LG HE4 18650 2500mAh Battery: Specs, Performance & Real-World Test

The LG HE4 has been around since late 2013, which in battery years makes it something of a veteran. It's still one of the most commonly recommended 18650 cells for high-drain builds, and there's a reason it hasn't been pushed out by newer releases: it does exactly what it's rated for, consistently, without much drama. Here's what the datasheet actually says, how it holds up against independent bench testing, and where it fits into your build.

What the HE4 Is Actually Built For

The HE4 is a 2,500mAh, 20A continuous-discharge cell — LG's answer to the question of how to pack high current delivery into a standard 18650 without sacrificing too much capacity. It launched just a few months after LG's HE2, and the two are close enough in spec that people still argue about which one is "better." The short version: they're nearly identical in raw numbers, but the HE4 was tested with a slightly more conservative cutoff voltage and has shown marginally better thermal behavior in side-by-side testing — worth knowing if you're choosing between the two, but not a reason to overthink it if you already have HE4s in hand.

Where the HE4 earns its keep is in devices that need real, sustained current — not the kind of "peak burst" numbers that show up in inflated marketing copy, but current the cell can actually deliver for extended periods without falling apart.

Full Spec Breakdown

One thing worth flagging directly: you'll occasionally see the HE4 listed as a "35A" battery. That number doesn't come from LG's official datasheet — the documented continuous discharge rating is 20A. If a listing quotes 35A without qualifying it as a short pulse figure, treat that as marketing inflation rather than a spec you should design around.

Safety features: The HE4 is sold as an unprotected cell, meaning the safety limits above — voltage cutoffs, max discharge current — are what the cell is designed to operate within, not something enforced by an onboard circuit. Devices or battery packs using the HE4 need their own protection circuitry (BMS) to actually enforce overcharge, over-discharge, and short-circuit protection. This isn't a flaw specific to the HE4 — it's standard for this class of high-drain 18650 cell, and it's worth understanding before you build anything with it.

Real-World Test Results

Independent capacity testing on the HE4, discharging at 2.5A down to the 2.5V cutoff, has measured actual capacity right around 2,493mAh — essentially matching the 2,500mAh nominal rating. That's a good sign; a lot of cells fall noticeably short of their labeled capacity, and the HE4 doesn't.

Discharge curve: The HE4 holds a steady voltage plateau through most of its discharge cycle before tapering toward the 2.5V cutoff, which is what you want to see — a cell that drops off sharply well before its rated cutoff is one that's going to underperform in real devices.

Heat under load: In back-to-back bench comparisons against the HE2 at similar discharge rates, the HE4 ran a few degrees cooler on average — roughly 34-35°C surface temperature versus 36-37°C for the HE2 under the same test conditions. It's a modest difference, not a dramatic one, but it does suggest the HE4's construction handles sustained high-drain use slightly more efficiently.

Storage behavior: LG's own documentation specifies different storage temperature windows depending on how long the cell sits unused — roughly -20°C to 60°C for short-term storage (up to a month), narrowing to -20°C to 45°C for three months, and -20°C to 20°C if you're storing it for a full year. The takeaway: if you're not using a set of HE4s for a while, keep them somewhere cool rather than in a hot garage or car, and don't store them fully charged — around 40% charge is the standard recommendation for long-term storage.

Where the HE4 Actually Performs Best

• High-output flashlights and headlamps — the HE4's steady discharge curve and 20A ceiling make it a solid match for lights running turbo or high modes for extended periods, not just quick bursts
• Sub-ohm vape mods and regulated devices — plenty of current headroom for most builds without pushing the cell to its absolute limit
• Power tools — cordless drills, saws, and similar tools that draw hard and often benefit from the HE4's proven cycle stability under repeated high-drain use
• E-bikes and scooters — commonly used in DIY and OEM battery packs where multiple cells in parallel need to deliver sustained current
• DIY battery packs generally — its predictable performance and wide temperature tolerance make it a forgiving cell to design around

It's not the right choice if your device needs more than 20A per cell sustained, or if capacity matters more to you than discharge rate — in that case, a higher-capacity, lower-drain cell will serve you better.

Pros, Cons, and What Users Actually Report

Pros

• Real-world capacity lines up closely with the rated 2,500mAh
• Clean, predictable discharge curve with no early voltage collapse
• Slightly cooler running than its close sibling, the HE2, under sustained high-drain loads
• Long track record — over a decade in circulation with a well-documented safety and performance history
• Widely available, which makes it easier to verify authenticity against a known datasheet

Cons

• Unprotected cell — requires external protection circuitry in any pack build
• 20A ceiling means it's not suited for devices that need higher sustained current
• Frequently mislabeled by resellers claiming inflated discharge ratings (that "35A" figure being the most common example)
• As an older design, it's gradually being supplemented by newer high-drain cells in some product categories

User feedback across flashlight and vaping communities is consistently positive within the cell's intended use — people report long service life and stable output when the HE4 is matched to a device that doesn't exceed its 20A rating. Most negative reviews trace back to counterfeit cells or devices drawing more current than the cell is built for, not the genuine LG product itself.

Frequently Asked Questions

How long does the LG HE4 actually last? LG rates it for 200 cycles before capacity drops below roughly 2,000mAh — an 80% capacity retention cutoff. The cell continues to work past that point, but with noticeably reduced runtime. Real-world lifespan depends heavily on how hard you discharge it and how well you store it; lighter, more moderate use will extend usable life well beyond that 200-cycle mark.

What's the self-discharge rate on the HE4? LG doesn't publish an unusually high self-discharge figure for this cell — it behaves like a standard, well-made lithium-ion cell, with low single-digit percentage loss per month under normal storage conditions. If a cell you own is losing charge noticeably faster than that while sitting unused, it's more likely a sign of a counterfeit or degraded cell than a chemistry issue.

Is the HE4 compatible with my device? Compatibility comes down to two things: physical fit (standard 18650 dimensions, so it fits most 18650-compatible devices) and electrical match (your device needs to draw 20A or less per cell, and your charger needs to handle standard Li-ion charging profiles — 4.2V max, up to 4A charge current). If your mod, flashlight, or pack is designed around genuine 18650 cells and doesn't demand more than 20A continuous per cell, the HE4 will work.

Can I mix HE4 cells with other battery models in a pack? It's not recommended. Mixing cells of different capacities, ages, or internal resistance in a series or parallel pack can cause imbalanced charging and discharging, which shortens the life of the whole pack and creates a safety risk. Stick to matched sets of HE4s from the same batch where possible.

Ready to Order?

We stock genuine LG HE4 cells verified against LG's official datasheet, so you're not gambling on a mislabeled or counterfeit "35A" knockoff. Check our LG HE4 product page for current stock, pricing, and available configurations, and reach out before ordering if you're not sure whether the HE4 or a different cell in our lineup is the better fit for your build.