I see the same question being asked by many newcomers here so I would like to shed some
VERY BASIC info on batteries used in esk8, notation, configuration, ratings, etc.
Common battery notation you keep seeing or will see is a (XX)s(YY)p battery with (ZZ) cells:
XX is the number of cells you have in series ( s ) type connection.
YY is the number of cells you have in parallel ( p ) type connection.
ZZ is the actual battery cell type used. Samsung 30q is by far the most common here. You will also see 18650 mentioned a lot. That is just the physical dimension of the battery cell, nothing to do with chemistry. It’s a battery 18mm wide by 65.0 mm long. Panasonic, Sony, LG, etc all make 18650 cells. Samsung makes them the best per price for our application. They also make other size cells like the 20700. Can you guess what size that is?
When you add cells in series, it adds to the total voltage available to your system.
ex. 30Q cells are 4.2V fully charged,
Ie. 10s is 42V, 12s is 50.4V, 100s is 420V etc.
When you add them in parallel, it keeps the voltage the same but adds to the capacity (measured in Ah or more commony mAh).
30Q cells are 3 Ah each (or 3000 mAh if you prefer).
Ie. 4p is 12 Ah (12000 mAh), 10p is 30 Ah, etc.
Very very basically, increasing series adds speed, increasing parallel adds range.
Battery Chemistry / Cell Type
If you use the esk8 calculator to design your build on paper before going shopping (highly recommended), you’ll notice there are a number of options in the Cell Type drop-down:
- Lithium-Ion Polymer (Li-polymer / LiPo) pouch packs - multiple chemistry options
- Lithium-Ion (Li-Ion) cylinder cells - multiple chemistry options
- Lithium Iron Phosphate (LiFePo4)
- Lithium Titanate (Li2TiO3 / Li4Ti5O12 / LTO)
- Lead Acid
- Nickel Metal Hydride (Ni-MH)
In 99% of cases, the question to answer is which lithium based battery is best for your use: LiPo or Li-Ion (sometimes LiFePo)?
Some of the following information may be a bit too in-depth (forgive me @Venom121212), but beginners will understand more as they read more. Hopefully this is a good reference that can be improved by the community and updated over time. Battery technology develops extremely rapidly, and some of this information will likely be out of date in only a few years.
LiPo (typically LCO chemistry, 3.7V nom, 4.2 - 3.6v safe range, polymer gel electrolyte)
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: 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
Read the Tattu lipo thread here: 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 above 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)
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: 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
Voltage discharge curve:
Read the P42A discussion thread here: Molicel P42A cell discussion
LiFePo4 (3.2V nom, 3.65V - 2.5V range)
Cycle_Life: Excellent (2000-5000 charge cycles) Energy_Density (Specific Energy): Poor (90-130 Wh/Kg) / poor range/weight Discharge_Rate: Excellent - 25C / 30A+ continuous Charge_Rate: Excellent (4C+) fast charge is proven safe. Voltage_Curve: Excellent (flat) - provides the same voltage across almost the entirety of discharge Cost: Low 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: Excellent, stable chemistry - the cathode material will not burn and is not prone to thermal runaway (fire). One of the safest chemistries. Operating_Temperature: -20 - 60 °C Aging: ≤ 6% self-discharge. More tolerant to being left at full charge voltage. Higher self-discharge rate than other chemistries. 10 year shelf life. Packaging: cells come in all forms including cylinders, pouches, and prismatic packs. Cell_Balancing: Requires a BMS to keep cells balanced Examples: A123 ANR26650M1B
Read the A123 thread here: A123 LiFePO4 Cells - the iron man’s battery
LTO (2.4V nom, 2.8V - 1.5V range)
Cycle_Life: Excellent (3000-7000 charge cycles) Energy_Density (Specific Energy): Bad (60-110 Wh/kg) Discharge_Rate: Excellent (5C typical, 30C+ maximum) Charge_Rate: Excellent (1C typical, 20C+ maximum) Voltage_Curve: Good Cost: High? Quality: Safety: Excellent - One of the safest chemistries. Operating_Temperature: Excellent, -10 to 40C charge, -30 to 75C discharge Aging: ≤ 5% self-discharge / month.. >10 years shelf life. Packaging: Cell_Balancing: Examples:
Voltage Discharge curve:
Lead Acid (2.0V nom, 2.3V - 1.8V range)
Cycle_Life: Poor (200-350 charge cycles) Energy_Density (Specific Energy): The Worst (30-40 Wh/kg) Discharge_Rate: Good (180 W/kg), 1C - 3C Charge_Rate: Bad (≤0.2C) Voltage_Curve: Cost: Low Quality: High, simple to manufacture Safety: Good. Although environmentally unfriendly Operating_Temperature: -40 - 50°C. Good low and high temp performance. Aging: 3-20% / month. Slight memory effect. Packaging: Cell_Balancing: Examples: automotive starter batteries
Ni-MH (1.2V nom, 1.4V - 1.0V range)
Cycle_Life: Poor (~500 charge cycles) Energy_Density (Specific Energy): Bad (60-120 Wh/kg) Discharge_Rate: Charge_Rate: Excellent - only battery that can be ultra-fast charged with little stress Voltage_Curve: Excellent - 'low internal resistance allows cells to deliver a nearly constant voltage until they are almost completely discharged. Cost: Low Quality: Safety: Good. Requires complex charge algorithm, sensitive to overcharge. Operating_Temperature: -20 - 50 °C. Aging: '1-4% self-discharge. Packaging - Cell_Balancing - Note - Similar to NiCd, but less toxic. Constitute less than 3% of the battery market. Examples: Eneloop rechargeable NiMH
Battery Cell Ratings
Yes, voltage and capacity (those mAh numbers) matter very much. Remember the examples above with series vs parallel?
25r cells are 2500 mAh cells and sag faster than 30q
30q cells are 3000 mAh cells - comparative example
40t cells are 4000 mAh cells and sags less than 30q
25r is what many prebuilts use and are fine. They just won’t carry you very long. Most newcomers I see are upgrading their prebuilt batteries with 30q packs.
You can not mix cell types. Also don’t mix cells of different age (how many times they’ve been used/charged - called cycles).
Each cell also has a listed amp draw rating. Mooch does great testing on cells and often finds reliable discharge and capacity ratings.
Example: 30q cells are rated at 15A discharge by Samsung, 20A by Mooch.
Your battery’s tot available amp discharge is your cell type’s individual amp draw times your number of parallel groups.
A 10s5p of 30q cells will have a max battery amp draw of 100A (20A per cell * 5 parallel groups)
Notice a 12s5p will still have the same max battery amp limit. This is where people will use larger cells to have higher available battery discharges without as many p groups. But the cells are also bigger so balance it yourself for your own use.
ESC - After the Battery Upgrade
Your motors are dumb devices. They will happily take whatever your battery sends at them even if it melts them into oblivion. This is where your electronic speed controller (ESC) comes in. It sets the limits of amps (and tons of other things) going to your motors using complex maths I won’t get into. As long as your ESC can handle the voltage rating of your new battery, you’re good to go. You will find this in the esc specs.
BMS and Charging
It stands for battery management system (BMS). It is wired to your battery and keeps the charge even across all of your parallel groups so your battery doesn’t get unbalanced and have problems.
You can charge your pack at different rates as long as they match your pack’s voltage. The charger will be rated in amps to let you know how quickly it will charge your pack. Might as well charge as quickly as possible right? Eh not so much. Charging too quickly is bad for cells and will shorten their lifespan. Charging slowly is best for your pack but worst for riding your esk8 around aot.
Here is a conservative charge rate formula that isn’t painfully slow either:
[# of parallel groups] * [cell type mAh rating / 3000]
For a 10s5p 30q pack (30q cells rated at 3000 mAh):
 * [3000/3000] = 5A charge rate.
Again, you can certainly charge faster or slower than that, this is just my personal recommendation.
Do not ever let your battery pack drain below recommended levels! For this reason, many bms and escs have a hard voltage cutoff where your board will cut all acceleration when too low (cutoff end). You see this happening most going up hills as this draws more power. Most escs used here take it a step further and implement a soft cutoff where, instead of throwing you on your face at a low voltage level, it will slow your board down gradually going to that point (cutoff start). Almost like you’re wounded and limping home to your charger. This brings up the next question, what is a safe discharged rating?
Battery Cutoff Settings
Read the ongoing thread: ESC Battery cutoff settings
10S li-ion conservative (42.0V charge)
cutoff start 35V
cutoff end 32V
10S li-ion aggressive (42.0V charge)
cutoff start 34V
cutoff end 30V
10S li-ion max-range (42.0V charge)
cutoff start 36V
cutoff end 30V
12S LiFePO4 (43.8V charge)
cutoff start 34.5V
cutoff end 33V
credit to @b264 for saving me the typing
Please keep comments to basic-moderate battery related questions. All advanced battery construction questions should be posted in the battery builders club thread and ONLY AFTER READING THE WHOLE THREAD please.
More general introduction guide here: Wiki for new users [Help Wanted (Example part list, FAQ)]
Welcome to esk8!