Here are solid, affordable smartwatches that are known for long battery life (short descriptions, typical battery estimates, and who each is best for). Prices and exact battery performance vary by settings and use; I’ve included recent sources for each pick.

Top affordable, long‑battery smartwatches

1. Amazfit Bip series (Bip 5 / Bip 6 / Bip U Pro family)

• Typical battery: ~7–14 days (depends on model and settings).
• Why buy: very low price, built‑in GPS on many models, lightweight, long standby.
• Best for: budget buyers who want core health/fitness tracking and multi‑day battery. (analyticsinsight.net)

2. Amazfit Active 2 / Amazfit GTS-style models

• Typical battery: ~7–10+ days in normal use.
• Why buy: AMOLED screens with long battery modes, good fitness tracking for the price.
• Best for: people who want a nicer screen but still long battery life. (trtom.com)

3. Redmi / Xiaomi Watch series (Redmi Watch 3 / Xiaomi Watch S3 / Watch S3)

• Typical battery: ~10–15 days (depending on model and use).
• Why buy: excellent battery for the price, decent AMOLED/LCD displays and activity tracking.
• Best for: value shoppers who want long battery and GPS. (compatibot.com)

4. Fitbit Inspire 3 / Fitbit Versa 4 (budget Fitbit options)

• Typical battery: Inspire 3 ~10 days; Versa 4 ~5–6 days.
• Why buy: strong sleep and health software ecosystem (Fitbit app), reliable tracking.
• Best for: users who value sleep tracking and a polished app experience. (budgetgearguide.com)

5. Garmin Forerunner 55 / Garmin Vivo or entry Forerunner models

• Typical battery: ~7–14 days (some Forerunner/Vivo models reach ~14 days in watch mode).
• Why buy: trusted fitness tracking and excellent GPS with multi‑day battery on simpler models.
• Best for: runners and outdoor users who want durability plus long battery. (wirefan.com)

6. Huawei Watch GT 3 / Watch Fit 3

• Typical battery: ~7–14 days (Watch GT/GT 3 often ~14 days in light use; Watch Fit 3 ~10 days).
• Why buy: long battery, attractive AMOLED screens, strong basic health features.
• Best for: users who want long battery and a premium look without the high price tag. (watch-buddy.com)

7. Nothing CMF Watch 3 Pro (budget stylish option)

• Typical battery: up to ~13 days quoted in reviews.
• Why buy: premium design at a budget price, multi‑day battery, modern UI.
• Best for: buyers who want style plus long battery on a tight budget. (techradar.com)

Quick buying tips

• “Battery life” estimates vary widely depending on always‑on display, continuous GPS, heart‑rate monitoring frequency, and notifications. Turn off AOD, reduce notifications, or use power modes to stretch battery.
• If you want reliable multi‑week battery (10+ days) prioritize fitness‑focused or simpler OS watches (Amazfit, Redmi/Xiaomi, some Garmin/Huawei models). Smartwatches running full Wear OS or watchOS (Apple, Pixel Watch) usually have shorter battery life (1–2 days). (techradar.com)

If you want, I can:

• Narrow this to the best picks under a specific price (e.g., under $100 or under $200).
• Check current prices and deals from US retailers right now and give direct buying links.