Cold weather RV battery tips



By Russ and Tiña De Maris

freezing 5er
j2davis2005 on

You know it’s cold out when, as my father-in-law suggested, “It’s colder than a mother-in-law’s kiss.” Yeah, that can be pretty cold.

For RVers, when it’s cold out, it can have a definite effect on our rig’s batteries. For the motorhomer, this can be a double-whammy, as when getting ready to up-and-go, a “click, click, click” noise from the starter is a sure-fire way to discover unhappiness. But for any of us, motorhomer or non-motorized user, cold batteries can result in more than just frustration — in some cases it can lead to a serious hit on the pocketbook.

Here’s the problem: Your battery is more than just a “bank” for power, it’s really a sort of chemical reactor. Cold temperatures tend to slow the reaction level down, make it more difficult to draw the needed power. That part of the problem is only compounded when a battery is called on for starting an engine. Why so? Because the colder the ambient temperature, the stiffer the lubricants in the engine become, creating yet more resistance to overcome when starting, hence, an even greater need for power.

But even for “house” batteries where turning over the engine is not an issue, cold weather still takes a toll. The demand for power in winter for an RVer tends to increase. The days are shorter, hence, more interior lighting is used. If you heat your rig with the factory-provided furnace, then you can be sure you’ll be pumping plenty of power to the furnace blower. A popular furnace produced by Suburban demands 8.5 amps per hour. Let’s say you run the furnace ten hours, at a 50 percent duty cycle. Run the math and you can say “Bye Bye!” to 45 amp hours. And with the ever-increasing popularity of electronic devices, the demand for battery power in our rigs just keeps growing.

But of course, we put it back in, right? If you are connected to shore power, then the power converter should be taking care of all our use, right? Perhaps, provided your use doesn’t outpace the ability of the power converter; in which case, you’re simply pulling that extra need from the batteries. And yes, the converter should act as a charger to start stuffing it back into those batteries, but again, not all converters are equal. Some converters charge at a rate as low as three amps.

But there’s another scenario to consider as well. When your RV is “at rest,” and not in use, if not hooked up to a charging system, the rig batteries will slowly run down. The matter is called “self discharge,” and can really make a difference. For common “flooded lead acid” batteries, the typical self-discharge rate runs about 5 percent of charge per month; more expensive gel batteries have a self-discharge rate between 2 and 4 percent per month. Let your rig sit for a few months and you may find on your return that it’s simply NOT ready to roll.

But worse, still, is that a discharged battery deteriorates faster than a fully charged battery. This is because of sulfation – and it’s part of that chemical reaction process we talked about earlier. Without getting into too much tech-detail, it works like this. The liquid in your battery, the electrolyte, contains two types of ions: hydrogen ions and sulfate ions. When the battery is called on to produce electricity, the sulfate ions move to the negative plates in the battery, while the hydrogen ions move toward the positive plates. Both join up with the lead in the plates, forming hydrogen sulfate. This material is an insulator, but happily, when the battery is charged, through the chemical reaction, much of this lead sulfate is put off. But if a battery is not charged, these nasty lead sulfate crystals grow and get harder. And the harder the crystal, the more resistant it is to going back into solution. The more this stuff builds up, the greater the resistance to charging, and the heavier it gets. Battery plates can literally break off; and the lead sulfate crystals then build up at the bottom of the battery, eventually reaching the base of the plates, killing the battery.

Add one more item to your list of battery problems: While a fully charged battery typically is freeze-proof, the more discharged a battery becomes, the greater the likelihood that it will freeze. Freeze the electrolyte, it expands; and expand it too much, break the battery. For some of us, breaking the battery can mean breaking the bank.

Bottom line: It’s essential to care for your batteries – they need to be regularly charged. And to protect it from overcharging, a “smart” charger, one which monitors the battery state of charge and reduces the charge current appropriately, is truly the only safe way to care for your expensive battery bank.


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