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lithium ion battery 11.1 v 4400mah rechargeable Pack 18650
Quick answer: An 11.1V 4400mAh pack is three 18650 cells in series — 3S — giving 11.1V nominal, 4,400mAh and 48Wh, charged to 12.6V and rated for about 4A continuous discharge. It carries a built-in PCM or BMS for balancing and protection against over-charge, over-discharge, over-current, short circuit and over-temperature, in an ABS casing.
The specification, decoded
| Parameter | Value | Note |
|---|---|---|
| Configuration | 3S (three cells in series) | Sets the 11.1V nominal |
| Nominal voltage | 11.1V | 3 x 3.7V cell nominal |
| Charge voltage | 12.6V | 3 x 4.2V full charge |
| Capacity | 4,400mAh | Total pack capacity |
| Energy | 48Wh | 11.1V x 4.4Ah |
| Continuous discharge | 4A (about 1C) | Higher rates available with higher-rate cells |
| Dimensions | 21 x 56 x 138mm | Reference ABS casing build |
| Certifications | UN38.3, MSDS, CE | Transport and market access |
The 3S configuration is why this voltage class is so common. Three 3.7V cells in series give 11.1V, and with the charge voltage at 12.6V the pack sits comfortably within the input range of equipment designed for a nominal 12V supply — which is most portable instruments and lighting.
The protection board
The pack is built around a 3S PCM or BMS, and its role is broader than protection. It balances the three series groups so they do not drift apart in voltage over the pack’s life, controls the charge and discharge current, and cuts the output if a fault is detected — protecting both the pack and the device it powers. On higher-specification builds it also carries a temperature sensor and reports state of charge.
- Over-charge protection — prevents cell damage from an over-voltage.
- Over-discharge protection — prevents the deep discharge that retires a pack early.
- Over-current protection — cuts the output above the rated current.
- Short circuit protection — isolates the pack instantly on a fault.
- Cell balancing — keeps the three series groups at matched voltage.
- Over-temperature protection — where the application requires it.
Why 18650 for this format
18650 cells are the most mature and most widely available lithium format, and their cylindrical geometry makes a 3S pack straightforward to assemble with predictable mechanical behaviour. The chemistry has no memory effect, has a low self-discharge rate and delivers roughly four times the energy density of lead-acid at about a third of the volume — which is why a pack of this size can replace a considerably bulkier sealed lead-acid battery.
| Property | 18650 lithium pack | Equivalent lead-acid |
|---|---|---|
| Energy density | High | Low — several times the volume for the same energy |
| Memory effect | None | None, but poor deep-cycle life |
| Self-discharge | Low | Higher |
| Maintenance | None | Terminal care, ventilation |
| Cycle life | Hundreds of full cycles with gradual decline | Fewer at comparable depth |
| Toxicity | No heavy metals | Lead and acid |
Applications
| Application | Why 11.1V suits it |
|---|---|
| Portable instruments | Nominal 12V design input, compact and light |
| LED lighting | Stable voltage across the discharge range |
| Medical and test equipment | Predictable output with documented protection and certification |
| Robotics | High energy per unit weight for mobile platforms |
| Security and monitoring | Long idle life between recharge cycles |
| Consumer electronics | A common design voltage with wide component support |
Charging and storage practice
Charge with a 12.6V constant-current/constant-voltage profile and a current within the pack’s rating, and never continue charging a pack that has not reached its end voltage within the expected time — that indicates a cell fault rather than an incomplete charge. For storage, leave the pack at about half charge in a cool, dry place and recharge every six months; lithium retains most of its charge over that period, but sitting for long periods at full or zero charge accelerates aging.
Custom builds and private label
The reference configuration is a starting point rather than a fixed product. Three variables are commonly changed: the capacity, by adjusting the parallel count within each series position; the discharge rating, through the choice of cell; and the mechanical envelope, which is defined by the device rather than by the format. Most builds also specify a connector type, a lead length and, where the device requires it, a BMS with communication output rather than a simple protection board.
For retail and OEM programmes the pack, the casing and the label carry the customer’s brand, and the documentation set is issued in the customer’s name. See private label and custom battery pack design for programme detail.
11.1V 4400mAh pack FAQ
What is an 11.1V 4400mAh pack?
Three 18650 cells in series (3S) with a nominal voltage of 11.1V and a total capacity of 4,400mAh, giving 48Wh. The cells are 3.7V nominal each, so three give 11.1V; the 4,400mAh comes from the parallel configuration within each series position.
What is the charge voltage?
12.6V. Each of the three series positions charges to 4.2V, so the pack charger must be set for 12.6V with a constant-current then constant-voltage profile. A charger set for a different cell count will either under-charge or over-charge the pack.
What is the pack’s discharge capability?
4,400mAh at a 4A continuous discharge rating, which is roughly 1C. Higher continuous currents are available with higher-rate cells, but the protection board and the connector must be specified for them as well.
What does the PCM or BMS protect against?
Over-charge, over-discharge, over-current, short circuit and, where fitted, over-temperature. It also balances the three series groups so they do not drift apart, and it cuts the output on a fault to protect both the pack and the device.
Which applications use 11.1V packs?
Portable electronics, instruments, LED lighting, medical and test equipment, robotics and any device designed around a nominal 11.1V or 12V lithium supply. The voltage is common because it is a natural three-cell result.
Can I replace a Ni-Cd or Ni-MH pack with this?
Only if the device’s charger and cut-off behaviour suit lithium. A 12V Ni-MH pack charges on a different profile and tolerates a different end-of-discharge voltage, so the charger or the device’s power path usually has to be adjusted before a lithium pack is substituted.
What is the pack’s physical size?
The reference build is 21mm x 56mm x 138mm in an ABS casing, which gives mechanical protection against impact and an insulated outer surface. A custom envelope is a normal variation, subject to the volume the cells require.
How should the pack be stored?
At about half charge in a cool, dry place, recharging every six months. Lithium self-discharge is a few percent per month, so a stored pack retains most of its charge, but leaving it fully charged or fully discharged for long periods accelerates aging.
Explore related pages
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- 18650 pack calculator
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Tell us the quantity, the connector and lead specification, the required discharge current and any certification target — we return a quotation against your build.
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