Battery upgrade (voltage or amp hours) for longer distance and speed

Get all your technical information about electric bikes here.
Post Reply
jordanjozsef   10 mW

10 mW
Posts: 23
Joined: Oct 03 2018 1:00pm

Battery upgrade (voltage or amp hours) for longer distance and speed

Post by jordanjozsef » Oct 19 2018 2:49am

I was thinking on, in theory the higher the voltage the less amps are needed to produce the same power. Let's say I want to upgrade from 48V to 96V, while everything is the same (controller, motor, battery capacity).

With 96V the motor can spin faster, and if the controller can give me enough amps, I could go faster too. But why not to go faster? The same (for example) 30A will be drawn from the battery when accelerating, but at 48V it means 1440W, however at 96V it means 2880W, so I just doubled the peak power.

The following situation would be true too. Let's say I just cruise around, about 30km/h, it would mean around 200W, roughly the ammeter showed 4 amps at 48V when I was cruising around that speed. I could hold this speed for a defined time. But if I increase the voltage to 96V, to produce 200W, I'll only need 2 amps, which means I could hold this speed for longer (as I mentioned the capacity is the same).

So when increasing the voltage, not only the speed and power increases, but the discance will increase too.
48V 7Ah = 336Wh
96V 7Ah = 672Wh
You have more energy available with higher voltage.

What's the truth? It's just my theory, but everyone says that the voltage is for speed and the amp hours is for distance, but the higher voltage can increase the distance too and can reduce the amp output which means less heat and you could have more power if needed (of course the faster you go the distance decreases, but if you hold the same speed with both voltages, you can go further with the higher voltage).

dilkes   100 W

100 W
Posts: 166
Joined: Apr 11 2012 7:51am
Location: Toronto, Ontario, Canada

Re: Battery upgrade (voltage or amp hours) for longer distance and speed

Post by dilkes » Oct 22 2018 10:46pm

If you think in terms of watt-hours per Km, then if you double the number of cells - either
(a) in parallel keeping the same pack voltage but doubling the amp-hrs
or
(b) in series, increasing the pack voltage but keeping the Ah the same

you will pretty much double your range - assuming you ride in exactly the same way and under the same conditions.

Increasing the pack voltage generally does give the opportunity to go faster, and if you succumb to that temptation (and it is difficult not to!), the faster you go, the more Wh/Km you will consume, thus lowering the range.

User avatar
motomech   1 GW

1 GW
Posts: 3263
Joined: Sep 11 2010 12:21am
Location: Punta Cana Baja Mexico

Re: Battery upgrade (voltage or amp hours) for longer distance and speed

Post by motomech » Oct 23 2018 10:04am

jordanjozsef wrote:
Oct 19 2018 2:49am
I was thinking on, in theory the higher the voltage the less amps are needed to produce the same power. Let's say I want to upgrade from 48V to 96V, while everything is the same (controller, motor, battery capacity).

With 96V the motor can spin faster, and if the controller can give me enough amps, I could go faster too. But why not to go faster? The same (for example) 30A will be drawn from the battery when accelerating, but at 48V it means 1440W, however at 96V it means 2880W, so I just doubled the peak power.

The following situation would be true too. Let's say I just cruise around, about 30km/h, it would mean around 200W, roughly the ammeter showed 4 amps at 48V when I was cruising around that speed. I could hold this speed for a defined time. But if I increase the voltage to 96V, to produce 200W, I'll only need 2 amps, which means I could hold this speed for longer (as I mentioned the capacity is the same).

So when increasing the voltage, not only the speed and power increases, but the discance will increase too.
48V 7Ah = 336Wh
96V 7Ah = 672Wh
You have more energy available with higher voltage.

What's the truth? It's just my theory, but everyone says that the voltage is for speed and the amp hours is for distance, but the higher voltage can increase the distance too and can reduce the amp output which means less heat and you could have more power if needed (of course the faster you go the distance decreases, but if you hold the same speed with both voltages, you can go further with the higher voltage).
First off, you are ignoring to added cost of system upgrades, like heavier wires, better connectors, pre-spark elimitnation, etc. that 96 Volts would require. And even if your current system(controller, motor)could continue to work at double the Voltage(likely the controller would blow), this approach to extending range is a false economy.
The sim. at Ebike CA shows that at an avg., usable cruising speed of 25 mph, system efficiency would fall by 3% and the increase in distance would only increase by 1.5%.
You would be much better off, using the money that would be needed to up-grade the system to handle such a high Voltage and put it into a 48 V battery w/ increased capacity.
Motomech

'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/10Ah Multistar Lipo rear 4Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, Crazy Bobs run ghetto tubeless. 25 mph. Mean Well HLG-320H-54A
https://endless-sphere.com/forums/viewt ... =3&t=83430
'07 GT Idive 4 4.0, Q100C 201 14S LiPoly elifebike 9-FET 20A controller. 23 MPH.
https://endless-sphere.com/forums/viewt ... 4#p1378484

User avatar
wturber   1 MW

1 MW
Posts: 1797
Joined: Aug 23 2017 8:52pm
Location: Fountain Hills,AZ
Contact:

Re: Battery upgrade (voltage or amp hours) for longer distance and speed

Post by wturber » Oct 23 2018 4:30pm

There is a reason that the ebike industry has settled on system around 48-52 volts. It is a good compromise for the speeds and powers needed for most ebikes. The reason you hear people saying more volts is for more speed is because that't the main advantage.

For the same number of cells, you don't actually get more power/capacity when you reconfigure for more voltage since some of the cells that were in parallel must now be placed in series to get the higher voltage. You only get more power/capacity if you increase the voltage by adding more cells. So the added power/capacity is actually a function of adding cells, not increasing voltage. For the comparison example you gave to work, you'd have to double the number of cells.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

billvon   100 MW

100 MW
Posts: 2653
Joined: Sep 16 2007 9:53pm
Location: san diego

Re: Battery upgrade (voltage or amp hours) for longer distance and speed

Post by billvon » Oct 23 2018 7:50pm

jordanjozsef wrote:
Oct 19 2018 2:49am
What's the truth? It's just my theory, but everyone says that the voltage is for speed and the amp hours is for distance.
Voltage is for speed.
WATT-hours is for distance.
but the higher voltage can increase the distance too and can reduce the amp output which means less heat
Higher voltage, same power output = less heat in battery wires (lower current) more heat in controller (less efficient) same heat in motor (same phase amps.)

But keep in mind that you mentioned the additional power that was available. Which is why, in general, you will run hotter with higher voltages - because people will use the extra power, which means more phase amps, which means higher motor temperatures.
--bill von

StuRat   100 W

100 W
Posts: 121
Joined: Mar 15 2018 7:18pm

Re: Battery upgrade (voltage or amp hours) for longer distance and speed

Post by StuRat » Oct 23 2018 8:17pm

jordanjozsef wrote:
Oct 19 2018 2:49am

So when increasing the voltage, not only the speed and power increases, but the discance will increase too.
48V 7Ah = 336Wh
96V 7Ah = 672Wh

You have more energy available with higher voltage.

What's the truth? It's just my theory, but everyone says that the voltage is for speed and the amp hours is for distance, but the higher voltage can increase the distance too and can reduce the amp output which means less heat and you could have more power if needed (of course the faster you go the distance decreases, but if you hold the same speed with both voltages, you can go further with the higher voltage).
Your 96v battery will be twice the size and weight of the 48v battery, so yes, it could double your range if you maintain the same speed etc.

To compare equally, with equally sized / weighted batteries...
48V 14Ah = 672Wh
96V 7Ah = 672Wh
... you will technically get the same range, but in real life you will use more power with the higher voltage because trying to keep the amp flow down is difficult unless you set a limit in the controller.

If you want long range; go slow, slower, slower...
I can ride all day with my 48v 14Ah when out touring about in places I've never seen, taking in the sights and smells.
Or, if I'm home I can throttle the life out of the same battery in 30 minutes.

User avatar
dogman dan   100 GW

100 GW
Posts: 34885
Joined: May 17 2008 12:53pm
Location: Las Cruces New Mexico USA

Re: Battery upgrade (voltage or amp hours) for longer distance and speed

Post by dogman dan » Oct 24 2018 8:51am

RE the first post, I did not check your math, but if you take the same cells and reconfigure them to a higher voltage pack, you did not add one bit of more energy to that pack. it will have the same watt hours it had before. But, if your amps was too high at 48v, then it can potentially deliver more watt hours if you lower amps, because it was too much before. If it was not too much before, then no gain will be seen. You wanna get more from any battery, lower its discharge rate by making each cell deliver less amps. The practical way to do this is to add cells. If you enable yourself to pull 3000w from the pack instead of 1000w, you will hammer that pack into dogshit.

The higher voltage can increase distance too, if you don't change speed, or rate of acceleration.

But you WILL. :lol: And then you will go less distance. And risk hammering that pack to dogshit.

You can ride slow with a high powered, high speed rig, and get very close to the same distance. If you do actually go slow, often only doable by some kind of limiting by CA or whatever means, then basically what happens is the wind resistance at 18 mph is the same no matter what the voltage, and it just comes down to watt hours you have, (ah). If you get 20 watt hours to the mile at 18mph, then you go 5 miles on 100 wh. ( about 3 ah of 36v)


There will be some differences in efficiency, but in general nothing you could not make up by coasting or pedaling slow for a half mile.

So bottom line is this, there is no real penalty in distance, if you must ride slow and get distance, you can. You wont without a lot of effort or a limiter, but you can. And its great to have some speed when you want it.

One thing to avoid though, is going so high in voltage you can't control the throttle to ride slow at all. More than 72v I would not go there, and really 60 v might be plenty of speed anyway, depending on your wants and needs.

And whatever you do, or want, you still have to limit your amps to a reasonable rate, so the cells don't get hot. just make your 48v pack bigger. Get another one, and parallel them. Then you will see more watthours from both, and go amazing distances. I learned this on the road, doing 60- 80 miles between charges. It works. And 48v is generally fast enough for the open road. In a city, 72v might be worth it to keep up, but on the open road, 48v speed is enough.

jordanjozsef   10 mW

10 mW
Posts: 23
Joined: Oct 03 2018 1:00pm

Re: Battery upgrade (voltage or amp hours) for longer distance and speed

Post by jordanjozsef » Oct 28 2018 8:34pm

My 48V System currently maxes out at 50km/h, which is nice, because it's a 350W controller with 14A max. output. I did the shunt mod, the torque was better the max. amp was 24A, but I still stuck at 50km/h, no matter how hard I leaned on the handlebars, because above 40km/h, the amp started to go back, even if I was on full throttle all the time. I did the 50km/h with only 10A, which is around 480W. The no load speed is around 60km/h, so I think the 48V System could make me go a little faster, but I think the controller won't allow it, because the shunt mod won't affect the full speed torque, or did I just reach the motor's peak RPM, so it can't accept more amps at that speed? I'm not an expert at this, but my other theory is that the controller just starts to cut off the amps when the speed increases, so another 48V controller (rated 500W or more) could maintain 60km/h on the road.

Post Reply