OKMO 100Ah LiFePO4: Budget Power with a Catch

I recently got my hands on the OKMO 12.8V 100Ah LiFePO4 battery, a budget-friendly option that promises solid performance. I wanted to see if it could deliver on those promises, especially when pushed to its limits. What I found was a battery that offers impressive value and surge capability, but with one crucial detail that any DIY solar enthusiast needs to be aware of.

Disclosure: OKMO sent this unit for testing. All opinions and test results are my own.

What I Built

To really put the OKMO battery through its paces, I set up a series of rigorous tests. The core of my setup included the OKMO 12.8V 100Ah LiFePO4 battery, a Medqpur 3000W pure sine wave inverter, and a Victron SmartShunt to accurately monitor all the power flowing in and out. For the discharge and overcurrent tests, I used a high-draw electric space heater and a heat gun. These appliances are known for their significant power consumption, making them perfect for stress testing.

Later, I hooked the system up to a 15,000 BTU air conditioner to see how it handled extreme surge loads. For the capacity test, I discharged the battery into an Anker power station, carefully tracking the amp-hours and watt-hours. Finally, to test the low-temperature charging protection, I placed the battery in a freezer to bring its internal temperature down significantly before attempting to charge it.

Why It Works

LiFePO4 batteries like the OKMO are popular for a reason. They offer a much longer cycle life, are safer, and typically lighter than traditional lead-acid batteries. The internal Battery Management System (BMS) is crucial for a LiFePO4 battery, protecting it from overcharge, over-discharge, overcurrent, and short circuits. Many modern LiFePO4 batteries also include low-temperature charging protection, which prevents damage by stopping the charging process if the battery's internal temperature drops below freezing.

A good battery and inverter combination should be able to handle not just continuous loads, but also significant surge loads from appliances like air conditioners or power tools. These initial power spikes can be several times higher than the continuous running wattage, making robust surge capability a must for many off-grid or backup power applications. The ability to connect 12V batteries in series or parallel also offers incredible flexibility, allowing users to build 12V, 24V, 36V, or even 48V systems to match specific inverter requirements or increase overall capacity.

Parts & Specs

• Battery: OKMO 12.8V 100Ah LiFePO4 (1280Wh)
• BMS: Rated for 100A continuous discharge
• Max Continuous Discharge Current: 100A
• Max Continuous Output Power: 1280W
• Low Temperature Charging Protection (LTCP): Yes
• Max Expansion: 4S4P (4 in series, 4 in parallel)
• Weight: 24.25 lbs
• Housing Material: ABS (Flame Retardant Plastic)
• Protection Class: IP65
• Inverter: Medqpur 3000W Pure Sine Wave Inverter
• Monitor: Victron SmartShunt 500A/50mV
• Load Devices: Electric space heater, Makita heat gun, 15,000 BTU portable air conditioner
• Discharge Load: Anker PowerHouse

Math & Run-Time Numbers

My tests revealed some interesting numbers for the OKMO battery:

• Space Heater (Fan Only): Pulled about 38W.
• Space Heater (Low Heat): Pulled around 880-930W, drawing 70-73A from the battery.
• Space Heater (High Heat): Pulled approximately 1384W, drawing 112A from the battery.
• Space Heater (High) + Heat Gun: Combined load reached up to 2417W, drawing over 200A from the battery.
• Capacity Test: The battery discharged 98Ah, totaling 1.3kWh. This is very close to its rated 100Ah / 1280Wh capacity.
• 15,000 BTU AC Unit: The battery and inverter successfully started and ran the AC unit. While the exact surge current wasn't captured, the fact that it started is impressive, as AC units typically have very high startup surges.

It's worth noting that the battery’s internal BMS did not trip or shut off even when pulling over 200A, which is twice its rated continuous discharge current of 100A. This means the battery's internal protections for overcurrent did not engage.

Pros & Cons

Pros

• Excellent Capacity: Delivered 98Ah / 1.3kWh, very close to its advertised 100Ah / 1280Wh.
• Impressive Surge Capability: Successfully started a 15,000 BTU air conditioner, demonstrating strong performance for high-draw appliances.
• Effective Low-Temperature Charge Protection: The battery correctly rejected charge when frozen, preventing potential damage.
• Flexible Configuration: Can be wired in series and parallel (up to 4S4P), allowing for versatile system designs from 12V to 48V.
• Good Value: Offers a lot of power for the price, making it a budget-friendly option for DIY setups.

Cons

• Critical Overcurrent BMS Issue: The internal BMS did not trip when discharge current exceeded 200A, which is double its 100A continuous rating. This means the battery itself will not protect against excessive current draw, requiring a properly sized external fuse for safety.

When To Use This vs. Alternatives

You should consider the OKMO 12.8V 100Ah LiFePO4 battery if you're looking for a cost-effective solution for your DIY solar or home energy storage needs. Its excellent capacity, impressive surge handling for starting motors, and reliable low-temperature charging protection make it a solid performer for the price. It's particularly well-suited for RVs, off-grid cabins, or backup systems where you need flexible voltage configurations and are willing to integrate external safety measures.

However, if you prefer a battery with a more active and robust internal BMS that will reliably shut off on overcurrent without external intervention, or if you need to consistently pull more than 100A without adding an external fuse, you should look at other options. For this battery, a properly sized external fuse is not optional – it's a critical safety component to protect your system and the battery itself from potential damage due to overcurrent.

Bottom Line

The OKMO 12.8V 100Ah LiFePO4 battery is a strong contender in the budget LiFePO4 market, offering impressive capacity, surge power, and essential low-temperature charging protection. It's a no-frills, get-the-job-done kind of battery that provides a lot of bang for your buck. However, the lack of internal overcurrent protection means you absolutely must install a correctly rated external fuse to ensure the safety and longevity of your system. If you're comfortable with that one extra step, this battery is definitely worth considering.

Final Wrap-Up

What do you think about the OKMO battery's performance? Let me know in the comments below. If you found this review helpful, be sure to subscribe to the YouTube channel for more hands-on tests and DIY solar projects. You can also check out my gear page for links to all the components I use in my setups.