The INR21700-50 comes in two builds with the same 5000 mAh nominal capacity:
the 50D (high-power, the -D in
the model-number system) and the
50E (energy type). On a datasheet skim they look interchangeable — same
capacity, same 3.6 V, same 15 A continuous discharge, same ≤72 g. The
differences sit in the test data, and they decide which one belongs in your
pack.
TL;DR
- Pick the 50D if the pack must charge at 1C — full in roughly 70–80 minutes. Shared e-mobility fleets, tools recharged between shifts, AGVs on opportunity charging.
- Pick the 50E if the pack charges overnight and cycles daily — 33% more rated cycle life, better heat and cold tolerance. Home and commercial energy storage, UPS, telecom backup.
What’s identical
| Parameter | Both builds |
|---|---|
| Nominal / minimum capacity | 5000 / 4900 mAh |
| Nominal voltage | 3.60 V (18 Wh per cell) |
| AC internal resistance | ≤18 mΩ |
| Max continuous discharge | 3C (15 A), 5C pulse |
| Weight | ≤72 g |
| Charge / discharge temperature | 0–50 °C / −20–60 °C |
| 28-day charge retention | ≥90% |
The five differences that matter
| Factory test spec | 50D | 50E |
|---|---|---|
| Max continuous charge | 1C (5 A) | 0.5C (2.5 A) |
| Cycle life to 80% | ≥600 (1C/1C) | ≥800 (0.5C/1C) |
| Relative capacity at 55 °C | ≥95% | ≥98% |
| Relative capacity at −20 °C | ≥60% | ≥70% |
| Max size with PET sleeve | Ø21.7 × 70.9 mm | Ø21.0 × 70.0 mm |
1. Charge rate is the headline difference
The 50D accepts 1C continuous charge — a full charge in well under 90 minutes. The 50E tops out at 0.5C, roughly two and a half hours. If your duty cycle has the pack back on the charger mid-day, the 50D is the only correct answer: charging the 50E at 1C would violate its rating and age it fast.
2. Cycle life favours the 50E — at its own charge rate
≥800 cycles versus ≥600 to the same 80% threshold is a 33% longer service life for a daily-cycled storage pack — but note the test conditions: the 50E earns its 800 at a gentler 0.5C charge. Cycle ratings are only comparable like for like — see why C-rate context matters.
3 & 4. Temperature margins
The 50E holds more capacity at both ends — ≥98% at 55 °C and ≥70% at −20 °C (versus ≥95% and ≥60% for the 50D). For outdoor cabinets, rooftop ESS or unheated sites, that −20 °C margin is the difference between a pack that meets its winter runtime spec and one that doesn’t.
5. The size detail that catches pack designers
The 50D’s maximum envelope with PET sleeve is Ø21.7 × 70.9 mm — about 0.7 mm wider and 0.9 mm taller than the 50E (Ø21.0 × 70.0 mm). If your holders, nickel strips or enclosure were CAD’d around a nominal 21700, verify clearances before committing to the 50D. We flag this on every quote; it is the most common surprise with this model.
Decision checklist
- Pack recharges in under 2 hours? → 50D, no further debate.
- Daily cycling, calendar life is the KPI? → 50E.
- Winter operation below −10 °C? → 50E for the capacity margin.
- Existing fixture tooled to Ø21.1 mm max? → 50E, or re-verify fit for 50D.
- Mixed duty? Tell us the duty cycle in the RFQ — we’ll match the build and binning.
Full test tables for both builds are in the INR21700-50 specifications, and the broader format comparison in 18650 vs 21700.
Samples of both builds can ship in one order so your lab can A/B them. Request 50D/50E samples & wholesale quote →