As the comprehension, why the battery should be registered, is poor between BMW users and even service centers, very often this procedure is simply skipped. The battery is replaced, and that’s it. Just sit and drive.

The proportion of vehicles with unregistered batteries – more than half!


How to recognize such a situation?

1. Car, older than 5+ years – no registered battery, even the battery installed at the moment, is not OEM;

2. SOH has reached ../F5/F5/F3 negative (!) value. Minimal SOH value: -2 .. -10 %;

3. battery charge/discharge balance ../F5/F5/F2 is not correct (correct: Ah of charging should exceed Ah of discharge for 4 .. 6%).


IBS: SOH value marked


IBS: total charge/discharge energy values marked


What are the consequences of such a situation?

SOH – negative? IBS system is not able to measure the capacity of the battery anymore, because it’s “aging” calculation component has determined, that the battery has aged. Accordingly – the warning regarding low charge state works improperly and also “surplus” consumers are not disconnected in such a situation. Of course, if the system doesn’t know the correct capacity of the battery, it’s full and correct charging is not ensured.


Incorrect Charge/Discharge values? In this case, SOC is calculated using simplified algorithms, not takin in account “past” indications. The inadequacy of charge/discharge counters can be due to IBS problems, or even, possibly, due to overfilled registers of these values (the vehicle has such remarkable mileage, that there is “not enough space” for the records).


The remark about diesel engines. Very common situation – the error messages regarding the performance of glow plugs. In the error list – all glow plugs, in the best case in the error message description is mentioned as “activation disturbed” or similar. In the worst scenario – simply “activation”. What is 90% of the case the service specialists are doing? Exactly – they replace the glow plugs, not even testing them. After “repair” the error message repeats? Then they replace the management module of the glow plugs. This also didn’t help? So there is no solution. Wher the true problem hides?

Unfortunately, the cause of the problem is completely different. Because of IBS problems (or, for example, due to reduced calculated remaining capacity or due to unexpected drop of the battery voltage), the glow plugs are prematurely (by purpose) disconnected. The glow plugs are a very powerful consumer.

In the situation, when the amount of energy, left in the battery, is not known, or it’s very small (truly, small, or IBS calculated is as small), or the onboard voltage in the moment of warming up the glow plugs is lower than required (or it drops rapidly), the starting of the engine is set as primary target. Accordingly – the “large” powerful consumers are disconnected.

Of course, the sellers of glow plugs and management modules don’t complain about this situation, but if we look from the side – endless sorrow stories from acquaintances or in the internet forums already for a long time are not even interesting.


Petrol engines. In the case of petrol engines, the following “defect” is possible – long cranking (at least 4 seconds). As already mentioned in other entries, the cause of this problem can be also the other hidden defect – oil pressure (insufficient oil pressure in the moment of starting or registered decreased oil pressure during previous driving sessions). But also the IBS system can be the “guilty” one. If the real technical condition of the battery is not known, IBS can regularly check it’s starting voltage/current – ability to start the car. For this purpose, the starter will turn the engine for at least 4 seconds (during this time the consumed current and the voltage of the battery), but the engine will not even try to start.


The second reason, why IBS will perform the procedure, mentioned before – during the previous starting, decreased voltage of the battery has been registered. Obviously, IBS has made mistake in its calculations (determining power parameters of the battery) and hurries to re-measure them. IBS is not totally “dumb”, and don’t perform such checks for the cold engine or, for example, with low SOC (calculated by IBS itself), but waits for a next starting of the warm engine.


So, if the car (sometimes + for warm engine) starts for a long time, additionally to self-evident things, for example, fuel pressure, also the (hidden) problems with the oil pressure have to be checked, also the IBS system (is the battery registered, are the IBS data reliable, SOH parameter) needs check-up, and, of course, the condition of battery terminals have to be checked.

Even poor contact of battery terminals can be a cause, why sometimes, when everything as if is in order with electricity supply (the starter “turns” perfectly), the car doesn’t want to start for a long while. Most probably, in the moments, when the contact is poor, IBS has detected reduced onboard voltage in the starting moment and hurries to check the technical condition of the battery.