May 7, 2021

TT# 123 12 Volt RV Battery and Control Systems, Care and More! (Part 4)

By: Rob Lowe

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This TechTip is the fourth in a series of six, that cover the twelve-volt (12V) battery and power systems used in modern RVs.  All RVs depend upon a reliable twelve-volt (12V) power source, however that venerable 12-volt system has been changing under the ever-increasing demands being placed on it. These TechTips will focus on the power sources that are found in a motorhome consisting of two independent 12V systems, one for the engine and the ‘on-the-road’ systems and the second for the ‘Coach’ or ‘house control’ system. Unlike motorhomes, trailers have a single Coach power system, lacking the complexity of having two independent co-existing systems.
The Topics covered in this group of TechTips are:
The impact of the use of Computerized Control (Multiplex) Systems (TechTip #120)
Battery Types and the Significance of Battery Type on usability (TechTip #121) 
Inverter/Charger systems and settings (TechTip #122)
New products that Improve Battery Longevity and Maintenance (TechTip #123) (This one)
The interaction between Chassis and Coach Battery Systems (TechTip #124)
An alternative battery maintenance approach while a Coach is in storage (TechTip #125)

Questions arise from a lack of understanding about how these systems operate, as expressed by new owners, as well as addressing the recent significant changes in the systems themselves, that are often overlooked by experienced RVers as they exchange their RV. This TechTip series will assist both in understanding the battery, the control and inverter systems. 

Modern Battery Maintenance Systems & Procedures:
Many RV makers continue to offer conventional Lead-Acid (or Flooded) batteries in their lower and medium-priced coaches, especially when there are multiple batteries. RV owners that have coaches with this type of batteries often replace them with similar batteries. In addition, the newest coaches often have an inverter to power the residential refrigerator. Frequently four GC2 (6-volt golf cart) batteries are installed to provide adequate power to the inverter, ensuring that the refrigerator has a dependable power source when not connected to the Park Power. This type of deep cycle battery has been a proven stalwart of Coach power systems. Improvements to both the batteries and their charging systems have kept them as a reliable source of RV power. 
Tight Battery Storage locations
The two most common drawbacks to using these batteries are the non-sealed (open) vent caps that allow corrosive gases to escape while they are being charged and the requirement to regularly check the individual cell ‘fluid’ levels and, if low, add distilled water.  Note that the water to be added is distilled not tap or bottled water. It is important to add distilled water, which has less (if not, no) impurities. Adding any other water, runs the risk of adding impurities that will cause some deterioration in the ability of the battery to properly charge, lessening their useful life.  

Battery Located Under Step Checking cell levels and adding water becomes even more of a challenge when the batteries are mounted high in a cargo compartment as in some coaches or under a coach interior entrance step on others. In the first case, these batteries may be placed on a slide tray (see Arrow) that often corrode from the gas emitted when these batteries are charged. This corrosion of the rack slide rails makes it awkward or even impossible to move the batteries to visually check or add water. The height of these batteries relative to the top of the cargo compartment they are in, also make it difficult to add water, especially if the door is one that flips up towards the RV body sidewall.
The under the step placement (see arrows) eliminates the slide tray issue however it requires a few minutes of step disassembly to access the batteries and then getting to the cell caps under the mass of cables in the area that were installed without any recognition that an owner may need to access the caps to remove, inspect and reinstall them. Frustration with this requirement has driven may RVers to buy AGM batteries to eliminate this maintenance requirement. 

Flow-Rite’s PRO-FILL™ On-Board Battery Watering System: 
Pro-Fill Battery Fill KitAs the saying goes ‘Necessity is the Mother of Invention’ and Flow-Rite has come up with a superb method to allow you to check and fill Flooded Lead-Acid Batteries. Flow-Rite’s PRO-FILL™ On-Board Battery Watering System [ www.flow-rite.com/battery-care/applications/pro-fill/ ] makes adding water as easy as connect, pump to fill and disconnect. Cells that do not need any water, do not fill (or overfill) and those that do, accept only enough water to attain the proper fluid level. The only caveat is that the batteries should be charged prior to adding water. 

New Battery Fill Caps installedThe system comes in numerous configurations to fit single or double 6-Volt or 12-Volt wet cell batteries popular in RVs and Golf Carts. For this article, we used two RV-2000 kits designed to check and fill four (4) of the GC2 (Golf-Cart Deep Cycle) 6-Volt batteries found under the steps on a new motorhome. The Step-by-Step installation instructions are clear, with good pictures of the components. Prior to commencing installation of these kits. fully charge the batteries. Installation begins by accessing the batteries and removing all existing vent caps, after ensuring that the top areas of the batteries are clean and dry. Next the new fill caps are inserted into the holes on the top of each cell and twisted about a ¼ turn to lock in place. Connections to water fill manifoldsThen for each battery a pre-assembled, three cell, flexible manifold is laid over the top of the caps and each of the three rotating swivel tees are pressed into the open hole on each fill cap until they snap into place and are seated. Final Water Fill hose connections Then short pieces of the supplied hose are used to interconnect the manifolds sections. A fill hose that has a connection that will accept the squeeze bulb hand pump is connected near the middle of the group of batteries and the open ends on the manifolds that do not have hoses connected are covered with red rubber caps. All the interconnecting hoses are carefully curled to lay flat without any kinks or stress on the hose. Battery Fill ConnectorThe Fill connector should be located where it can be accessed to allow the hand squeeze bulb filler to be connected without having to disassemble the step or move the batteries on the tray. The rubber protective end cap should be installed on the connector and this end should be secured so that it is easily to find and access when the batteries need to be filled. 

Fill ConnectionFilling the cells to the correct level requires a hand squeeze bulb filler (that is purchased separately), being connected to the battery hose connection, after priming the bulb with clean distilled water. Battery Fill ConnectionsThe distilled water jug should be kept below the top of the batteries being filled. Firmly squeezing the bulb moves the water into the cells that are low while the cell caps prevent cells that are full, from accepting any additional water. When the bulb becomes firm, all cells are full and it can be disconnected, both ends covered with their dust caps and any excess water in the squeeze bulb tubing can be pumped back into the water jug. Remove the line from the jug, coil up the squeeze bulb and store for the next use. The system is simple to use, however it should be always removed after filling. Fill Hand Bulb PumpThe Pro-Fill™ RV system can be left on the batteries during winter storage however the system will not be operational when the temperatures are below freezing. While this system does not explicitly confirm the individual cell levels, it is designed to provide water to all cells and the cell caps will only accept water if that cell is low in water. Implicitly by regularly filling, the cells will be full. A separate electronic accessory is available should one want to monitor the level of each cell, although it may be a little ‘overkill’ in a RV application. 

Using the Pro-Fill™ system eliminates the biggest hassle with Flooded Lead-Acid batteries. It allows a cost effective, dependable power source to be maintained and used for many years. It is important to select the correct system for the existing battery system and it should be transferred to any replacement batteries when the original batteries reach the end of their useful life. For older coaches that do not have the AGM1 or AGM2 charging profiles stored in their chargers, or coaches that are equipped with Flooded Batteries, this system allows the convenience of AGM batteries to be enjoyed with only a slight inconvenience to check and fill them. A very worthwhile addition to a proven technology.


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