I see the same question being asked by many newcomers here so I would like to shed some BASIC info on batteries used in esk8, notation, configuration, ratings, etc.
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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. At the time this article was written, Samsung 30q was by far the most common here. You will also see , , etc mentioned a lot. That is just the physical dimension of the battery cell, nothing to do with chemistry. An is a battery 18mm wide by 65.0 mm long. Panasonic, Sony, LG, etc all make cells. They also make other size cells like the . Can you guess what size that is?
Series
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.
Parallel
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 mAh if you prefer).
Ie. 4p is 12 Ah ( mAh), 10p is 30 Ah, etc.
Very very basically, increasing series adds speed, increasing parallel adds range.
This is assuming you keep all other parts/conditions the same.
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
- Lithium-Ion (Li-Ion) cylinder cells
- 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 in depth, 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 Battery technology develops extremely rapidly, and some of this information will likely be out of date in only a few years.
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
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 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-IonGeneral Characteristics:
Cycle_Life: Good (- 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: = 18mm dia x 65mm L, = 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 NCRC and NCRA
Example discharge curve:
General Characteristics:
Cycle_Life: Excellent (- 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: Good, 0 to 55°C charge, -30 to 55°C discharge
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 ANRM1B
Read the A123 thread here: A123 LiFePO4 Cells - the iron man’s battery
LTO
General Characteristics:
Cycle_Life: Excellent (- 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 40°C charge, -30 to 75°C discharge
Aging: ≤ 5% self-discharge / month.. >10 years shelf life.
Packaging:
Cell_Balancing:
Examples:
Voltage Discharge curve:
General Characteristics:
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
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
Yes, voltage and capacity (those mAh numbers) matter very much. Remember the examples above with series vs parallel?
25r cells are mAh cells and sag faster than 30q
30q cells are mAh cells - comparative example
40t cells are mAh cells and sags less than 30q
25r is what many prebuilts used to use and were fine. They just won’t carry you very long. Most newcomers I saw when I first joined were upgrading their prebuilt batteries with 30q packs. Currently (as of 12/30/21), the Molicel P42a is the cell of choice for power discharge, high charge rate, and all around solid performance.
JOINSUN Product Page
@Battery_Mooch is a gentleman and a scholar and also conducts professional cell discharge tests that analyze cell performance under various conditions. If you ever want no BS, solid rating values for cells, search “Mooch insert cell type here” and you should find his results. Mooch, if you have a preferred link you’d like me to drop, Lmk and I’ll fix or adjust the wiki yourself
[Mooch’s response] Thank you @Venom for your kind words!
All my test results and tables can be found here: https://www.e-cigarette-forum.com/blogs/mooch./
While I post some content here I also post to my Mooch Facebook page.
You can not mix cell types. Also don’t mix cells of different age (how many times they’ve been used/charged - called cycles). I don’t want to hear any of that “well technically you can if…” talk. This is a battery basics thread!
Each cell also has a listed amp draw rating. The aforementioned Mooch finds reliable discharge and capacity ratings so that we don’t kill our packs faster than we should.
Example: 30q cells are rated at 15A discharge by Samsung, 20A by Mooch (as long as they don’t overheat!)
Your battery’s total available amp discharge is your cell type’s individual amp draw times your number of parallel groups.
I.e.
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 physically bigger so factor that in as well.
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 and you stay within its acceptable operating range, you’re good to go. You will find this in the esc specs.
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.
Charging should be done through the bms to prevent overcharging of individual parallel groups. If the pack is unbalanced after discharging, some of the groups can reach their maximum voltage before others and before the charger would reach its cut off voltage. The bms monitors the individual cell voltages and cuts off charging if any one parallel cell group exceeds its maximum allowable voltage preventing damage and or fires
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 / ]
For a 10s5p 30q pack (30q cells rated at mAh):
[5] * [/] = 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?
Read the ongoing thread: ESC Battery cutoff settings - #6 by b264
12S lipo (50.4V charge)
cutoff start 45.24V
cutoff end 44.52V
12S li-ion; super-conservative (50.4V charge)
cutoff start 43.2V
cutoff end 40.8V
12S li-ion; conservative (50.4V charge)
cutoff start 42V
cutoff end 38.4V
12S li-ion; aggressive (50.4V charge)
cutoff start 38.4 - 39.6V
cutoff end 36V
12S li-ion; max-range (50.4V charge)
cutoff start 43.2V
cutoff end 36V
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!
If you are looking for more details, kindly visit Cells for Electric Drive Systems.
So my question is how many of the cells that he uses in the video would I need to put in series and how many in parallel to get a top speed of at least 110mph?Lots of variables to consider, but if you want a top speed of over 100mph, you're looking at somewhere in the range of 120-150v battery pack. 100v minimum. Especially if you want a hub motor. Try the grin motor simulator to play with some of the variables.
Also, the battery and motor combination should support a range of at least 100 miles, and 0-60mph in under 4 seconds (3.5s would be nicer though)You are suggesting that you yourself want a range of at least 100 miles? This is overly optimistic. But just for argument sake. My motorcycle gets 100wh/mile range, because I never go above 60mph, and usually keep it to 45mph. And you want to go faster. So assume 120wh/mile. Times 100 miles, means you'll want a battery pack with 12kwh. From my voltage estimate above, let's say you go with a 100v nominal battery (this would be 28 in series, fyi). Meaning you'll want 120ah. The cells you listed are 5ah cells.
I'll try to briefly answer what you came to the forum to ask about:Okay this is very helpful, thank you. I had another question about range, in the stats of his first e-moto, he gave a range up to 100km and that was with a 4.3 kWh battery pack. From what you are saying, this range estimate is way off. Is this true? 120Wh/mile seems a bit high to me, and from what I’ve read on here, efficiency of hub motors does not really change with speed, although some people have misinterpreted that simulator’s results and thought it does (from what I gathered).
Lots of variables to consider, but if you want a top speed of over 100mph, you're looking at somewhere in the range of 120-150v battery pack. 100v minimum. Especially if you want a hub motor. Try the grin motor simulator to play with some of the variables.
You are suggesting that you yourself want a range of at least 100 miles? This is overly optimistic. But just for argument sake. My motorcycle gets 100wh/mile range, because I never go above 60mph, and usually keep it to 45mph. And you want to go faster. So assume 120wh/mile. Times 100 miles, means you'll want a battery pack with 12kwh. From my voltage estimate above, let's say you go with a 100v nominal battery (this would be 28 in series, fyi). Meaning you'll want 120ah. The cells you listed are 5ah cells.
So with all of those back-of-the-napkin quick estimations, your hypothetical battery for 100mph top speed and 100 mile range, with those cells, would need to be 28s24p. 672 cells total.
Hopefully that will get you started thinking about what you might need and/or want. My advice is that your speed and range requirements are a bit high, so I would try to compromise on that a bit.
FYI, James's first e-moto 4 years ago was my inspiration to build one. I love that guy. Looking forward to him finishing his upgrade, if he ever gets around to it instead of one budget CNC or laser engraver review after another.
Okay this is very helpful, thank you. I had another question about range, in the stats of his first e-moto, he gave a range up to 100km and that was with a 4.3 kWh battery pack. From what you are saying, this range estimate is way off. Is this true? 120Wh/mile seems a bit high to me, and from what I’ve read on here, efficiency of hub motors does not really change with speed, although some people have misinterpreted that simulator’s results and thought it does (from what I gathered).Since I've seen and followed this guy, I know the first bike you're talking about as well. From his video description:
efficiency of hub motors does not really change with speed,That may or may not be true, I have no idea where you're getting that from, but what I'm referring to is that energy draw increases with speed, exponentially not lineraly. Meaning, when I estimated that you'd get 120wh/mile with your 100mph top speed, I was estimating a figure based on what it seemed like your riding habits might be:
I will probably be going around 65mph (our highway speed here) mainly and sometimes I like to go about 85-90mph when the road is clear for some long stretches of open road.Faster means it takes more energy to reach and sustain those speeds. If your riding habits require more energy to achieve, then that's coming from your battery. If you stay at 25mph at all times, you could see something like 50-60wh/mile. Thats why you read about all the ebikes, emotos, and electric cars having lower range when your speed is high. And that's why I suggested that if you compromise on one of your project goals - range or speed - the other goal will become more achievable.