E Torque 48 V Battery

[AFD]

The starter isn't the wear item, it's the 12v battery. The AGM batteries in our vehicles hate charge cycles. They like to stay topped off. If you're constantly bringing it down to 60-65% SoC due to stop/start you're going to have to replace it much sooner than you'd expect. This is why our batteries are known as "junk". If you don't use stop/start and don't let it sit for long periods of time they easily last 5 years.

If you're a stop/start enthusiast you're lucky to get two years out of them. If a vehicle comes in with <10v we replace it. We don't bother testing it as they will recharge and test just fine then be dead 3 days later.

Agree that the 12V AGM appears to be junk, just from reading everything around here for years.

So do you know 100% in the eTorque whether the accessories are pulling from the 48V or the 12V with engine shut off during start/stop?

If everything is drawing from the 12V during that time, then I could see that being a valid negative to using start/stop. I was always under the impression that the 12V is used for nothing other than the initial engine start, therefore making absolutely no difference as to whether or not you use start/stop.

The vehicle is started by the 12V and then the BSG charges the 48V, while the 48V charges and maintains the 12V (with engine on or off, afaik).

Using ESS does seem like unnecessary wear on the engine. Personally, I just manually disable it at every start and only re-enable it if I'm coming to a red light (or construction stop) that I'm expecting to sit idle at for several minutes. I also turn down my radio and turn off the HVAC at that time, just to avoid any unnecessary draw.

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[alphawolff]

Agree that the 12V AGM appears to be junk, just from reading everything around here for years.

So do you know 100% in the eTorque whether the accessories are pulling from the 48V or the 12V with engine shut off during start/stop?

If everything is drawing from the 12V during that time, then I could see that being a valid negative to using start/stop. I was always under the impression that the 12V is used for nothing other than the initial engine start, therefore making absolutely no difference as to whether or not you use start/stop.

The vehicle is started by the 12V and then the BSG charges the 48V, while the 48V charges and maintains the 12V (with engine on or off, afaik).

Using ESS does seem like unnecessary wear on the engine. Personally, I just manually disable it at every start and only re-enable it if I'm coming to a red light (or construction stop) that I'm expecting to sit idle at for several minutes. I also turn down my radio and turn off the HVAC at that time, just to avoid any unnecessary draw.

The MGU charges the 48V battery pack. The 48V then converts this to 12-14.6v to charge and maintain the 12v battery akin to a normal alternator charging cycle. It does not maintain the 12v battery when the engine is not running, as all power is reserved for the eventual re-crank of the engine. It's a really small battery pack. Its only job is to make stop/start more seamless and substitute as a normal alternator. It does not interact with the 12v system in any other way.

If you're seeing ~12.8V during an engine stop event, that's just surface voltage slowly bleeding off. Depending on your batteries health this might bleed off instantly if it's already discharged/low state of health. In a 4XE the 400v's IDCM will continuously charge and maintain the 12v battery even during engine off events, including when the vehicle isn't being driven. If you have a 4XE and plan on storing it for awhile, you can fully charge the 400v battery and it'll maintain your 12v battery while you're gone. I had to hammer our sales team into charging our 4XEs/Pacificas during PDI/Intake so they weren't constantly dying while sitting on our lot for 12 months.

 

[AFD]

It does not maintain the 12v battery when the engine is not running, as all power is reserved for the eventual re-crank of the engine.

With engine off during start/stop it's not maintaining the 12V, but with the engine off (overnight) or while running it does, correct?

Still failing to see how using start/stop on the eTorque would have much, if any detrimental effect on the 12V.

I just started monitoring my voltage readout recently and it's a bit odd, but fairly predictable. The system likes to keep my 12V very close, if not exactly at 12.0V overnight (viewed with engine off in "run"). After starting, the system immediately climbs up to either 14.5 or 15.0V (closer to 15V if the temps are sub-32° and the 48V is drained from the cold or ~14.5 if it's above freezing). Once the 48V is recharged (usually after my 30 to 45-minute commute), it drops down and stays closer to 13V. When the engine shuts off during a start/stop, the voltage reads exactly the same as whatever it was just prior and never seems to change at all. Shutting the vehicle down manually and then re-checking the voltage immediately after usually reads ~13V.

Those are just my observations with the OEM 12V AGM I've had for a little over 2 years, but I really never paid much attention to the voltage readout with the vehicle manually shutdown (in "run") til just recently.

 

[alphawolff]

With engine off during start/stop it's not maintaining the 12V, but with the engine off (overnight) or while running it does, correct?

Still failing to see how using start/stop on the eTorque would have much, if any detrimental effect on the 12V.

I just started monitoring my voltage readout recently and it's a bit odd, but fairly predictable. The system likes to keep my 12V very close, if not exactly at 12.0V overnight (viewed with engine off in "run"). After starting, the system immediately climbs up to either 14.5 or 15.0V (closer to 15V if the temps are sub-32° and the 48V is drained from the cold or ~14.5 if it's above freezing). Once the 48V is recharged (usually after my 30 to 45-minute commute), it drops down and stays closer to 13V. When the engine shuts off during a start/stop, the voltage reads exactly the same as whatever it was just prior and never seems to change at all. Shutting the vehicle down manually and then re-checking the voltage immediately after usually reads ~13V.

Those are just my observations with the OEM 12V AGM I've had for a little over 2 years, but I really never paid much attention to the voltage readout with the vehicle manually shutdown (in "run") til just recently.

No. The 48V acts like an alternator. Whatever a normal alternator would do. So engine running? Charging. Engine off? Not charging. Sitting overnight? Not charging.


The 4XE, on the other hand, does charge and keep the 12v topped off (usually, anyway.)

 

[Tncdrew]

The idea of saving fuel for a few seconds at a stop, at the detriment of loss of instant oil pressure during startup, heat soak etc. while you're waiting at an intersection seems ludicrous to me. Not to mention the added tax on a charging system.
I mean, how much fuel are you really saving in the long run.

Maybe I'm completely wrong here, but it just seems silly.
I don't do much stop & go driving, so I'm probably not the target candidate.

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