Why LiFePO4 batteries became our go-to for off-grid & backup energy systems

For 48 years, I ran a general store serving ranchers and off-grid homeowners across Montana, Idaho, and Wyoming. We sold generator and hybrid battery-inverter systems long before solar panels were even remotely practical.

For decades, flooded lead-acid batteries were the cornerstone of most systems. Heavy, smelly, and high-maintenance, they required regular attention. Our conversations revolved around fluid levels, sulfation, equalization, and corrosion—not to mention the constant tweaking of charging parameters. Despite these challenges, lead-acid batteries were cost-effective and had a well-understood lifespan and behavior. We could add value to customers by helping them navigate issues associated with lead-acid batteries, and it was a good business.

About 20 years ago, AGM (absorbed glass mat) batteries gained popularity. Though still lead-acid, these batteries used a gel solution. They cost twice as much but needed less maintenance and were sealed and odorless. However, both flooded and AGM batteries still required a full charge every few days to prevent sulfation. Sulfation in a battery is like emphysema for the human lung, significantly reducing battery life and efficiency.

Charging these lead batteries involved a specific process. A generator would perform a hard initial bulk charge, then quickly move to the absorption charge rate to prevent overheating and cell damage. The final float charge was a long, slow process that kept the generator running even though the batteries couldn't absorb much power at this stage. Since recent charging or discharging affected battery voltage, accurately determining the state of charge required using a messy hydrometer to check each cell individually.

That is how it was for the last 30 years.

Our world was revolutionized by the introduction of the lithium-iron-phosphate (LiFePO4) battery in a closed-loop communication relationship with the inverter. Battery performance issues over time have vanished. This has led to a dramatically improved user experience—for those familiar with off-grid living, it seems almost too good to be true.

In 2017, we installed our first Victron inverter system with LiFePO4 batteries for a homeowner who wanted to try something better. We were initially  hesitant  because we had heard horror stories about expensive lithium batteries failing.

Before Victron became available in the US, we hadn't found a battery-inverter system we truly trusted. Many inverter manufacturers didn't support lithium, and some still don't. Our customer's enthusiastic feedback about the system's performance spread quickly. His neighbors told their neighbors. Within months, it was clear that lead-acid batteries were on their way out. Our new challenge was helping off-grid customers upgrade their systems  to take full advantage of this new battery technology.

Today, our customers using LiFePO4 batteries report significantly reduced generator run times and fuel costs. We see customers whose systems meet, and often, exceed their expectations. The self-balancing, well-protected cells in quality LiFePO4 batteries provide more accurate charge state readings. They require no maintenance and produce no odor or mess. And due to their stable chemistry, LiFePO4 batteries don't pose the thermal runaway risks associated with other lithium batteries, making them safe for in-home use rather than requiring storage in sheds or garages.

Typically, lead-acid and LiFePO4 batteries are compared using performance parameters that don't provide a complete picture.

While many factors are involved, two are particularly crucial to compare:

Battery Cycle Life and Depth of Charge

Cycle life is often cited as a significant factor (6 years for lead-acid vs. 16 years for lithium). Depth of discharge is also frequently mentioned (30% vs. 98%), but this can be misleading. The primary advantage for off-grid users is that lithium batteries don't require regular full charges to maintain their chemical health. A larger lead-acid battery discharged to 30% might have the same capacity as a smaller lithium battery discharged to 98%. The key difference is that lithium batteries don't need to be charged every night. If a lithium battery is discharged to 50% and still has enough capacity to get through the night, there is no reason to start the generator. In contrast, a lead-acid battery discharged to even 20% for any length of time, you should start the generator and get it topped off.

Another major benefit of lithium batteries is their charging profile—they can charge at maximum bulk rate up to 98% capacity. This dramatically reduces generator run time, often by half. This reason alone is why many people have chosen to upgrade their systems using lithium batteries. For those new to off-grid living, traditional lead-acid batteries required more frequent and longer charging sessions than lithium. These older batteries were like pouring a glass of root beer—a quick initial fill followed by a long, slow top-off which could last until your next birthday. Consequently, generators were often oversized and very inefficient for much of their run time.

Long-term system health & performance

There's another unexpected benefit of lithium systems: improved solar performance. Without the need for a float charge, solar panels can operate at full output until the battery is fully charged. This efficiency relies on seamless communication between the inverter, solar panels, and batteries. High-quality lithium batteries from manufacturers like Pylontech and BYD feature intelligent battery management systems (BMS) that communicate effortlessly with Victron inverters. The BMS accurately reports the battery's charge status, ensuring the generator starts only when needed and signaling when the battery is fully charged.

The closed-loop battery systems that we sell enable the battery to protect itself and maintain itself better than was previously possible with isolated batteries. These systems keep all batteries balanced and working in harmony, maximizing overall capacity. This level of communication makes it challenging to damage batteries through overcharging. As the batteries age, the system automatically adjusts to ensure the longest possible lifespan.

If you're preparing to investing in a lithium battery for an off-grid or hybrid system, it's worth trying to get the best value. Remember, that equation includes more than just the battery—it's about how well the inverter, solar charge controller, and batteries work together as a system.

If you're naturally suspicious like me, you might find the lack of documentation and real-world, third-party performance data on the influx of new lithium-ion batteries concerning. (For more on this topic, read Aaron's blog post about our process for selecting a battery to distribute with our Victron product line.)

Our desire is to confidently recommend battery-inverter combinations that offer world-class performance. The two batteries described below are, in our opinion, the best options on the market today: 

Pylontech

We've been selling Pylontech US5000 and US3000C 48V rack-mount LiFePO4 batteries for the past five years, primarily for residential use, and have had 4 warranty issues on over 1,000 batteries sold - 2 of which we could not easily resolve with a BMS replacement. These batteries have proven resilient even when installed in less-than-ideal temperature and humidity scenarios—think crawl spaces and seasonal cabins subject to extreme temperature fluctuations. 

Pylontech's US5000 is engineered for rack-mounting, with impressive power output. Six US5000 batteries can deliver over 28.8 kW of usable power. Pylontech also makes a 12 Volt 100Ah battery, the RT12100G31, ideal for small compartments in boats and RVs. More recently, we started carrying the UP2500, a 24V rack-mount and the Pelio-L-5.12, a modular, self-contained 48V lithium battery. 

To ensure optimal performance, we recommend pairing these batteries with Victron equipment. Many older systems aren't designed to support lithium batteries effectively—it's unfair to the batteries to connect them to inverters and solar inputs that can't properly manage them. 

Related Reading >>> Victron & Pylontech: a Robust Inverter-Battery Combination for Off-grid Energy Systems

BYD's Battery-Box Premium LV

BYD Battery-Box Premium LVL is the number one 48 Volt lithium battery sold in Germany and boasts an impressive global track record with 250,000 installations. It comes with a nice 15.4kw cabinet, and you can stack two batteries vertically, making for a very compact and nice-looking 30+ kw battery.

It also has tight integration with Victron Energy, and the communication is closed-loop. The BMS has some additional advantages and is external on the BYD, which can offer some advantages for larger systems and can also be monitored remotely on its own.

BYD is a global leader in lithium battery and electric vehicle manufacturing, with an electric bus factory in Los Angeles. Warren Buffett is a major shareholder. All to say: BYD is probably the world's most stable, reliable, vertically integrated battery manufacturers—a company built to last.

Conclusion

We encourage customers shopping for a lithium battery to consider the following:

Manufacturer Credibility 

Does the battery manufacturer have an excellent performance history, a global track record of successful installations, and a clear warranty process? There is a glut of companies, but most are merely battery assemblers, not battery manufacturers.

Is the battery-inverter combination proven to work well together? Don't assume compatibility just because they're sold together on the same website. Look for existing documentation and software support from both the inverter and battery manufacturers. Without this, it's unclear if their R&D departments have any real collaboration at all.

Product Reliability 

Does the company own its technology? Many battery companies don't manufacture their own cells or battery management systems (BMS). Instead, they rely on a generic BMS that they didn't program, meaning it is not designed for their battery cells. A failed BMS can be just as common as cell failure.

Technical Support

Can you confidently access technical support during installation and for future issues? Batteries are expensive and can be challenging to dispose of properly. They should last a long time, but if they don't, you should be able to get the support you need quickly.

Proper initial setup is crucial for these systems to work well. That's why Intelligent Controls, as both a Victron and Pylontech distributor, is positioned to offer specific guidance to installers and end users with a very high degree of confidence.

With this battery-inverter combination, we can quickly resolve any issues because we understand how the system should work and can troubleshoot problems remotely.

Looking for guidance on battery options? Send us a note or email me directly at grant@icmontana.com