Devon,
I use Li-Po batteries in most of my converted loco’s and the same batteries in R/C planes, cars, trucks and drones. As you suggest they are plentiful and offered in different shapes, physical sizes, capacities and voltages at very reasonable prices. Can they be problematic, yes same as Li-Ion as either offering is comprised of like chemical matrixes. Either technology reacts to abuse with the same potential as the latter.
Li-Po batteries are widely used in everything imaginable, cell phones, laptops, personnel electronic devices (Bluetooth headsets and more). Li-Po or more correctly Li-Ion Polymer cells market share in the Lithium world is second to none…
I list below minimally the variables of typical Li-Ion and Li-Po cells with regard specifically to integral safety features:
Li-Ion cell:
1). Standardized metal tube surrounds which offer some protection from physical damage.
2). Integral mechanical pressure relief vent.
3). Integral positive thermal coefficient switch (PTC). Reacts to heat rise becoming resistive. Or acurrent interrupting device (CID) either device provides short circuit protection.
4). Not capable of high discharge currents.
Lithium-Ion Polymer cells (Li-Po):
1). Flexible foil-type polymer laminate pouch form factor (provides expansion relief with heat gain).
2). Capable of High discharge currents.
PCM/PCB protection circuit boards are ancillary devices typically utilized and installed via second party battery assemblers/resellers of assembled battery packs, these devices can be utilized with either Li-Ion and or Li-Po cells/batteries.
PCM/PCB protection circuits are widely integrated into Li-Ion batteries and are just as applicable to Li-Po batteries (yet seldom used due to high current needs/desires attainable with Li-Po’s). For our train purposes Li-Po’s and PCM/PCB’s work as well as they do for their Li-Ion battery counterparts.
With Li-Po’s I use SMART chargers with cell balance features. This provides the ultimate cell/battery protection undercharge/discharge/cycling. The balance feature monitors individual cell performance/values and adjusts the need and or reacts to the individual cell while connected to the charger. This protection and cell balancing technology is FAR superior to any PCB/PCM currently offered. I also have my Li-Ion batteries fitted with balance charge pigtails in lieu of onboard PCB/PCM’s. Caveats; no onboard voltage monitor, which can be provided by other ancillary devices. Protection for short circuit and excessive current draw provided by the appropriate simple fuse.
The propensity for problematic behavior under charge is well known and mostly realized in the early exposure to end users. Human error was/is markedly the well documented reason for these failures. Improper chargers, improper charge values, improper charge regimens, excessive time under charge, errors in cell/battery values and requirements and such leads to failure modes.
FWIW: Not all Li-Ion battery packs have integrated PCB/PCM’s. As I allude to above these are ancillary devices added by the battery packagers/resellers or not! This secondary safety feature obviously help mitigate the aforementioned human error factor.
We’ve all heard or read about the horror stories, I’ve never had a failure and worked through hundreds of batteries over the years. I’m not aware of any friends or associates experiencing failures either. It’s my belief that we hear of the problems thousands times over as compared to the happy camper. In other words of the 12 billion or so Lithium cells sold since 1995, how many failures truly exist?
Michael
I typically get between 2 - 4 hours out of one of those packs, which is more than ample for most operating days. Since the packs are usually removable, I can just swap them out to recharge them. In instances where the batteries are not removable, I try to fit higher-capacity packs in the locos if I can, but that’s not always possible.