1 big battery or 2 small ones?????

General Discussion about electric bicycles.
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Grider   100 mW

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1 big battery or 2 small ones?????

Post by Grider » Feb 16 2019 1:41pm

1) 72v 20s6p (120 cells)......OR
2) 2 x 72v 20s4p (2 smaller batteries with 80 cells each)

I know it's a matter of personal preference but Is it better to have one big battery? Or to have 2 smaller ones? I'm about to build one (or two). They will be used for a daily commute. :bolt: :bolt: :bolt: :bolt: :bolt: :bolt:

Tommm   10 kW

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Re: 1 big battery or 2 small ones?????

Post by Tommm » Feb 16 2019 2:20pm

Grider wrote:
Feb 16 2019 1:41pm
1) 72v 20s6p (120 cells)......OR
2) 2 x 72v 20s4p (2 smaller batteries with 80 cells each)

I know it's a matter of personal preference but Is it better to have one big battery? Or to have 2 smaller ones? I'm about to build one (or two). They will be used for a daily commute. :bolt: :bolt: :bolt: :bolt: :bolt: :bolt:
You will be able to get much less amps using a small one. Size your pack planning on using 25-75% only.

ScooterMan101   1 MW

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Re: 1 big battery or 2 small ones?????

Post by ScooterMan101 » Feb 16 2019 2:36pm

Grider,

What motor do you have ?

What controller do you have and what is the max amperage it can draw from the battery pack ?

When you ride what is the highest amount of amps you draw from the pack consistently ?

How long is the commute ?

For a general answer , depending on what motor you have ...
If you regularly operate at 20 amps or below consistently I would build 2 packs.
If you regularly operate at 25 amps , 30 amps consistently I would build 1 large pack.
My first conversion ... Sold

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It's 2018 already, lets get some real , improved e-bike / e-velomobile / e-motorcycle designs .

Voltron   1 MW

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Re: 1 big battery or 2 small ones?????

Post by Voltron » Feb 16 2019 8:14pm

Are you going to parallel them up? That is, use them at the same time, or swapping a fresh one in?

markz   100 GW

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Re: 1 big battery or 2 small ones?????

Post by markz » Feb 16 2019 10:53pm

All depends on how far you ride in a day before you want to charge. Some people charge up all the time, others every now and then.

Keep in mind of the discharge rates for the packs. The easier you are on the packs the longer they last, its always a give and take. Less discharge amps, lasts longer. Fewer charges, lasts longer. Shallower use of packs, lasts longer.

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dogman dan   100 GW

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Re: 1 big battery or 2 small ones?????

Post by dogman dan » Feb 17 2019 7:32am

Based on my own experience with 72v, you intend to haul ass a lot. So the solution with 8p cells beats the one with 6p. And even 8p may still whack those cells with a lot more discharge rate than they like.


Also, just carrying the damn thing. Two motorcycle saddlebags slung as low as you can may be the only way to carry that much battery, and still have a stable enough ride to avoid speed wobble when you do haul ass. Both these bikes I built with that in mind, to be able to carry 40 ah of 48v on one, 80 on the other. Carry your battery wrong, and your 40 mph bike will be unable to go faster than 25 mph without going tank slapper.

One big battery is hell to carry. Its not usually going to fit in just any bikes triangle. Carry what you can there is good, then add more elsewhere on the bike. So its two batteries, maybe one that is 6p in the triangle if it fits, then more in panniers. Maybe you carry 48v in the triangle, and then series in 24v you carry someplace else on the bike.
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markz   100 GW

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Re: 1 big battery or 2 small ones?????

Post by markz » Feb 17 2019 9:43pm

Trying to lift a bike with a heavy batteries up some stairs or onto a bicycle rack on a bus is always fun when your having one of those days. Heck even going down stairs with a heavy ebike is joy joy fun fun. Up/down a single wide escalator is another one.

You just never know what your eriding day may entail. Maybe you twist that throttle a little too much going around a corner on a rainy day, do some fish tailing. How will the battery be attached, will the mount last? All questions one has to ask themselves.

edit
Oh forgot another one, what about lifting that heavy ass ebike onto a truck bed.

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