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The engine computer software designers know that the engine will start most often with a state of charge of perhaps 60% so for whatever reason and anything above that is a luxury. Well that is what it seems like anyway so if the question is how to extend your battery life, then put it on a maintainer every few months. Quote
There is an easy way to fix this and ensure the battery gets fully charged by the alternator and lasts far longer than the manufactures intended.
The charging system is as already said smart, it`s intent is that when the vehicle is under ICE power it should charge said vehicle as little as possible, this is to leave room in the battery for maximum regeneration, to enable this to happen the computer needs to know the SOC of the battery. Disconnecting the sensor on the negative black lead of the starter battery disables this smart system, the computer then instructs the alternator to charge in standard default mode (continuous charging at between 13.8 and 14 3 volts), same as the old days, the benefit is, battery lasts longer, No stop/start, a fully charged battery at all times, no need to register new battery and the car will now accept any lead acid battery as long as the sensor is not reconnected, if that occurs another AGM must be used. There are no down sides to this other than a very slight increase in fuel consumption. My cars have just passed their UK MOT`s with the sensor disconnected, there are NO EML`s and the stop/start light stays yellow (off) on my C-Class coupe and goes out(off) on my SLK.
I have been running my 2 Mercs with the sensor disconnected for the last 8 months, try it, if not happy reconnect, it`s only like a failed sensor.
PS, If the battery is mounted inside the vehicle an AGM or similar spill proof battery must be used.
Rob.
I failed to update my other thread, but I will comment on my experience trying the procedure you mention.
My truck is a North America spec 2012 LR4 5.0 V8.
Experiment 1. Disconnected BMS sensor and replaced with straight ground cable. Result was a charging system fault on dash.
Experiment 2. Cleared fault and replaced BMS sensor ground strap but disconnected wiring harness connector to BMS sensor. Result was a charging system fault.
Experiment 3. Disabled BMS sensor via IIDTool. No fault, but over time charging voltage migrated back to the 13.2-13.5 volt realm regardless of engine RPM, which makes me think the "smart" strategy is still in play somehow.
My conclusions so far are that:
1. It is not possible to run the truck in factory configuration but BMS sensor removed without triggering a charging system fault.
2. Disabling the BMS via the IIDTool provides some short term benefit in charging voltage, but the system seems to migrate back toward crappy performance.
3. Resetting the vehicle/disabling the BMS sensor provides some short term improvement (charging voltage tracks at 14.2-14.5V) for a while after either of the aforementioned operations, but migrates back toward crappy performance.
Maybe the control logic is different in the Euro spec version and it works for you guys. Or, if you see a problem with my methodology to run the truck without the bms sensor, by all means, please let me know.
For the time being I think us North Americans are stuck with the crappy charging algorithm.