Topic: Engine battery drain is a pain in the A….? (Read 6438 times) previous topic - next topic

My engine battery on. 2021 unity seems to only last about 7-10 days when not in use and setting idle. This is getting to be a real downer when you want to go on a trip and the LTV won’t start. It seems odd to have to disconnect the battery if it sets for a week just to make sure it will start. Cars can go for a month no problem.

Any suggestions why it is happening and what could be tried to fix this. The obvious is leave it p,urged in which is not an option always or disconnect main battery by foot well which is not always remembered. Thanks.

Based on the answer I received in the forum from my recent post, it would not help you to plug in the camper even if you could. What I have been doing for my car when we are off on long trips is to put a small solar panel trickle charger hooked up to the car battery when we are away to keep it from going dead.
I plan to start using that same solar panel to trickle charge the MB chassis battery when we are home. Amazon has a good variety of these. I have used one on the dash of my toad for the last 9 months to keep our toad's battery charged up.

See the post on the communication between the house and chassis batteries.  If the link is active (I only took 18 months to figure it wasn't after buying a used Unity) you can actually start the chassis battery with the generator running or the reverse.  With the confusion I previously bought a jump battery (Clore Automotive Jump-N-Carry JNC325 12 Volt Lithium Jump Starter for up to 8-Liter Gasoline and 6-Liter Diesel Engines) which can be used to run start either the engine or the generator.

I have had no issues with a drain like you mention, except when the battery went bad or a renter left the running lights on overnight.

Solved that problem with a Trik L Charge but Good only if you have solar on roof

I had the same problem on my 2022 Unity RL. Found the following solution in MB operational manual:
1. With the ignition on and the engine off scroll to "vehicle" on the main touch screen.
2. Scroll down and choose standby mode.
3. The next screen will ask you whether you want to activate--CHOOSE the YES response.
4. Turn off the ignition.
After a few minutes (15-30) the firefly display will read 0.1 volts. This should be good for approximately 26 weeks of non-use. I rarely go more than a month without starting the MH and have never had a problem using this method.

On our last Sprinter based RV, A Galleria, I found that having the Propane turned to the "ON" position caused the solenoid to draw about an AMP.  This would kill the chassis battery in a couple of weeks.  Don't know if our LTV works the same, but I leave it off if the coach is not in use.

Be sure and lock the sprinter cab doors with remote.  This will allow the sprinter/chasses to turn off ALL its computers.  This is a known M-B problem.  I have been doing this for years on various sprinters and it seems to help. 

Oh Hell! Is the LP solenoid powered by the chassis battery? No wonder I've had problems keeping it charged. Over the winter I like to leave the heat (LP) on at a low setting to make sure my house Lithium batteries are warm enough to charge.  I have shore power to power the house side, and use a NOCO Genius10 on the chassis, but once in a while I get a "partially charged " alert from the Mercedes app.

The LP regulator/solenoid is off the coach batteries.
I have the AGM battery in the chassis - i pull the battery isolation cable beside the gas pedail (2016) with no trickle charge.
for later models you need to also pull fuse #32 which diconnects the small auxiliary battery
Temps in storage are as low as -15C / 5F for a period of 6 months

The MB instruction manual for my 2015 guarantees that the truck battery will run down after a couple of weeks if the engine is not run. Plan A is a trickle charger on the truck battery if you have power where you store your van. I don’t have power so I use plan B, which is to disconnect the truck battery. There is a pop on, pop off disconnect located next to the accelerator pedal. Inconvenient, and the connector can be difficult at times, but even after several months, the engine starts when I reconnect the battery. You will have to reset your clock.