Is making battery pack of 32ah made out of Samsung 40T cell better than a battery pack of 40ah made with LG21700M50T?

[ryuhda]

Hi,
I was trying to get a additional battery pack to use for my 750w bafang motor ebike.
My initial plan was to get a LG21700M50T battery pack, which would be 48v 40ah.
however, one of the store manager told me that actually getting 48v 32ah of Samsung 40T batteries would be
much better, rivaling the actual distance that it could travel.
Is this true?
I kind of get the idea that Samsung 40t does have higher discharge rate, and that somehow helps(thought how it helps is sill lost to me), but I thought having higher Ah over all would make the battery run for longer period of time, which would mean that It would be able to cover more distances.
How 32Ah battery pack can outdistance 40ah battery pack still baffles me.
I would be very grateful if anybody can explain what is going on here

 

[john61ct]

Without addressing which cell is "better" or not.

You are correct that range comes from energy stored, measured in Ah.

Higher **power** discharge capacity may result in better longevity at high average C-rate discharge

but accelerating faster, carrying more weight, doing wheelies will actually result in higher Wh used per mile

thus shorter range.

Sounds like a salesman optimising his commission.

 

[markz]

You are correct that range comes from energy stored, measured in Ah.

Interesting, I was debating to myself which is a more accurate way for the term, I was leaning towards watt-hours.
It came down to having a 52V 14.5Ah battery and a 36V which I believe is at 20Ah, both have approximately the same distance ridden, so it has roughly the same watt-hours, 750wh. Splitting hairs I know, but I was trying to determine if I made both batteries equal, it would obviously be 2 52V or 2 36, but what about 48V instead of 36? Then its 750Wh/48=15.6Ah. Its neither here nor there, but I like solving math questions, and trying to do it without paper or pen or calculator. Here, I obviously did it by W10 calculator. But a week ago, it was the math riddle I came up with.


Random website
Watt-hour (Wh) is the energy capacity of a battery
The energy capacity of a battery as it more accurately determines the energy that can be stored in a battery.

ampere-hour (Ah) is the charge capacity of a battery
The amount of charge that can be available in a fully charged battery. This amount of charge is what determines the amount of current that can be discharged from the battery and its discharge time.

But back to the OP, which comes down to the old age question of "Better"
Better in what way?
Quality of battery cells.
Both are 21700 so a better size isnt it.
What about "better" chemistry?
Which is the better brand?
Better price
Is more watt-hours better, for riding longer, has its benefits for less stress hence shallower discharges so you dont drain it completely whhiich better then leaving fully charged overnight or days, or heating up the cans, higher discharge. More P the better.

 

[john61ct]

Yes Wh is the better unit for comparing domains of different nominal voltages.

Otherwise stick to Ah, more accurate for stored energy modeling

can always derive Wh when needed

 

[goatman]

8p batteries
i think it depends on your climate
if youre in cold weather, you might want a p42a instead of a 40T

if youre not pulling 7 to 10amps (60 to 80amps from the controller) per cell how are you going to get the 40t or p42a cells upto operating temperature?

if youre only pulling max 40 amps, (5amps per cell) you might be better off with that lg

 

[ZeroEm]

More ah's is better. Only reason not to go farther is lack of self control. When people get higher voltage or more amps they tend to use them or ride faster.

 

[docw009]

The LG21700M50T is rated for 5000mah and 10A discharge
The Samsung40T is rated for 4000mah and 35A (?) discharge

For an 8P battery, either pack will have more than enough peak current to run your 750W motor. Both should easily handle 50A and you probably won't use more than 26-28A. However, the LG will give 25% more range. It's 2000 watt-hours vs 1600 watt-hour.

The Samsung might be the better choice if you were building a 13S2P battery. The LG version would only be rated for 20A, and too low for your 750W. It would probably sag and shut off when the battery was at half capacity. motor. If Samsung isn't lynng about 35A, it should work and give you better performance even though the range is less. .

 

[john61ct]

Yes, within a given size and chemistry family, batteries must be designed for **either** energy density (more mAh) **or** power capacity, they are goals in opposition, can only compromise between them, not optimize for both.