Battery discharging while parked

Dougherzog · 07-12-2021, 04:44 AM

Again, any suggestions on why my chassis battery looses up to 1.2 volts per day if I don't run the engine? Something is discharging it and I can't figure it out. Winnebago View 24 V 2018. Good thing I have the battery boost feature.

Doug

Morich · 07-12-2021, 07:04 AM

First thought might sound like I'm being picky about how you are checking, so please take a bit to think how well you really understand the battery charge questions as it is not as simple as a voltage reading. Do you know about "surface charge" which can often be a really confusing things when first dealing with it?

When you mention running the engine to charge, it makes me jump to the idea that the battery is not really getting fully charged and that sets you what looks like a really fast discharge.

Just guessing without full knowledge but what I might GUESS is this! The battery gets used down, you drive or run the engine and maybe test the voltage which says 12-14 volts so you feel it is all good and store it. While stored the voltage goes down a bit and you run the engine for 30- 40 minutes and the voltage looks good again, but each time you check the voltage has dropped dramatically as the surface charge has given you a faulty idea of the true state of charge.
It takes long hours to fully recharge a drained battery and it is far longer than most of us run our engine on Rv, so we see folks having battery problems due to the battery charge not actually getting back to full.

Again, I want to say there is a lot of guessing in that idea but it is a common problem. Just a first thought which I often see here. Review what YOU actually do and reject the idea if not correct!! The 6-8 hours to recharge a battery, combined with parasitic discharge can be a real shock and it gets much quicker when it combines with the last discharge cycle.

DavidM · 07-12-2021, 07:58 AM

Let me take a slightly different tack on Morich's post above. I suspect that you are seeing maybe 14 volts just when you shut the engine off, and a day later you see 12.5 volts. That is almost normal, 12.6-12.7 volts a few hours after shutting off the engine would be normal.

But you can't start the engine after a day. Why- because your battery is bad. It's voltage is dropping more than normal after shutting down and even though a good battery should start the engine at 12.5 volts, yours won't because it is bad.

Replace the battery and see what happens after that.

David

Morich · 07-12-2021, 09:49 AM

Quote:

Originally Posted by DavidM

Let me take a slightly different tack on Morich's post above. I suspect that you are seeing maybe 14 volts just when you shut the engine off, and a day later you see 12.5 volts. That is almost normal, 12.6-12.7 volts a few hours after shutting off the engine would be normal.

But you can't start the engine after a day. Why- because your battery is bad. It's voltage is dropping more than normal after shutting down and even though a good battery should start the engine at 12.5 volts, yours won't because it is bad.

Replace the battery and see what happens after that.

David

Totally agree with this as possible as well. The devil is really in the details of how and what you have tried and all the little details of the battery and how it is used.
They seem so simple and we all have some experience with using them in cars but we use the RV so much different that it sneaks up on many of us.

Dougherzog · 07-12-2021, 10:13 AM

I'm sure it is Surface Charge because after I run the engine, the voltage on the display panel reads 14 volts DC. Then after just a few days the voltage drops into the 11's. At around 11.5 volts, the engine will not start. If I let my RV sit for two weeks or so, do I have to put a external battery charger on or pull the negative terminal? You seem like you know what you are talking about. Wow would I like to talk to you. Mercedes told me to run the engine every week to charge (partly) the batteries because parasitic discharge will drain it. Can I talk to you? Thanks alot Doug

Dougherzog · 07-12-2021, 10:17 AM

Thanks David, I did have Mercedes change the battery under warranty last year, after I really complained. I just checked the water levels and all seems well. This discharging of the chassis battery cannot be normal.

Doug

DavidM · 07-12-2021, 10:54 AM

Quote:

Originally Posted by Dougherzog

Thanks David, I did have Mercedes change the battery under warranty last year, after I really complained. I just checked the water levels and all seems well. This discharging of the chassis battery cannot be normal.

Doug

Hmmm, water level in a starting battery?? Starting batteries are either sealed lead acid or AGMs and they do not have top filler ports to check water levels. House batteries do have filler ports. Well the foregoing is probably 99% true, maybe there are a few starting batteries with filler ports.

But that doesn't explain the slow discharge of your chassis battery. You have some ongoing load that pulls it down over a short while. Since the coach battery stays good then it can't be the BIM or Trombetta relay not disconnecting. It has to be some routine load that is powered by the chassis battery like the entry step motor that isn't turning off. Or maybe a dash radio, although mine is powered by the coach batteries.

How about the parking lights staying on as a result of their relay sticking?

David

Dougherzog · 07-12-2021, 11:07 AM

These are standard lead acid batteries as far as I can tell with screw caps. I did add a bit of distilled water. I thought about the step motor. I also had tire pressure monitoring booster pack added to the chassis battery, but the LED on the booster turns off when the ignition is turned off. Any other ideas, I really appreciate it??? Doug.

imnprsd · 07-12-2021, 11:13 AM

You are saying A) There is a external short drawing down the battery; or B) there is an internal short inside the battery.

The internal battery short is easier to EXCLUDE because you say it only takes 2 days for your engine battery to drop below 12V. So can you just remove the positive battery cable and wait 2 days to confirm the results.

If it drops then one of the battery cells are shorting, and then you can go get the battery "load tested" at any Napa or O'Rielly or Les Schwab or even Walmart for free.

...And if the voltage remains at 12.4-12.5V then you can reconnect your engine battery... pull the 4-prong step power... and check the battery voltage in another 2 days. (I assume your step has a 4-prong connector?)

QUESTION: How do you repair a step that is drawing current when it shouldn't? Do you have to replace the motor?

...But my guess is that your Battery Boost Solenoid has an internal short in the coil. This is the solenoid that connects your engine battery to your house battery; and the most common replacement is called the Trombetta "Bear" Solenoid as shown below with the most common Battery Disconnect Solenoid (BDS).

...Also the Ignition Key device or the Starter Solenoid/Relay may be another cultrate, but these I would check last.

Dougherzog · 07-13-2021, 09:20 AM

Thanks to everyone in this forum that helped me with the premature battery discharge. I did fine out that I normally leave my steps OUT when the RV is parked in my driveway. There is a small light that stays ON all the time the steps are out. I will keep my steps retracted from now on when parked and, hopefully, will not have the chassis battery drain nearly so fast. THANKS TO ALL.

Morich · 07-13-2021, 10:10 AM

Very good, hope that gets you on the road in better shape. Having to jump start things is NOT fun!

I think I mentioned I was also having trouble with a starting problem?
I think I have also found my problem in a dirty connection! Finding thast connection was the fun part, cleaning it was pretty easy.

powercat_ras · 07-13-2021, 04:56 PM

Quote:

Originally Posted by Dougherzog

Thanks to everyone in this forum that helped me with the premature battery discharge. I did fine out that I normally leave my steps OUT when the RV is parked in my driveway. There is a small light that stays ON all the time the steps are out. I will keep my steps retracted from now on when parked and, hopefully, will not have the chassis battery drain nearly so fast. THANKS TO ALL.

The Kwikie Step Light is supposed to go out after the step is extended 5 minutes.
Unless:

1. IF the step is extended AND the step logout switch is ON AND the door is open. Then the light stays ON.

2. IF the Purple Wire that is not in the 4 wire connector is connected to 12 volts, then the light will be ON, with step either in or out. This is normally connected to the output side of the porch light switch.

imnprsd · 07-13-2021, 05:41 PM

Here's a common Kwikee Step Diagram

Dougherzog · 07-14-2021, 04:57 AM

Oh no. That is bad news for me. I just checked and my chassis battery voltage is 11.1 VDC. Will need battery boost to start it. I'm back to the drawing board and will do some of the earlier suggestions. Thanks all. Doug

Morich · 07-14-2021, 06:58 AM

I've just got the message for about the 23 time that starting with the battery voltage and making certain it is right ALL the way from battery to operation is critical!
I might suggest going back to start, charge the battery fully with a charger if on hand, disconnect the negative as safer or the positive lead but use more care and then let the battery set for some time like overnight and check that it actually holds that charge fully while just setting.
When the battery is then full verified, one might start looking at the wiring with a meter to see if there is some one specific wire which shows a resistance reading to ground. It will be normal to find some like those feeding the ignition or any thing which does stay active whie the engine is not running to show some level of resistance connected through to ground, so that will require sorting what is normal versus any that might be a fault like a wired rubbed on the frame, etc.

But while that sounds really tough, I keep in mind that things like wires rubbi9ng ground tend to be pretty good solid shorts that blow fuses rather than the little ticky- tac super high resistance shorts which might drain a battery but not at a rate to blow any fuses!

Resistance that it takes to blow a 15 amp fuse can be found by dividing the voltage (12) by the current it takes to blow the fuse (15) and you get a really really small number! Most shorts to ground will be more like dead shorts for this use.

I actually seem very stubborn when saying it may be a battery problem or bad connection but then that IS where I find most trouble.....

kmessinger · 07-18-2021, 04:28 PM

Phantom charges like CO2 detector. Propane regulator has a draw also when on.

thataway4 · 07-18-2021, 05:02 PM

With the Mercedes chassis, I disconnect the chassis battery if I am not going to be running the engine in 2 to 3 days. Once you have run a battery down to less than 11 volts it has been damaged. Do it many times, and the battery should be replaced. I try and not to discharge any of my lead acid battery to less than 12.2 volts, which is 50% discharged.

ldfeat · 07-18-2021, 05:18 PM

Quote:

Originally Posted by Dougherzog

Again, any suggestions on why my chassis battery looses up to 1.2 volts per day if I don't run the engine? Something is discharging it and I can't figure it out. Winnebago View 24 V 2018. Good thing I have the battery boost feature.

Doug

Like most coaches, the manufacturer of your coach did not design it to charge your engine battery when plugged into shore power. You need an after-market shore power charging system installed. Larry, 2014 Reyo P.

Sailorman76 · 07-18-2021, 05:32 PM

While stored, I disconnect the chassis battery via the quick disconnect located next the accelerator pedal. This avoids any parasitic drainage. Remember to wait 10 minutes after reconnecting the disconnect to let ECM reboot before starting the engine. Still on original chassis battery after 6+ years!

Sailorman76 · 07-18-2021, 05:56 PM

While my View is in storage, I use the quick disconnect (located to the right of the accelerator pedal) to avoid parasitic drainage. Remember to wait 10 minutes to let the ECM reboot before starting the engine. Still on Original chassis battery in 6+ years!