How to choose batteries for your project [INFO GUIDE]

ESK8 Electronics
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1

Hello everyone, i will try to make a thread about how to choose batteries for your project

So guys on the forum will be able to understand better how to get the best value for money.

Here are some parameters need to consider when you choose you battery.

  • size
  • weight
  • discharge rate ©
  • working voltage
  • safety
  • number of cycles
  • using BMS / yes or no
  • budget - price you have for your project
  • voltage sag - how low the voltage drop when you drain power from the battery pack - or in simple words to what voltage the voltage drop when you’re skate is with load.

…

It is important to understand you need to find the best solution for you’re project with out exaggerate with over kill battery parameters but not also choose batteries with lower performances for your project.

Example: you would like to build electric skate board with those parameters:

  • working current 30A
  • peak current 50A
  • nominal voltage 36V
  • capacity 10AH
  • motor working power 1100W
  • peak 1800W

…

I choose 18650 cells for this project - but how to choose the right cell?!

If we know we need cells which can handle 30A working current at 10AH capacity its 3C -

It is better to choose cell which can do a 15-20% more to enjoy healthy battery pack for long time.

So we need cells which can do 36A working current at 10AH capacity which is 3.5C at least.

…

We can choose Samsung 30Q for example which is rated 6C

It is important to understand there is no point to choose above 6C rated cells and pay more for more expensive cells

For example Sony VTC6 is over kill for this project and you spend more money for no good reason.

But from the other side not be cheap for yourself and choose cells rate lower than 3.5C.

…

Conclusion: choose the closest cells rated close to your project power, do not go over with high rate cells which won’t give you anything different, but do not go lower than needed.

*if you choose to get cells with less weight, more cycles, or smaller size, more safer - its ok to pay more for those.

  • if you wish to have many cycles and have battery pack can work 2-3 years but you do not care about size, weight, high prices- you should go for lifepo4 cells OR Lithium prismatic cells.

  • if you wish to have the max power for the size and weight , an pretty standard price, less safety you should go for Lipo

  • if you wish to go for the balanced option - small size , light weight, medium cycle life and good price point you should go for li-ion NCM 18650/ li-ion NCM pouch cells / Li-ion to match the power on your project.

Typical sources to get 18650 ‘bare’ cells:

[EU]

https://eu.nkon.nl2 Pros: Good variety & Prices, Offers to add nickel tabs for extra fee, Volume discounts

[US]

[Asia]

http://www.gearbest.com

Good luck for all the new and old builders. Have fun skating

5 Likes
2

Thanks man…very useful

3

Good info, to be honest, I hope you dont mind I might re-organize it a bit and bring out the big points?

I think it should be included in other places as well, good intro to basic battery knowledge

Hello everyone, i will try to make a thread about how to choose batteries for your project

So guys on the forum will be able to understand better how to get the best value for money.

Here are some parameters need to consider when you choose you battery.

  • size
  • weight
  • discharge rate (C)
  • working voltage
  • safety
  • number of cycles
  • using BMS / yes or no
  • budget - price you have for your project
  • voltage sag - how low the voltage drop when you drain power from the battery pack -

or in simple words to what voltage the voltage drop when you’re skate is with load.

It is important to understand you need to find the best solution for you’re project with out exaggerate with over kill battery parameters but not also choose batteries with lower performances for your project.

Example: you would like to build electric skate board with those parameters:

  • working current 30A
  • peak current 50A
  • nominal voltage 36V
  • capacity 10AH
  • motor working power 1100W
  • peak 1800W

I choose 18650 cells for this project - but how to choose the right cell?!

If we know we need cells which can handle 30A working current at 10AH capacity its 3C -

It is better to choose cell which can do a 15-20% more to enjoy healthy battery pack for long time.

So we need cells which can do 36A working current at 10AH capacity which is 3.5C at least.

We can choose Samsung 30Q for example which is rated 6C

It is important to understand there is no point to choose above 6C rated cells and pay more for more expensive cells

For example Sony VTC6 is over kill for this project and you spend more money for no good reason.

But from the other side not be cheap for yourself and choose cells rate lower than 3.5C.

Conclusion: choose the closest cells rated close to your project power, do not go over with high rate cells which won’t give you anything different, but do not go lower than needed.

  • if you choose to get cells with less weight, more cycles, or smaller size, more safer - its ok to pay more for those.
  • if you wish to have many cycles and have battery pack can work 2-3 years but you do not care about size, weight, high prices- you should go for lifepo4 cells OR Lithium prismatic cells.
  • if you wish to have the max power for the size and weight , an pretty standard price, less safety you should go for Lipo
  • if you wish to go for the balanced option - small size , light weight, medium cycle life and good price point you should go for li-ion NCM 18650/ li-ion NCM pouch cells / Li-ion to match the power on your project.

Good luck for all the new and old builders. Have fun skating

4

Typical sources to get 18650 ‘bare’ cells:

[EU]

Pros: Good variety & Prices, Offers to add nickel tabs for extra fee, Volume discounts

[US]

[Asia]

[To be updated in future, feedback from users / customers who shopped there and at different sites are welcome, let’s build decent battery info base for esk8 purposes then :wink: ]

5

Hey, So I’m new to Eboard and I need some help choosing the right batteries for a board with a “Electric Skateboard Motor 6355 190KV”.

6

@Jman more details would be welcome… i assume u want to choose ready made solution and go with lipo packs right?

1 Like
7

i have bought nothing yet, just wanting to do the most research i can before i start. i just need to know some good products for and electric board. and the motor thats looks good diy-electric-skateboard-kits-parts/electric-skateboard-motor-6355-190kv/ whats would the ideal lipo pack be? and where can i get them from?

8

I would say - start with this calculator:

http://calc.esk8.today

Early on you should also decide - what controller are you going to use?

If you have an idea to order Vesc, like many people do, then it does not matter and you probably should / will choose either 8S / 10S or 12S setup.

Though, this will make it a bit more difficult for you to charge the batteries, if you dont buy bms and correct voltage power supply.

But it is possible to get around this, if you ‘split’ your pack in half, and have 2x 4s, 5s or 6s modules connected together to get 8s, 10s, or 12s for example.

8S means 8cells connected in Series, if you dont know that so far. (though there are threads which describes this in great details)

–

Ok voltage talk away… once you know with what voltage you are going to go with, you should choose what Power Demand you are going to get / will need.

This will come either in max continous amps / discharge current, or C rating of battery. Though I think a good figure to go with in terms to power, is Watt rating of your battery, and you can nicely see it in calculator I gave you link for.

Once you know what max power you want / need, you can estimate how big capacity (amphours) pack you want to reach the desired range of your eboard.

You should include some extra buffer zone to you range, as your board wont perform the same at every step of battery level. It will be ‘weaker’ / less fast when battery is more empty, so extra battery life is a plus to stay in higher speed / power zone more. (though this might not be a case for lipo as much as it is for li-ion, I think)

Calculator should give you a good estimate for elongboard range.

–

So quick steps:

Desired voltage for pack Desired power output Desired range (capacity for pack)

(In between - how are you going to charge it - how fast you want to charge it )

Charging part is actually also quite relevant, as it might make it a pain in the ass to charge it, if you dont plan carefully and dont buy the right parts and ‘system’ before hand.

Final notes:

You can adapt the Power Demand needed by what your motor / controller can supply.

Though, this does not mean you cannot make weaker or stronger battery than that.

Motor might max take 60-80Amps, so people usually try to build 60Amps capable packs… In watts this is usually more than 1.5kw (2160Watts to be exact) at their voltage level (36v) anyways.

– And yes, about range - just increase AH value in calc, until you get desired range.

Formula for range = Your desired range + 30% battery life.

At 30% battery level, board might become weak and if it is li-ion pack, peformance might decrease drastically but I think also for lipo pack this might hold true but for li-ion it will hold more true because of voltage sag and little power left in battery.

So, if your desired range is 10km / 6miles, aim for about 13km / 7.8 miles or so (I would say at minimum)

–

As of now Ive got a pack capable of 20-25km distance, since the most I ride usually anyways is 15km max I think. This allows to fast charge the battery pack, not charge it as often, and more importantly, spend ‘more time’ in 30-80% range of battery life, which is more healthy for the pack.

By not charging fully your pack, you will also save cycles out of it at the cost of increased capacity, though not all chargers might allow to do this, as you need to set the balancing action for cells sooner then.

Final final note

Referencing to real capacity of battery pack and range, a ‘claimed’ 5ah battery might not be always be able to give you 5ah of energy. Maybe more like 4.8ah or so.

It would be also preferred that you only partially discharge it (like take about 3-4ah from it most of the time anyways, not till it gets totally empty)

You will see this more clear, if you plan to go the 18650 cells route, as these cells get more ‘sensitive’ to higher discharge loads and their capacity might be a lot less, if you take 10amps from the cell versus, if you discharge it at only 2A.

I think for lipo this might not matter as much, since most lipo packs come at relatively high discharge currents and it might be more troublesome for 10c and low capacity or such rated packs probably.

2 Likes
9

Most common source for lipo battery:

You can check what other people use, I think it is usually 5ah packs, as these are the most common / conveniant, in terms to size and other parameters.

10

i see people with 2/3 lipo packs. they then usually set them up in parallel. Question is whats the ideal number and should they be set up on parallel or in series?

11

Do you think this is good for what I’m looking for?

12

“Hey, So I’m new to Eboard and I need some help choosing the right batteries for a board with a “Electric Skateboard Motor 6355 190KV”.”

have you read the thread? you need to deside for what chemistry you go for and what type of cells /battries you want. you can try at this site - i know they can build what ever battery you wish try to connect them http://e-greenmotion.com/index.php?route=product/product&path=111_129&product_id=285

13

Yes, but to make it 6s, you gonna need 2 in series (you gonna need the right connectors for that!)

To make it 12s… you gonna need 4x of them, Capacity is quite good for the pack you gave a link for.

15

Hey yeah i have read it. i just want a “not so safe” Lipo. Something kinda cheap.

16

Thanks, so how many of those (the pack i linked) would you recommend?

17

Enough to get your desired voltage. 8ah and 30c goes well enough together i think

18

I’m building on this ones for a 10s4p

http://www.ebay.com/itm/2-Tesla-Model-S-18650-Lithium-Ion-Cells/112396421025?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Almost equivalent to ncr18650b 3.4A unprotected, can be driven burst to about 3C (10A) and normal 2C (6.8A), but i really dont need that much current for my build. Also the chemistry seems to be more safe and tolerant to overdischarge (i’m still using a bms).

1 Like
20

im using a 36 volt 100kv 22A max 800watt hub motor… (what does “max amp” for a motor mean? the max it will draw?)

what kind of battery should i use?

will a battery with “working current” of 25A be suitable? what is “working current”?

i assume a 10s#p 36v battery is the way to go for a 36v hub motor?

i want to use 18650 cells because they have a BMS that i can use a standard wall outlet chord with… and wont need imax b6 or some elaborate setup just to charge…

thanks

21

Are these good numbers for an electric skateboard battery? 42

22

They’re not great. It equates to about 9A max discharge per cell and a capacity of 2600mAh. The weight estimation also seems really coarse. You can get a lot better batteries for sure, a 30Q pack would have about 15% more capacity and can handle like 70% higher discharge rates. It all depends on your application and budget though so in order to give a proper judgement we’re gonna need more info. Have you got a link to the battery pack you mentioned?