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Discussion Starter · #1 ·
I have a 45V 45AH 2kWh module (from a Chevy Volt) powering my 8kW electric motorcycle.

My top speed is ~38 MPH & the range is ~20 miles

I believe adding another 2kWh section, connected "in parallel" would create a 45V 90AH pack which should (roughly) double my range
...but, since the voltage is still the same (~45V), my top speed would/should not increase

Now, if (2) Volt modules were connected "in series" creating a 90V 45AH pack, my top speed should increase
...but, since the Amp Hours are still the same (~45AH) my range would/should not increase

My question:
Would running @ 90V be more efficient (drawing less Amps) (8,000/45= 177A vs. 8,000/90=88A)
...& also having the ability to "crank up" more speed (thus the motor not always having to run @ full speed) theoretically, increase my range any?

Thanks, Kevin
 

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I have a 45V 45AH 2kWh module (from a Chevy Volt) powering my 8kW electric motorcycle.

My top speed is ~38 MPH & the range is ~20 miles

I believe adding another 2kWh section, connected "in parallel" would create a 45V 90AH pack which should (roughly) double my range
...but, since the voltage is still the same (~45V), my top speed would/should not increase
Assuming that the top speed is limited by the voltage available to the motor, that is correct.

Now, if (2) Volt modules were connected "in series" creating a 90V 45AH pack, my top speed should increase
...but, since the Amp Hours are still the same (~45AH) my range would/should not increase
Oh... so close. Yes, if top speed is limited by voltage available to the motor then doubling battery voltage will increase top speed. But you have twice the energy available, so your range will be doubled. Driven the same way motor current will be the same, but with this configuration battery current will be cut in half.

My question:
Would running @ 90V be more efficient (drawing less Amps) (8,000/45= 177A vs. 8,000/90=88A)
...& also having the ability to "crank up" more speed (thus the motor not always having to run @ full speed) theoretically, increase my range any?
Why would you assume that lower current means greater efficiency? 8 kW is still 8 kW regardless of the battery configuration. That power will be half as much in proportion to battery capacity by doubling the battery capacity (which is good), whether the battery modules are in series or parallel.

The motor speed won't be changed by the battery voltage. Are you considering changing gearing?
 

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Going any faster will drastically increase consumption Ah per mile.
The assumption of doubled range due to doubled battery energy capacity assumes the same driving pattern - a more demanding pattern (such as higher speed) will reduce range from that. It is the energy consumption (Wh/mile) which depends on speed; amp-hour per mile consumption depends on the battery configuration (one Ah from the series configuration corresponds to two Ah from the parallel configuration).
 

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I've never seen anyone with increased speed capacity fail to use it.

Otherwise what's the point?
True, but that ability doesn't need to be used all of the time, so the effect on range is undetermined. Everyone with an engine-driven car has more power than they need to drive, and many will never use the full available power in the entire time they drive the car. It is normal to buy a vehicle with a more powerful engine than needed to be able to occasionally merge onto a freeway or climb a grade, but to drive it most of the time at the same speed as they would drive any other vehicle. In traffic in maintain the same pace in my Mazda compact hatchback as a Ferrari; in most cases I even accelerate away from stops at the same rate. Of course, when adding capability to a marginal vehicle that capability is more likely to be used.
 

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I'm just pointing out a fact for OP to take into account

not looking to argue for / against / about anything else
 

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Discussion Starter · #8 ·
Assuming that the top speed is limited by the voltage available to the motor, that is correct.
Oh... so close. Yes, if top speed is limited by voltage available to the motor then doubling battery voltage will increase top speed. But you have twice the energy available, so your range will be doubled. Driven the same way motor current will be the same, but with this configuration battery current will be cut in half.
Why would you assume that lower current means greater efficiency? 8 kW is still 8 kW regardless of the battery configuration. That power will be half as much in proportion to battery capacity by doubling the battery capacity (which is good), whether the battery modules are in series or parallel.
The motor speed won't be changed by the battery voltage. Are you considering changing gearing?
So to power my 8,000W motor, at either 45V or 90V, the same amount of "actual" energy is drawn from the batt pack
...it's just that if running @ 90V (as opposed to 45V) the "pressure" (amps) will be less because it's running thru a "wider path" (higher voltage)

As far as speed vs. voltage, the motor specs listed 72 RPM's per volt of input.
Also, when I first did the conversion (back in 2017) I only ran it @ 36V (3-12V 35AH SLA's) & the top speed was ~25 MPH.

Then, when I upgraded it to 48V (4-12V 35AH SLA's) the top speed increased to ~35 MPH

The acceleration was SUPER (0 to top speed in ~3 seconds)
...but, it "topped out" (35 MPH) quickly & the motor really seemed to be "racing" all of the time

So, recently, in an effort to increase speed, I reduced the gear ratio from 5.4:1 down to 5:1
I figured that would/should increase my top speed a bit, with out sacrificing too much acceleration/torque
...& by adding a bit more "load" the motor shouldn't be "racing" so much.

I ended up finding out that this modification did reduce my acceleration level a bit (as expected)
...& it only brought me up, a few MPH (~38 MPH)
...but, (unanticipated) it also, reduced my "max" range a bit too (from ~25 miles down to ~23 miles)
* I consider ~20 miles (range) as my safe zone

As far as increased speed capacity, I don't really want to go a lot faster
...but, with only a 38 MPH top speed, I'm quite often running WOT (full speed) just to maintain/keep up with traffic

So, a 45-50MPH top speed would give me the ability to run ~40 MPH to "keep up with traffic"
...but, not be running @ "full throttle" (so, the motor isn't always "racing")
...& still have some acceleration power (more speed) "in reserve", if needed

Also, (another question) I got 1,600Wh out of my 2kWh pack, (last video) is this normal?

Thanks for the replies, fellas
 

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The motor 'racing' isn't necessarily problematic, but some reserve power is a great idea (say, if you need to get out of trouble quickly).
1600Wh out of a 2000Wh pack is not abnormal, usually you won't get all of the power out due to internal resistance and degradation. I'm not sure what your voltage range is though.

If your motor and controller can handle it, 90V would be a good configuration. It would theoretically double your top speed, but at that point I'd suggest more gearing down -- that should improve efficiency.
 
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