Winter Adventures Made Easy: How Self-Heating Batteries Keeps Your Power Going
Since we’ve been traveling in our solar powered vintage camper full-time since the fall of 2012, we’ve chosen a different region in which to basecamp each winter. We typically try to stay in warmer climates so we can spend more time outside. Some winters we’ve enjoyed the California coast, others we’ve explored the deserts of the southwest, and we spent one holiday season on the beach of Padre Island National Seashore in Texas. Even with our attempts to avoid cold temperatures, we’ve always encountered some unexpected winter weather events along the way – several nights below freezing in the southwestern deserts in 2019, the two-week Texas “deep freeze” in 2021, and this year we’ve been hit with snowstorms, ice storms, and several weeks of below freezing temps in the southeast! Being able to roll with these changes is part of living life on the road, but it can be hard on both you and your deep cycle batteries.
We first learned this lesson the hard way a couple of years ago when we woke up to 6 inches of snow on the ground the day after Halloween, then experienced frigid temperatures for several days. While our LiFePO4 batteries continued to power our electrical needs, we didn’t realize that the batteries could actually freeze inside of our camper while we were out and about and not heating the camper during the day. We came back to frozen batteries after a morning snowshoe with friends, and no way to charge them back up - even though there was plenty of sunshine!
When our LiFePO4 battery bank core temperature dropped below 32°F (0°C), we couldn’t charge them until they thawed out because the internal chemical reactions in the battery slow down or stop altogether – a problem which plagues all types and chemistries of deep-cycle batteries. The LiFePO4 battery’s BMS actually shuts down all charging when it’s too cold – known as the low temperature protection mode.
So, there we were trying to blow heat from a small fan strapped to the top of our portable propane heater into our solar component cabinet. We even tried a hair dryer to warm the batteries up. Finally, we moved our camper so that the sun was hitting the side where the solar cabinet is located, hoping to warm the wall next to it. This comical process took several hours and caused us much frustration!
To help prevent it from happening again, we added some insulation between the battery bank and camper floor / exterior wall, which helped a bit, but wasn’t enough in severe winter temps. We found that every time we were not actively heating the camper to keep ourselves warm, the batteries would drop below freezing and we were stuck with the same scenario. What we needed was a self-heating battery bank so we didn’t have to use up all of our propane and personal time just to warm up our battery bank so they could charge again!
What is a Self-Heating LiFePO4 Battery?
Most modern LiFePO4 batteries have a Battery Management System (BMS), a small computer chip that controls the safe operation of the battery. But, there are some major differences between how the BMS responds in a standard LiFePO4 battery (with no self-heating) and how it responds when a self-heating function is present.
Basically, when the BMS of the standard LiFeP04 senses that the core temperature of the battery cells (not just ambient temperature) is below 32°F (0°C), it protects the battery by shutting down the battery’s ability to charge while frozen. But, when the BMS of a self-heating battery senses that the core temperature of the battery has dropped below 41°F (5°C) AND has at least 4-10 amps of power coming from any charging source (depending on the battery’s self-heating power requirements), a small internal heating pad kicks on to keep the battery at an optimal charging temperature – allowing it to recharge normally. As you can imagine, this self-heating feature is a complete game changer for adventurous folks like us who travel year round!
After all the crazy fluctuating winter temperatures we’d experienced over the years, we realized that we needed self-heating batteries to give us peace of mind! We now have 2 of Renogy’s 100Ah LiFePO4 PRO batteries inside our camper’s solar component cabinet and a brand new DuoHeat 100Ah Mini Core battery in our truck to power our 12V ICECO fridge freezer. With this new set-up in place, we have finally found the perfect battery solution that can seamlessly handle all of the challenges that winter might throw at them! This eliminates any “winter battery anxiety” because we know that we’ll be able to recharge our batteries anytime and anywhere we need to by using solar power, our 50A DC to DC charger, or our 20A AC to DC charger.
Renogy’s Solution: DuoHeat Technology
True to its name, the DuoHeat Mini Core battery has two internal heating pads (one above and one below the internal battery cells) to gently warm the battery. Basically, when the DuoHeat Mini Core battery is frozen, the self-heating function will begin heating the battery when both of these conditions are met:
The internal temp is below 41F (or 5C).
- AND -
There is a charging source equal to or greater than 10A.
When the battery cells are above freezing, it will begin charging. Once the battery cells reach 50°F (or 10°C), the heater turns off. Simple, right?
We’ve been impressed by the DuoHeat battery’s ability to seamlessly power our 12V ICECO fridge freezer located in the back of our truck (where there is no insulation from the cold) using our 50A DC to DC Charger with MPPT as a power source while traveling in some sub-freezing temperatures this winter. But, we were curious about just how quickly the battery could heat up from freezing, so we put it through some extreme tests!
We ran several rigorous freeze-thaw tests to see how well it performed, and compared these results to our previous self-heating batteries in order to note any differences. Spoiler Alert! We were amazed by the results of this little dynamo! You can watch our review video here for all the nerdy details!
DuoHeat Battery Testing Results
After putting the DuoHeat battery in the freezer overnight, we transferred it to a cooler packed with ice so it would be less affected by the higher ambient temperature during testing. To monitor the battery, we connected the frozen battery to our camper’s electrical system and used the Battery Shunt 300 and our Renogy ONE Core monitor to watch its progress. Here’s a quick summary of our results:
First, we tried discharging it while it was still frozen at 17.8°F (-7.9°C). It handled a load of >14A while at a very low SOC of 28% for several minutes.
Next, we tried to start charging it up again using our 400W Lightweight Solar Suitcase and/or our 20A AC to DC Charger. These charging sources could provide the necessary amperage (>10A) it needed to begin heating the battery cells.
During each of the 4 times we did this freeze-thaw test, it took between 11 - 20 minutes to heat the battery from well below freezing to above 32°F (0°C) so that it could start charging. Now, that’s fast, y’all! Note: The amount of time it took to heat depended on how cold the battery cells were at the beginning of each test.
Bottomline, the frozen cells discharged appropriately, even at a very low SOC. And, in the time it took us to make coffee and a quick breakfast, the batteries were heated and were already charging. Impressive!
For comparison, when we tested our 100aH LiFePO4 PRO batteries in a similar manner last year, they took just over an hour to heat up enough to begin charging. To be fair, they are larger batteries with more mass overall, use less power to heat (100V vs 110V), and only have one heating pad as opposed to two in the DuoHeat.
Does the DuoHeat Have Any Limitations?
While DuoHeat Tech solves many wintertime problems, nothing is perfect. Extreme cold like -40°F (-40°C) can still affect battery performance.
Here are a few things to keep in mind if you plan to live/travel in EXTREMELY cold weather:
Protect your batteries with insulation or store them in a warmer location whenever possible.
Never connect a high load or a powerful charging source to a battery that is near its cold temperature cutoff – i.e., anywhere close to below 0°F (-18°C).
To get the battery out of protection mode when the low-temperature protection is triggered, bring the battery into your living space (above freezing) and let it slowly warm up before connecting it to a heating / charging source.
If you aren’t using it during the winter months, store it well above -4°F (-20°C) in order to protect it and extend the life of the battery.
Additional Benefits of the DuoHeat Battery
This little dynamo weighs in at just 21 pounds and its small size allows it to fit just about anywhere in your RV, van, boat, cabin, ice fishing shanty…you name it. In addition to being able to flawlessly deliver power in just about any conditions that Mother Nature can throw at it, it charges up fast and has a 5000+ cycle lifespan.
For additional peace of mind, the DuoHeat Mini Core BMS has 25 safety features that will extend the life of the battery, including: overcharge, over-discharge, over-current, short-circuit, and low/high temperature protections, as well as a battery balancing feature to boot!
If you’ve found yourself feeling some “winter battery anxiety” like we have several times over the past decade, upgrading to a DuoHeat battery will give you the confidence you may need to extend your adventures into the colder seasons without having to worry about not being able to recharge your batteries. Next winter, you’ll be able to take your rig up to the slopes to do some snowboarding or skiing. Or, get one of these powerful, compact batteries to run a small heater that’ll keep your ice fishing shanty warm and toasty. Sometimes, just having peace of mind is worth every penny!
☝Don't forget to use our Solar System Sizing Worksheet to determine your energy needs, learn more about the components you need to build out a system, and even put together an order with all the wiring, fuses, monitor, and accessories you need. It's a super helpful tool to simplify this complex process. Remember to use our link AND promo code CANLIFE at checkout to save a bundle on Renogy components! And, of course, holler back with questions. We love to help!
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