308 T9 Battery Management Unit -- any testing data ?

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Our 308 t9 2.0Hdi has been suffering a rash of seemingly unrelated fault code readings and after being left standing a week, the battery was almost flat. (Battery is a couple of month old, correct fit).

For months, the time to go into economy mode for the electrics has been just about 5 or 10 minutes, whereas on our C4 -- same engine and age) it's near half an hour.

It's not an alternator issue -- charging voltage is a healthy 14.7 or thereabouts.

I am increasingly suspecting the battery management unit, but as they are quite an expensive piece I really would like to test it first.

Does anyone have any data for testing them -- what to look for on what pins or links ?

Thanks, Mike.

[GiveMeABreak]

I really don't think this won't be causing the drain. It is just used to test and measure certain battery dynamics and then passes this onto the BSI to fine tune the energy management.

If you have a drain, there is likely to be something else causing the drain and might be worth doing a parasitic drain test.

[Paul-R]

Pretty sure he's misreading the multimeter. 0.25 is not 25mA but 250mA. Which is also quarter of an Amp and sounds rather high to me. Or maybe that's normal for an American vehicle such as a Jeep?

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Well, just for once got it right first time !

Swapped out a known good battery management box from my C4 onto the Pug and hey presto ! Rash of fault warnings gone and economy mode gone from 5 minutes aood to 20+.
Not too bad a job, but there are 18 connections to the thing.

Mike.

[GiveMeABreak]

So we're talking 2 separate things here. You are referring to the Battery and supplies management unit, which is nothing to do with the Battery Charge Status Unit I thought you were referring to, so glad you have a result.

Just beware these may be totally different parts between the C4 and the 308 T9, and if not the correct one can cause issues with systems and equipment down the line (different electronic architectures and equipment).

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Hi Marc..

Thanks for your note regarding potential conflicts. I think I'm safe enough wiith this one. For this piece, there seems to ba a commonality of part number across quite a few Pug and Citroen models. As it happens our Pug and the C4 are pretty close manufacture dates and fortuitously both have the same engine ECU.

I think it's also an interesting issue, this whole question of what certain components are called. I've lost count over time of the occasions in Citroen's own parts list where on one page something is referred toas 'x' andthen elsewhere, 'y'.

One thing worth notong is that this device is stuffed full of fuses or fusible links (?) and I have never seen these mentioned anywhere in reference to electrical issues on htese cars. There are also one or two mini blade fuses, as well. If you do ever wind up replacing the piece, be aware that for all its hefty price tag, you don't get the mini blade fuses with it. Penny pinching or what ! Weirdly however, you do get a new support bracket.

Mike.

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PS.

Should have added, for anybody pondering the job, this unit doess not require coding in. Just plug and play.

Mike.