48v 500w versus 350w

[stone]

Apologies for these questions as I know its obvious to you guys but I really have no clue.

Would a 350w ebike battery last longer than a 500w ebike if everything is the same? the Batts are 48v 20A and supposing I am traveling 20km, the logical thing is that the 350w would last longer but wouldnt the 500w with the added power require less watts to move?

The reason I am asking is that I am considering buying a bike and range is important to me but the 500watts bike has got disc brakes which i really like.

is there much of a range difference between a 350 w and a 500w? what about power ? I have never tried a 500w before.

thanks in advance.

 

[johnrobholmes]

Keeping all else equal, the 350w bike will have better range from the slower acceleration. Assuming the 500w bike goes faster, the range would drop a bit more.


Now if you were careful on the throttle you could get the same range from the two kits, but that rarely happens. Most people like to use extra power when they have it

 

[stone]

whats the best way to use the throttle? I read somewhere that these bikes motors are most efficient at 80 or more of its maximum speed. Is that right?

Its the acceleration that saps the most power? Absolute noob here, sorry.

I notice that the locals here in china are very gentle on the throttle and as far as I can tell the throttle is usually not in full. Its just enough to let them go at the desired speed and thats all.

 

[TylerDurden]

Hi,
Start with the basics...

It takes power (Watts) to reach a specific speed.

It takes energy (Watt-Hours) to maintain that speed for any length of time.

A motor will convert the electrical energy in a battery to mechanical (with efficiency losses).


The motor specifications should indicate which one will be more efficient at the speed you want to go.

The higher rated motor could provide more power (and therefore speed), but more power eats more energy in your batteries.


The typical trade-off is speed v. range... go slower to go farther.

If you get a 500W motor, you can go the same speed as the 350w; but have the potential to go faster.

 

[TylerDurden]

 

[stone]

Thanks for the info, is it correct to say, If i were to be gentle on the throttle and go slow on a 500w bike, the range would be about the same as that of a 350w?

The bike I am eyeing is this because it got disc brakes, but my wife thinks range is more important.

 

[Drunkskunk]

Thanks for the info, is it correct to say, If i were to be gentle on the throttle and go slow on a 500w bike, the range would be about the same as that of a 350w?

Yes. Assuming that the motors are built for the same speed, the bigger motor will use the same power to go the same speed. It has the potential to use more power, but you are in controll of the power it uses by way of the throttle.

An analogy might be to compare it to a dinner plate. having a larger plate doesn't mean you will eat more food. it just means you have the ability to eat more if you decide.

 

[dogman dan]

In my world, the 500 watt motor would last longer. Why? the way I ride, up the hills I climb to get home. I'd be whomping a 350 watt motor pretty hard. But it would take more watthours to get up the hills a bit faster.

Buy the 500 watt one, because you really want 750 watts, or even 1000, when you have a hill, or a stiff headwind.

However, it does not have to be a watthog because it's a higher wattage motor/controller set. It just depends on your ride, and your throttle hand. I've tested many different types of motors, and nearly all use the same 300-400 watts to go 20 mph on flat ground.

Once you aren't on flat ground, or have that wind, you get real glad if 350 watts is not your maximum.

Range is important. That's why you want to ditch the lead batteries if the bike comes with them, and replace em with lifepo4. The same size package will weigh half as much and go three times farther.

 

[stone]

thanks for all your help.
I cannot change to lifepo4 because it can cost as much as a new bike or even more.

I bought the 500 48v 20ah bike. the difference between the 350w and the 500w is quite a bit. It has got better startup and cross traffic junctions better. I end up on full throttle when the weather was 2 degrees C but when Its warmer it is faster.

I supervised the installation and the shop refused to install a fuse citing that it may trip on acceleration. This is quite common in Shanghai, I noticed. Can I install one myself in the battery pack by extending the + terminal to a fuse holder? What ampere should I use?

I was offered a 1000w for under 100usd more...perhaps I should have gotten that instead.

 

[lfairban]

whats the best way to use the throttle? I read somewhere that these bikes motors are most efficient at 80 or more of its maximum speed. Is that right?

Its the acceleration that saps the most power? Absolute noob here, sorry.

Correct on both points. You may wish to look at the simulator at http://ebikes.ca/simulator/. Even if you can't find a motor to match your characteristics, you can play with the parameters like the throttle setting. The part about max efficiency at 80% will be obvious.

 

[dogman dan]

A 50 amp fuse would still protect you from a fire if you had a major short circuit, but be extremely unlikely to stop you because you hit the throttle hard on a 500 watt bike. 30 amp is actually pretty common to find on a 500 watt setup. Perhaps more imortant than a fuse itself, is to protect any wiring likely to short with some extra cable sheath. So a bit of armor around the wires from the battery to the controller would make that short the fuse is for so unlikely you don't need the fuse.