Lithium Iron Phosphate (LiFePO4) and A123 batteries

PERHAPS THE BEST BATTERY TECHNOLOGY AVAILABLE

Imagine if we could combine the safety and durability of nicads with the capacity and light-weight of LiPos. Wouldn't that be the best of all worlds?

Well that's pretty much what you get with the latest battery technology known as Lithium Iron Phosphate (LiFePO4).

Batteries based on this technology have almost the same power to weight ratio as LiPos but are far more tollerant of over and under-charging.

In a situation where a LiPo might explode into flames, the LiFePO4 cell will probably just vent some harmless gas.

LiFePO4 Pro's:

• very high power/weight ratio
• very low self-discharge
• more tollerant of over/under-charge/discharge
• can be used for RC gear without needing regulators

• Only a limited range of battery capacities currently available
• Odd-sizes for most cells (not AA, C, D, etc)
• LiFePO4-capable charger needed

LiFePO4 and A123, what's the difference?

Some people tend to use the terms LiFePO4 and A123 interchangeably -- but there is a significant difference between the two.

The fact is that A123 is a brand name for a specific type of LiFePO4 battery that incorporates nano-technology to significantly increase the current-handling capabilities.

The capabilities of an A123 battery are truly impressive -- with a 2300mAH pack being able to deliver currents of up to 100A for 10 seconds or more without damage. That's a 40C rating.

A standard LiFePO4 battery by comparison, may have only a 3-5C rating which is perfectly adequate for most RC applications but nowhere near as suited to hi-current applciations (such as electric power) as a true A123.

When to use

Well the answer to this is simple -- use LiFePO4/A123 batteries whenever it's possible.

I've switched to LiFePO4 batteries for all my models now and have had absolutely zero problems.

My NiMH receiver packs now sit unused in a drawer under my bench, having been replaced by some 1350mAH packs I built myself for under $10 each.

My 30% Extra now has dual 2300mAH A123 batteries that can handle the nine hi-torque digital servos without even blinking.

Given that LiFePO4 batteries are cheaper, smaller, lighter and better in just about every way than any of the other technologies when used as receiver pack, I'd say there's little reason not to use them.

I also notice that hi-current LiFePO4 batteries are now becoming available to replace LiPos for electric power. They're a little higger and heavier than the equivalent LiPo but for many folks, this will be a small price to pay for the dramatically increased safety and robustness they offer.

Back: Lithium Polymer batteries (LiPo)