geonic said:
So here are my questions:
- Is it definitely necessary to reset the BMS when replacing the battery? I will install the same Varta battery that was built-in from new, so no changes in battery parameters necessary.
Any shunt based battery management system, which the DS BMS is, will gradually drift out of sync with the actual state of charge (SOC) of the battery, so it will periodically recalibrate itself by going through a deep discharge and recharge cycle over a couple of days. When the dealer installs a new battery they will force this recalibration to happen over a few hours. So, if you install a new battery yourself without the tools to do a forced recalibration, your system will be out of sync until such time that it does one of it's periodic recalibrations and then all should be well.
- Would it maybe help to charge the battery to full, then reset the BMS without replacing the battery at all?
A battery will gradually lose capacity over it's life, and so the voltage may be showing fully charged, but the BMS will be telling the ECU that it's not fully charged because the BMS works on an 'bank balance' basis of energy in versus energy out. So, the dealer can also initiate a 'new battery capacity reset' on an existing battery to reset the capacity figure in the BMS to the actual capacity of the installed battery so this mismatch doesn't happen. Unlike the periodic and automatic SOC recalibration described above, I believe this capacity reset procedure can only be done by the dealer.
- Is there a diagnosis unit (like the IID tool) which is capable of resetting the BMS by myself? I have that stuff for my Volkswagens, but unfortunately this doesn´t help with the DS.
I don't believe so. I think only the LR diagnostics can force a SOC recalibration and capacity reset.
- And lastly, what is the best method to charge the battery? Dealer says, directly at the connectors. But I think in this case I will bypass the BMS sensing module resulting in the BMS not recognising the charging at all. Would it be better to connect minus to ground?
With any battery charger, but particularly today's smart multistage chargers which rely on accurately sensing the voltage and temperature at the battery to determine the charge they put in, it's best to attach as close to the battery terminals as possible. However, you are correct that you do not want to bypass the BMS, so the negative should not be attached to the battery post itself, but to where one of the existing wires bolts on, or if you want to be ultra safe - to where the battery negative wire attaches to the chassis ground point.
I should add that all this is just my limited knowledge of how it works based on having a battery problem on my DS, reading the workshop manual, and what the dealer has said he's done. I cannot guarantee it's complete accuracy.