Mikeyrides:
one for lifespan
While we’re talking about lipo pouch packs vs other options, and since this is one of the main threads that pops up when searching “lipo”, I’d like to highlight lifespan as perhaps the biggest drawback to be aware of (other than safety concerns). Generally well treated lipo pouch packs seems to handle a couple hundred cycles, while well treated li-ion cylinder packs seem to handle 4-7x that. Depending on intended use, replacement costs should be factored into the decision.
On the other hand, as most people already know, the discharge rating and discharge curve (voltage sag) are much better for lipo pouch packs than li-ion cylinder packs.
Lipo pouch packs vs li-ion cylinder cells (18650s, 21700s, etc) is almost an apples to oranges comparison, with substantially different ideal use cases. See the battery basics thread with general
LiPo (typically LCO chemistry, 3.7V nom, 4.2 - 3.6v safe range, polymer gel electrolyte)
General Characteristics:
Cycle_Life: Poor (50-300 charge cycles)
Energy_Density (Specific Energy): Good (100–200 Wh/kg) - Heavier for a given capacity than li-ion / roughly 2x the weight for the same range
Discharge_Rate: Excellent - Highest discharge rates / C rate (“punchy”). Can get much higher discharge on smaller packs if not concerned about range. (10-25C actual / 200A+)
Charge_Rate: Average (1C typical, 3C maximum)
Voltage_Curve: Good - Flatter curve / minimal voltage sag / maintain a higher voltage under load for longer
Cost: Average. Easy to purchase, widely available
Quality: Average - more prone to swings in manufacturing quality, dimensions, and weight
Safety: Poor - Most sensitive to piercing / blunt damage / thermal runaway. Requires hard case for safety. Easily damaged by discharging too far (will unbalance rapidly below 3.6V.
Operating_Temperature: Average, 5 to 50°C charge (damage will occur if charging at over 60°C)
Aging: Poor- easily damaged if left above recommended storage charge for '3+ months
Packaging: pouch packs come in compact ‘bricks’ of varying sizes, encased in a semi-flexible shell. No standard size exists. Easy to replace / swap / carry extra backups, but added complexity of multiple battery packs.
Cell_Balancing: Requires a BMS or balance charger to eliminate state of charge (SOC) mismatch.
Note: Inaccurate manufacturer C rating is very common (typically around 2-3x exaggerated)
Examples: Gens Tattu, Turnigy Nano-Tech, Turnigy Graphene, Venom, MaxAmps
Read the more detailed lipo thread here: thinking about going lipo Does anyone have experience with Tattu lipo batteries?
Lipos are safe if you maintain them well. If not, they can puff and cause fires. A lithium ion (cylinder) battery pack like discussed below can still burst into flames if you wire it wrong or don’t protect it but are generally safer and easier for beginners. They can give slightly more voltage (power) but also sag faster.
Li-Ion (typically NMC/NCA chemistry, 3.6V nom, 4.2V - 3.2V safe range, liquid electrolyte)
General Characteristics:
Cycle_Life: Good (1000-2000 charge cycles)
Energy_Density (Specific Energy): Excellent (160–260 Wh/kg) lighter for a given capacity
Discharge_Rate: Good (250-430 W/kg) - CDR largely depends on cell and manufacturer (15-35A continuous typical)
Charge_Rate: Average (1C typical, 4C maximum)
Voltage_Curve: Average - Depending on cell, can have significant voltage sag in the last half of the discharge (voltage curve)
Cost: High - significant upfront cost includes individual cells plus the materials and labor to build a finished battery pack with BMS electronics, although individual cell prices have steadily decreased over time.
Quality: Excellent - Extremely tight manufacturing tolerances by large global brands ensure high quality cells. Tend to be higher quality packs than LiPo when assembled by a quality builder
Safety: Average - sensitive to physical damage and short circuiting. Requires hard case for safety.
Operating_Temperature: Good, 0 to 60°C charge, -40 to 60°C discharge
Aging: 0.35% - 2.5% / month. Good - better at sitting for long periods of time unused.
Packaging: cells come in cylindrical steel canisters of precise dimensions, with overpressure vents (most common: 18650 = 18mm dia x 65mm L, 21700 = 21mm dia x 70mm L)
Cell_Balancing: Requires a BMS to keep cells balanced
Note: Tend to be over the limit for air flight (99 Whr), aka cannot travel with an assembled pack.
Examples: Molicel P26A and P42A, Sony Murata VTC5D, VTC5A, and VTC6, Samsung 30Q, 30T, and 40T, LG HG2 and HG6, Sanyo NCR2070C and NCR20700A
Example discharge curve:
Read the P42A discussion thread here: Molicel P42A cell discussion