Engine Battery Drain

[bratbros]

Hello
I just purchased a 2017 Siesta Sprinter new. The engine battery will not hold a charge for more than two days. The dealer was terrible and actually hid the problem from me. I took the coach to Mercedes and they just said it was a loose connection on the battery terminal, charged me $280 and sent me home. I knew that wasn't the problem..now the battery is dead again after 2 days. The battery tests good, so there is a drain on the system somewhere. This is evidently an known issue.

Has anyone had this problem and got it fixed?

Thanks.

[JamieGeek]

We all just install a battery disconnect switch and call it problem solved. Its far easier doing that than trying to chase down every little draw on the battery.

[KC8RXQ]

I bought a cheap solar panel that plugs into the 12VDC accessory socket (a. k. a cigarette lighter) and it does a "fair" job of dealing with parasitic draws. It's a very common issue with Sprinter-based motorhomes (even Winnebago) and some owners install an aftermarket trickle charger and some use it as an excuse to take the rig for a drive!

[Bob Denman]

Originally Posted by JamieGeek

We all just install a battery disconnect switch and call it problem solved. Its far easier doing that than trying to chase down every little draw on the battery.

We did the same thing. Our rig's batteries used to draw down to just about 11 volts in only three days...
After installing the switch: they stayed at 12.7 volts for ten days!

[gmc]

Originally Posted by bratbros

Hello
I just purchased a 2017 Siesta Sprinter new. The engine battery will not hold a charge for more than two days. The dealer was terrible and actually hid the problem from me. I took the coach to Mercedes and they just said it was a loose connection on the battery terminal, charged me $280 and sent me home. I knew that wasn't the problem..now the battery is dead again after 2 days. The battery tests good, so there is a drain on the system somewhere. This is evidently an known issue.

Has anyone had this problem and got it fixed?

Thanks.

On a new coach - I would go back to Mercedes... There is no reason for the chassis battery to run down in 2 days... or even a week or more...

There is either a load remaining on the battery - or the battery is bad and won't hold a charge...
(Certainly check and be sure you have nothing plugged in to any source powered by the chassis that might remain on with ignition off...)

From other threads - Mercedes doesn't allow the chassis battery to be charged from anything but the alternator (not on shore power, generator) - so you would have to disconnect every time you parked. I don't view that as an acceptable solution.

Either case should be fixed under warranty in my opinion.

[Tupelo Kid]

Originally Posted by Bob Denman

We did the same thing. Our rig's batteries used to draw down to just about 11 volts in only three days...
After installing the switch: they stayed at 12.7 volts for ten days!

Bob, what happened after 10 days?? Run down again even with the switch?
Mine ran down but it took about 25 - 30 days. I would have no idea what could be drawing power.

[Tupelo Kid]

Originally Posted by JamieGeek

We all just install a battery disconnect switch and call it problem solved. Its far easier doing that than trying to chase down every little draw on the battery.

Jamie,
Tell me more about the disconnect switch.
What did you do? And where (on the MH) did you do it?
I may need to do this or add a trickle charger perm attached. Which will not help much if I don't have access to shore power for a while. Mine rand down in about 25 - 30 days of no use. Dad to run the charger for a while for start. Then left it overnight to top off good.

Thanks

[Laco]

We have that same Mercedes Sprinter, and the chassis battery is isolated from all of the house electrical. Ours has sat for as long as a month, when I check the chassis battery its shows a full charge. If yours is discharging, get it back to Mercedes to trouble shoot, it should not be doing that. I plan to eventually permanently install a small smart charger, connected to the chassis battery and to a 120 volt outlet in or on the motorhome, so when plugged into shore power it will automatically charge the chassis battery.

[JamieGeek]

Originally Posted by Tupelo Kid

Jamie,
Tell me more about the disconnect switch.
What did you do? And where (on the MH) did you do it?
I may need to do this or add a trickle charger perm attached. Which will not help much if I don't have access to shore power for a while. Mine rand down in about 25 - 30 days of no use. Dad to run the charger for a while for start. Then left it overnight to top off good.

Thanks

I put one of these (Amazon) on the chassis battery, and one like this one (Amazon) on the house battery.

[Tupelo Kid]

Originally Posted by JamieGeek

I put one of these (Amazon) on the chassis battery, and one like this one (Amazon) on the house battery.

Thank you.

[gnach]

Originally Posted by JamieGeek

I put one of these (Amazon) on the chassis battery, and one like this one (Amazon) on the house battery.

@Jamie- where did you install that house battery disconnect? Any photos by chance? TIA, Gary

[JamieGeek]

Originally Posted by gnach

@Jamie- where did you install that house battery disconnect? Any photos by chance? TIA, Gary

I don't have any photos sadly. Our Axis only has 1 house battery so I have room in the area under the step for a switch. I simply screwed it to the metal side there--I lift the step and switch the disconnect.

[gnach]

Yeah, one battery would make a big difference. I can't get to mine yet, I don't know if the two negative cables tie together and one disconnect would take care of it. I'll see.

[Budman]

Originally Posted by JamieGeek

I put one of these (Amazon) on the chassis battery, and one like this one (Amazon) on the house battery.

Jamie, looked at ur suggestions. Curious why on the knife disconnect it states to put on negative side. The second switch states (in drawing) to install on positive side. I thought disconnects always go on negative?
Anybody know the difference or suggested differences? Thx, Dennis.

[JamieGeek]

Originally Posted by Budman

Jamie, looked at ur suggestions. Curious why on the knife disconnect it states to put on negative side. The second switch states (in drawing) to install on positive side. I thought disconnects always go on negative?
Anybody know the difference or suggested differences? Thx, Dennis.

I put both on the negative side.

For the knife switch: It will only fit on the negative post--the posts are different sizes.

Note that the knife switch is all exposed metal thus if it was on the positive side and any part of the knife switch hit the frame you'd have a direct short from + to ground--probably why they say put it on -.

[Bob Denman]

Originally Posted by Tupelo Kid

Bob, what happened after 10 days?? Run down again even with the switch?
Mine ran down but it took about 25 - 30 days. I would have no idea what could be drawing power.

I'm sorry: I was only 10 days into the testing... I should have explained that.
It held at12.6 volts right up to today. We dropped the rig off at the dealership for warranty work, winterizing, and some "goodie-adding".

[Travelin' Texans]

If the chassis battery won't hold a charge then you have a bad battery or a direct short somewhere, both of which should be covered by your rv dealer as they sold you the rv with a 1-2 year bumper to bumper warranty or through the chassis manufacturers 3 year/??? mile warranty at no cost to you.

[Budman]

Originally Posted by JamieGeek

I put both on the negative side.

For the knife switch: It will only fit on the negative post--the posts are different sizes.

Note that the knife switch is all exposed metal thus if it was on the positive side and any part of the knife switch hit the frame you'd have a direct short from + to ground--probably why they say put it on -.

I understand and agree. I guess that’s why I always thought the disconnect should be on negative. Cuts out all issues!!! Thx Dennis.