Battery advice needed
- Thread starter gadabout
- Start date
Some thoughts:
What does "satisfactory" mean to you, under what specific conditions?
Meaning:
--what specific job (speed, acceleration, power, etc) do you need the system to do for you?
--under what riding conditions?
--with what gearing from motor to wheel?
--in what wheel size?
--and if there are multiple windings of the motor in question, which one are you using?
--and what is the minimum battery voltage the controller you're using?
Those are necessary bits of information to be able to answer your question.
If there is a minimum power level for your worst-case speed/load/riding conditions, then the voltage has to be high enough for the controller, at it's current-capability, to generate that much power.
If there is a minimum worst-case speed, then the voltage has to be high enough to reach that given the motor winding, the gearing, and the wheel size, under whatever riding conditions you have that place however much load on it.
If the controller has a minimum operating voltage, then the voltage has to be higher than that even under worst-case loading conditions on the battery when it is just above empty.
Etc.
What does "satisfactory" mean to you, under what specific conditions?
Meaning:
--what specific job (speed, acceleration, power, etc) do you need the system to do for you?
--under what riding conditions?
--with what gearing from motor to wheel?
--in what wheel size?
--and if there are multiple windings of the motor in question, which one are you using?
--and what is the minimum battery voltage the controller you're using?
Those are necessary bits of information to be able to answer your question.
If there is a minimum power level for your worst-case speed/load/riding conditions, then the voltage has to be high enough for the controller, at it's current-capability, to generate that much power.
If there is a minimum worst-case speed, then the voltage has to be high enough to reach that given the motor winding, the gearing, and the wheel size, under whatever riding conditions you have that place however much load on it.
If the controller has a minimum operating voltage, then the voltage has to be higher than that even under worst-case loading conditions on the battery when it is just above empty.
Etc.
offGridDownUnder
1 kW
I've noticed some overall tendency towards thinking of 'faster' in the posters here. Perhaps they just write more.
My approach is definitely not 'faster', although 'more efficient' and 'more effective' (not the same) are involved.
I'm interested in going up steep hills, possibly with a trailer, when I'm old(er than now, even) and exhausted after a long day.
On the other hand, from my prior motorcycle riding days, I know that serious acceleration is a safety tool - sometimes I needed to get out or the way and stay away from other traffic.
I wanted to throw that in to balance the impressions you might get from reading. Cast your net widely in thinking about what you want to do, now and in the future.
My approach is definitely not 'faster', although 'more efficient' and 'more effective' (not the same) are involved.
I'm interested in going up steep hills, possibly with a trailer, when I'm old(er than now, even) and exhausted after a long day.
On the other hand, from my prior motorcycle riding days, I know that serious acceleration is a safety tool - sometimes I needed to get out or the way and stay away from other traffic.
I wanted to throw that in to balance the impressions you might get from reading. Cast your net widely in thinking about what you want to do, now and in the future.
? I didn't see any posts in the thread about "faster"?
The project vehicle is a re-engineered 1947 Swallow Gadabout 125cc vintage scooter modified to electric power and only intended for occasional light-duty use in a flat suburban area.
If I use a 48V BAC2000 controller with a QS90 1KW motor driving a 14T sprocket connected by a #420 chain to a 45T rear sprocket on a 16 inch diameter rear wheel - what capacity 48V battery would be required?
The scooter will only be used for a couple of hours of intermittent operation and a maximum of 25/30mph, with gentle acceleration will be more than adequate.
If I use a 48V BAC2000 controller with a QS90 1KW motor driving a 14T sprocket connected by a #420 chain to a 45T rear sprocket on a 16 inch diameter rear wheel - what capacity 48V battery would be required?
The scooter will only be used for a couple of hours of intermittent operation and a maximum of 25/30mph, with gentle acceleration will be more than adequate.
Jordan325ic
100 W
- Joined
- Aug 5, 2020
- Messages
- 121
What range are you looking for? “Intermittent operation” over a couple of hours could be 5 miles or 75 miles. That’s the biggest factor on battery size, energy capacity.
The next consideration is how much power you need. You say you only need to go 30mph max, but you chose a controller produces 5x as much power than you need. Any reason for that?
To give you an idea, I built a 25mph, 25 mile range Tomos moped with 16” wheels. The motor controller was 1000w output (20A @ 48vdc). I used a 48v17Ah battery.
The next consideration is how much power you need. You say you only need to go 30mph max, but you chose a controller produces 5x as much power than you need. Any reason for that?
To give you an idea, I built a 25mph, 25 mile range Tomos moped with 16” wheels. The motor controller was 1000w output (20A @ 48vdc). I used a 48v17Ah battery.
Last edited:
This one?
Swallow Z50 – electric scooter
The Swallow Z50 scooter is based on a re-creation of the Swallow Gadabout, the first post-war British motor scooter which predated the Vespa and Lambretta invasion into the UK. The origin of this project was the intended conversion a 1947 Swallow Gadabout scooter with a 122cc Villiers 9D...
endless-sphere.com
This is a different question than your post started out asking. The questions I asked before to lead you to the answer apply to the original question, which was "What is the lowest battery voltage at which a combination of a QS90 motor and a BAC2000 controller would operate satisfactory?". More info is needed to answer your new question, since you have decided on a 48v battery now.
For what range? Is that a couple of hours *at* 30mph? Or something else?
If you have any wh/mile usage data from your existing conversion usage, it would help you calculate the minimum required Wh capacity of the battery; you just multiply the wh/mile by the miles of range required.
Otherwise, guesstimates of power usage of the system must be made (for instance by using the simulators at ebikes.ca), so that can then be used to guesstimate wh/mile usage, to then do this calculation. Current limit set in the controller needs to be known to determine potential max power usage; weight of vehicle, rider, and anything being carried, and whether or not it is continuous riding or stop/start traffic--the former meaning weight doesn't matter much, but the latter means weight is very important to the calculations. Also need to know how much range required, worst case, even under worst case conditions (whatever the worst case winds you would have, etc).
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