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The KTM 450 EXC has run electric start since KTM introduced it in 2003, with a kickstart lever alongside it for years afterward as a backup; the 2017+ EXC-F Six Days generation moved to e-start only (kick kits exist as an aftermarket add-on). Battery case size also changed across that span — pre-2017 bikes generally take a YTX5L-BS-size battery, while the 2017+ EXC-F Six Days takes a larger case. Confirm your exact year against the battery’s listed fitment before ordering; don’t assume every “450 EXC” battery fits every year.
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | Yuasa YTX5L-BS AGM | $49-$61 | Amazon · eBay |
| 2 | Antigravity XPS Extreme Power Lithium (AG-SC-1) | $110-$120 | Amazon · eBay |
| 3 | Antigravity ATZ-7 RE-START Lithium | $125-$135 | Amazon · eBay |
| 4 | Shorai LFX14L2-BS12 Lithium-Iron | $150-$155 | Amazon |
| 5 | EarthX ETZ5G LiFePO4 | $135-$145 | Amazon |
| 6 | EarthX ETX12A | $165-$175 | Amazon · eBay |
The picks, in detail
Yuasa YTX5L-BS AGM
The OEM-spec sealed AGM battery size used on pre-2017 450 EXC models — the safe, no-surprises baseline choice.
- Sealed, maintenance-free AGM
- OEM-equivalent case size (YTX5L-BS)
- Yuasa factory-activated option available
- Matches stock fitment and electrical characteristics exactly on pre-2017 bikes
- Widely available at any powersports retailer
- Heavier than any lithium option below, which matters more on a dirt bike than a street bike
Antigravity XPS Extreme Power Lithium (AG-SC-1)
A compact lithium battery from a brand built specifically around powersports lithium conversions, aimed at riders swapping off AGM for weight savings.
- Lithium-ion chemistry
- Built-in battery management system
- Small case size for tight dirt-bike battery boxes
- Significant weight savings over an AGM battery of similar cranking output
- Purpose-built brand with dirt-bike-specific case sizing
- Lithium batteries are more sensitive to deep-discharge damage than AGM if left unused for long stretches
Antigravity ATZ-7 RE-START Lithium
A step up from the XPS with Antigravity’s RE-START jump-restart button built in, useful if a lithium pack ever drops into low-voltage protection mode mid-ride.
- Lithium-ion with RE-START push-button jump feature
- 150 CA rating
- Built-in BMS
- RE-START button gets you going again in the field without jumper cables if the BMS cuts out
- Higher cranking rating than the base XPS
- Costs more than the base XPS for the added RE-START feature
Shorai LFX14L2-BS12 Lithium-Iron
Sized specifically for the larger case on the 2017-2018 KTM 450 EXC-F Six Days — check this fitment carefully since it’s a different size than the pre-2017 battery box.
- Lithium-iron phosphate (LiFePO4) chemistry
- Sized for 2017-2018 EXC-F Six Days battery case
- Lightweight compared to AGM
- Confirmed fitment for the larger post-2017 battery case, not just a generic small-case lithium
- LiFePO4 chemistry is more thermally stable than other lithium types
- Wrong size for pre-2017 bikes using the smaller YTX5L-BS case — check your year first
EarthX ETZ5G LiFePO4
A dirt-bike-focused lithium pack marketed as a direct swap for the stock lithium/AGM battery on most dirt bikes in the YTX5L-BS size class.
- LiFePO4 chemistry
- Built-in battery management system
- Marketed specifically as a dirt-bike stock-size replacement
- EarthX is one of the more established names in powersports lithium, with a track record beyond just dirt bikes
- Sized to replace the smaller stock case without a battery-box modification
- Pricier than a basic Yuasa AGM for the same case size
EarthX ETX12A
A larger-capacity EarthX lithium option for riders who want more cranking margin or run additional electrical accessories (heated grips, aux lighting).
- Higher-capacity LiFePO4 pack than the ETZ5G
- Built-in BMS with over-discharge protection
- Eco-Friendly lithium construction
- More headroom for accessories than the smaller ETZ5G
- Same reputable EarthX build quality
- Physically larger — confirm it clears your battery box before buying
Buying tips
- Match your bike’s year to the correct case size before ordering — pre-2017 450 EXC and the 2017+ EXC-F Six Days do not share the same battery box dimensions.
- Lithium batteries lose charge differently than AGM and can trip into a protective shutdown if drained too low; a lithium-compatible charger/maintainer matters more than it does with AGM.
- If you’re on a kickstart-equipped year, a smaller/lighter lithium pack is lower-risk since you have a mechanical backup; on e-start-only 2017+ bikes, some riders prefer the predictability of AGM or a lithium pack with a RE-START button.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.