Dead Batts - How Best to Recover?

[DougInOr]

Ok, so I, as with many others here, just went out to start the RV after being connected to 20A shore power all winter (I'm kinda new at this) and found that not only could I not get even dash light indicators to turn on, but also the inverter wouldn't turn on either. I have a Thor Hurricane 29M 2018 (30A).

I've tried the STORE/USE switch (which is a single press spring loaded switch) a few times, but the relay doesn't seem to be triggering. Also, when I unplug the shore power I have no power what so ever. Voltage test on the coach batteries show about a 1.43V reading. Yesterday I tried to tinker with plugging in and unplugging and I thought I had a 13.9-ish Volt reading so left it at that over night and now it's showing the 1.43.

I've checked the 50A and 100A circuit breakers in the coach battery compartment and they aren't tripped. Ditto with the 15A fuse that is likely the converter fuse in the coach batt compartment as well. I've also checked the coach fuse box and all fuses look good and the breakers aren't tripped. The GFCI in the coach is also good to go.

Ok, so dead batteries... yay. What's the best way to recover from this? Should I get a battery charger from Lowes or Home Depot and throw that on the coach batteries? Should I disconnect them first? Is it OK to charge them while they're in series?

Secondly, while checking the fuse/breaker panel I noticed the CO2 sensor is green lit, but flashing red. I'm thinking maybe because of the red it was triggered and maybe drained the batteries? Don't know, but if you do, please let me know.

Thanks for your help all!

[Bob Denman]

Hook your charger right to the coach batteries.
Good luck!

[Travelin' Texans]

I'm not familiar with your particular coach, but I suspect the chassis (engine starting) battery is separate from the coach batteries. Use of a charger or jumper cables should charge enough to start the engine, but if it's been totally dead it's probably done for.
If so the chassis battery will not be charged by plugging into shore power. Some other drain on it is causing it to discharge.
The coach batteries should charge by shore power provided the factory disconnect is in "USE" mode, in "STORE" mode they will not charge. Also the factory disconnect does not totally disconnect ALL drains on those batteries, disconnecting battery cables is the only sure way.
The CO detector flashing is indicating low coach batteries as it's hardwired to those batteries & is one of the drains that is not disconnected with OEM disconnect.
When constantly charging by shore power the batteries will require checking the water levels often & topping off with distilled water.
Now the bad news. If all of your batteries, chassis & coach, have sat totally discharged then replacing all of them is most definitely in your future.
When replacing the chassis battery it's a different type than the coach batteries. The chassis needs cold cranking amp rating (CCA/CC) while the coach needs true deep cycle with amp rating (Ah) the higher the better.

[16ACE27]

I suspect you placed the USE/STORE switch in STORE when you put it away. In that condition the house batteries will not charge from your Converter/Charger and neither will the chassis battery.

Even good house batteries will drain in a few weeks with the USE/STORE switch in STORE due to parasitic loads like the CO detector.
Chassis batteries take much longer to drain but they too will drain over several months or quicker if they are not in good shape.

How to Recover?

The USE/STORE relay gets the power to move from the house batteries so they gotta get some charge on them either by an external charger or by running the coach if you jump start it AND the BIRD/BIM is working correctly. Once the USE/STORE switch moves the latching relay (you will hear the familiar clunk) then the Converter/Charger can start charging the batteries. You should have at least 13.6 VDC on both the house batteries and the chassis battery for them to be charging.

Then the only question remaining is: will the batteries recover to be usable?

[Lt Keefer]

If your batteries are 'dead' there is no coming back for them. They will have to be replaced. If they are severely discharged they may be recoverable. Put a seperate charger on the chassis battery and charge it up. Start the coach and get the coach in use mode and let the converter go to town on the coach batteries. Make sure you check the water level in the coach batteries while you're at it. I had the same thing happen to me about 10 years ago. I had to replace all the batteries in that coach. I winter with no charging or water maintenance will kill a lead acid battery.

[GVP-The Boxcar Children]

[QUOTE=DougInOr;231373]Ok, so I, as with many others here, just went out to start the RV after being connected to 20A shore power all winter (I'm kinda new at this) and found that not only could I not get even dash light indicators to turn on, but also the inverter wouldn't turn on either. I have a Thor Hurricane 29M 2018 (30A).

I've tried the STORE/USE switch (which is a single press spring loaded switch) a few times, but the relay doesn't seem to be triggering. Also, when I unplug the shore power I have no power what so ever. Voltage test on the coach batteries show about a 1.43V reading. Yesterday I tried to tinker with plugging in and unplugging and I thought I had a 13.9-ish Volt reading so left it at that over night and now it's showing the 1.43.

I've checked the 50A and 100A circuit breakers in the coach battery compartment and they aren't tripped. Ditto with the 15A fuse that is likely the converter fuse in the coach batt compartment as well. I've also checked the coach fuse box and all fuses look good and the breakers aren't tripped. The GFCI in the coach is also good to go.

Ok, so dead batteries... yay. What's the best way to recover from this? Should I get a battery charger from Lowes or Home Depot and throw that on the coach batteries? Should I disconnect them first? Is it OK to charge them while they're in series?

Secondly, while checking the fuse/breaker panel I noticed the CO2 sensor is green lit, but flashing red. I'm thinking maybe because of the red it was triggered and maybe drained the batteries? Don't know, but if you do, please let me know.


Hello, and welcome!

Your batteries, if 12V each should be wired in "Parallel" not Series" as a Series arrangement would result in 24V DC and a fire hazard.


So, if they're maintenance-free they should be 12V; if they have 3 fill caps on top they are likely 6V.

GVP

[DougInOr]

Hello, and welcome!

Your batteries, if 12V each should be wired in "Parallel" not Series" as a Series arrangement would result in 24V DC and a fire hazard.


So, if they're maintenance-free they should be 12V; if they have 3 fill caps on top they are likely 6V.

GVP

Thanks! They are Interstate SRM-27 batteries. I'm assuming by their size that they're 12V, but honestly haven't looked it up. At any rate, Positive to Positive jumper and negative to negative jumper is in "series" correct? Is there a wiring diagram that's available to look at for this RV such that I could check (and make sure things are hooked up right when I replace them)?

[16ACE27]

Originally Posted by DougInOr

Thanks! They are Interstate SRM-27 batteries. I'm assuming by their size that they're 12V, but honestly haven't looked it up. At any rate, Positive to Positive jumper and negative to negative jumper is in "series" correct? Is there a wiring diagram that's available to look at for this RV such that I could check (and make sure things are hooked up right when I replace them)?

No, that'a parallel.

Take good pictures of your existing wiring before replacing.

Label each cable end as you remove it.

[GVP-The Boxcar Children]

Originally Posted by 16ACE27

No, that'a parallel.

Take good pictures of your existing wiring before replacing.

Label each cable end as you remove it.

Ditto 16 Ace You've got it now! Happy to help!

GVP

[DougInOr]

Just wanted to follow up with you guys on this.

Replaced two house batteries: My dealer put in two brand new 12v Interstate batteries last year so they were under warranty with Interstate. Interstate took them, tested them and found one of them to be bad. The second one they said wasn't bad, but they replaced it anyway for no cost to me.

Replaced the chassis battery: The chassis battery was a Ford 65-750 (750 Cold Cranking Amps) so replaced that one too. Bought a 65-850 (850 Cold Cranking Amps) from Interstate at a nice discount.

I talked with Thor MC (they're very low staffed at the moment - I think the guy said they only had 6 people working right now - TOTAL - due to COVID-19) and they got me going with a user account with access to all sorts of documentation - including the coach battery wiring diagram (phew!).

First thing, I replaced the chassis battery... no picture was needed, it's literally only one positive connection and one negative connection as all the wiring is connected on each single batt connection. Very easy to replace, no issues with space or anything of the sort.

Next, before firing anything up, I first tripped the 3 breakers just to be sure I wasn't going to fry anything while connecting them. Then, I followed the wiring diagram (as close as I could - TMC took a few minor liberties to connect things just slightly different than their diagram - if you need details I can explain) to reconnect the two house batteries. Once connected, I reset the 3 breakers (100A for the generator AND the jack pump together, 100A for the inverter and a 50A for the house control/breaker panel) to ensure things were connected.

NOTE: The shore power was disconnected for this.

First, I checked the battery disconnect switch (the STORE/USE switch). After pressing it, I heard the relay trip giving me power - confirming this was why they drained dead in the first place while connected to shore power. All lighting worked, heater worked, inverter worked (14.5V reading), etc. Seemed all good to go.

Next, I started the engine. It started up without any issue what-so-ever. Full power right away confirming, yes, the chassis battery was dead as well. Next, shut the engine off and started the generator. It started without any issue as well. Ran that for a few minutes and then shut it off.

Bottom line, all things appear to be connected properly. No fuses were blown, no equipment went south, etc. The whole issue cost me about $136 bucks to recover from it so I'm feeling pretty lucky.

[Cllowe]

I accidentally let mine drain ( forgot to put in store mode ). When the battery got so low it put a strain on the inverter and blew the 2 40 amp fuses that went to the charger and the fuse behind the radio. Low voltage does weird things to electronics.

[Paulred]

The chassis battery is isolated from all coach functions. It will not charge on shore power. It will not power any coach devices. It can only be charged by the alternator, or an external battery charger. In some coaches, there is an emergency switch on the dash that allows the coach batteries to start the vehicle engine, but only if properly charged.

The chassis battery can be run down over time, but only by devices wired to the chassis battery. For example, leaving the radio on for a long time, or, in my case, testing the emergency lights and forgetting to turn them off. If parked for a long time, the battery may slowly lose charge because of very minor bleeds on the battery.
two solutions: You can buy a disconnect device. Connect the + battery cable to it, and then attach the other end to the battery. It has a cut off switch that you can use to isolate the battery. just remember to switch it back on when needed. Of course, you can just disconnect the terminal, and cover the end so it does not touch anything.

Get a booster pack. I purchased one of those boosters. Its a combo battery booster, battery charger, air pressure pump, and even has plugs for USB charging. When used as a charger, just keep it plugged into an AC source and it will charge any battery house or chassis.

[DougInOr]

Originally Posted by Paulred

The chassis battery is isolated from all coach functions. It will not charge on shore power.

Actually, I have a BIM installed. Reading the docs on that bad boy I'm under the assumption that the BIM actually manages a charge for both depending on the situation. Here's a snippet from the introductory paragraph in the BIM manual:

"The Battery Isolation Manager (BIM) isolates the two battery systems, chassis, and coach, in a motorhome. This prevents loads in one system from discharging both. It also connects the two battery systems together during charging. Both batteries are charged if either is being charged. The coach battery is charged while driving and the chassis battery is charged while plugged into Shore Power at a campground."

So, what you're saying isn't exactly the full story simply because of the BIM. I'm not sure what models have it, but mine does and I've read that pretty much anything newer than 2015 has this. Adding this not to say, "you're wrong!" but to instead just give people reading this a bit of information should they actually have a newer RV that may have a BIM. This also makes having a Trik-L-start type of thing from being necessary on those models that do have it.

Here's the full manual for the model I have installed:
http://www.precisioncircuitsinc.com/...ger-Rev7-1.pdf

[gmc]

Originally Posted by Paulred

The chassis battery is isolated from all coach functions. It will not charge on shore power. It will not power any coach devices. It can only be charged by the alternator, or an external battery charger. In some coaches, there is an emergency switch on the dash that allows the coach batteries to start the vehicle engine, but only if properly charged.

...

It depends...
On most Thor/Ford Class A gas rigs, there is a BIRD or BCC that connects the batteries at times to allow charging the coach batteries from alternator AND charging coach batteries from shore power/generator

On most Thor Class C rigs -Ford/Mercedes - the chassis battery is only charged by alternator as you stated.

In both cases, the batteries should be isolated when no power source is present.

Easy to verify with voltmeter.
The only thing consistent between our rigs is the Thor name... and the SOB owners even change that! Lol

[16ACE27]

Originally Posted by Paulred

The chassis battery is isolated from all coach functions. It will not charge on shore power.

One truism about motorhomes - any blanket statement like that will be wrong.

What applies to your coach or class (C vs A) or even model, may not apply to other coaches, classes, models, or even the same model as yours in a different year. In fact, even if you have verified your converter does not charge the chassis battery, it doesn't necessarily mean it isn't supposed to. Many people have found defective and mis-wired BIRDs, BIMs, and BCCs.

Most Class Cs on the MB chassis fully isolate the chassis and house batteries.
Some C lass Cs on Ford and Chevy chassis isolate the chassis and house batteries.
Few Class A's isolate the chassis and house batteries during charging operations.

[16Pal36.3]

If you try to recover from this using your inverter or engine alternator, you may destroy your built in charging equipment. Have your batteries replaced, or if you know what you are doing; replace them. It is far less expensive than replacing your alternator and / or inverter. I got in a position where I failed to monitor the condition of my battery cables. I wound up in a similar position and that was the outcome with a 2005 Fleetwood Bounder Turbo diesel about 8 years ago. The most expensive part was then 2.5 KW Xantrex inverter/charger. Start by replacing the batteries. Inspect all the cables carefully and use corrosion inhibitor on all Battery connections unless they are sealed.