Almost every custom pack enquiry we receive comes down to this decision at some point. It is worth understanding, because getting it wrong is expensive in one of two ways: either the pack does not fit, or it does not last.
The short version
Li-ion (NMC) stores more energy per kilogram and per litre. If the battery compartment is tight, or the product is carried by hand, this is usually the answer.
LiFePO4 survives several times more charge cycles, tolerates heat far better, and is chemically more stable. If the pack is installed outdoors, cycled daily, or expected to last years without attention, this is usually the answer.
Why heat matters more here than in the datasheets
Cell manufacturers rate cycle life at 25°C. A battery inside a sealed enclosure on a Malaysian rooftop does not live at 25°C — it can sit well above ambient for most of the day, every day. Elevated temperature accelerates the ageing of any lithium cell, but it degrades NMC noticeably faster than it degrades LFP.
This is why a solar street light battery that would give years of service in a temperate climate can disappoint here within a couple of seasons, and why we default to LiFePO4 for anything permanently installed outdoors.
Space and weight
The trade-off runs the other way for portable equipment. LiFePO4 cells are physically larger for the same stored energy, so a LiFePO4 pack that matches an NMC pack's capacity may simply not fit the space you have, or may make a handheld product unpleasant to carry.
When a compartment is fixed and small, NMC is frequently the only chemistry that gets the required runtime into the available volume.
A practical way to decide
- Cycled daily and installed outdoors — solar lighting, standby power, monitoring equipment: LiFePO4.
- Carried, or fitted into a tight existing housing — portable speakers, handheld tools, instruments: Li-ion.
- Occasional use, indoors, replaced every few years — either works; cost and fit decide it.
- Safety-critical or unattended installations: LiFePO4, for its thermal stability.
What this means for your enquiry
You do not need to have made this decision before contacting us. Tell us what the battery has to power, where it will live, how often it will be cycled and how much space there is. The chemistry follows from those answers, and we will explain which way we would go and why before anything is built.
Send us the voltage, capacity, discharge current and the space you have — or a photo of the battery you are replacing. We will come back with a specification and a price.