Mystery Battery Draw

[mbutts]

Howdy,


I have 2017 FR Forester 3011 DS on a Ford E-450 chassis. It was built in January 2017 with a 2017 model year chassis. With the battery switch off, the two AGM group 27 batteries go flat in a day or two. The batteries are Deka/Duracell brand and are less than 8 months old.



With my previous TTs, I used to manually disconnect the positive cable. I thought my fancy-schmancy MH wouldn't require that.



When I turn the switch off, everything 12 V seems to turn off (TVs, radio/DVD player, lights, touch panels) with the exception of the entryway light that turns on/off when opening the door. I've turned this light off using its built-in switch.


Before I start tracking this down, I wanted to see if anyone else experienced this problem and found the draw.

[CHICKDOE]

i don't know your specifics but there are most likely several devices that are permanently connected to the batteries that are not affected by the setting of the battery disconnect switch. i think i found at least 5 in our trailer.

easiest solution would be to remove a battery cable like you used to. or install your own disconnect switch that disconnects everything.

also, are you sure that the batteries were fully charged before you stored the MH? obviously if the batteries were not fully charged they would drain even faster. at this point i'd get the batteries onto a charger and let the charge up for some time to see if you can recover them. that would be my first priority. hopefully they are not damaged.

[newRVer]

I have a 2016 3011 and discovered a number of things. First, there are few items which are connected directly to the batteries and bypass the cutoff switch. If you have levelers on your RV, that would be the first thing to look at. These are generally connected directly to the batteries as they draw a lot of current when operating and is probably too much for the cutoff switch. Another would be the battery isolation manager (BIM). There are a few other items which could create parasitic power consumption and I have seen them documented in other threads, so if you do a search, you'll probably find a more comprehensive list. I know in my rig, I have measured up to .5 current draw with the disconnect switch off. However, this should not discharge the batteries in a day or two unless the batteries are weak to begin with.

That being said, my batteries took a beating the first year I had it as it was at the dealer frequently for warranty repair, sometimes sitting for weeks with no charging on the batteries. I probably should have replaced the batteries after the first season of use, but I managed to limp through a second season before replacing them.

Before replacing them I installed a solar charging system so now the parasitic draw is no longer a concern and my batteries are always charged.

So in your situation the order of things to look would be the batteries first, make sure they are good. Next, measure your current draw using an inductive ammeter just so you know how much current is actually being used with the cutoff <OFF>. At that point you may discover an issue, i.e. a short, devices that should not be bypassing cutoff switch, etc and can fix it. Or, just put another manual switch at the battery and call it a day.

RVr

[mbutts]

We replaced the original super cheapie no brand batteries last summer. We assumed they were killed while the MH was at the dealer for a short FIVE MONTH service visit.


I'm popping over to the storage lot tomorrow with an ammeter to see how much is drawing with the cut off turned off.


The Big Foot leveler control panel stayed on when I disconnected the house batteries so that must be drawing from the chassis.


Thanks for the tips!

[newRVer]

Yes. On the levelers what your most likely seeing is probably 12V from the chassis battery being cut through using the battery isolation manager when you have the house batteries disconnected. It's a good idea to understand how the BIM operates as it has the ability to connect house and chassis battery connections under certain conditions.

Originally Posted by mbutts

We replaced the original super cheapie no brand batteries last summer. We assumed they were killed while the MH was at the dealer for a short FIVE MONTH service visit.


I'm popping over to the storage lot tomorrow with an ammeter to see how much is drawing with the cut off turned off.


The Big Foot leveler control panel stayed on when I disconnected the house batteries so that must be drawing from the chassis.


Thanks for the tips!

[mbutts]

Thanks for bringing up the BIM. Although this is our 4th RV, it's our first MH. I originally thought a BIM only isolated the chassis' starting battery from going flat, not that it also controlled which batteries were being charged and when.



Any idea where this bugger typically is placed? I'd like to find out the manufacturer's name & learn how it works.

[mbutts]

I ran over to the storage place and found the disconnected batteries at the same voltage that they had a few days ago.
Connected directly to the batteries were the Big Foot levelers, the battery isolator, and a line to the converter. For now, I'm disconnecting all three, but I'll get a second battery cut off switch to install on top of the battery.
I found the BIM located behind a panel to the left of the stairs.

[babock]

Put a multimeter measuring current between one of your battery leads and the battery and start eithe pulling fuses or disconnecting items to determine which is causing the draw.

Personally, the disconnect switch on my trailer disconnects EVERYTHING except the solar. The only reason I don't have it disconnect solar is that I have the solar on the battery side of the switch so solar doesn't power the trailer with the disconnect switch in the off position. I have a separate switch for the solar.

[mbutts]

I forgot to mention that I did put my very old and crappy meter on between the ground and the battery's negative terminal, but the ammeter reading was wavering around too much. I'll borrow or buy one from the modern era & test this again.