Part of our Building Your First Ham Radio Station guide.
Sealed lead acid, SLA, was the default portable ham radio battery for decades, and lithium iron phosphate, LiFePO4, has largely taken over that role for good technical reasons. Both still have a place, and the right choice depends more on your specific use case than on which chemistry is objectively better.
Weight and size
This is where LiFePO4 wins decisively. A LiFePO4 battery delivering the same usable capacity as an SLA battery typically weighs less than half as much, and takes up noticeably less space. For a base station that never leaves the shack, this barely matters. For a manpack, a POTA activation, or anything you are carrying any distance, it is often the deciding factor by itself.
Usable capacity
An SLA battery should not be discharged below about 50 percent of its rated capacity without meaningfully shortening its lifespan, which means a 20Ah SLA battery really only gives you about 10Ah of comfortable, healthy use. LiFePO4 batteries handle much deeper discharge cycles, often down to 80 or even 90 percent of rated capacity, without the same damage, so a 20Ah LiFePO4 battery genuinely gives you close to 20Ah of usable power. In practice this means a LiFePO4 battery rated at roughly half the capacity of an SLA battery often delivers similar real world runtime.
Lifespan and cost over time
SLA batteries are cheaper upfront but typically tolerate a few hundred charge cycles before capacity degrades noticeably, especially if they are ever deeply discharged. LiFePO4 batteries cost more per battery but commonly handle several thousand charge cycles while retaining most of their capacity, which usually makes them cheaper per year of actual use even though the sticker price is higher. If you cycle a battery often, field days, regular POTA trips, weekly nets away from home, LiFePO4 pays for itself. If a battery mostly sits as emergency backup and gets cycled rarely, the SLA cost advantage matters more.
Cold weather and safety
SLA tolerates cold charging better than LiFePO4, which generally should not be charged below freezing without a battery management system that halts charging until temperatures rise, though most quality LiFePO4 packs now include that protection built in. LiFePO4 is also considerably more thermally stable than other lithium chemistries, without the fire risk associated with lithium ion or lithium polymer cells, which is part of why it has become the trusted choice for ham radio use specifically.
The practical recommendation
For anything portable, a manpack build, a POTA kit, an HT charging station you actually carry, LiFePO4 is worth the extra upfront cost almost every time. For a stationary backup battery that sits in a closet and gets tested occasionally, a well maintained SLA battery still does the job at a lower price, as long as you respect its shallower discharge limit and do not expect it to survive being run flat over and over.