Connecting Batteries in Paralell

[jrs665]

Have recently had a bafung motor put on my ICE Sprint X 26 Tour.

Have 2 batteries on the trike, only one connected to the motor, the other just a spare to swap over when 1st dies.

Does anyone know of somebody in Edinburgh area that can connect the 2 batteries in parallel to double my range?

Robert Queen was recommended , but do not have contact details.

[Will]

There is a company in my neck of the woods: https://www.ebike.scot/

and a company search shows that it has a director called Robert Queen:

https://find-and-update.company-informa ... 1/officers

I assume this is the person/company you are looking for.

Will

[Brucey]

discharging batteries in parallel presents no great difficulty provided the batteries are 'the same'. However, even if they are identical when new, they are unlikely to stay that way.

[jrs665]

There is a company in my neck of the woods: https://www.ebike.scot/

and a company search shows that it has a director called Robert Queen:

https://find-and-update.company-informa ... 1/officers

I assume this is the person/company you are looking for.

Will

Thanks

[ChrisF]

E-bike batteries include a lot of electronics to help them charge and discharge correctly without damage. I doubt they would take very kindly to being wired in parallel.
Maybe this question should be moved to the e-bike thread; there may be better experienced replies there..

[Cyclothesist]

E-bike batteries include a lot of electronics to help them charge and discharge correctly without damage. I doubt they would take very kindly to being wired in parallel.
Maybe this question should be moved to the e-bike thread; there may be better experienced replies there..

^^^^
This. Unless you know exactly what circuitry is incorporated into the battery I'd be very wary of bodging a second in parallel. As a minimum I'd expect each battery output to be fronted by a diode to prevent a fully charged battery rapid charging an empty one in a non balanced fashion.

[Cowsham]

E-bike batteries include a lot of electronics to help them charge and discharge correctly without damage. I doubt they would take very kindly to being wired in parallel.
Maybe this question should be moved to the e-bike thread; there may be better experienced replies there..

^^^^
This. Unless you know exactly what circuitry is incorporated into the battery I'd be very wary of bodging a second in parallel. As a minimum I'd expect each battery output to be fronted by a diode to prevent a fully charged battery rapid charging an empty one in a non balanced fashion.

Yes that was my first thought -- there's no guarantee what circuitry there is to prevent charging from one battery to the other ( and you could damage that ) but there is a better way to double the range safely. Just add a change over switch ( ie on -- off -- on ) or a double pole double throw with an off position in the middle. Calculate what current rating the switch needs to handle and x by 1.5 as a safety margin.

[Cyclothesist]

That is a much safer way for sure. Some of these motors take considerable peak power, much more than the 250W continual rating. A 37V system at 600W is carrying over 16 amps. You'll need a hefty switch and wiring. Best not to switch over when the motor is engaged.

[bikes4two]

> You really need to understand what you're doing if you are considering paralleling two batteries.
> For instance if say you had two 36v batteries, you can indeed parallel them PROVIDING they are at the same charge state [as measured by the voltages which should be around 50-100mV of each other].
> If they are not, then you could be looking at damaging your expensive batteries or worse.
> Having said that you can bye 'Y' cables with suitable electronic boxes that allow batteries of dissimilar charge states to be paralled.
> To get a flavour of the complexities, have a read through this post https://www.pedelecs.co.uk/forum/thread ... ion.45664/

[jrs665]

There is a company in my neck of the woods: https://www.ebike.scot/

and a company search shows that it has a director called Robert Queen:

https://find-and-update.company-informa ... 1/officers

I assume this is the person/company you are looking for.

Will

Thanks

Spoke to robert. He does not do modifications of pre existing ebikes due to insurance. The ebikes he works on are created by himself from he ground up.

[jrs665]

E-bike batteries include a lot of electronics to help them charge and discharge correctly without damage. I doubt they would take very kindly to being wired in parallel.
Maybe this question should be moved to the e-bike thread; there may be better experienced replies there..

Spoke to Robert. he connected batteries in parallel as a project but considers it very dangerous as they can overheat and catch fire.

[jrs665]

That is a much safer way for sure. Some of these motors take considerable peak power, much more than the 250W continual rating. A 37V system at 600W is carrying over 16 amps. You'll need a hefty switch and wiring. Best not to switch over when the motor is engaged.

The 250W bafung motor uses 5A at optimal 81 RPM producing 150W with 18Nm torque, current increasing as RPM drops. It uses 15A whenever the RPM is below 70 RPM with peak power of 400 Watts and torque of 55.5 Nm at 70 RPM. As the rpm decreases , the power drops but the torque increases to 100 Nm at 20RPM, the current still at the cap of 15A.

The current used is a function of power and torque.

https://www.ebike-solutions.com/media/p ... W-V1-0.pdf

[Cyclothesist]

Thanks for the info. 400W at 15A equates to 26.6V across a standard dc motor. If the circuitry is using PWM to regulate the power to the motor (which is standard ebike power control) the instantaneous current may be higher than that 15A depending on how they measured it. Most ebike battery packs sit within 36 to 48V supply.

[Cowsham]

Seems like a lot of hassle to fit a load of switch gear and the associated wiring instead of just unclipping the spent battery and then clipping the spare battery on.

Is there any particular reason you want to do that?

[jrs665]

Seems like a lot of hassle to fit a load of switch gear and the associated wiring instead of just unclipping the spent battery and then clipping the spare battery on.

Is there any particular reason you want to do that?

Convenience. Saves stopping at the side of the road to switch over, But yes, it doesnt take long to swap batteries.

Having recently had a motor put on the trike, was expecting only 20-40 miles on max assist. Have found though that am getting 80+ miles on max assist per battery, so swapping over won't really be an issue.