Smart Charging Secrets: How the 80/20 Rule Protects Your Power

The 80/20 Rule for Lithium Batteries: Maximize Performance and Longevity

Proper care for your lithium-ion batteries can be overwhelming, whether it’s campers, marine applications, powersports or industrial setups, you’ve probably wondered how to get the most life and performance out of them. The truth is actually very simple: your charging habits make a huge difference. The rule of thumb when it comes to your lithium-ion batteries is “the 80/20 rule”. It sounds technical, but in reality, it’s an easy guideline that helps your batteries last longer and stay reliable. So, what does it mean and how can you use it day-to-day?

First of all, let’s clarify the key moments your battery needs to be charged. If you’re using your lithium battery regularly, for example, on a camping trip, sailing or a race, it’s best to charge your battery above 80% before using it to have enough energy for your needs.  This is when the 80/20 rule plays a role. Avoid letting the battery discharge below 20%.

If the season is over and you want to store your battery, don’t leave it too full or too empty before storage. We recommend:

• Charging the battery to 100%, and discharging 5% of the battery using any arbitrary consumer device
• Disconnecting all devices from the battery to prevent drain from ‘hidden’ consumers or if available
• Use the on/off switch in the app or battery switch
• If applicable, disconnect the CANbus from the battery since constant communication also consumes considerable energy.
• Cover the terminals
• Check every three months if it needs to be topped off.

If you’d like to accurately track the SoC (state of charge) use the Be in Charge App on your smartphone, or the Be in Charge Software on your PC.  

Lastly, when it’s time to pull the battery back out after a long break, ALWAYS charge your battery up to 100% before using it again. It may take longer depending on your battery type, since it will only show as “fully charged” when all the cells have rebalanced.

Rebalancing is crucial and should be repeated monthly or every two months. Why? Because each individual cell discharges at a different rate. So, when your battery display says it’s at 20%, that number is the average charge of all the cells, the individual cells inside the battery may vary slightly and we never want them to fully discharge. This balancing happens automatically if you allow a proper full charge with the right charger, but in some cases, it can also be done manually by applying a constant charging curve recommended in your user manual.

Is it okay to charge lithium batteries to 100%?

Yes! Lithium-ion batteries can be charged to 100% daily when they’re being used, the 80/20 rule ensures battery longevity and health when applied regularly, which doesn't mean that charging your battery to 100% is bad.

The 80/20 rule for lithium batteries recommends:

• Charge up to 80% for daily use.  
• Charge to 100% only when needed, such as before a long trip or a full discharge cycle.
• Avoid letting the battery discharge lower than 20%. This is to ensure having enough energy reserve for emergency use and also be on the safe side if you forget charging your battery.

By following this approach, you protect the battery while still accessing full capacity when necessary.

The reason why people discourage charging batteries up to 100% is that it causes more stress to the cells if the battery stays at that level without being discharged. Think of it like this:

You own a small café in Paris. It’s 8 am and people start entering in big groups. Your café is now filled with 100 people, families squeezed into the same tables, all of them ordering coffee at once.

Is that comfortable for the guests or for the employees attending to these guests? No. But after an hour, the people will start to leave after finishing their drinks. When the café reaches a capacity of 80 people or below, the employees can finally breathe again, and the guests can finally place their elbows on the table again. Once in a while, this can happen, and your employees (a.k.a. your batteries' BMS) will be able to handle it, but when this happens daily, after some months or years, the employees will be burned out and won’t offer the best service anymore.

Your battery feels the same. The high-voltage charging increases chemical stress inside the battery, which over time reduces its lifetime, so if you don’t need the 100% capacity, don’t charge it unnecessarily.

Should I charge to 80% every night?

Yes! Daily charging to around 80% is considered optimal for long-term health. Most lithium-ion batteries, including LiFePO₄ (LiFePO4), perform best when they avoid extreme high or low states of charge.

Charging to 80% every night has benefits, it:

• Reduces heat and stress inside the battery.
• Increases the number of cycles your battery can achieve.
• Provides enough usable energy for most daily applications without sacrificing lifespan.

This method is especially helpful in RVs, marine setups, or solar-powered systems, where batteries see frequent partial cycles.
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How to keep your LFP battery healthy

Beyond the 80/20 rule, there are several tips to extend lithium battery longevity:

1. Avoid deep discharges – keep the battery above ~20% whenever possible.
2. Store partially charged – if storing for weeks, 80% is ideal.
3. Keep temperatures moderate – avoid extreme heat or freezing conditions. Keep the storage temperature between -20°C to 45°C / -4°F to 113°F, depending on your battery type, these temperatures may vary, but for all the batteries, these temperatures are safe. If you fear the temperatures may exceed the batteries’ limits beyond these specifications, consider insulation or actively heating/cooling the battery compartment. Find your battery model and check the specific temperatures your battery can withstand on our product page if needed.   https://www.super-b.com/products
4. Use quality chargers – a charger with built-in battery management systems (BMS) prevents overcharge, over-discharge, and thermal stress. Only LFP chargers are well-suited for these batteries. Check your charging manual to ensure you are using a charger that has been approved by Super B.
5. Monitor usage – some systems allow real-time monitoring to track voltage, current, and cycles. We mainly work with the Victron integration, which can be found here. https://www.super-b.com/victron
6. Compatible systems – ensuring your battery is paired with a proper inverter, solar, or alternator system that respects charge limits will also benefit your batteries’ lifespan.

When applied consistently, these strategies maintain battery performance, reduce degradation, and ensure you get the most energy from your investment. This can drastically improve the effective lifespan of a lithium-ion battery compared to neglecting charge cycles.

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