Why Does My RV Battery Keep Dying? (Every Reason I Can Think Of!)

“Stop! Don’t go into the light!”

If you’re constantly begging your RV not to give up the ghost, then read onward. I have some ideas why your RV house batteries might be dying so quickly.

… But before I begin, can I dispel a common myth?

You’ve often been told that batteries have a “chemical memory.” If you only charge a battery to half full, for instance, eventually the battery will remember that level and won’t charge above it.

That is false. Lead-acid batteries don’t have chemical memories. That’s an effect mostly limited to nickel-based batteries.

There. Got that off my chest.

To be clear, you can certainly lose battery capacity by only partially charging, but that’s because of sulfation, not the memory effect!

Let’s get into the good stuff.

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Table of Contents

18+ Reasons Your RV Battery Dies So Quickly

1. Do the No-Brainer Checks First

Not to insult your prodigious intelligence, but we all make silly mistakes sometimes. I have often searched for my cell phone using my cell phone’s flashlight, for instance.

So before you do anything else, take these steps first.

  • Have you checked the batteries for loose power wires?
  • Have you removed corrosion from the battery terminals?
  • Is the battery disconnect switch turned ON?
  • Did you accidentally trip the inline battery circuit breaker?
  • Is the battery fuse (often a 40A fuse in your converter fuse box) burned out?

Everything look normal? Then consider one of these other common causes of a dead battery.

2. You’re Running the Fridge Off the Battery

There are veeeery few RV refrigerators that can run efficiently off a 12V battery. Most draw a tremendous amount of energy! Absorption refrigerators convert all that energy to heat; AC/DC fridges use that electricity to operate the compressor.

Unless you’re operating a really tiny 12V fridge, like an Isotherm van fridge or an ARB portable fridge/freezer, you can drain a battery in just an hour or two by running the RV fridge.

Better idea: Run your 3-way refrigerator off propane! Or at least install some solar panels as a sidekick to help generate all that electricity.

3. You’re Running the Furnace All Night

Many RV owners are surprised to learn how much power their furnace fan draws. If you’re running the furnace off the battery, you can drain a full 100Ah battery in a single night!

You can use this interactive calculator to estimate just how long your battery bank will last. And you can visit my list of common energy requirements for RV appliances for even more information.

4. You’re Leaving the Lights On

  • Question: How do army ants devour large prey in their path?
  • Answer: One at a time!

Small electrical loads, when combined, can drain a lot of power. Operating your radio, playing music through speakers, turning on ceiling lights and reading lights, cycling the water pump, ventilating with a roof fan, charging your smartphones, heating the Sensi wax warmer – it all adds up!

Reduce your parasitic loads, especially when boodocking or storing your RV.

P.S. Your weapon in the fight against parasitic and/or cumulative battery drain is a Kill-A-Watt Meter! You can use one of these awesome tools to measure the actual electrical load of any appliance.

5. You’re Not Using a 3-Stage Battery Charger

If you’re still rockin’ an antiquated single-stage or two-stage battery charger, please, sell that thing to the Antique Roadshow and get with the times!

A good 3-stage battery charger (essentially every modern battery charger or RV converter) has three stages:

  • Bulk: 0-80% state of charge
  • Absorption: 80-95% state of charge
  • Float: 95-100% state of charge

Let’s look at the absorption stage. Usually, AGM batteries require 14.4-15.0 volts during the absorption stage; wet lead acid batteries require 14.2-14.8 volts (check your manufacturer’s recommendation).

Hang with me here! No more math, I promise. What I’m trying to say is that if your battery charger doesn’t output a high enough voltage, it’ll never charge the battery to 100%! And old chargers are notorious for either under- or overcharging batteries.

6. You Have a Loose Ground Wire

If your battery is completely, completely dead, then you might want to make sure your ground wires are all connected. Check the connections:

  • On your ground battery terminal
  • The grounding bars behind the converter
  • At the lugs on the main frame/chassis

A disconnected ground wire will not allow the battery to charge.

7. You Baked the Poor Battery

If you think you hate hot days, your battery hates them more!

High heat reduces battery service life by half for every 18 degrees increase from 77 degrees (Fahrenheit).

That’s a little confusing, isn’t it? Basically, battery engineers rate battery life at a specific temperature, normally 77 degrees. But if you’re storing and using your battery at higher temperatures, you’ll slash the life.

So at 95 degrees, you’d get about half the service life out of your battery as expected. If you vacation in Texas, Arizona or Florida, take note!

8. Your Solar Power System Needs Some Love

If you’re relying on solar panels to recharge your batteries, here are some things to consider:

  • When did you last clean off the solar panels? Accumulated dust, grime, and bird poop can significantly reduce efficiency. A clean solar panel is a happy solar panel!
  • Is your solar controller large enough? If you added an additional solar panel or two without upgrading the amperage rating of your solar controller (say, from 10A to 30A), then you might be limiting how much power can be delivered to your batteries!
  • Are your solar panels damaged? Hail, tree limbs, and high heat can all kill solar panels.
  • Is the wire big enough? Small wires lose electrical energy through resistance. The voltage drops along the length of a wire, and by the time it reaches your battery, maybe there just isn’t enough voltage to fully charge your battery.

10. The Battery Has Sulfated

If your battery isn’t holding a charge hardly at all, the most likely cause is sulfation.

Battery sulfation is kind of like barnacles growing on the hull of a ship. Big, ugly lead sulfate crystals attach themselves to the battery plates. As the crystals grow, the usable surface area of the plates decreases. Eventually, the plates become completely covered, and the battery is useless.

Sulfation occurs when the voltage drops below 12.5 volts, or about 80 percent state of charge.

Battery sulfation is the chemical equivalent of old age: It happens to all lead-acid batteries eventually. But if you store your RV batteries in a hot place, don’t trickle charge it, and don’t keep it fully charged, you’ll speed up the sulfation process. You could kill a battery in just one off-season!

And remember: Batteries self-discharge. They lose energy at a rate of 3-10% per month (the hotter, the faster). So don’t assume you can put away a full battery in November and take it out in April! You need to put your battery on a trickle charger during the off-season.

If you don’t have a trickle charger, just plug in your RV for at least 8 hours once a month.

P.S. A lot of people confuse a sulfated battery for the alleged “memory effect!” They notice that when a battery is only charged to, say, 70 percent, it won’t hold a full charge after a while. That’s NOT because of a memory effect; that’s because of sulfation.

That’s why it’s so important to charge/discharge your battery regularly! Some smart battery chargers feature a “battery maintenance” or “equalization” mode, which hits the battery with a high voltage boost to break up any lead sulfate crystals. Some marketing materials refer to these as “4-stage” chargers.

11. You’re Running Your Inverter

I hate to be the bearer of bad news. Still, unless you’ve significantly upgraded the capacity of your battery bank, your battery simply isn’t capable of operating your inverter for very long (unless it’s a small 150-300W portable inverter).

Your inverter itself isn’t the culprit. It’s whatever your inverter is powering, like a TV, microwave, etc. Most AC-powered devices, like microwaves and coffee machines, just require too much energy.

For instance, did you know running a 900W microwave for just 30-40 minutes can completely discharge the typical RV house battery?

And running your air conditioner – ooops, actually, it isn’t usually possible to run your A/C off an RV battery. But if you had an inverter large enough, you could drain your battery in just 5-15 minutes!

12. You Didn’t Wait Long Enough

Unfortunately, lead-acid batteries charge slowly. Well, kind of. They charge really fast from empty, but that last 20 percent can take longer than the other 80 percent!

A typical RV converter/charger can take 6-10 hours to fully charge a dead RV battery!

So don’t be impatient. Leave your RV plugged in to a power pedestal as long as you can.

P.S. If you’re constantly on the go, you might to check out lithium batteries. They can charge 4-5x faster than a lead-acid battery!

13. You Fully Discharged the Battery

I’ve written about this problem many times before. You can’t discharge a lead-acid battery all the way! Even deep-cycle RV batteries are only designed to be discharged to 40-50 percent.

Many lead-acid batteries suffer irreparable damage when discharged below 20 percent. It only takes a few deep discharge cycles to catastrophically shorten the lifespan of your house batteries.

Again, if you want full use of your batteries, check out lithium ion RV batteries. They’re eyebrow-raising expensive, but IMHO, worth it for serious travelers.

14. You Have a Bad Alternator

Driving a motorhome? The alternator is supposed to charge your house batteries while you drive. But if you have a bad alternator, the batteries simply won’t charge.

Many people find out they have a bad alternator when the starting batteries don’t have enough juice to turn over the starter motor, and you’re stuck until the tow truck arrives.

If you suspect a bad alternator, take your RV to a service shop or an auto parts store. Most auto parts stores can test for a bad alternator, even if they might not have your model in stock.

15. You Tried to Charge a Frozen Battery

Can a battery freeze?

Sure. Lead-acid batteries can freeze at a variety of temperatures depending on the state of charge. Lithium batteries can freeze as soon as the thermometer hits 32 degrees!

If you try to charge a frozen battery, there’s a good chance you’ve killed it. Or make it explode. Don’t do that.

(Although even if you don’t recharge a frozen battery, you still might have killed it. Water expands when it turns to ice, remember? If enough of the electrolyte inside freezes, the “internal organs” of the battery might have fractured or collapsed.)

To avoid a frozen RV battery, keep your batteries charged all the way! And keep your lithium batteries in a heated compartment or insulation wrap.

16. You Boiled the Battery

Like humans, batteries are mostly water. And if you overcharge a battery, the water in the electrolyte will boil out. Literally like a tea kettle. If you overcharge your battery, your battery will be thirsty!

Most smart chargers have (mostly) eliminated this problem with the final float stage. And if you’re using an SLA/AGM battery, as long as the internal pressure stays below a maximum threshold, the electrolyte will be reconstituted within the battery. So this problem isn’t as common as it once was.

But if you’re using old tech, you could be overcharging the battery. If you have a wet/flooded lead-acid battery, you should check the electrolyte cells every month and refill with distilled water, if necessary.

17. It’s the Tow Vehicles Fault!

If …

  • A) Your umbilical cord charges your house battery through a direct connection (very common)
  • B) There’s no isolation solenoid between your trailer and your tow vehicle (also very common)

…. Then your tow vehicle could be draining power from your RV battery! In particular, if you left on your headlights or blasted the radio, you could drain your RV batteries in just a few hours.

And if you’re relying on your tow vehicle to completely charge your RV house batteries … tsk tsk … you might be disappointed. I actually wrote an entire article about this common myth.

18. You Didn’t Accurately Measure the Battery Voltage

“But Ross!,” you say, “My battery charger said my battery was 100% full!”

  • First of all, never trust a cheap battery charger!
  • Secondly, even if you’re using a voltmeter, there are all sorts of ways to mess up measuring battery charge. If you’re reading a voltage difference between the terminals, you need to let the battery rest for 4-6 hours without being connected to a load for the voltage to stabilize.
  • Thirdly, are you sure you’re measuring the correct voltage for your battery? AGM batteries have slightly higher open-circuit voltages than flooded lead-acid batteries, for instance.
  • Fourthly, if you have multiple batteries in your bank, did you check them all? One could be good, and the rest bad! This is a common problem if you only replace one old battery in a multiple battery bank.

***

If none of these sound like your problem … then I’m completely stumped. You’re welcome to send me an email about your problem. I’ll noodle over the problem. And if you’ve signed up for my monthly newsletter, you’re guaranteed an answer (just not necessarily an accurate one).

Happy camping!

Ross

RV engineer by day, intrepid blogger by night (and occasionally weekends). This website is all about how RVs work, and sometimes why they don't. Bookmark pages that you find helpful, and join my email list for exclusive monthly awesomeness.