasons for taking off the negative first, however I was wondering about any purely electrical reasons ? I would hazard a guess there aren't any since its just too easy to pop the positive off. I could be wrong though, possibly its easy access for fire prevention?
 

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Discussion Starter #5
Also, what sort of ECU data loss can I expect if it's disconnected on a 2009 207 for half an hour ?

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There is no electrical reason not to disconnect the battery positive first. The fact that it has a quick release eliminates the danger of earthing the positive terminal whilst disconnecting.

It is important, with Peugeots, to allow the BSI to "go to sleep" before disconnecting. See here for the full procedure and reasons.

Afaik, there is no time period associated with ECU data retention. Data is either written to non-volatile memory (i.e. retained indefinitely) or it is lost when power is removed. One assumes that the designers have made appropriate choices. However, if the above disconnection procedure is not followed, memory can become corrupted, such that key registrations are forgotten, and the like. In such cases, Peugeot Planet 2000 diagnostic system has to be used to recover some corrupt functions, but others are overcome by the reboot procedure (sometimes multiple attempts are required).
 

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Discussion Starter #7 (Edited)
There is no electrical reason not to disconnect the battery positive first. The fact that it has a quick release eliminates the danger of earthing the positive terminal whilst disconnecting.

It is important, with Peugeots, to allow the BSI to "go to sleep" before disconnecting. See here for the full procedure and reasons.

Afaik, there is no time period associated with ECU data retention. Data is either written to non-volatile memory (i.e. retained indefinitely) or it is lost when power is removed. One assumes that the designers have made appropriate choices. However, if the above disconnection procedure is not followed, memory can become corrupted, such that key registrations are forgotten, and the like. In such cases, Peugeot Planet 2000 diagnostic system has to be used to recover some corrupt functions, but others are overcome by the reboot procedure (sometimes multiple attempts are required).
Great, thanks for this. I hope the designers did make the appropriate choice as I will be disconnecting. I read in a few places that some trim settings were lost & would need to be learned again once the car is driven & it may run a bit rough for a while, not sure if this applies to Peugeots though.
 

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The 3 minute rule is the only thing you need to worry about ignore this and you risk a non starting car.

As for the quick release most modern peugeots have this on BOTH terminals but on some models you cant see the negative terminal till you pull the battery forward

I bought a peugeot 307 last week accident damaged roof non functioning and drivers window stuck half way would not budge even using planet done a reset following 3 minute rule window now works roof needs a boot catch and it will work too but without the reset window would never have worked.
 

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... I read in a few places that some trim settings were lost & would need to be learned again once the car is driven & it may run a bit rough for a while, not sure if this applies to Peugeots though.
I have encountered this on old Suzuki Vitaras, X90s and Cappuccinos. New Suzuki models from 1997 did not suffer. My guess is the industry, as a whole, has not perpetuated this issue beyond about 1999.
 
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