Coach Loses Charge--Dead in 3 days

[coachrb]

I'm not currently using my RV, Winnebago Adventurer P35, but I start it about every three days....in the last 2 weeks it's gone dead three times.
I have no idea why it doesn't hold a charge.
I've tried to keep the house and chassis toggle switches on=dead
I've tried to keep in the house and Chassis toggle switches off=dead

It seems that something is pulling juice from the batteries, but I don't know what it is. Any help you can provide would be very much appreciated.

thanks, Randy Brown

[hank857]

how old are batteries? If original your rig is a 16 so about time for battery RR&R.

[sundog964]

Do you run it long enough to actually recharge the battery from the starting process? That can drain an older battery enough to cause starting problems.

[coachrb]

I've taken trips of 12 hours and others of 45 minutes, it just depends. I had two new coach batteries installed in early December 2020. The engine battery has not been replaced and could be the problem, then.

What kind of battery do you recommend for engine?

[coachrb]

The two house batteries were replaced new in December 2020, but the engine battery is original I believe. It is a 2016 coach, so it could be the engine battery.

What kind of engine battery do you recommend?
thanks, Randy

[creativepart]

I agree with everyone else... your battery(s) is telling you to replace it.

I can't tell from your post if you're speaking of your starting battery or your house batteries. But on a 5-year old coach it's likely time to replace both kinds.

If you have an RV fridge you likely have 2-100aH Napa Commercial Deep Cycle 12v house batteries (with a residential fridge you get 4) and one flooded lead acid. It might be under the middle stair in the stair well for the chassis starting OR mounted next to your two House batteries on the battery tray.

I could only find the spec for the 2018 F53 RV Chassis and it was 78 Amp-hr., 750 CCA. I'm sure you could look at your current battery and get the info you need. Seems fairly common and similar to what comes on Fords F550 pickups.

[Morich]

Before automatically changing the battery, though it does sound likely, I like to keep in mind there may be other things as well.
One is keeping the m charged and knowing that when we store the RV, there are drains still on the batteries, even when we use the cutoffs! That means that the start battery may have drains like the ignition, radio presets and sneaky things that get the battery down over time. Then we need to keep in mind that battery charging is a long slow process, even though we may look at the voltage and it says good. This is often called "surface charge" and is something for every RV owner to be aware of and not let it confuse us. What may happen is the battery gets a bit low and we think we have it charged but it is only 75 %, so we repeat and do it again until it just can't do it.

On the coach batteries, there are things like the propane and CO detectors and steps
that are safety items and not cut off by the switches.

So it can often be batteries but keep in mind the same result can come from something as simple as dirty cables on either the positive or the ground side, so a look at BOTH ends of the cables is often a cheaper way out!

[hank857]

I got a maint free one from autozone for the chassis, just put 2 new maint free ones from wally world about 2 weeks ago.

[LeonardoBF]

Is it the chassis battery that goes dead in 3 days or house batteries

[Elkman]

The cab or engine battery can pull down the house coach batteries and devices called BIM or battery isolation managers are designed to prevent this from happening.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

The coach has a DC circuit from the batteries and also an AC circuit going from the batteries to the inverter and to 120V AC items. There are two disconnects as a result near the battery compartment. The Perko type switch should disconnect everything in the coach but does not disable the connection to the cab.

At least with the Navion it is easiest to remove the passenger seat and then install a BIM. I went with one for lithium phosphate batteries as I planned to replace the factory lead acid ones with lithium-phosphate batteries.

I have a couple of auto battery chargers but added this one that has a lithium battery charge profile for use with the RV and it is compact and works very well.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

If you have two 12V batteries are wired in parallel then disconnecting one and running off of only one battery becomes a way to verify that you do not have a defective battery in the equation. Also if one battery recharges much faster than the other one it is likely defective as when it holds a lower SOC it gets back to 100% SOC much faster as fewer amp hours are needed.

[Scotch]

I always recommend people buy and learn to use a multimeter when they own a coach. So many questions can be answered by connecting two leads to a battery.

When you recharge the battery, are you running it for an hour? A depleted battery will take quite some time to charge back up. 10 minutes on your alternator will not suffice. best way to know is to put a meter on the batteries as they charge. average alternator and converters put out 13.6-14.1 VDC. If your battery shows anything less than 13.4 VDC then it's still charging. A depleted battery will likely show more like 12.2 Volts once the engine is running.

A "bad battery" will never climb past 12.5 VDC, most not even moving past 11.X VDC. That means that the lead banks are too far used up to generate electrolyte any longer. Time to change.

Another feature of a Multimeter is to check amp draw. You should youtube how the leads should be set up for this, and how to check amps properly (which involves pulling off one of the leads to the battery and connecting in series). It's better to watch and see than me to describe here, but this will tell you if you have a parasitic draw on your battery from the coach. As has been listed here already, there are a number of things that can cause this, but my guess is still that it's time for a new battery.

Best of luck!

[BobC]

A multimeter that will read DC amps via a clamp-style probe eliminates the need to disconnect anything and are invaluable in chasing down "parasitic" loads and measuring amp draws for other reasons. They're reasonably priced on Amazon and most that measure DC amps also measure AC amps. The reverse, however, isn't always be the case so read the specs carefully, even if it's in the link below. You don't need super accuracy for this so you should be able to find one to your liking in the $30 range:

https://www.amazon.com/s?k=multimete...f=nb_sb_noss_1

[Scotch]

bob is probably right. I engineer and repair avionics so I am an exact type of person when it comes to this. I have little use for clamp readings unless we're dealing with 10 amps or more for load analysis. Plus I'd rather only have one test set than carry the clamp as well as a multimeter.

To each their own.

[imnprsd]

There are a number of circuits that can drain the house battery, but only a few that affect the engine battery.

So focusing on the engine battery, which I think the OP is referring to, but I can't be sure let's also consider that the alternator has a voltage regulator and diodes inside that can fail. Most of the time your dummy light will come on in these situations, but not always.

I.e., if the diode shorts to ground, the alternator may still charge, but in storage it will be blead the current out of the battery in 1-3 days.

Note: If your battery is dead, as in low volts dead, then an external short is likely the culprit. On the other hand, internal battery shorts often only affect one cell. And this why the good old hydrometer test is useful, but on a sealed battery you can't do this.

So then, your next best way to go is to find a Napa or Les Schwab who will will often do a load test and do a charging circuit test for free. These tests provide good data points, that often backup what you can learn from your multi-meter.