AI19 - What drains the Sprinter Battery

[ITSNO60]

This pretty much explains it........the dead battery stuff starts at 2 minutes in.

https://www.youtube.com/watch?v=lTj5j6pe0MA

[ChristineM]

Originally Posted by ITSNO60

This pretty much explains it........the dead battery stuff starts at 2 minutes in.

Perfect!

I recall seeing somewhere that there is a cord we can disconnect near the accelerator, that and something under the drivers seat.

Thanks for this Laugh too, always a treat to be made to laugh!

[pfm41]

Originally Posted by ChristineM

Perfect!

I recall seeing somewhere that there is a cord we can disconnect near the accelerator, that and something under the drivers seat.

Thanks for this Laugh too, always a treat to be made to laugh!

Sprinters have a battery disconnect by the throttle pedal that should be disconnected whenever it sets for awhile. I always disconnect it when I don't anticipate starting it for a week. It is very simple, press the red tab and pull. The cable that is disconnected is the only cable connected to the negative post of the battery so nothing will drain it unless AS connected something else to the negative post. I stored mine all winter long and checked the battery every month and charged only if needed. In the spring it was as simple as pushing the cable back on the post and starting it up. Mine was a Winnebago Class B but a Sprinter is a Sprinter. You can read about the disconnect in the MB Sprinter owners manual.

[Hawk-ination]

Been reading some posts about the batteries in the newer Mercedes-Benz. I’d just like to throw a general warning out there, even though I don’t have the specific information in front of me.

Many of the newer vehicles DO NOT like to loose voltage or have odd voltages than normal so I would highly suggest checking into a very reliable source before jump starting, unhooking your battery connect, etc.

I have moved away from the sales end of our auto parts business, but I know there are specific vehicles that need to have a battery tender plugged in before servicing a vehicle, and some of the newer vehicles do not like to be jump started. I believe I read the newer model Sprinters are included in this bunch, but I’m not 100 percent sure on that.

I’d ask my MB service advisor but have found either MB or this dealership is very closed lipped about any questions I’ve had so far on our Mercedes-Benz. If you have a reliable service advisor or MB mechanic, and I had a 2020 plus model, I’d be asking them what the best plan of action is in case you need to know how to treat your electrical system on your chassis.

Just FYI, my Volkswagen Touaregs go dead in about a month or less if they sit. There’s a lot of draws on the newer vehicles and the AGM batteries do not hold their voltage well like the old lead acid batteries did.

[uncle_bob]

Hi

Ok, the new batteries all by themselves hold a charge every bit as well as the old batteries. Charge them up, put them on a shelf, they do fine. Unfortunately that's not how we use them in a vehicle.

If anything they are a better battery than what we used to get "back in the day". What has changed is a massive focus on weight. Any vehicle these days gets engineered to be as light as they can practically make it. ( practical = without running the price up to crazy levels).

On the battery side this light weight means putting in the smallest battery you possibly can. Possible is judged by who knows what metric. The result is a battery with very few amp hours ( and not much weight) compared to what a similar vehicle got "back in the day".

Again, this isn't specific to vans or to MB. Pretty much every vehicle gets this treatment. On big trucks, they give you an option to go with bigger batteries. Check out what the standard battery was on the same truck back a decade or two .... hmmm ..... looks bigger than that "big battery" option I just paid big bucks for ... hmmm .....

When Ford sends you the message about your car sitting in storage, it simply says it has shut off further messages "to conserve battery energy". They don't mention anything about the battery voltage getting low. Yes, it's less alarming than the MB message. Maybe they need to reword their alerts

Bob

[DAWg134]

One common cause of MB Sprinter chassis battery drain is due to incomplete microprocessor shutdown resulting from a not-quite-closed door. When you lock the vehicle with the key fob, you should see the lights blink three times - anything less than three times means that a proper shutdown did not occur. Go back, open and shut each door soundly, then re-lock the vehicle and you should see three blinks. Every single door may have indeed latched, but that doesn't mean the sensor necessarily says the door is closed.

The Sprinter has dozens of tiny microprocessor or logic circuits that control various functions throughout the vehicle. When you lock the vehicle, most circuits turn off completely (i.e., powered OFF) whereas others go into SLEEP or MONITOR mode at reduced power consumption. However, if the shutdown process is interrupted by a partially open door, many of the processors will remain ON, drawing an amp or more of continuous current.

I ran an experiment once by inserting a current meter between the Battery Disconnect connector pair located near the accelerator pedal. During a normal shutdown, the battery current momentarily shoots up to 7.5 amps while the doors lock, then drops back down to 4.5 amps. Over the course of the next seven minutes, the current continues to drop in very distinct steps until it reached its final value of 95 mA steady-state. 45 mA is the normal steady-state current draw, but my after-market Viper alarm added another 50 mA.

Leaving the sliding door slightly "ajar"; i.e., closing it gently until it barely latched closed, the vehicle went into a similar shutdown sequence, but the current draw stabilized at 2.5 amps after three minutes. 2.5 amperes of current will most assuredly kill a vehicle battery in a matter of days.

[Mansderm161]

Originally Posted by pfm41

Sprinters have a battery disconnect by the throttle pedal that should be disconnected whenever it sets for awhile. I always disconnect it when I don't anticipate starting it for a week. It is very simple, press the red tab and pull. The cable that is disconnected is the only cable connected to the negative post of the battery so nothing will drain it unless AS connected something else to the negative post. I stored mine all winter long and checked the battery every month and charged only if needed. In the spring it was as simple as pushing the cable back on the post and starting it up. Mine was a Winnebago Class B but a Sprinter is a Sprinter. You can read about the disconnect in the MB Sprinter owners manual.

Mercedes is very aware of their computer systems draining the battery. The infotainment system drains it too as does locking your doors.

Definitely put in a switch to totally turn off the infotainment system. This in itself buys you more time.

After having Mercedes install the 3rd battery in 4 years, Mercedes agreed that unless you drive it every week you should definitely disconnect the battery mentioned in this post as being near the gas pedal.

Now, I have not done that because currently I cannot open my driver door lock with the key...I must use the fob and I don't know if the locks depend on both the chassis battery and the fob battery. I could always climb in the back and I will figure it out soon as I will be away a month and have never left it more than 7-10 days without driving or starting the engine.

The drivers side lock problem, according to Mercedes, will require removing the door and at least $500. Mine has been like this since day 1 and would have been a warranty issue but I failed to mention it. I initially thought it was some kind of security feature but it is not. Make sure you can open all your locks by just using the key.

[MountainLife]

We had a dead chassis battery once and the fob did not work. Actually makes sense when you think about it.

[SWH]

It may very well be that you need to get the work done in this Airstream Technical Bulletin. I have the full copy if you want to send me your e-mail via PM.

We also found at the Mercedes dealer that our 2021 24GT was missing a Mercedes accessory battery, and they installed (one under warranty).

Since getting the work done in the technical bulletin, and getting the accessory battery installed, we have had no further issues with chassis battery drain on our coach.

[StogieMan]

Originally Posted by SWH

It may very well be that you need to get the work done in this Airstream Technical Bulletin. I have the full copy if you want to send me your e-mail via PM.

We also found at the Mercedes dealer that our 2021 24GT was missing a Mercedes accessory battery, and they installed (one under warranty).

Since getting the work done in the technical bulletin, and getting the accessory battery installed, we have had no further issues with chassis battery drain on our coach.
Attachment 419679

It appears that these are two separate issues. The Magnum Inverter replacement or adjustments is for folks with Lithium batteries side and if I read it right charging to those. The other is from Mercedes and seems to be for the chassis battery discharge. Do you happen to have the the info for the Mercedes side by chance?

[SWH]

Originally Posted by stogieman

it appears that these are two separate issues. The magnum inverter replacement or adjustments is for folks with lithium batteries side and if i read it right charging to those. The other is from mercedes and seems to be for the chassis battery discharge. Do you happen to have the the info for the mercedes side by chance?

[SWH]

Originally Posted by StogieMan

It appears that these are two separate issues. The Magnum Inverter replacement or adjustments is for folks with Lithium batteries side and if I read it right charging to those. The other is from Mercedes and seems to be for the chassis battery discharge. Do you happen to have the the info for the Mercedes side by chance?

There’s a lot in the bulletin… unfortunately I can’t attach the whole thing. PM me your email and I’ll send it to you.

[KBW]

My interstate 19's chassis battery died and I had Mercedes check what was drawing current from it. They reported it came from this cable, an airstream add on, which is attached to the chassis battery.

[KBW]

My interstate 19's chassis battery died and I had Mercedes check what was drawing current from it. They reported it came from this cable, an airstream add on, which is attached to the chassis battery.
mbpsca.mktext08.com/p/uy4Tef.jpg

[StogieMan]

Originally Posted by KBW

My interstate 19's chassis battery died and I had Mercedes check what was drawing current from it. They reported it came from this cable, an airstream add on, which is attached to the chassis battery.
mbpsca.mktext08.com/p/uy4Tef.jpg

Have you figured out what that cable is for or goes to? It looks like is thick enough for the Victron Buck Boost but I thought that would have come off the fuse buss bar that is tied to the chassis battery.

[KBW]

Hey Stogie, no I haven't figured it out yet. Haven't had the time but will get to it, but I maintain the chassis battery in the interim

[WeekendBob]

Originally Posted by StogieMan

Have you figured out what that cable is for or goes to? It looks like is thick enough for the Victron Buck Boost but I thought that would have come off the fuse buss bar that is tied to the chassis battery.

Can confirm, that is the 6 Gauge cable to the Buck Boost that is causing a parasitic drain.

“But wait, there’s more!”

At the other end of that cable where it attaches to the Buck Boost, Airstream also ties in the chassis BatteryMinder and SolarMinder. All 3 of those devices have LED status lights. So that's 3 (minimum) Airstream induced parasitic drains on the chassis battery in addition to the Mercedes OEM drains.

To sum this all up, I used an ammeter to check the current being pulled from my chassis battery “at rest" and it registered a .54Ah parasitic draw. That's enough to deplete the 95AH AGM chassis battery in a little over a week if no solar or shore power is being provided.

[KBW]

Very helpful Stogie, in fact this entire thread has been excellent in sorting out this somewhat complicated problem of Chassis battery drain.
I must have dysfunction in the chassis battery minder and trickle charger as the draw down happens when connected to shore power and the van sitting in the sun if I don't turn off the main house power switch. If I turn the house power off while the van is sitting no battery draw occurs.

[StogieMan]

Originally Posted by StogieMan

Fair enough so let me take a crack at it....

On our 2015 and like yours, the tank heat pads, lounge motor, generator and solar panel are wired direct in through the thermal breakers. When the 12V main switch is turned off, these items still function and not disabled. When everything is shut down on the house battery side and no shore power connection, these items still work. Even with the van shut off so they must be drawing from the chassis battery.

Just to follow up and for accuracy, this is not the case. After rewiring our 12V fuse box/120 electrical panel I found out otherwise and this is not the case.

They are wired into a separate Thermal fuse buss though.

On 11/08/22 post #108 on my Mod thread, I clarified this and wanted to do the same here just so that everyone has accurate information.

I wrote then:

"My thinking of what powered these items when power was shut down was all wrong. I thought that they were powered by the chassis battery via the BIM but are not and are powered by the house batteries and just bypassed to the thermal fuse bar that is connected to the house batteries"

Thread here:

https://www.airforums.com/forums/f24...-234941-6.html

[Rocinante]

We gave up thinking about this a long time ago. When we park in storage, we plug in a battery tender and connect it under the hood. Keeps the chassis battery happy, and thus keeps us happy.

I should probably also mention that we disconnect the coach batteries while in storage via a big red switch (BRS). The coach batteries are LiFePO4 and hold their charge indefinitely when disconnected.