308 T9 2017 Battery Charge Fault

[G1980]

Hi there. I have a 2017 308 SW II 1.6 BlueHDi 120, and a Battery Charge Fault warning light has recently appeared.

When I bought the car I was told that a used alternator had been fitted (9807995580), and have a garage receipt stating that they were unable to program the ECU so an engine light was on. I visited an auto electrician who flashed the ecu with firmware from Peugeot and the ECU light went out, then the stop start system started working and has been running well since. Entering this part number into the Valeo website though suggests it is not the correct part for the car however. I believe it should be a 180amp unit (9810527180) where this is 210amp. Please correct me if I am wrong on this as these units appear to be cheaper in price to what I was expecting and don't state they are reversible etc on the Valeo website.

I have put a multimeter across the battery, and it shows 12.6v, but occasionally will show 14v in which case the warning light will go out, but will reappear shortly later, where the voltage returns to 12.6v and if left running gradually decreases. 14v showing is especially true when starting from cold or after I have charged the battery using a charger.

I have already replaced the BPGA unit with an OEM one as the cover was missing and it was highly corroded, wire brushing the terminals as I went, but this did not solve the issue.

My mate has plugged a diagnostic computer in and the live data shows some alternator output activity which then flatlines after a short amount of time. I will also attach photos of the fault codes, which suggest the brushes have gone (I'm guessing in the regulator?).

We have also unplugged the sensor on the negative terminal of the battery which also made no difference.

Any help or experience would be greatly appreciated. This may be a simple case of replacing the alternator, but given the price of a new one, I would like to eliminate other options first. I can provide the VIN if needed.

Thanks all in advance.

[dram773]

A 'smart' alternator is controlled by the ECU, so I would suggest checking the wiring loom between the alternator and ECU and connections for corrosion etc.
If possible, check with live data / oscilloscope. The signal from the ECU to the alternator should be a square wave that changes with load request - if there is no change it is likely that the ECU is at fault. The signal from the alternator should be a constant square wave. If the signal mirrors the pattern from the ECU, it is more likely to be the alternator.
(It is also possible to disable the 'smart' function to see if the alternator then works normally when not controlled by the ECU but I wouldn't recommend this).

[PaulC5]

I think smart alternators vary the voltage depending on need. If there is little demand it might give around 12.5 volts but if high demand with things like the headlights and window heater on it will give around 14 volts. Try putting on a few things and see if the voltage changes. I first came across this when a neighbour was trying to jump start his car from one with a smart alternator, the good car had to put on lights and heater to get enough voltage to charge the second car a bit. This can also be a problem for caravans wanting to run the fridge whilst moving. I have no idea about the problems you are having though.

[G1980]

Thanks for your replies, I will feed this back to my mate. From what I recall there was a square wave indicating something switching, but the pattern from the alternator was all over the place followed by a flatline. Would you know how to disable the smart function for testing purposes?

We put a heavy load on the battery, switched on A/C, blowers, heated screens etc, but this didn't make the alternator kick in and the battery discharged to under 12v.

[xantia_v6]

Has the battery been replaced? is it the correct chemistry and rating for the car?
If the battery has less capacity than the ECU is expecting, the ECU can allow the battery to run flat before enabling the alternator to charge, because it thinks that the battery should still have reserve capacity.

[G1980]

Hi there, yes the battery is AGM and of the same capacity with a manufacture date of July '23.

[dram773]

On the 208 there is/was a recall for a software update to fix problem of ECU not calling for alternator output. Maybe 308 also affected; I don't know. If you search YouTube for "Peugeot 208 battery not charging" you'll see how to unplug the ECU cable on the alternator and check that the output is then 14V. This is just a temporary check and you perform it at your own risk.
Might be worth contacting local dealer with your VIN to see if your vehicle is affected by the recall.

[G1980]

We changed out the alternator and the problem has gone. Thanks for all your help.