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Comparison — components
Ni-MH vs lithium battery packs: an OEM comparison
Every equipment buyer eventually faces the chemistry question: the mature, forgiving nickel-metal hydride platform, or the denser, fussier lithium family. Both appear in this catalogue's own products — Ni-MH in the garden lights and as a component family in its own right, lithium cells inside the security lights and ceiling lights — which makes the comparison concrete rather than theoretical. This post compares the two as an OEM would: on the criteria that decide a programme.
Energy density and format
Lithium wins on density, full stop: more watt-hours per gram and per cubic centimetre, in both cylindrical cells (the 18650 format used in the catalogue's security and ceiling lights) and in large-format banks (the 20 AH LiFePO4 battery in the corridor bulkhead). Ni-MH's counter is format flexibility at small scale — button cells and configured packs of standard cells, with a published designation system in this catalogue that encodes cell count, type, capacity, configuration and connector, so a pack is specified as a code rather than engineered as a project.
Safety, transport and compliance burden
Ni-MH is the low-drama chemistry: thermally tolerant, electrically forgiving, and far simpler to ship — air-freight restrictions and dangerous-goods paperwork that attach to lithium largely do not apply. Lithium programmes carry protection circuits, stricter packing and testing documentation, and carrier limits as standing overhead. For low-value, high-volume equipment, that overhead can exceed the cell cost difference. (Certificates and test documents for any specific pack are confirmed per order — certificates available upon request.)
Cycle behaviour and service model
Lithium generally delivers more cycles at deeper discharge, and holds charge longer on the shelf. Ni-MH self-discharges faster but tolerates overcharge and abuse that would end a lithium cell, and its cells are individually replaceable in many pack designs — a service model that suits equipment expected to be maintained rather than replaced. In solar garden products this is why Ni-MH persists: a 600 mAh Ni-MH cell in a lawn light is cheap, safe, solar-chargeable without complex management, and field-replaceable.
Cost structure
Per watt-hour, lithium usually wins at large capacities; per programme, Ni-MH often wins at small ones, once lithium's protection, certification and freight overheads are counted. The honest comparison is total programme cost at your capacity point — which is why both chemistries survive in one catalogue: below a few watt-hours in simple devices, Ni-MH is the rational default; above that, or wherever runtime per gram sells the product, lithium takes over.
| Criterion | Ni-MH | Lithium |
|---|---|---|
| Energy density | Lower | Higher |
| Small-format flexibility | Button cells, coded pack system | Strong in standard cylindrical/pouch formats |
| Transport burden | Low | Higher — DG rules, testing, packing |
| Abuse tolerance | High | Needs protection circuitry |
| Shelf self-discharge | Faster | Slower |
| Typical catalogue home | Garden lights, component packs | Security/ceiling lights |
The Ni-MH family — cells, button cells and configured packs — is documented on the Ni-MH batteries page. For how pack decisions interact with harness specification, read wiring harness design; for the systems these packs power, see the home backup sizing guide.
The designation system: specifying a pack as a code
The Ni-MH catalogue's quiet advantage is administrative. Its designation system encodes the pack — cell count, cell type, capacity in mAh, combination form and connector code — into a single ordering reference, with a connector cross-reference (M for MITSUM-M63, J for JST-HER-02, X for MOLEX-5264-02, with further codes U, W and T in the same table) doing the same for the interface. The five recorded combination shapes for button-cell packs (A, B, E, G, L) cover the geometries small equipment actually uses. A buyer can therefore specify, quote and reorder a custom-shaped pack in one line of text, with no drawing exchange and no ambiguity about which of forty variants shipped last time. Lithium programmes can of course be documented the same way, but in this catalogue it is the Ni-MH family that arrives with the system built in — a small thing that compounds across years of reorders.
End-of-life and replacement economics
The last comparison is the one made at year three. A Ni-MH pack in serviceable equipment is a replaceable component: standard cells, a coded configuration, a swap a technician performs in minutes — the equipment's life is not hostage to a proprietary battery programme. A welded lithium bank in a sealed product is a different contract: more energy while it lasts, and a product-level decision when it fades. Neither is wrong; they suit different product philosophies. Equipment designed to be maintained — the kind this component range largely serves — should price the replacement path at design time, and that pricing conversation routinely moves borderline programmes back to Ni-MH even after lithium has won the density argument.
A decision rule buyers can actually use
Compress the comparison into a rule and it reads like this. If the pack is small, the device is simple, the freight is long and the product will be maintained — choose Ni-MH and spend the savings on the rest of the programme. If runtime per gram is the selling point, the capacity is large, or the product is sealed and premium — choose lithium and budget its overheads honestly: protection, testing, packing and freight. If the answer is genuinely borderline, price both as programmes rather than as cells; the cell-level comparison is the one most likely to mislead, because the two chemistries distribute their costs so differently across a programme's life. The catalogue keeps both because its customers keep landing on both sides of the rule — usually, on inspection, correctly.
What the solar catalogue teaches
It is worth closing where this comparison began: inside one catalogue that runs both chemistries side by side. The garden lights chose Ni-MH because their batteries are small, their charging is uncontrolled sunlight and their price points are unforgiving. The security and ceiling lights chose lithium because their runtime claims are the product and their enclosures are sealed. The corridor bulkhead chose LiFePO4 because a 20 AH bank behind a radar sensor is a capacity argument nothing else answers. No committee decreed a chemistry policy; each product's physics and economics picked its own winner. OEM buyers facing the same choice for a new programme could do worse than to interrogate their product the same way — the chemistry question, asked honestly per product, tends to answer itself.
A last practical note: whichever chemistry a programme chooses, the pack specification should be filed with the same rigour as the product's own record — configuration, connector, capacity, and the confirmation documents agreed at order. Battery decisions outlive the staff who made them, and the programme that can produce its pack file in one thread, years later, reorders in days. The chemistry debate gets the attention; the filing habit earns the money.