Sean Very North
New Member
In your opinion ....
Drop-in car battery DIY?
- Thread starter danroonie
- Start date
How about we get back to the topic of the post that started the thread?
Vigo
Solar Addict
In order to change the battery of a stop-start vehicle in any way you first need to know what the vehicle is monitoring and what it expects to see. As far as i know, basically all stop-start vehicles use shunts or current sensors at or near the battery terminals to watch power in and out of the battery. From this we can easily infer that the vehicle expects to see certain correlations between current and voltage signals based on what it thinks a stock battery should do. This in addition to other signals like HVAC request and engine coolant temp etc, is how it determines whether auto stop-start should be allowed or disallowed, whether the system is in a fault mode due to poor battery state of health, whether to restrict other electrical loads to preserve battery energy, etc.
Unfortunately, even factory service information usually won’t go into full detail on this stuff and will only give you enough to be able to fix it (if it has broken in a normal/predictable way..) but not necessarily enough to modify it and stay within the lines to avoid faulting out (ie trick it into working in an unintended fashion). There are LOTS of stories about dealerships unable to resolve stop-start issues, and im not saying every single one of them has a real badass on staff but it lends credence to the idea that even having access to all factory service information very well may not be enough.
Obviously if you put a smaller battery into a stop-start vehicle it would appear similarly to a stock battery that is somewhat degraded, but what happens if you install one with a higher resting voltage, totally different peukert factor, and higher capacity? The system may not recognize those conditions as poor or suboptimal and fault out for THAT reason, but that’s not the only possibility.. almost all monitored circuits or systems have ‘windows’ of acceptable signal range, outside of which the sensor/circuit is assumed to be reading inaccurately and thus the system takes some kind of action, usually: storing a trouble code, giving the driver a warning, and disabling/limiting some functions. Lots of signals are also cross-referenced against other signals when those signals should change in some kind of predictable relationship to each other. ‘Checking plausibility’.
So, what im saying is dont spend a bunch of money installing a different starter battery in a stop start vehicle unless you’re ok making it a new hobby of reverse-engineering some poorly documented programming, OR you have seen someone else do the exact same thing on the exact same vehicle and have it work. Theres a pretty good chance a car will react to a ‘better’ battery by giving you some ‘signal out of range’ or ‘signal implausibility’ errors and refusing to work. ?
Unfortunately, even factory service information usually won’t go into full detail on this stuff and will only give you enough to be able to fix it (if it has broken in a normal/predictable way..) but not necessarily enough to modify it and stay within the lines to avoid faulting out (ie trick it into working in an unintended fashion). There are LOTS of stories about dealerships unable to resolve stop-start issues, and im not saying every single one of them has a real badass on staff but it lends credence to the idea that even having access to all factory service information very well may not be enough.
Obviously if you put a smaller battery into a stop-start vehicle it would appear similarly to a stock battery that is somewhat degraded, but what happens if you install one with a higher resting voltage, totally different peukert factor, and higher capacity? The system may not recognize those conditions as poor or suboptimal and fault out for THAT reason, but that’s not the only possibility.. almost all monitored circuits or systems have ‘windows’ of acceptable signal range, outside of which the sensor/circuit is assumed to be reading inaccurately and thus the system takes some kind of action, usually: storing a trouble code, giving the driver a warning, and disabling/limiting some functions. Lots of signals are also cross-referenced against other signals when those signals should change in some kind of predictable relationship to each other. ‘Checking plausibility’.
So, what im saying is dont spend a bunch of money installing a different starter battery in a stop start vehicle unless you’re ok making it a new hobby of reverse-engineering some poorly documented programming, OR you have seen someone else do the exact same thing on the exact same vehicle and have it work. Theres a pretty good chance a car will react to a ‘better’ battery by giving you some ‘signal out of range’ or ‘signal implausibility’ errors and refusing to work. ?
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