CEF50 External battery build

[mike_kelly]

Not possible. The Bafang charge connector is only designed for 2amps, the wires are not big enough to handle the current to drive the motor.

 

[hamncheez]

Not possible. The Bafang charge connector is only designed for 2amps, the wires are not big enough to handle the current to drive the motor.

My proposal is to leave the frame completely unmodified, and the auxiliary battery would connect directly to the charging port, which is again unmodified, so the power goes into the main battery.
I've tested mine with the supplied charger, the motor still turns on and runs when external power is supplied.

 

[mike_kelly]

All you are going to do is charge the main battery from the external, slowly, from the external battery. Not going to help much in a ride. For a 360whr 36v battery 360/36= 10amps 10/2=5 hours or more considering the external battery voltage will drop and as soon as it is lower that the main battery it will stop transfering energy.
If the charge port is simply in parallel with the main output port you risk all the dangers, with the exception that the small 2 amp charge wires would probably act as a fuse as they catch fire and burn.

 

[hamncheez]

All you are going to do is charge the main battery from the external, slowly, from the external battery. Not going to help much in a ride. For a 360whr 36v battery 360/36= 10amps 10/2=5 hours or more considering the external battery voltage will drop and as soon as it is lower that the main battery it will stop transfering energy.
If the charge port is simply in parallel with the main output port you risk all the dangers, with the exception that the small 2 amp charge wires would probably act as a fuse as they catch fire and burn.

So what you're saying is I should have ordered the 700wh battery!

 

[mike_kelly]

yep. If you are riding for two hours after work every day the 360whr is fine and lighter. if you want to do epic all day rides you need more juice.

 

[hamncheez]

yep. If you are riding for two hours after work every day the 360whr is fine and lighter. if you want to do epic all day rides you need more juice.

I got the custom 410wh battery, which sounds fine compared to the competition, but I ride at 5am and on my natural bike I like to do at least 2,400 feet of climbing, sometimes over 3,000. I was hoping to go even bigger on an ebike, but this motor in B mode reports a consistent 580+ watts, so if you do the math you aren't even getting 45 min before you hit the 20% cutoff to Eco mode. At first I was a bit frustrated, but physics is physics.

 

[mike_kelly]

I got the custom 410wh battery, which sounds fine compared to the competition, but I ride at 5am and on my natural bike I like to do at least 2,400 feet of climbing, sometimes over 3,000. I was hoping to go even bigger on an ebike, but this motor in B mode reports a consistent 580+ watts, so if you do the math you aren't even getting 45 min before you hit the 20% cutoff to Eco mode. At first I was a bit frustrated, but physics is physics.

Yes the motor is not designed to be used in boost except for short steep climbs. Bafang warns against using it for continuous boost riding and 700whr or larger batteries designed to enable this type of riding. Just not the right motor.

 

[Freda]

Off-topic, but I finally built an extender for my LCE930. It is a 13S1P battery with 2170p cells. Connected with a battery balancer between main- and extender battery to motor.

I didn’t want to make additional holes in the frame and connecting via charging port seemed too complicated, so I made a hole in the battery cover. Might well work on the Cef50 as well, it has been a lot of discussion about those!

Cable could be a few centimeters shorter for perfect fit. One benefit from a smart bms on the main battery is that I can switch it off and run only extender if I want to.

 

[thaeber]

Did You already test it? Can You draw enough amps from only 1P configuration?

 

[patdam]

Who really needs range extender ? with 480W i doing 21km with 1300m D+ and i have 50% of the battery left. As physically with the M820 help i will not try more 1500 D+ with my 100 kg weight. I whould like understand who needs range extender and for doing what ?

 

[Freda]

Did You already test it? Can You draw enough amps from only 1P configuration?

Cells are rated 12.5A continuous. Highest I have seen on display is 620W, I rarely go over 500W. With 48V system should not be a problem.

 

[Freda]

Who really needs range extender ? with 480W i doing 21km with 1300m D+ and i have 50% of the battery left. As physically with the M820 help i will not try more 1500 D+ with my 100 kg weight. I whould like understand who needs range extender and for doing what ?Who really needs range extender ? with 480W i doing 21km with 1300m D+ and i keep 50% of the battery.

Good question! I have two main batteries, on ~480Wh and one ~720Wh. Summertime I use the small one. I can ride around 3h and 40km on that one. I use mostly S assistance. Extender is nice when riding to my local hill, 30 minute journey, leave it in my backpack when going up and down the hill and then connect it again when going home. No need to worry about battery saving mode.

Big battery is for below zero Celsius riding temperatures, it takes a lot from the battery. And I also found building batteries very interesting, so I just need to come up with reasons to build them.

Also 50% battery left on bafang display is really not much at all.

 

[patdam]

Good question! I have two main batteries, on ~480Wh and one ~720Wh. Summertime I use the small one. I can ride around 3h and 40km on that one. I use mostly S assistance. Extender is nice when riding to my local hill, 30 minute journey, leave it in my backpack when going up and down the hill and then connect it again when going home. No need to worry about battery saving mode.

Big battery is for below zero Celsius riding temperatures, it takes a lot from the battery. And I also found building batteries very interesting, so I just need to come up with reasons to build them.

Also 50% battery left on bafang display is really not much at all.

you would mean that with 50% left for example, i couldn't doing 5km with 300 m D+. If i already done 1200 m D+ in 21 km for the first 50% ?

For the moment, i never emptyed the batteries with the M820,. but with the 15Ah i consumme at most 40% to doing 1700 m D+. (i can't do more phisically). it's my first use of the 10 Ah, but consumtion seem in line.

 

[voigtkampff]

In my experience displayed 50% battery realistically indicates sth like 25-30% juice left

 

[Freda]

you would mean that with 50% left for example, i couldn't doing 5km with 300 m D+. If i already done 1200 m D+ in 21 km for the first 50% ?

Of course I cannot say exactly but seems correct. Comparing rides is hard with so many variables. I just really dislike the battery percentage shown and battery saving mode starting early. The extender is one way to have a light bike with enough energy normally and then add it when the need is greater.

 

[temon10]

Who really needs range extender ? with 480W i doing 21km with 1300m D+ and i have 50% of the battery left. As physically with the M820 help i will not try more 1500 D+ with my 100 kg weight. I whould like understand who needs range extender and for doing what ?

Need it when doing long ride with full power and big battery friends.

 

[temon10]

Of course I cannot say exactly but seems correct. Comparing rides is hard with so many variables. I just really dislike the battery percentage shown and battery saving mode starting early. The extender is one way to have a light bike with enough energy normally and then add it when the need is greater.

agree

 

[TheIntolerantMan]

Apologies to drag this up again, I have not even got a frame yet but I am trying to think ahead.
While my initial idea was to just go with the bigger 720wh battery, I'm now thinking that a smaller battery will be fine for 90% of the time, and a substantial extender will cover all other eventualties, a conclusion many of you have come to already. I've seen a few different connectors used but I'm keen to use the existing charging port placement.

Looking at the attached PDF had me questioning whether we need 4 ports or whether we could make do with 3. In the diagram the diodes are only controlling the positive sides and the 'main' negatives bypass the circuit boards.
Is the any reason I cannot connect the charging negatives with the main and extender negatives?

Therfore I end up with a socket in the frame that has 3 ports, 1st port is a common negative shared by main battery charging and extender -ve, 2nd is the charger +ve to the main battery BMS, 3rd port would be the extender +ve.
Obviously the Extender battery plug would have 2 wires and so would the charging plug, common negatives but different positives.

An Amass MT30 socket could be installed in the existing charging port with a bit of 3D printing trickery.

Hope that makes sense.

 

[mike_kelly]

Since you are not charging and using the external battery at the same time you can probably get away with that. But you need a connector that supports big enough wire for the current required and the connector is not going to be designed to solder two wires to the same point. You don't want to do anything that causes a bad solder joint that acts like a resister.

 

[TheIntolerantMan]

Since you are not charging and using the external battery at the same time you can probably get away with that. But you need a connector that supports big enough wire for the current required and the connector is not going to be designed to solder two wires to the same point. You don't want to do anything that causes a bad solder joint that acts like a resister.

Thank you.
Good catch on the cable sizing, XT30- 16AWG max. The M820 has an XT30 socket for the battery I think.
Plan is for a 13S 2P battery which in theory will give a continous 25A max.
People are reporting seeing 550watts in Boost, maybe allow 600w using 48V battery on a 43V motor/firmeware.
600w/48v = 12.5A, 16AWG seems possible but feels counter intuative.

 

[mike_kelly]

I am not sure where they are getting those numbers. Lets face it, it is a 250w motor. The question is can you get two 16g wires in one of those sockets with a solid solder job.

 

[TheIntolerantMan]

I think the whole 250w thing is similar to the VW diesel emmisions fiasco. Even allowing for gearing etc. I doubt alot of these ebike motors quoting 75nm+ are only doing it with 250w.

Not a 'cat in hells' chance of getting 2 wires on those terminals, was not planning to either, an XT60 inside or an extra connection on the BMS or combination of both etc.

 

[mike_kelly]

Well again if you are not charging and using the ext bat at the same time it is not an issue.

 

[Tilt]

I placed them under the crosspiece

 

[mike_kelly]

Loki Fat? How do you like it. Weight?

 

[Tilt]

Loki Fat? How do you like it. Weight?

super fat weight with 720wh battery

 

[mike_kelly]

Very good!

 

[TheIntolerantMan]

I placed them under the crosspiece

View attachment 149186 View attachment 149187 View attachment 149188

It looks the 'Dogs Danglies', is it 23.43Kg without the machine gun mount!

 

[mike_kelly]

A couple of further thoughts. With my new 720wh battery came a battery-off switch that fits in the top tube opening of the stock frame. With that you can simply solve the dual battery problems with just turning off the internal when you switch to the external and vice versa.
Also for traveling I am working on an external that using a frame made for individual 18650 cells. You can't take emtb on airplanes with internal batteries but you can take individual cells on the plane in the cabin. So I have a battery box that holds 30 cells and the frame that I assemble at the destination which has the battery holders and all the BMS etc for a battery pack.