Battery dilemma - Voltage

Hi, i have a dual motor DD hub bike that runs on 72v but at top speed it's amp consumption drops to mid 30's.
Now, i intend to build a battery, but it occured to me that i could increase it's voltage, by option is between:

20S8P - 160 Cells - 72v - 16.8Ah - 240A Max Continuous Discharge
or
24S7P - 168 Cells - 84v - 14.7Ah - 210A

Sony VTC4 2100mAh 30A

Is it better to give up on some Ah on favor of more voltage or the other way around?
Im affraid that the more voltage, even if i limit the current a bit to compensate, will drain the battery faster than keeping the 72v.

careca said:

Hi, i have a dual motor DD hub bike that runs on 72v but at top speed it's amp consumption drops to mid 30's.

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That is inherent in the basic laws like Ohm's.

For a given power, (Watts) as speed (Volts) increases then current (Amps) must drop.

At low speed/volts, the power is going into torque (weight, hills, initial overcoming startup inertia).

Increasing pack / system voltage will only gain top speed.

And **lose** torque at lower speeds, for that **lower** voltage is more efficient.

Or if you stick with 72V, increase Ah capacity to get higher Amps output at a lower C-rate, and increase range and longevity as fringe benefits.

Going to a **higher** C-rate cell instead will keep the weight down, may help with short term boosts, but not help longevity nor range,

If you want to spin the wheel faster, and have enough power to break thru the air, more voltage or a controller with flux weakening can both do that.

If you ride faster, you will use more power.

Get a bigger battery than you can afford if you have any doubts. You will be very pleased.

Thank you for your inputs. Very appreciated.

Unless you have a controller with >100v rating, then moving to 24s will most likely end in disappointment with a fried controller. There are many tales of people getting away with it for a period of time in the pursuit of peak performance, but that's not really relevant any more in this age of more advanced controller designs.

More pack voltage will allow for more top speed, but it will be worse in almost every other regard.

john61ct said:

And **lose** torque at lower speeds, for that **lower** voltage is more efficient.

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This does not make any sense to me, can you explain how this can happen?

Here is an example:
https://www.ebikes.ca/tools/simulator.html?bopen=true&batt_b=B4823_AC

I just took whatever was in the calculator and compared to the same with higher voltage.
They look the same to me at low speeds (limited by phase amps) then the higher voltage gives more power and speed.