How to prolong the life of your lithium batteries

TIP 1 Ideally, try to keep the battery state of charge around 30-80%.

Step 1: Prevent overcharge and overdischarge

Overdischarging a LiFePO4 (Lithium Iron Phosphate) battery can cause significant damage and reduce its lifespan. Over-disharge:

Exacerbates cell imbalances.
Causes chemical degradation.
Can cause structural damage.

The battery management system will have a discharge cut off voltage, for example 8.8V, but this is typically set to protect the battery from serious damage rather than to prolong the life of the battery.

To prolong the life of a lithium battery do not discharge below 20% state of charge. It is important to install a reliable battery monitor to know the state of charge.

Overcharging causes similar issues to over-discharge.

The battery management system will have overcharge protection. However, tyring to keep the battery in the 30-80% range will prolong its life.

Slow charging also prolongs the life of lithium batteries.

Step 2: Balance the cells

Cell balancing is an important process for maintaining the health and performance of lithium batteries.

Cell balancing ensures that all the cells in a lithium battery pack have the same voltage level. This is important because lithium cells can have slight variations in capacity and self-discharge rates, which can lead to imbalances over time. Removing the imbalance is important to:

Prevent overcharging and undercharging.
Prolongs the overall lifespan of the battery pack by ensure no single cells are overstressed.
Improves performance by maintaining capacity of the battery.
Safety since prevents overheating of individual cells.

Lithium batteries require a specified “cell balancing voltage” for the battery management system to trigger cell balancing. This should be specified in the datasheet. For example, a datasheet may say 3.45±0.1V. For batteries with 4 cells in series this means the battery management system requires at least 13.8V (3.45V x 4) theshold to trigger cell balancing.

Just ensure that you bring the voltage above the threshold of 13.8V once a fortnight for 1 hour (not required when stored).

TIP 2 Fully charge the batteries once every other week.

Step 3: Store the batteries correctly

Storing the battery at a 100% or below 20% can reduced the lifespan of the battery.

If not using the LiFePO4 batteries for over 2 weeks, disconnect all loads and charging sources.

Then store the battery at 50% state of charge.

Check the battery every 6-12 months.

When putting the battery back into use, charge to 80% before using.

TIP 3 Store the batteries at 50% state of charge.

Step 4: Keep the battery at the optimum temperature

In the UK, most boats and campervans will naturally fall within the optimal operating conditions.

Try and keep the battery within the recommended operating range. Extreme temperatures can negatively impact the battery’s performance and lifespan.

Modern solar charge controllers and battery to battery charge controllers have a setting where you can choose the minimum charge temperature to prolong the life of your battery.

TIP 4 Try and charge discharge and store your battery within the ideal operating temperature range shown in the table.

Good practices

Do not install the battery in the engine compartment.
Do not leave the batteries in direct sunlight.
If travelling to very cold climates, insulate the battery compartment or consider external battery heating. Internal battery heaters are ineffective when storing LiFePO4 batteries since they require current to operate.
If travelling to very warm climates, consider passive or active ventilation.