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Old 06-20-2017, 09:56 AM   #101
n7slc
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Quote:
Originally Posted by TehRegulator View Post
I just reversed this mod... Not worth it.
Quote:
Originally Posted by Perscitus View Post
Please elaborate. What negative impact have you noticed and hopefully documented? Or are you just worried about the marginal extra load on the alternator?
Yes, please elaborate.
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Old 06-22-2017, 06:33 AM   #102
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Did this two weeks ago and it definitely works. Car would drop to 10 volts constantly before the modification, and my AP would shut off multiple times on my 35 mile trip to work daily. This was all with a brand new Optima Yellow Top since my OEM battery took a ****.

Now I haven't seen it below 12.9 and its only a quick dip there for the most part before its back up to ~13+ - I may do the alt-s fuse as well to stabilize it a bit more. The car starts stronger and my AP has not shut off a single time since (that alone was worth it to me).

I also do a hard calculation of my gas mileage every time I get gas (reset mileage and fill till pump shut off every time). I drive pretty consistent every day, and would average 27.5 MPG before the modification. Iv'e filled up twice now since this mod and it came out to 27.4 & 27.7 MPG. If there is a gas mileage hit from the extra load because of this, it is negligible.
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Old 06-22-2017, 11:02 AM   #103
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Has anyone done the ALT-S fuse upgrade on a 2015+? I saw maybe 1 or 2 people talk about it.
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Old 06-22-2017, 11:18 PM   #104
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There are at least a few FA20DIT equipped Subarus with the ALT-S fuse mod both in North America and throughout Europe, even more in Australasia.

WRXs, FXTs, Levorgs, Legacy/Liberties.

Both the 7.5A and the 10A micro-fuse MK3 flavors or a home-made, slightly less elegant and far larger solutions will work.
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Old 08-14-2017, 06:19 AM   #105
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after my original battery died at 24k miles, (not unheard of), I will now implement this mod again.. i been watching my car NOT charge as i drive around all the time, and with my short trips, i think this could hurt my battery a bit. im going to make it charge always, or ill end up with the same situation again in a couple years.
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Old 08-14-2017, 09:28 AM   #106
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27K and no problems yet.
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Old 08-17-2017, 09:07 AM   #107
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i had a huge idea.. (in my eyes...) you know how LED's can flicker at idle.. like my wifes new JDM Astars.. thqat is because they are not getting enough voltage.. i think this alternator "fix" would fix that 100%. and not let the voltage drop at idle when LED's start to flicker... hmmm.. maybe ill do it on her car too..
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Old 12-11-2017, 11:37 PM   #108
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Some real-world before/after results showing what this does in conjunction with the ALT-S fuse replacement: https://forums.nasioc.com/forums/sho...postcount=1400

Suffice it to say, AGM closed or spiral cell as well as most *-ion type batteries finally get some optimal charging voltage instead of operating in the perpetual state of deepening discharge (thx stock setup).
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Old 12-12-2017, 12:09 PM   #109
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I think having an ECM controller alternator is good.

If you watch the voltage on the battery you should see the following:
~12.5V during light acceleration or constant throttle
~13.8V - 14.3V if your headlights are on
~13.8V - 14.3V if you have hit >2K RPM and have let of the throttle (coast)
~13.8V - 14.3V if you are WOT above 4K. (need to confirm this because my eyes are more on the road)

I have agree the factory battery is weak, and after 3 years I swapped it out for a Deka AGM Intimidator battery.

Per Deka:
Optimum charge voltage is ~15.1V - 13.6V (from <40F to >120F)
Maximum charge voltage is ~15.4V - 13.9V (from <40F to >120F)
Optimum float voltage is ~14.2V - 12.8V (from <40F to >120F)
Maximum float voltage is ~14.5V - 13.0V (from <40F to >120F)

I'd rather be slightly under optimum than over. I assume car does not have the ability to float charge the battery, so I can focus strictly on charge voltage. To me, this is well within the range required for the battery.

I logged the car today on the way into work, and I'll post up a graph that illustrated the above conditions.

More than anything, I just think the factory battery doesn't hold its charge well. This mod seems to compensate for this by just brute charging the battery as long as the car is on.
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Old 12-12-2017, 12:36 PM   #110
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Its not that simple, and the conditions and ranges you mention are just the tip of the iceberg. Log away though.
Battery Voltage logging and overlaying with various operating conditions using SSM params over CAN was done on Subaru's long before the 2014/15s first rolled off the assembly lines in Japan.

And it didn't look all that pretty even back then...
and yet still 'within spec' though according to SoA and their very professional dealership network.

Bone stock even with a brand new or fully trickled charged and maintained battery, these newer Subarus will see dips of Battery V down into the 10-11V range, and average a mid 13V while steady-throttle cruise charging.

Barely adequate for lead-acid batteries, not so much for AGM and the like. Especially for garage queen or weekend toy duty or short city commute trips. The batteries will just end up in a perpetual state of discharge and eventually barely crank or just outright no longer hold a charge, short some cells, sulfate up, etc.

No start stop or cylinder deactivation gimmicks with these econoboxes so no need for floating point alt output and ECU DC control (which in practice translates to sensor reference voltage and output voltage fluctuations, aux system and gadget/gizmo issues).

As we know, all previous gen Subarus did just fine without this extra control circuit and its not needed here too, short of hitting some CAFE standards or satisfying other useless regulation.

At the end of the day, its really whatever works for each driver. Keep the charging system stock and replace stock batteries every few years, switch to AGM or other replacements and replace those too - just maybe a tad less often, ALT-S replacement, ECU control circuit disable or both and potentially still replace batteries every few years, maybe never or only once before you get rid of the car.

Last edited by Perscitus; 12-12-2017 at 01:26 PM.
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Old 12-12-2017, 03:01 PM   #111
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I think from the data points, it appears the alternator is providing too much voltage. The idea would be so stay under 14.4V to prevent the battery from boiling.

I also don't think an alternator should be working at 100% capacity every time the car is on. The alternator increase voltage to deal with component load from the accessories in the car; headlights, radio, etc.

It is debatable whether or not the alternator will prematurely wear due to running at 100% all the time.

Your car, your alternator, just providing a counter point to everything here.
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Old 12-12-2017, 03:27 PM   #112
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Quote:
Originally Posted by Boggie1688 View Post
I think from the data points, it appears the alternator is providing too much voltage. The idea would be so stay under 14.4V to prevent the battery from boiling. I also don't think an alternator should be working at 100% capacity every time the car is on. The alternator increase voltage to deal with component load from the accessories in the car; headlights, radio, etc. It is debatable whether or not the alternator will prematurely wear due to running at 100% all the time. Your car, your alternator, just providing a counter point to everything here.
Fair enough and thanks for doing so.

The alternator DC was well below 100% most of the time during both of these ~20 minute logs. No battery V dips below 13V and no spikes above 15V in either case, voltage average and mode in the happy-zone for AGMs (14.3-14.6V). Battery temp perfectly fine during both hot summer days stuck in traffic as well as single digit winter night highway cruises.

On cold starts the alternators output a steady 14.7-15V which fairly quickly drops as the engine, alternator, battery warm up to say 14.2-14.6V.
Perfectly fine and actually good for AGMs, not so much for lead-acids... for those the OE output is better, minus the dips down to 10.x-11.x.

Optima Red/Yellowtops, Interstate AGMs, Bosch AGMs on various recent-gen Subarus and Toyotas with the ALT-S fuse replacement and/or the change outlined by the OP here hold a charge longer and show a higher resting voltage vs stock after 5-7-14 days rest.
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Old 12-12-2017, 03:35 PM   #113
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So the TL;DR is ALT-S fuse and an Optima Yellow/Red to fix the horrible stock battery?
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Old 12-12-2017, 03:44 PM   #114
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ALT-S fuse, ECU control circuit disable and any good AGM battery which will enjoy the supplied voltage, yes, one possible way to skin this cat.

On the other hand, to each his/her own. Even the OP gave up trying to make his point.
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Old 12-12-2017, 04:58 PM   #115
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Pardon the noob question here but is it possible that this voltage issue could cause LED headlights/foglights to burn out prematurely? And could it possibly affect the MAF harness and sensor?
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Old 12-12-2017, 05:47 PM   #116
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Certainly possible as voltage dips can impact LEDs, HIDs, sensors, many accessories too... all depends on how sensitive each is to voltage dips and if using drivers/ballasts, how sensitive those are.
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Old 12-13-2017, 01:15 PM   #117
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Quote:
Originally Posted by Perscitus View Post
Certainly possible as voltage dips can impact LEDs, HIDs, sensors, many accessories too... all depends on how sensitive each is to voltage dips and if using drivers/ballasts, how sensitive those are.
This is great info, thank you. My foglights, headlights and one DRL all went out at the same time and I could not figure out for the life of me what the cause was. I initially thought it was a bad ground but I checked and the grounds were fine. Definitely going to give this fix a try now before replacing the MAF sensor and harness on my car.
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Old 12-13-2017, 03:17 PM   #118
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Related to this, looks like even Subaru took note of the battery charging fiasco and modified the control circuit logic somehow in their latest reflashes across effectively the entire fleet of cars sold today.

https://forums.nasioc.com/forums/sho...postcount=1287

If you're on a stock tune or can grab a hold of a COBB map versioned off of one of these new/est Subaru reflashes... it would be great to see some before/after Battery V logs.

Might be the only way we'll see what the net effect is of whatever they've done in the control routines.

Particularly because whoever types up the release notes is more confused than Mme Yellen.
And with the rampant robo-translate from Japanese to English, the best we can hope for is something along the lines of 'All your base are belong to us'.

Last edited by Perscitus; 12-13-2017 at 03:28 PM.
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Old 12-14-2017, 07:03 PM   #119
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Just found this whole thread today!

Took my car in to the dealership today. Cause my car needed to be jump started last night took it to OReilly, they tested the battery (said the battery is on its way out) and alternator (alternator is good).

The dealership said the battery was dead and was going to replace it since the car is only a year and a half old. The dealership told me they were going to reflash something for the ECM but they could not since my Access port plug was plugged in. So they just replaced the battery. They have put in an Interstate battery as confirmed by the parts manager as well.
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Old 12-15-2017, 10:40 AM   #120
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Quote:
Originally Posted by Perscitus View Post
Related to this, looks like even Subaru took note of the battery charging fiasco and modified the control circuit logic somehow in their latest reflashes across effectively the entire fleet of cars sold today.

https://forums.nasioc.com/forums/sho...postcount=1287
Is this as simple as going to the dealer and asking for a reflash? They don't seem to push these out and notify customers of new updates.
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Old 12-15-2017, 11:30 AM   #121
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Yup indeed - quote the PAK to them to really get their blood boiling lol.

Just make sure you're on a stock or Stage0 flash and if you normally run COBB or any other tune,
make sure they have an updated definition or support for these new ROMS or you'll have to wait for COBB to update using you as the guinea pig,
then have your tuner reapply the tune on top.

Effectively something like this:

Stock tune (any version) -> go to Dealer and flash to latest, get them to verify the PAK used and CID/CALID after

COBB tune -> unmarry, flash back to Stage0 -> go to Dealer and flash to latest -> attempt to marry COBB back
if it works, already supported, if not you'll have to wait for COBB to update their definitions, re-apply your tune on top.

ECUTEK tune -> wait for Ecutek to have the updated CIDs/CALIDs in their DB, have tuner migrate the tune to base off of those.

Last edited by Perscitus; 12-15-2017 at 11:38 AM.
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Old 12-15-2017, 11:40 AM   #122
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Quote:
Originally Posted by Perscitus View Post
Yup indeed - quote the PAK to them to really get their blood boiling lol.

Just make sure you're on a stock or Stage0 flash and if you normally run COBB or any other tune,
make sure they have an updated definition or support for these new ROMS or you'll have to wait for COBB to update using you as the guinea pig,
then have your tuner reapply the tune on top.

Effectively something like this:

Stock tune (any version) -> go to Dealer and flash to latest, get them to verify the PAK used and CID/CALID after

COBB tune -> unmarry, flash back to Stage0 -> go to Dealer and flash to latest -> attempt to marry COBB back
if it works, already supported, if not you'll have to wait for COBB to update their definitions, re-apply your tune on top.

ECUTEK tune -> wait for Ecutek to have the updated CIDs/CALIDs in their DB, have tuner migrate the tune to base off of those.
I'm on the stock tune. I've got an apt tomorrow for the HK audio recall, I'll ask about the ECM update then. Thanks!
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Old 12-15-2017, 11:45 AM   #123
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Quote:
Originally Posted by SycsFinest View Post
I'm on the stock tune. I've got an apt tomorrow for the HK audio recall, I'll ask about the ECM update then. Thanks!
Sounds good. Please get them to confirm the CID/CALID after they're done.
They will know exactly how to do this, takes 5 seconds so don't take any BS excuse.

Let us know what the CALID is to help understand where these latest reflashes are in terms of revision and naming convention.

Ideally they should give you:

CID/CALID before (when you come in)
PAK file applied (reflash)
CID/CALID after (once done)

If you have any data logging capability and can capture Battery Voltage in the log, please please log your trip to and from the dealership.
If they indeed apply the PAK file that has the charging logic change, it might be apparent what it results in from before/after logs.
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Old 12-15-2017, 11:51 AM   #124
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None of the recent COBB OTS notes call out charging specifically, maybe v300?

v302 –

2017 USDM WRX CVT/MT: Fixed an issue where real-time tuning and real-time map switching was disabled for the "MAF Calibration" table which caused the ECU to always use the reflashed values only for this table.
Note: Please REFLASH a v302 map to address this.

v301 –

Fixed bugs associated with v300 maps preventing real-time and launch control feature changes from working.
Addressed issue causing check engine light from being thrown for Stage2 maps

v300 –

Supports latest Subaru ECU revision. Merged Subaru calibration for latest injector timing changes.
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Old 12-15-2017, 12:35 PM   #125
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I know very little about COBB or their AP but I believe those are too old (even v302) and pre-date the latest batch of SoA PAK files for the 2015-2017 WRX MT/CVTs.

What's the release date or timestamp on those v300 301 302 maps?

If before late April/May or maybe even June/July 2017 (COBB would need some time to get the latest ROMs off stock cars, check if they need to re-define or just add them to their DB)
then they are definitely not built on top of the newest CALIDs (maybe the Dec-2016 ones).

Also, release notes from COBB wouldn't likely mention any changes to a ECU routine they can't or have no interest in defining/controling
and their client base likely doesn't care about (charging, alt control routine fits that bill).

Last edited by Perscitus; 12-15-2017 at 12:58 PM.
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