How to decide between LiPo or LiFePo for robot battery

Question

When choosing a battery for a robot, should you use a LiPo or LiFePo?

For LiFePo, the pros:

• can deliver higher sustained amps
• many are built to be drop-in replacements for lead-acid batteries and can use the same charger

The cons:

• enormously expensive (about $1/watt*hour/kg)
• lower energy density than LiPo (around 110 watt*hour/kg)

For LiPo batteries, the pros:

• cheaper (about $0.2/watt*hour/kg)
• over twice the energy density than LiFePo (around 250 watt*hour/kg)

The cons:

• more complicated and unsafe to charge (see videos of LiPos catching on fire)
• most can't safely deliver high amps

Is there anything I'm missing? I see LiFePo batteries used on a lot of larger platforms, probably due to the higher continuous amp rating. I see Ebay flooded with tons of cheap high-capacity Chinese LiPos, but almost none of them have documentation, which probably means they're junk.

When should I use LiFePo vs LiPo?

Answer 1

Lots of robots safely use LiPo batteries, see almost all multicopter setups. There are plenty of batteries designed for the RC market that are capable of high sustained amperage, along with a plethora of pre-made chargers for LiPo batteries and plenty of options of chips designed to be integrated that do all of the charging logic for you as well. What applications are you targeting? It is true that LiPo batteries can be very dangerous if mishandled, but unless there is a pressing reason to use LiFe batteries I would not.