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Old 05-07-2023, 11:02 AM   #1
Just Cruisin
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Join Date: May 2020
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Default Understanding my Cabin Batteries

I have a 2018 BT Cruiser 2951 C class. I have tried different things and read articles, etc and still don't understand why my batteries go dead.

I have a battery disconnect that doesn't seem to matter if it's On or Off. Each month I let both the engine and the generator run for approx 40 - 60 minutes. I keep it connected to my home's 110 outlet.

With all of those things my battery still dies. I may be wrong but I think the generator gets it going again but it could possibly be the engine since I run both of them at the same time.

The local guy that helps me with any RV issues found that it only had one battery for the cabin. He has always seen two in other RVs. He added a second one but had difficulty following the wiring so wasn't sure if adding it was correct. I can say I haven't seen the second battery help with anything.

Can someone help me understand what I should do to keep the batteries charged and also if the second battery is supposed to be there?

Thank you for your help
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Old 05-07-2023, 12:31 PM   #2
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There are a lot of battery "experts" out there, so I hesitate to contribute. I will throw a couple things at you and maybe it will help regardless.
First, ensure your battery connections are clean and tight. As for any other connections you can access. The house battery needs to be a deep cycle battery at minimum. Best bang for the buck is AGM, but not necessary.
Suggest you get the battery load tested. If you don't have the hardware to do it, many auto parts shops will do it for free (test your battery). Charging a bad battery is like trying to teach a pig to sing.

>IF< you decide to go with two batteries, nothing wrong with that. Two 12V batteries in parallel will last longer than just one battery. Keep this in mind however; the two batteries will only perform as well as the weakest battery. It is imperative to ensure the two batteries are matched. Best to buy two with same date codes sitting on the shelf next to each other. That way you get best possible performance.
With the batteries sitting idle, and fully charged you should read around 12.7 volts. Plug in your shore cord, with battery disconnect ON and the converter in your coach will provide between 13.2 to around 13.7 volts across the batteries (depending on their state of charge).
Your generator typically powers your converter the same as shore power, to charge your batteries. Some generators can and do charge direct, but not most.

Once the batteries are fully charged and you are not going to be using your coach, the battery disconnect will isolate your batteries to extend their state of charge, Keep in mind batteries have a typical 4% discharge rate internally, so you will nee to periodically charge them, (I leave you RV plugged in 24/7 AND I have solar to always have a charge ie: maintenance charge on my batteries. This is where the "experts" will start offering their insights and pros and cons of what I just said . . . .Whatever).
Oh and be sensitive to the fact people will connect add-ons to the batteries not paying attention to the fact they are defeating the purpose of the disconnect.

Hope some of my ramblings helps.
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Old 05-08-2023, 01:23 AM   #3
Leisure Time Larry
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I agree with Rich above, and here is my take. Your battery is 6 years old and has gone dead. It is probably done for and needs replacing. What type of camping you do is the best indicator of what type and how many batteries you should get and use as replacement. Are you always at a park with hookups? Are you always "boondocking" and rarely plugged into electric? 50/50, 90/10, or 25/75? If mostly plugged in, then you can get away with one battery. Watch this...

I'm not sure about your 2018, but BT Cruisers of past are wired as such to be able to provide charge to the "house" battery(s). 1) From the vehicle's chassis engine/battery. A large wire connects the engine battery positive to a constant solenoid. The other side of the solenoid connects to the positive of the house battery. When the engine is running the solenoid connects them and charge is given to the house battery from the engine alternator and charging system just as it is to the chassis battery. 2) The onboard converter also is a battery charger. The converter takes the 120v AC electricity from shore or produced by the generator and converts it to 12v power. When connected to shore power or the generator is on, the converter should be charging the house battery. Not all RVs are the same, and some are wired so the converter will charge the battery no matter what position the disconnect is in, but some are wired so that this will only work with the disconnect switched to ON.

I would watch that YouTube video and then keep watching and learning there. The more you learn and can do yourself the more $ you can save. If that is not a concern, then you can pay away the problems as they come. Best to you either way.
2005 22' BT Cruiser 5211, Chevrolet 3500 chassis w/6.0L Vortec V-8; 6'x12' Cargo Trailer; Honda CB500X motorcycle for street and ADV riding; Yamaha TW200 motorcycle for dual-sport and trail riding...All of it for fun and adventure!
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Old 05-12-2023, 09:00 PM   #4
Just Cruisin
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Default Thanks for the help

Thank you both for your help. I just got back this evening from camping a few days. I will check the batteries tomorrow morning and see if there is a charge. I suspect you will be proven correct and that I need at least one new battery. If I can get this straightened out, I may add a battery monitor so I can easily see the charge on them.
Thanks again for the help
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Old 05-14-2023, 03:37 PM   #5
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Look under the hood, right up against the firewall you should see a breaker, make sure it's not tripped. You have a dual charging system on the coach.
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Old 05-15-2023, 11:18 AM   #6
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Not sure if you are talking COACH BATTERY OR ENGINE START BATTERY?.. but, 1) plugged in, COACH BATTERY MUST be switched ON to charge/ maintain charge (ONLY turn OFF to store without shoreline power); 2) Many CHASSIS/ engine batteries do NOT charge from Coach automatically, but my 1999 Class-C has the MANUAL EMERGENCY START SWITCH, and I use that every few weeks to charge chassis battery for 4-8-hrs or overnight and top it off. I monitor battery charge status w/ this type:
2000 Conquest LE 6266, Class-C on 99-E450SD, 6.8, 2v, V-10
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