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Post by dv52 (Australia) on Sept 18, 2022 23:01:01 GMT
kator77 : Hi - there's nothing wrong with your command of the English language (I wish that my Spanish was as good)! So, as I understand - the objective here is to allocate as much of the battery's Cold Cranking Amps (CCA) to the starter motor by switching off the Brake lights (and possibly, ALL lights) while the ignition key is turning-over the engine. hmm.......... interesting!! CCA is defined the electrical amperes that a new, fully charged 12V battery can deliver for 30 seconds while maintaining 7.2V at 0°F (-18°C).
Are you sure this change is worthwhile - or asked another way, how much of the battery's capacity is actually used by the Brake lights during cranking?
Here's my calculation based on the equation Watts = Volts * Amps = Volts2/ ohms = Amps2 * ohms
- If the tail lights use incandescent lights : the brake lights will use a W21W lamp on each car side. So, each lamp consumes 21 Watts. Using my formula above, each lamp has a nominal design resistance of about 7 ohms (@12v). When the battery volts fall to 7.2 V, each brake light will draw about 1 Amp - so the 2 x brake lights draw a total of about 2 Amps from the battery during the lowest voltage for the definition of CCA
- if the tail-lights use LED lamps: the brake lights will be a group of 23 x individual LEDs with a electrical load of 6 Watts/car-side. Using the same analysis as for incandescent lamps above, the equivalent battery load for LED based brake lights will be about 0.6 Amps during the lowest voltage for the definition of CCA
The typical CCA of a modern battery is of the order of multiples of 100 amps - so the brake lights don't add much additional electrical load to the battery during the cranking period!!
Don
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Post by dv52 (Australia) on Sept 19, 2022 21:41:24 GMT
kator77 : OK.... If you have gotten 9 years of faithful operation from the one battery on your Merc - then I suspect that the remarkable achievement is primarily the result of the battery (albeit I'm not discounting that the vehicle design may have made a contribution). From a fundamental design perspective and notwithstanding the decade difference in build between both cars, my guess is that both the Merc and the Golf use USD/ODX modules (these are industry standard with pretty much the same technology). In the Golf, ALL the modules are put to sleep shortly after the ignition key is withdrawn to reduce battery drain. However, there is still a quiescent current draw from the car when in the comatose state. This residual electrical current isn't much and it's increased when the car owner installs options such as anti-theft system and (some) cameras. But of course the basic problem is the way the car is used (or rather, is not used) - it is just not an ideal modus-operandi !! Coincidentally, I have just completed making a simple harness for a friend that uses her mk7 Golf in much the same manner as you have described (i.e. very infrequently). As I said, it's not complicated - It involves bringing out two wires to the front grill that are connected at the other end to the battery terminals and terminating these wires onto a 2 x pin weatherproof connector (I included an in-line fuse into the +ve wire (located close to the battery terminal) for added electrical protection). When the car is garaged, it is hooked-up to a trickle charger onto which I have spliced a mating plug. Because the plug on my harness is outside the engine bay, it's easy to make the charger connection and I've even secured both the plug and the charger socket in a manner so that no damage is caused if the driver forgets to disconnect the trickle charger before driving away!!
Don
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Post by dv52 (Australia) on Sept 22, 2022 23:17:47 GMT
kator77: As a general rule - if you have purchased a genuine BEM battery, then it will have a sticker containing ALL the requisite information for entry into the adaptation channels. Of course, if you have this data - use it! The problem arises when a non-BEM battery is installed (as is often the case)! IMO, the actual serial number of the battery doesn't carry any usable information for the module. I've seen countless instances of MQB platform cars that have been factory coded with a string of ones as the serial number. The point of changing the serial number to anything that's not the old serial number is to tell the Gateway module that a new battery is installed (the actual serial number doesn't matter). As for the question of "Fleece" versus "Binary AGM" - it really depends on how the new battery is constructed. "Fleece" refers to the more popular AGM batteries that are almost universally available to mere mortals (like us both) - these batteries have the normal flat plate design. However, if you have purchased a "spiral-wound" AGM battery, which is a special higher spec. battery (expensive too) - then use the setting "Binary AGM". But, my guess is that your new battery is "Fleece"!! As for the manufacturer ID, if the battery manufacture is Johnson Controls, use JCB, if it's Varta use VA0 - but my guess is that it makes little difference! to the way that the Energy Management System operates! Don
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Post by dv52 (Australia) on Sept 30, 2022 0:02:33 GMT
kator77 : I've never found the need to use a "memory-saver" when swapping a battery - I just drive the car for a bit after the swap and the errors clear. But yes, I am aware of commercial devices that plug into the OBD port that keep module memory alive during the swap process. There are ostensibly 2 x versions; a 9V battery version and a 12V version (see picture below - it plugs into the ciggy socket on a donor ca/jump-start battery).
So, I'm not sure about your auxiliary power supply - but I very much doubt that the voltage on the USB socket will be able to keep the volatile memory in the module live during the battery swap. The supply from the USB port will be 5V and likely the memory in the module will also use 5V at the chip - but this is not the point of connection for the "memory saver". The OBD port pin that connects to the "memory-saver" is pin#16 (see below)
As you can see - it needs +12V. Yes, some commercial memory savers use a 9 Volt battery - but this simulates a low-end battery voltage. I would be very surprised if 5V was sufficient as a surrogate +12V supply to keep volatile memory alive
Don
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Post by dv52 (Australia) on Oct 1, 2022 23:17:48 GMT
.............It is true that the LED warning lights on the dashboard "disappear", but the Star-Stop, for example, continues to give "failure" in the infotainment - "vehicle status"...............
kator77 : hmm....... first, well done on making your own "memory saver". As I have said, battery changes have not been a problem for me (and I've done lots).
Anyhow, dealing with this issue is ostensibly a personal risk-management matter and hence, there are no correct answers (many different solutions are equally acceptable)
So, in respect of the your point above (I've not faced this error message) - but I suspect that the error might be related to the battery monitor control module (it's called j367 in the wiring diagram) that lives on the negative battery terminal connector- see below:
If your car has SS, it will have a J367 unit installed. The role of J367 is many-fold, but one of it's tasks is to provide a continuous stream of data about the battery condition to the car's Energy Management System (EMS) over the life of the battery (yes, the EMS is sufficiently sophisticated to tailor the battery charging regime to the battery age).
If the battery voltage is lost when replacing a battery, this data stream is interrupted and that's why it's important to reset the EMS's "history records" for the old battery. The presence of J367 is also the reason why the negative battery lead on a jump-start battery/charger should NEVER be connected directly to the negative battery terminal of the car battery (because J367 must always be "in-circuit" to maintain an accurate record of battery usage)
So, when changing the battery, the EMS needs to be told that a new battery is installed - this resets the old battery's history records and restarts the EMS information collection function as well as updating data about the new battery - liked changed Amp-hour rating, if applicable)! This is done by changing 4 x adaptation channels in the Gateway module which lives @ address hex19 on the CAN network. I suspect that this might be useful in dealing with the SS error - maybe?
In any event, the use of your "memory saver" will not obviate the need to tell the car's EMS that a new battery has been installed
Don
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