Battery Help

[Scottyf]

Can anyone point me in the direction of a Decent Lithium Ion Battery seller would would be able to build me the following :-

12volt 10ah (2c Max Discharge) Lithium Ion Battery.

I'm basically overvolting my bafang system from 36v 9ah battery.
(I know about the controllers etc..)

My general use is commuting but would really like a bit more support when going past the 15mph limit.

I only tend to use about 5ah max when using the bike on the commute both ways.

14.2ap, 33.75 vm, 496wp are the average stats i've collected so I may be able to push a little more Current through the controllers but ideally want another 5mph.

On the latest ride I did 7.4 miles and used up 1.521ah so i don't really know if i am just riding over the support but I don't use the assistance to much untill i come to a hill.

 

[NRG]

Depends on what Bafang motor you have and wheel size. Bafangs Are available in different RPMs. If you have, let's say, a motor for 26" wheel then very approximately 2v will give an extra 1mph....but this is for an unloaded wheel. 12v would give you 6mph more or less unloaded....this would be lower on the road of course.

Can't advise on anybody to build the battery for you, however, a 3cell RC lipo battery gives a nominal 11.1v or 12.6v fully charged and are cheap and easy to buy. You'll just have to workout how to splice it in-line with your existing battery and also work out how to set up a low voltage alarm for the pack (easy enough to do there plenty of RC modules around that will alarm when the battery gets to a user set voltage).

Hope this helps.

 

[Scottyf]

Wheel size is 700c. And the above does help me. I.ve already spliced in a watt meter etc... I would be adding it in series with my current battery.

 

[Scottyf]

Oh and could you mix the battery chemistrys though?

 

[averhamdave]

My Ezee Torq 1 uses a Bafang 36v, 250w motor and is 700c

It does 22mph and pulls ok on hills. From memory it pulls 17.5a peak.

I use a 36v 15ah Chinese duct tape Lipo4 and it has so far been excellent.

Because I had issues with the Hall sensor wires I obtained a sensorless controller from e-crazyman which is probably contributing to the performance.

I'm pleased with it although I have thought about upping to a 350w motor as I have plenty of battery capacity in hand. - I can easily do 30 miles in hilly terrain which is good enough for me.

 

[Scottyf]

I take it that controller is what your getting that extra power from as its increased the draw current from the battery. As mine would not go above the 15amp controller. I don't think the wind on the 700c would allow it to go faster unless you over volted.

 

[NRG]

Mixing chemistries is not a good idea generally, however, if you are careful and monitor the LVC on the new add-on pack so the cells don't go below the safe low voltage it would work. Of course if you can get the same chemistry and cell type for the add-on battery then it would be more simple, you probably would still need a BMS or LVC monitor though.....

 

[averhamdave]

I take it that controller is what your getting that extra power from as its increased the draw current from the battery. As mine would not go above the 15amp controller. I don't think the wind on the 700c would allow it to go faster unless you over volted.

.....Then your cheapest and easiest option would be to change the controller?

 

[Deleted member 4366]

Just done a little experiment this afternoon. We swopped the front wheel of my neighbour's San Eagle (250w Bafang) for a 350w Bafang BPM wheel, which cost about £150 for a complete kit (less battery) from BMSbattery, to see how it performed using the existing controller and battery. It was more powerful giving about 4 mph more on the flat, but it carried on pulling to about 25mph downhill, while as the previous motor couldn't assist much over 15mph. I'm still trying to get my head round whether any harm can come to the battery or controller. I can't think of any reason why it should. We checked the controller temperature after a couple of top speed runs and it wasn;t even warm. So, this might be an alternative solution for more speed. A least you won't be stressing the motor. The main downside would be the reduced range because the controller will be feeding it with high power all the way to it's max speed, while as before, no power would be given over 15mph without throttle, but then you'll get the same by over-volting.

 

[Scottyf]

Morning D8veh,
Interesting given the larger motor managed to propel the bike up to the increased speed.

What controller was you using and do you have any peak readouts it all?

Maybe another option where by i just order the bpm motor with a faster rpm wind to alloy the faster speed and see if i can get a controller that will alloy a slightly higher current. But i'd be running quite close to the battery max discharge rate.

 

[banbury frank]

motor speed

Hi
Just out off interest our Nine continent motors we stock are simple direct drive

input from 36 volts to 72 volts depending on the windings we stock the 7 windings which give 9 X RPM per volt so faster on 700 C or plenty off grunt on 20inch wheel not for speed but more torque

all our small controllers are 36 v or 48 v with automatic detection

our 18 mosfet controllers are link selected between 48 v and 60 v

so to increase the top speed more volts I would say get at 48 volt controller

12Mosfets Universal Brushless Hub Motor Controller for EBike - BMSBATTERY

and link the battery's to give you 48 volts make sure the motor will cope it is only the insulation on the windings that will brake down under higher voltage caused by overheating

Frank

 

[jbond]

I'm pretty sure that the BPM motors are wound to a faster no-load speed as they are outside the general regs in most countries and so legality is not an issue. A BPM marked as 36v 26" in a 26" rim will reach about 24mph no-load, while a 26" QWSX is more like 20mph, no load. The extra power means it will still climb hills at lower speeds and it will perhaps get closer to its noload speed. Real world, flat road speed is about 20mph.

There's two options to getting assist at higher speeds with these small hub motors. Over-Volt and lacing a small rim motor in a big rim but keeping the volts the same. Whether the motor will actually power you to those higher speeds without pedalling depends on actual power produced.

There's quite a good argument for using a 20" wind QWSX in a 26" wheel, staying at 36v and pushing up the max current to compensate for the lower torque available. The increased current then means a bigger battery to cope but at least at 36v, 15AHr or even 20Ahr is still acceptable where a 48v-20AHr is seriously heavy and big.

 

[Scottyf]

Interesting Analysis of the parts.
I understand there are only several ways of which to improve the speed of the system.

The new BPM motor may be an avenue I go down really as I could just buy the BPM motor for say a 24inch wheel (compromise between its highest speed and still ok hill climb although not as good as what I currently have as I'd lace it into a 700c wheel), Get a slightly higher amp controller (Up to 18amp peak inline with the battery 2c charge).

Thus keeping the same battery (An possibly controller if the performance is ok speed wise) as I am relativly fit and to be honest I want the assist for maintaining more of a 20mph average instead of the 14.3 mph average I am currently doing. Espcially as I get faster and faster and riding.

Also the commute wach way I am only using up 2.2amp/h of the battery and then charging at each end.

Interesting to know that just a controller limit would help out that higher speed though. But I don't think my poor battery would take over the 2C discharge.

Hence why I initially thought of adding another battery in series to ovevolt my current motor to effectivly get the same result. Cost wise they probably end up quite similar...