How to Keep Your RV or Motorhome Battery in Good Condition
Battery Care and Maintenance Are an RV Owner's Top Responsibilities
It is important to understand that if you take care of your RV's batteries, they'll take care of you, because they are the heart of your RV's operating systems and most of the equipment. As a retired engineer, I can hardly restrain myself from starting a jargon-filled technical lecture on the design of batteries, cells, charging systems, and so on. But you can Google all of that battery technology information yourself on thousands of sites on the web. So before you move on from boredom, let me explain that in this article, I will provide simple and common sense information on the batteries in your RV that you can use to not only camp safer but also save money.
Typical Set of Coach Batteries in a Motorhome
Coach and Chassis Electrical Systems
First of all, you should understand that there are two basic categories of battery powered 12-VDC electrical systems that should concern RV owners.
In all motorhomes, regardless of type, the 12-VDC electrical systems are called either CHASSIS or COACH systems.
Towable RVs such as fifth-wheelers, camper trailers, and even your simple pop-ups will utilize what is referred to as a COACH electrical system and the batteries are there to provide 12-VDC electrical power for the interior electrical systems in the tag-along.
And, of course, as RV designs evolved these simple camper-centric electrical systems were duplicated in your motorhomes and were kept separate from the motorhome's CHASSIS systems.
Over the years, all of the camper designs continued to utilize variations of the same COACH battery(s) for such things as;
- interior lights,
- safety alarms,
- temperature control systems,
- 110-VAC power control systems,
- 2-way Fridge control circuit boards,
- and more.
You should understand that the original motorhomes were built on commercial bus chassis', they were diesel powered and they installed COACH electrical systems for the interior 12-VDC electrical systems.
But, these large diesel-powered motorhomes were expensive, and to reach more potential customers, RV manufacturers quickly moved over to building a much lower cost motorhome on gasoline-powered truck chassis'.
So, that truck chassis already had its own engine and all of the electrical equipment needed to drive it safely down the road. This 12-VDC electrical system in your motorhome is what is referred to as your CHASSIS electrical system.
The CHASSIS electrical system powers such things as;
- the engine operating system,
- the exterior motorhome lights,
- the dash radio,
- the front audio systems,
- the powered leveling jacks,
- and other electrical equipment you will typically find in a truck manufactured today.
Simple Batteries Power Both CHASSIS and COACH Systems
So, each of these electrical systems may have exceptions or additions as RV designs evolve, but they will normally be seperate systems.
One system, the CHASSIS electrical system keeps the motorhome going down the road, and the COACH electrical system supports many of those accessories and appliances that keeps your camper, whether a motorhome or a towable camper, comfortable.
These two systems are powered by simple lead-acid type batteries, put together in different configurations. Of course, there are several more high-tech battery designs of batteries that can be installed into your RV's electrical systems, but the vast majority of Rv's are still designed and manufactured with lead-acid batteries.
NOTE: I should note here that your CHASSIS battery is a standard automotive battery and is kept charged by the battery in the engine compartment but it is recommended that the COACH batteries be what are called deep-discharge batteries. These deep-discharge batteries are designed internally to take the stress of being charged and then drained alost empty of charge numerous times without being damaged. (Click here to read a slightly more technical discussion of "deep discharge").
The other system, the coach system, generally provides the 12-volt DC power for everything in the RV coach.
Since fifth wheelers, travel trailers and even pop-ups are towed by another vehicle, they will just have the "coach" system. Newer models, especially, of these towed campers will have many of the same appliances as larger RVs.
Some Typical Battery Configurations
There are several different configurations of batteries used in motorhome COACH systems, and they exist to provide more current when necessary to power the variety of 12-VDC loads in different RVs.
A pop-up camper or a towed camper trailer might have one standard 12-volt deep-discharge battery which provides adequate power for the electrical equipment in these smaller campers.
Many of these batteries generally get recharged when the camper is connected to the towing vehicle and the towing vehicle's motor is running. Or they may require being recharged separately by a built-in AC-to-DC Converter.
Older (and smaller) motorhomes might have a single coach battery and a single chassis battery, each being a 12-volt battery, while the larger ones may use from two to four 6-Volt or 12-Volt batteries wired in configurations that are all designed to provide 12-VDC at higher current level.
It is pretty standard to have a "bank" of four 6-volt coach batteries wired in a 12-volt configuration just for this higher current demand inside the motorhome.
Why 6-Volt batteries?
Since DC electrical systems in coaches are 12-volt systems, typically two 6-volt coach batteries can be wired in series to provide the same 12 volts as two 12-VDC batteries and have significantly more current storage capacity.
Some motorhomes will utilize four 6-volt batteries, and when wired properly, these four will provide much more current than two 12-volt batteries.
These 6-volt batteries are usually deep-discharge batteries and are the same designs as those used in electric golf carts and marine appliations.
Preventative Maintenance for Batteries
Remember, all your batteries require regular preventative maintenance.
Like many "Full-Timers", and even "Part-Timers" I recommend that you perform the following preventive maintenance, as a minimum, on a regular basis:
- Inspect Connections - Inspect your batteries and the whole battery compartment along with wiring that is visible. Remember your RV is bouncing over bumps and swaying around curves. Perform a good and thorough visual inspection of your batteries before a trip,
- Inspect for Damage - after you set up at your campsite, you can save you a lot of heartache later if you check for such things as loose wires, frayed wires, a cracked battery case, spilled battery fluid, or battery acid build-up on your terminals that may have been caused by your travels.
- Battery Fluid Level - Before every trip, check all battery fluid levels and refill any cells that are low on fluid as necessary, with distilled water only.
- Road Ready - Before every trip, check that all battery connectors are tight, and are clean of any oxidation residue.
- Storage Inspection - When storing your RV for an extended time, check the batteries at least once a month and either utilize a small Solar Trickle Charger or run your generator until they are fully charged. See the Table below for relative battery capacity.
- Residual Current leakage - Remember, these electrical systems, even with the switches turned off, will leak low currents and this will, over time, discharge your batteries.
- While Camping Inspections - When camping at a campground for an extended time, check the batteries at least every 2-4 weeks, especially the fluid levels in the coach batteries. Remember, these batteries are powering most of your lights and many appliance control systems, so even though you are plugged into 110-Volts AC at your site, they are constantly being re-charged and can lose fluids over time.
- Start Engine Monthly - Also, when camping for an extended time, start your coach engine at least every 30 days, and run it for at least 30 minutes to keep every thing lubricated in the engine system, but also to re-charge your chassis batteries.
Keep Your Chassis Battery Fresh
Battery Cut-Off Switch - Once you have parked and set up your RV, turn the CHASSIS battery switch OFF (if you have one). That way the chassis batteries will remain fresh longer and be more likely to start your engine when you are ready to leave your campsite.
And you want to keep those chassis batteries fresh. Because when both switches are on, and you are not connected to 110-volt AC power—you know, boondocking, rough camping, whatever you want to call it—your 12-volt accessories are pulling power from all of your batteries including the chassis batteries.
It is very embarrassing to get ready to pull out at a campsite, and find out you don’t have enough juice to turn over your engine, or even your generator.
Access to Your Batteries
The considerate manufacturer has these coach and chassis batteries stored on a pull-out shelf for ease of service, usually near the engine and generator, if for no other reason than to minimize the length of the high-current wires required.
Typical RV Battery Voltage
I have to get at least a little technical on you. Here is some good information on what battery voltages should be in fully charged and partly charged batteries.
Your typical 12-volt battery, when fully charged, and with no load, should read 12.6 volts DC (VDC).
When you start your vehicle, the alternator will charge the battery, as controlled by its regulator circuit, starting at 13.2 to 14.4 VDC, depending on the amount of current the battery draws. It will drop to 12.8 to 13.2 VDC when it is fully charged.
The following table shows what the open-circuit voltage (with no load applied) will be under different static conditions, and the approximate estimated percentage of charge remaining on the battery:
Voltage and Charge Levels for RV and Auto Batteries
Notes About Charging
1. After fully charging a battery, wait at least 12 hours to check the actual open-load voltage. This will allow the plates of the battery to stabilize and will provide a more accurate reading.
2. Almost all RV’s today, like automobiles, utilize numerous computers in their electrical systems, and it is not recommended to utilize fast-charge jumper chargers or booster packs to start an RV or car quickly, as the higher voltages can damage the computers.
If your batteries are maintained and used properly, you should never need a jump; but if you do, it is recommended to utilize a slow charger to avoid damage to the batteries and the RV electronics.
Coleman 10W Solar Battery Trickle Charger
I added one of these to my older Winny a few years ago, and it was great, as it kept my batteries charged when I had my RV in storage.
Good to Know: Electrical Battery Selector Switches
Again, I am staying away from describing all of the different electrical systems and accessories in RV’s and campers today. But, I do want you to know some simple facts about switches.
Manufacturers found out years ago that they had to include a selector switch (and often breakers or fuses) in battery wiring systems, for safety if nothing else.
It was quickly obvious to them that the potential current flow that had to be turned off and on was so high (under some conditions) that it was safer to use a low-current switch to control a higher current solenoid (or relay).
This is now pretty much the standard with all RV's.
Your RV will have a cabin on/off switch for turning off the 12-volt power to most of the cabin items that use this voltage. Whenever you leave the RV for a day or two, you should turn this switch off. This will reduce the drain on your coach batteries while you are away.
The coach switch location varies by vehicle design, but is usually near the coach entrance for owner convenience. Often the switch has an Indicator light of some kind on them to indicate that they are on.
Also your RV or camper will have a pair of master breaker switches that engage and disengage the two sets of batteries from the chassis and coach electrical systems. These switches are supposed to be used during long-term storage to reduce the current draw on your batteries. Also, they provide additional safety when you are maintaining your batteries.
RV Battery Disconnect Switch
To keep my RV battery charged, I had an electrician add one of these switches to my RV wiring and it worked great for me.
RV Battery Maintenance Tips
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
I have purchased a 78 Kingshighway, and it has electrical problems galore as far as I can tell. Is there a way to make sure that all the wires that are connected to the batteries are on the proper polarity? There is a major discharge in the system, and many battery wires were disconnected when I got it
First of all, there should typically only be one or two wires on the negative battery terminals. One will go to Chassis Ground, and the other (if it exists) would often go to a sensing circuit in your RV.
All of the other wires should connect to the Positive terminals of the battery.
As to your discharge problem, it looks like the previous owner had a problem himself, so it's hard to say what your problem may be.
One of the wires on the positive terminal is to the RV's Converter (Charger) which keeps the COACH batteries charged. So, make sure this is operating properly before you go chasing your discharge problem.
Then, I would check that EVERY accessory and appliance that runs on 12-VDC is working properly before moving on.
© 2010 Don Bobbitt