Introduction:
There is a new level of sophistication that comes with owning an RV and compared to tent camping, quite a bit more responsibility. Often some of the most fundamental RV practices are overlooked by novice owners and these oversights can be detrimental to the camping experience, not to mention the unit itself. It is important to educate oneself on how to properly operate and maintain an RV so that fun and relaxation can be at the forefront of a camping trip.
One of the most common complaints we get from RV owners relates to issues with power. Folks are often stunned and disappointed when they discover their appliances and accessories or other features are not working despite being plugged into shore power. Unfortunately, this is a common scenario which might be avoided by a little education on 12V systems.
Types of Lead Acid Batteries:
Most campers come equipped with a 12V system, meaning the essential componentry in the unit is designed to draw power from a 12V power source – in this case, a 12V house battery bank. Most of the campers we supply are equipped with a 12V – or (2) parallel connected 12V – lead acid battery bank. A lead acid battery breaks down into two main categories: Cranking and Deep Cycle. Cranking batteries are designed to discharge a great amount of current over a short period of time. These batteries are ideal in vehicle applications to start engines and then be quickly recharged by the alternator while driving. The second type of lead acid battery is a deep cycle and they are commonly used for RV house battery applications. The capacity of a deep cycle battery is rated over a 20hr period, designed to be discharged over the course of a full day and recharged across several hours. There are also hybrid or dual-purpose batteries which share qualities from both types.
Types of Deep Cycle Lead Acid Batteries:
To break things down further, deep cycle lead acid batteries fall into three main categories: wet cell (flooded), AGM (Absorbed Glass Mat), and GEL (Gelled Electrolyte Lead). All three types have lead plates which place them in the category of lead acid.
Wet cell, commonly referred to as flooded batteries, are one of the most economical types used in RV applications. They get their name from the lead plates being fully submerged in liquid. They have caps which allow them to outgas and for the liquid to be replenished. As a result, they need to be stored upright and in a well-ventilated compartment. Under charging conditions, hydrogen and oxygen split and escape from the battery which is why over time the liquid level may drop. These batteries should be monitored to ensure the liquid level is above the lead plates and if they become low, the user should add distilled water. Also, because they outgas, it is important to monitor the terminals to make sure they stay clean of corrosion.
Unlike flooded batteries, the next two types are sealed – often referred to as “maintenance free.” In the case of AGMs, the liquid is suspended in a glass mat which allows hydrogen and oxygen to recombine rather than escape. Similarly, GEL batteries achieve this effect by suspending the battery electrolyte in a silica (gel-like) material. Since neither outgas, they are fully sealed allowing them to be positioned on their side. The versatility that comes with an AGM or GEL battery is not without compromise. At around twice the cost of a flooded battery and further investment in ensuring they have the proper charging equipment, these batteries do not take the same abuse as a flooded battery.
Interstate Flooded Batteries Common Stock Options:
With their tried and true reputation and economical price, we often outfit our campers with Interstate’s flooded batteries. Below is a list of the three sizes that are typically found on our campers with specifications related to the Ah capacity and physical dimensions. Note that the capacity listed below is reflective of total battery capacity. To get the most life out of any lead acid battery, it must not be discharged beyond 50% of its rated capacity. For example, the SRM-24 battery rated for 81Ah has a useable capacity of 40.5Ah.
SRM-24:
Voltage: 12V
Capacity: 81Ah
Group Size: 24DC
Footprint: 11”(L) x 6 ⅞” (W) x 9 ½” (H)
Weight: 46.3lbs
SRM-27:
Voltage: 12V
Capacity: 88Ah
Group Size: 27DC
Footprint: 12 ¾” (L) x 6 ¾” (W) x 9 ½” (H)
Weight: 50.3lbs
HD24-DP:
Voltage: 12V
Capacity: 64Ah
Group Size: 24DP
Footprint: 11” (L) x 6 ⅞” (W) x 9 ½” (H)
Weight: 41.2lbs
Polarity:
The color of your cables will be an indication of polarity (positive or negative). White is always negative. If the cables are white and black, then white is negative and black is positive. If they are red and black, then red is positive and black is negative. Some manufacturers use housing color codes (White/Negative and Black/Positive) and some use automotive color codes (Red/Positive and Black/Negative). Ultimately, the safest way to know cable polarity is by testing it with a voltmeter.
How Battery State of Charge (SOC) Affects Appliance Performance:
The responsibility of taking care of your house batteries becomes more crucial as it relates to the performance of the appliances and components in your camper. A depleted or degraded battery can have a negative impact on some of the following 12V appliances in your RV:
Refrigerators: Despite 2-way or 3-way capabilities, your RV refrigerator control board will always run off 12V. Regardless of whether you are running in propane mode or plugged into shore power, the controls require 12V electricity. A weak battery can throw off the controls which can result in spoiled food and worse yet, shorten the lifespan of your refrigerator.
Furnaces: A low battery will not give the blower motor enough power to run the blower wheel fast enough for the furnace to ignite. These furnaces are very sensitive so if there is not enough air movement from the blower wheel, the furnace will not work properly.
Slide Outs and Leveling Systems: Slide outs and leveling systems require a lot of power to operate. Hydraulic slide outs and 4 and 6 point leveling systems operate off 12V. Having the trailer plugged into 110V and expecting the converter to provide enough converted 12V is not sufficient. You will need a good battery to supply adequate power to these systems for them to function properly.
LP Leak Detectors: Gas leak detectors are a constant discharge on your batteries. If a trailer is left idle for a few weeks while the battery is still connected, the small light on the LP Leak Detector will eventually drain the battery down. When this happens, a “chirp” noise will come from the detector (similar to a smoke detector in a house with a low battery).
Charging:
Not only will a depleted or improperly charged battery impact your appliances, it can also be detrimental to the battery. By exposing a battery to incomplete charge cycles or depleting it beyond 50% of its rated capacity, you risk sulfation diminishing the battery’s capacity which will eventually result in premature battery failure.
This brings us to the more controversial topic of chargers. Anytime you apply a charging source to your batteries it should (and almost always does) have a built-in charger which is designed to regulate the amount of current going into the batteries. Some chargers allow a lower, but steady amount of current into the batteries while more sophisticated chargers can charge a battery in stages. A multi-stage charger is designed to carry a battery through the following charging stages:
Bulk: When the batteries are below 80-90%, a charging source can apply a great amount of current to the batteries allowing them to charge as quickly as possible. This will occur until the batteries reach their absorption voltage.
Absorption: In absorption mode, the current backs down and a steady voltage is applied to the batteries. When the charge current falls below the pre-set threshold or enough time has lapsed, the batteries are fully charged.
Float: The battery is fully charged and a float voltage is applied to the batteries to keep them full. Until the voltage drops below float voltage at which point a new charge cycle will begin.
Generator Charging:
A generator can very efficiently carry a battery through bulk stage by applying as much current as the battery can handle. However, the remaining 10 – 20% of charging in absorption mode is much more time-consuming and the generator run-time required isn’t very economical given the price of fuel. Additionally, if you are powering the entire camper while charging the battery bank, the generator’s current output will be shared among your living power demands and the battery’s charging demand. A typical scenario we come across is folks trying to charge their deeply depleted batteries using generator power alone. They’ll rely on the monitor panel inside the unit which provides information on tank and battery levels to determine whether or not the batteries are fully charged. When the monitor panel registers that the batteries are fully charged, they’ll switch back to living off their batteries but become frustrated when they discover a few hours later that their batteries are fully depleted again. The issue with this is, the battery levels on the monitor panel are judged by an in-the-moment battery voltage reading. Battery voltage is influenced by charging sources and loads. The monitor panel interprets the higher voltage, produced by a charging source, as the batteries being fully charged when in reality they’re not. We suggest bulk charging using your generator for a few hours and then switching to an alternative charging source (ie. shore power or solar) for the remainder of the charge cycle.
Shore Power Charging:
Your on-board converter/charger or inverter/charger is what allows you to charge your batteries by plugging into shore power and to draw power from shore rather than your batteries. If you just have a converter/charger, you will actually be required to plug into shore power if you want to utilize 110V (AC) appliances. While nowadays the stock converter/chargers are multi-stage, the voltage at which they charge your batteries is very conservative. As a result, it could take several days, especially for deeply depleted batteries, to fully charge. When scheduling a camping trip, allow for 2-3 days shore connection in advance to ensure your batteries are fully charged. As an extra measure of ensuring your converter/charger is supplying power to the trailer, see if the clock is displaying on your microwave when you’re connected to shore power. If the microwave clock is not on, then:
- The camper 110V source is no good
- The camper 30/15A adapter is no good
- The Main breaker in the Converter/Breaker Box is tripped
- One of the 30 or 40 Amp fuses on the fuse panel is no good. (These fuses are there to protect the converter in case of power surges or batteries being hooked up improperly).
The above items should always be checked when 12V is not working in a camper.
Tow Vehicle Charging:
Batteries can also be charged from tow vehicles that have a charge line. However, this method usually only provides a small trickle charge which often isn’t sufficient to charge a deeply depleted battery bank.
Determining the State of Charge of Your Batteries:
We briefly touched on how battery charge levels can be misleading on your camper’s monitor panel. Really, the best way to ensure your batteries are reaching a full charge is to install a true battery monitor. A true battery monitor has a shunt which intercepts the negative side of your battery bank. Because electrical current can take different paths but always winds up flowing through the negative side of the battery, intercepting there ensures you’ll measure all current – both loads and charging sources. In doing so, the monitor is able to gather net voltage rather than an in-the-moment voltage readout. A good battery monitor will provide a percent state of charge readout, how many Ah you’ve consumed, how much time you have left at your current rate of discharge, alarms if your battery state of charge falls below a set threshold, and more. These informative devices usually come with remote displays and some with built-in bluetooth so it can be paired to a device. Ideally, every camper would have one but we understand these devices aren’t stock and sometimes not in the budget.
There are other approaches to measuring battery state of charge but they require more discernment. As we just mentioned, an in-the-moment voltage reading can be influenced by charging sources and loads. For example, when you run the slideout, the battery voltage will drop for those few moments but spring back up when the load is released. Likewise, the voltage will increase when applying a charging source and settle back down when the charging source is disconnected. As long as the batteries are connected to either loads or charging sources, the battery voltage will be influenced. In order to get the most accurate representation of battery voltage, a reading should be taken when the battery is in a quiescent state – completely disconnected from all loads and charging sources – for a least 4-hours. While doable, it is less convenient than having an in-line source for this information. This is why we take the battery level readouts on the monitor panel with a grain of salt and recommend several days of shore connection to ensure your batteries are fully charged.
Storage:
As mentioned earlier, there are some loads, like the LP detector, which are a parasitic draw on your battery bank. If you plan to store your RV for an extended period of time, it is a good practice to make sure the battery is completely disconnected from all loads and fully charged. If you are storing during the winter and concerned about your flooded battery freezing, note that a fully charged flooded Interstate battery won’t freeze unless it encounters temperatures exceeding 75 degrees below zero. However, a discharged flooded battery is susceptible to freezing and Interstate does not provide a temperature or charge threshold for this scenario. If there is any concern that your RV might endure the freezing conditions mentioned above and/or the battery is stored discharged, take the extra step of removing your battery from the RV and keeping it in a dry, cool place that is well-ventilated and inaccessible to children and pets. Oliver’s Camper’s recommends charging your battery fully and removing it and storing it inside for the winter. This extra precaution should extend the life of your battery. It should go without saying but never try charging a frozen battery as it could explode.
Conclusion:
The last thing you want to worry about while you’re out camping is whether or not you will have power. Implement these tips we have shared with you so that you can focus on making great memories with family and friends on your next outing. Happy camping!
