The volatility of Lithium batteries..?
 

I just bought a set (2) of those 12v Lithium batteries (see below) to power an external monitor for my XL2 and some onboard LED lights hack, (altogether about 3Ah). However, while doing my research after the fact of buying them, I now discover that there's an "unique drawback of Li-ion batteries since the service life dependents upon aging (shelf life)".

So I'd like to know if I need to get some NiMH (or whatever) as a backup or replacement.

Any advice or enlightenment appreciated.

-- peer

There are Lithium Iron Phosphate batteries that don't have these issues. Search for LiFePO4 and there should be some in 12v capacity. Lithium Manganese are also good Lithium variants but aren't quite as common in plain battery packs (they are used in tools frequently). NiMH batteries won't last as long as regular lithium so don't bother with that route.

The primary reason to choose NIMH over Lithium variants would be for larger current draw applications or better low temperature performance.

Edit: as well, airline "flightability" in larger watt hour configurations would also be a nod for NIMH.

The Li-Ion batteries age naturally at about 10%/year, which is not that bad comparing to the other chemistries. Depending on the cell quality and internal safety electronics, they can fail sooner and unexpectedly, so pay attention to the warranty, and save your receipt ;-)

I forgot to add that Lithium batteries are best stored in neither completely charged or discharged states. Keep them in the mid-range of charge when storing for a while. I believe the cells die on full discharge and can grow dendrites on the cathode when fully charged which also damages the cells. Lead batteries are best kept fully charged. I think NiCads don't care and I don't know about NiMH but they should never be allowed to overheat. NiMH battery packs should be slow charged to avoid heat.

I have some Lithium Ion batteries that date back to when the VX1000 was first introduced. Jeez, when was that? Easily over 10 years ago. They don't have the capacity that they used to have but they are still working pretty well. And I never did follow any particular practice to make them last longer.

I built a couple of battery packs using A123 Systems cells.

A123Systems :: Products

Three of these cells in series provides 13.2 volts and 2.3 amp-hours, which works for lights, small LCD monitors and some other devices.

They recharge quickly, have a higher cycle rate than NiMH batteries and are lighter than lead-acids. I got the cells by taking apart a 36-volt DeWalt drill battery. I kept the original tabs in place to allow them to be soldered without heating the battery. Afterward I enclosed them in a thin layer of craft foam and heat shrink.

The charger comes from FMA Direct. You have to build the packs yourself and include what's known as a "balance tap" which charges each cell in the pack individually. This maximizes pack life since the charger will monitor the charge state of each cell.

FMA Direct : Cellpro Product Line

And as for safety, here's a report about an A123 cell being drilled:

Safety of A123 battery cell FutureDrive

My battery packs have been in my hand carry luggage several times and have gone through the usual TSA inspection without a fuss.

NiMH are rated for 2X more charge cycles then Lith Ion. while they are heavier, they still have decent weight / watt ratio. after 3 years of use, my NiMH paks are working every bit as well as when they were new. sometimes they get used every day, other times they may sit for a month. I put them on charge before going out the nite before.

I also find NiMH batts work well in the cold - meaning often 0-25 F

the problem with lithion batteries is if they every ignite, you can't put the fire out. it burns very hot and intense. having watched video of lith ion batteries go up, its a scary sight, and you'd understand the flight restrictions on them once you see how they burn.

if you have batts that work, use them. when they get tired, then consider what types are available. what you have should work fine.