# How to decide between LiPo or LiFePo for robot battery

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?