Sprinter MY2019 Emergency Battery

While looking at the Daimler Vans Upfitter portal today I notice the attached new Technical Bulletin about preserving the "Emergency Battery" when you disconnect the main battery for more than an hour. I had no idea that the 2019 Sprinters had an Emergency Battery.

Does anyone have more knowledge about this battery? Wondering if this only applies to the new gas engine Sprinters as the Technical Bulletin says the emergency battery powers the ignition unit? Or is this just an error and the emergency battery powers the ECU, which makes more sense.

https://www.upfitterportal.com/en-us

Could be the same or original one that is used to power the factory alarm system when the main is cut....

OK - got into the EPC and the new 2019 (VS30) Sprinters do have a battery backup system for the 7G-TRONIC PLUS and 9G-TRONIC transmissions.

Don't have WIS access so I can't speculate on the function this battery provides to these transmissions. It clearly does not power the ignition as quoted in the attached Technical Bulletin I posted above.

After a little more research – determined that a second auxiliary or backup battery are very common on many Mercedes-Benz models. Some non-USA NCV3 Sprinter had a 12V/10-12AH auxiliary battery (E34 BUFFER BATTERY FOR STARTING PROCESS).

But the smaller 12V/1.2AH backup battery now in the new VS30 Sprinters is related to the 7 or 9 speed automatic transmission that both have electric transmission oil pumps. The attached clip from the 9G-TRONIC transmission system description describes the functions of electric oil pump that might need a backup battery for the emergency park function.

Here is a link to a bit more info on this battery. . .

https://www.autohausaz.com/pn/15987305-000000004039

This discussion on MB World forum seems to clarify the function of the backup battery with G-TRONIC transmissions.

https://mbworld.org/forums/e-class-w213/698580-how-put-into-neutral-dead-battery.html

“The backup is to shift the car into park only, to keep it from rolling away, not the other way around. There is no emergency neutral shift mechanism.

The 725 transmission actually has 3 ways to put itself into park as safety backups, but it can only release the way it normally does with battery power (it actually runs the transmission's auxiliary oil pump and hydraulically lifts the park pawl locking pin). The backup battery power can be used to force it into park if the whole system dies electronically, but it's a one-way solenoid that pulls a pin that retains a spring so it snaps into park.”

. . . and then there is this from owners manual display messages pages.

Does anyone know where the auxiliary battery is located in the VS30 cutaway chassis? The owners manual says on pg. 115 in the engine compartment or base of the passenger seat. I can't find it in either location, yet have an error message for a faulty aux battery.

Shadow5501 said:

Does anyone know where the auxiliary battery is located in the VS30 cutaway chassis? The owners manual says on pg. 115 in the engine compartment or base of the passenger seat. I can't find it in either location, yet have an error message for a faulty aux battery.

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Is it possible that the battery is not installed? That would probably give the error message.

Boxster1971 said:

Is it possible that the battery is not installed? That would probably give the error message.

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The error message started after a month of storage with the main battery disconnected. I skimmed the owners manual too quickly and didn’t catch the sentence about the emergency battery. Not that it matters, since I can’t find it to disconnect it! Will pull fuse 32 next time it goes back into storage. So I’m sure it’s out there...somewhere.

I think the emergency battery recharges with driving so we’ll see if it comes back to life during a road trip.

Shadow5501 said:

The error message started after a month of storage with the main battery disconnected. I skimmed the owners manual too quickly and didn’t catch the sentence about the emergency battery. Not that it matters, since I can’t find it to disconnect it! Will pull fuse 32 next time it goes back into storage. So I’m sure it’s out there...somewhere.

I think the emergency battery recharges with driving so we’ll see if it comes back to life during a road trip.

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I hope you realize this is a very small battery. It is only about 4 x 2 x 2 inches in size. same size as a typical 1.2AH backup battery used in most home alarm systems.

because of its small size it could be well hidden.

I've just found some more info on the emergency battery location and how to replace it:

https://xenons4u.co.uk/blog/mercedes-benz-auxiliary-battery-malfunction-explained/

And it does include info specifically for Sprinters!

Keith.

Boxster1971 said:

I hope you realize this is a very small battery. It is only about 4 x 2 x 2 inches in size. same size as a typical 1.2AH backup battery used in most home alarm systems.

because of its small size it could be well hidden.

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Yes, I am familiar with the battery and the function it provides - this is my 10th or so Mercedes. I just haven’t been able to find it! That said, I have only invested about 15 minutes in looking so far.

Oh, and after 6 hours of driving yesterday it did not come back to life. No real surprise there, when you kill a lead acid battery that dead, it generally stays dead.

Cheyenne said:

https://xenons4u.co.uk/blog/mercedes-benz-auxiliary-battery-malfunction-explained/

And it does include info specifically for Sprinters!

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Reading through that, i would *guess* that the EmergBatt is either tucked up above the passenger's left foot
*or* (more likely, i think) under the "hump" on the top of the instrument panel.

Why there?
Because that's where MB hid the SKREEM security module in the older T1N models.
It stands a good chance of being relatively easy to get to.

--dick

Hello everyone new to the forum. The auxiliary battery is under the driver’s seat rear left corner. Hope this helps

Update: Dealer replaced the auxiliary battery under warranty at no charge. All is good again. I still haven’t laid eyes on it, but hopefully I won’t have to do so...

Brand new 2019 I had disconnected the main ground wire down by the gas pedal while I worked on the van - it has sat fro probably 5-6 weeks like this. Finished up interior work today and reconnected it and now it says 'Aux Battery Malfunction'

Van literally has 50 miles on it - I just now saw the bulletin about also pulling the fuse when parked for a long time with the ground disconnected. Did I just completely drain that little battery and will some drive time reset/charge it??

Thanks! and unfortunately closest dealer in 4-5 hrs away (van was trucked here hence the low miles)

Agnes16 said:

Brand new 2019 I had disconnected the main ground wire down by the gas pedal while I worked on the van - it has sat fro probably 5-6 weeks like this. Finished up interior work today and reconnected it and now it says 'Aux Battery Malfunction'

Van literally has 50 miles on it - I just now saw the bulletin about also pulling the fuse when parked for a long time with the ground disconnected. Did I just completely drain that little battery and will some drive time reset/charge it??

Thanks! and unfortunately closest dealer in 4-5 hrs away (van was trucked here hence the low miles)

Click to expand...

A small battery float charger can bring the batteries back if theyre too low. Mercedes side that hooks upto the auxiliary batteries reads voltage as well as distributes a trickle charge to the small batteries while the vehicle is running.
if you can get the auxiliary batteries back up to 11.3 volts and it hold that charge the system will take care of it and get the battery back up to 13.4v.
Other errors may arise when the battery loses voltage , traffic sign and distance assist, lock issues , transmission park issues . All will usually go away after the buffer /aux battery voltage is brought back up to Mercedes tolerances . {11.3-13.5v}

It would certainly be helpful to know:
1. The auxiliary battery Must be disconnected for storage along with the main battery disconnect.
2. For the 2019 MB 3500XD Cutaway Cab Chassis, the small auxiliary battery is located under the drivers seat. (Left)
3. The auxiliary battery can also be disconnected by pulling the #32 fuse (10 amp) located on the side of the drivers seat base under the vinyl curtain.
Failure to disconnect the auxiliary battery during storage periods will result in a dead battery, inoperative Distronic cruise control and other issues which require the dreaded Appointment/Code Clearing

Would you need to disconnect the negative main battery AND pull fuse 32 to avoid the SRS warning light when removing seats?

Fairly sure the answer is that it’s not related. For SRS just make sure all electrical connections to the seats are firmly connected before pressing the start button. If you do that it doesn’t matter what the battery state is.

Seems when removing (and unplugging) the seats causes SRS warning light to go on and need to be reset at dealer. Some suggest (and state have had success) disconnecting the main battery with the negative ground lift to prevent this, which didn’t help for me. I still got the light.