Battery Basics for Beginners Wiki [Serious]

The Citadel - Essential References for Esk8
#14

For series/parallel, both adds range, as to why they both do, probably donā€™t need to be mentioned in this basics guide.

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#15

Constructive criticism: add a brief explanation of C

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#16

Or just simplify it that total number of cells regardless of configuration determines the total watt hours, or the ā€œsize of your gas tankā€. 10S5P with 50 cells has a very slightly higher capacity than 12S4P with 48 cells for exampleā€¦

And if necessary expound upon it by saying itā€™s your total (nominal) voltage x total Ah per P group. Using the previous example:

  • 10S x 3.6v per cell nominal x 3Ah per cell x 5P per P group = 540 Watt hours
  • 12S x 3.6v x 3Ah x 4P = 518.4 Wh
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#17

Is it just me or are C ratings totally backwards and unintuitive when you just want to know how many amps your battery can handle? This is a great suggestion.

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#18

Agreed, Voltage and Ah are already in the text, might as well define Wh.

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#19

Thanks for this writeup, Justin :smiley:

More information about cutoffs can be found over here

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#20

This is kind of like soldering on cells. You should never do it. Those that do it, know exactly what they are doing and why, and what damage it can cause, and how to solder in a way that drastically minimizes that. But I would still recommend never doing it. Anyone who knows enough about it to do it, knows they can disregard that advice, because they know enough about it and whatā€™s happening inside the cell.

Yes, this :arrow_up: So basically, never do it.

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#21

Dude, this is awesome! Thank you for putting the time into thisā¤ļø

Would a discussion on capacity vs discharge of a pack be helpful? For example, I often figure on more P groups in a battery because I want it to be able to dish out them AMPS. Range is nice tooā€¦
:beer:

Edit:
Seems @bonesaw and @Rojitor had similar recommendationsšŸ‘

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#22

excellent work @Venom121212 and @b264 i linked to this page in the glossary of terms with the other Math and Science of Electric Skateboarding series @mmaner published

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#23

Also there is the ESK8 CALC in the banner that will help with estimating battery use. And @thisguyhere 's tool http://esk8life.com/batt/index.html

perhaps its too advanced but we could also discuss discharge rate and data sheets for above mentioned cells

18650-Samsung 18650 30q
Capacity: 3,000mAh
Constant Discharge: 15A

18650-Samsung 25r
Capacity: 2,500mAh
Constant Discharge: 20A

18650-Samsung 40T
Capacity: 4,000mAh
Constant Discharge: 30A

18650-LiFePO4
Capacity: 1350mAh
Constant Discharge: 50A

20700-Samsung
Capacity_Nominal: 3500mah
Constant Discharge: 30A

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#24

I tried to write something similar, take as much as you want
http://esk8.uk/#/wiki/batteries

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#25

I am working on another thread about how to set up your esc. This will be focused on there.

@krindor yeah yeah less amp draw I get you :wink:

@Rojitor C value is the most inflated battery measure Ive ever seen. I personally hate it and try to avoid using it as itā€™s a controversial topic.

@wandagoner that would make an awesome topic. Inviting you to a pm chain shortly

@anubis thank you, I will happily use that and give you credit for saving me work haha

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#26

Does that also apply to a 40T battery, i.e. if I have a 40T 12S2P battery I have to charge it with 2.7 A, since [2]*[4000/3000] = 2.66?

#27

Iā€™ve heard ā€œ2 amps per parallel groupā€ thrown out as a theoretical safe max for 30q.

40T has a higher discharge current so I imagine it can handle a higher charge current as well but Iā€™ll call on @MysticalDork and @BluPenguin for some back up advice / clarification.

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#28

Okay Iā€™m so confused by that formula. General rule for charging is 0.5c or less per cell for longevity. C rating being the capacity of the battery. I would say that for optimal speed vs life, 0.2c-0.5c multiply by # of cells per P group is a good place to be. So for 2P of 4Ah cells, you can charge it at 2A x 2 so 4A charger. Less is better for cell life but will take longer.

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#29

As mentioned above, I hate c ratings as they are often inflated and confusing. They seem like a floaty variable that changes based on usage case.

Iā€™ve always understood it to be a discharge rating over time at a standard amp rating.

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It seems to me like a battery can really be any c rating within reason regardless of what the manufacture recommends. That formula was a quick, multiplying factor to avoid using c ratings.

Thank you for clarifying on the amp charge of the cells.

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#30

Discharge C ratings can be inflated, but the C number itself is a constant. 1C = Ah of the battery. 3Ah cell at 1C is 3A, 0.5C is 1.5A. The C is just a multiplication of the cellā€™s capacity. So itā€™s easy to claim 0.5C charge rate because it works for any cell. Just divide the cellā€™s nominal capacity by half and charge at that amp rate.

In a perfect world, 3Ah cell discharging at 3A (1C) gives exactly 1 hour of use. In real life due to losses and inefficiencies, it comes to less than 1 hour.

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#31

Hi, quick question
how many bms do i need to connect 2 6s lipos in parallel?
can i connect both batteries in parallel to the bms
or
connect each lipo to a bms and then to the VESC/Charge cables in paralllel?

Thanks in advance for your answer

#32

Just one. You will always only need 1 BMS per set of battery. For example 10S battery requires 1 BMS just like 12S battery requires just 1 BMS. The only situation for 2 or more BMS is if you have 2 or more 10S batteries in use. Even then, depending on wiring, you could probably get away with 1 BMS.

Yes, you can connect 2 6S lipo in parallel to a single BMS.

What are you running thatā€™s only 6S though? I think 6S is the bare minimum for vesc to operate?

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#33

thanks for your reply @annihil8ted
iā€™m upgrading an old e-scooter and iā€™m trying to get more distance range.
at this moment iā€™m using 2 lead acid batteries in series with the vesc so iā€™m looking lipo to accomplish that

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