battery query.

Electrically assisted bikes, trikes, etc. that are legal in the UK
Post Reply
jags
Posts: 636
Joined: 3 Oct 2007, 3:11pm

battery query.

Post by jags »

will any 250watt battery drive 250watt hub motor ?
Jdsk
Posts: 24478
Joined: 5 Mar 2019, 5:42pm

Re: battery query.

Post by Jdsk »

Those numbers don't have to match.

For the motor that 250 watt is a measure of power.

For the battery that should probably be 250 watt hour and is a measure of energy. In this case that's the energy that the battery can store and deliver to eg a motor. You'll also see energy storage of batteries (eg car batteries) measured in amp hours and at a given potential difference those two methods of description carry the same information.

Batteries and motors do have be matched, especially in the potential difference (usually measured in volts) at which they operate and the current (usually measured in amps) that can be delivered.

For eBikes what the energy storage tells you is how long the battery will power the motor, but of course a 250W motor is often operating at much less power than that rated value. A battery that stores more useful energy will power the motor for longer.

Jonathan
Red Kite
Posts: 47
Joined: 10 Sep 2012, 5:20pm
Location: Hertfordshire, UK

Re: battery query.

Post by Red Kite »

jags wrote: 24 May 2021, 11:48pm will any 250watt battery drive 250watt hub motor ?
What matters is the voltage and the current it can supply. A 12V. A 12V 500Wh battery such as the one in many cars wouldn't be much use even if it didn't weigh 15Kg..

A typical e-bike battery now is 36V nominal. It needs to be able to supply up to a reasonable current (I'd guess on a scale of 10A) without too much voltage drop.
Cube Touring Hybrid One e-bike, Brompton P6R with Swytch conversion
hemo
Posts: 1438
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: battery query.

Post by hemo »

A battery needs to have a continuous discharge rate in amps that is greater then the max current rating in amps of the controller. The ah or wh rating matters not, all it determines is how far one can ride, it does though need to be of the correct nominal voltage to of the controller in use.
jb
Posts: 1782
Joined: 6 Jan 2007, 12:17pm
Location: Clitheroe

Re: battery query.

Post by jb »

jags wrote: 24 May 2021, 11:48pm will any 250watt battery drive 250watt hub motor ?
No
Cheers
J Bro
jags
Posts: 636
Joined: 3 Oct 2007, 3:11pm

Re: battery query.

Post by jags »

theres a reply i can understand. :D
hemo
Posts: 1438
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: battery query.

Post by hemo »

Look in the battery specs, any good battery should be able to manage 20a continuous.
Post Reply