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Old Mon, Jul-02-2018, 05:44:03 AM   #881
bimmerdriver
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Default Re: MSS52 / MSS54 / MSS54HP Binary Modification Tool

Quote:
Originally Posted by geargrndr View Post
Two answers...

Ideally.... you always use some kind of a charger that:

1. has a 'programming' setting that puts the system voltage up in the 14-15 range and holds it there, and
2. supports enough current (amps) so that it can maintain that voltage level while regardless of might be activated/drawing during the flash period.

There's a whole debate about how BMW now specs some 100A charger and so people think it needs 100A of actual current to program but that's BS. Even granting that F-series do apparently suck a lot more power down, its not remotely the "70A" or whatever it is that BMW says someplace. I'm pretty sure that's a massive misinterpretation of a combination of CYA on their part, and, the fact that in order to spec a quality, reliable, dealer-abusable unit, it also happens to be a high amperage unit. Like if you want a really reliable pro-use generator, you could end up with way more wattage than you need cuz you can't get a low power one with the best quality.

But we're back here in the ancient times of E46's anyway, and things aren't nearly so problematic. To keep an 'ignition on but blower fan off and door closed' E46 at voltage, its generally in the single digit amps not 100's. Its really not a big requirement.

But... Practically/pragmatically... IME, a rock solid battery and no major consumers on in the car will manage a quick 'data only' flash fine, as long as your car has no issues (and the battery is truly fully charged / no issues). Honestly the bigger danger is that you kick the cable out with your foot or it falls out because it didn't quite seat perfectly.

In the real world:
- I have flashed my cars on a solid battery only plenny of times.
- If I'm working on somebody elses car I always put a charger on that can supply up to 25A, because - CMA too, and, I'd hate to have the one time freak-brick be on sombody elses' ride.
- Even on my cars, if I'm programming for any length of time - like more than one quick flash - I'll hook up something. But sometimes that well might be one of the couple little ~1A-ish tenders I have, just as 'light insurance'.
- If I'm flashing the program too, (not just data) then I'll prob hook up a bigger charger, because of the increased flashing/programming time and increased hassle if it bricks mid-flash

So... yes ideally best if you have a fat charger on it with a 'programming' mode, but, a known good/charged battery and tender should be fine.
I agree with much of what you say. The requirement for high current chargers is valid for newer BMWs (although, perhaps not 100A), but not for the E46. I have an HP laboratory power supply that I use as a battery charger / power supply while coding. When I set it to the float voltage (13.6V) with the key turned on, the car will draw around 10A. (That's with all accessories turned off, although my car has DRLs.) While you can probably get away without a charger if you have a new battery, depleting a battery reduces its life. It's better for the battery and safer if you use a charger. I suggest getting a good quality charger that puts out at least 10A.
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