eBike Demo 8 I

[Kirill]

Hi everyone!

I built an ebike based on a Specialized Demo 8 I 2010.
I decided to put in a new powerful battery.

I'm getting ready to assemble. Can you are tell me if there are any errors, where I am doing something wrong?

MW: MAC 8T without modifications.
Charger: 1000W.
Cells: EVE LF50K, 50Ah, Grade B, 16 pcs.
BMS: SmartBMS JBD-AP21S001
Balancers: not provided.

Connection: jumpers 100-120 mm long (copper stranded cable 20-25 mm2) with crimped lugs.

Installation: in three hermetic cases on the frame, in the central 4 and in the side 6 cells each. With an additional layer of isolation of the case of cells. Without insulation.

To prevent failure, all open contacts will be protected by liquid rubber (liquid electrical tape) The ingress of moisture into the housings will be minimized, protection is made due to the possible occurrence of condensate.

Ready to hear any advices or comments.

 

[SlowCo]

Why such an incredibly large and heavy battery pack on a bicycle?
And is the charger the right one for a 16S LiFePo4 pack?

 

[fechter]

Yes, that will be an incredibly heavy battery. Splitting into sections is a bit tricky too as you have to run all the BMS sensing wires to a single BMS. If the main power wire between sections gets disconnected when the sensing wires are attached, it can blow up the BMS. That said, I have done something similar on my Sur-ron and it works well.

 

[Kirill]

Why such an incredibly large and heavy battery pack on a bicycle?
And is the charger the right one for a 16S LiFePo4 pack?

For sustainability.
I'm too light on the road. The front wheel is not loaded at all. I have three motorcycle cases in the back. Of course, I don’t fully load and in the future I’ll control the weight.

Charger 1000W
https://sl.aliexpress.ru/p?key=8cxexF3

 

[Kirill]

Yes, that will be an incredibly heavy battery. Splitting into sections is a bit tricky too as you have to run all the BMS sensing wires to a single BMS. If the main power wire between sections gets disconnected when the sensing wires are attached, it can blow up the BMS. That said, I have done something similar on my Sur-ron and it works well.

Not so much. At least 22 kg per 16 cells. Yes, I designed the montage. The division into three parts is even better. Each part lighter than all cells together.
I will make the connection between the parts with a copper cable. And the same jumpers will be between all cells. Since if I will use different connections, they will have different resistances. And it will negatively affect the battery. Is it right?

 

[Kirill]

I don't want to make an extra 16 balancers.
16 additional devices predicted to break.
16 additional devices that need to be protected from mechanical damage and water.
My BMS has a balance current of 200mA.
Let the balance be long. In any case, balancing is best done rarely. For example once a month. Is it so?

 

[fechter]

There will be a little voltage drop along the cables used to connect the battery sections which will affect the low voltage cutoff under load slightly. If charge current is fairly low, it won't be an issue during charging.

You can see how I did a split pack in this build thread:
https://endless-sphere.com/forums/viewtopic.php?f=10&t=101441&hilit=sur+ron#p1482940

 

[E-HP]

Why such an incredibly large and heavy battery pack on a bicycle?
And is the charger the right one for a 16S LiFePo4 pack?

For sustainability.
I'm too light on the road. The front wheel is not loaded at all. I have three motorcycle cases in the back. Of course, I don’t fully load and in the future I’ll control the weight.

Charger 1000W
https://sl.aliexpress.ru/p?key=8cxexF3

I have that charger. It's designed for 20S Li-ion, and the voltage isn't adjustable (current is).

 

[Kirill]

Why such an incredibly large and heavy battery pack on a bicycle?
And is the charger the right one for a 16S LiFePo4 pack?

For sustainability.
I'm too light on the road. The front wheel is not loaded at all. I have three motorcycle cases in the back. Of course, I don’t fully load and in the future I’ll control the weight.

Charger 1000W
https://sl.aliexpress.ru/p?key=8cxexF3

I have that charger. It's designed for 20S Li-ion, and the voltage isn't adjustable (current is).

Not only for 20S li-ion.
There is a knob to adjust the voltage.
At least that's how they answered me in the technical support of the manufacturer.

 

[Kirill]

There will be a little voltage drop along the cables used to connect the battery sections which will affect the low voltage cutoff under load slightly. If charge current is fairly low, it won't be an issue during charging.

You can see how I did a split pack in this build thread:
https://endless-sphere.com/forums/viewtopic.php?f=10&t=101441&hilit=sur+ron#p1482940

1000 watt charger. For 58.4V means 17A.

 

[E-HP]

Not only for 20S li-ion.
There is a knob to adjust the voltage.
At least that's how they answered me in the technical support of the manufacturer.

This is the one I got, the 72V version. It comes in 36V, 48V, 52V, and 72V, with variable current from 2A to 12A. The knob is labeled "Current Regulation". The switches on the other side are for on/off and for selecting what appears on the LED readout, which is either the output current setting, or the actual battery voltage (the charger only turns on if attached to the battery). The only pot I could find inside only calibrates the volt meter, not the actual cutoff voltage. The unit stops charging right at 84V.
https://www.ebay.com/itm/234168569503

Seems to match up with the specs from your link:

 

[Kirill]

Not only for 20S li-ion.
There is a knob to adjust the voltage.
At least that's how they answered me in the technical support of the manufacturer.

This is the one I got, the 72V version. It comes in 36V, 48V, 52V, and 72V, with variable current from 2A to 12A. The knob is labeled "Current Regulation". The switches on the other side are for on/off and for selecting what appears on the LED readout, which is either the output current setting, or the actual battery voltage (the charger only turns on if attached to the battery). The only pot I could find inside only calibrates the volt meter, not the actual cutoff voltage. The unit stops charging right at 84V.
https://www.ebay.com/itm/234168569503

Seems to match up with the specs from your link:

Quite so!

 

[Kirill]

Ok. No cooper jumpers.
Take a usually busbars.
Can I use two or three length of busbars?

 

[Kirill]

I will use cooper bar 3х16 mm. To cut their for 3 different lehght. Short and middle for connecting cells between themselves and two long for connecting between parts.

 

[Kirill]

So the job is done.
All assembled and installed.
All contracts coated with liquid rubber.
I made two flexible busbars for connected between parts.
All the rest are 16x3 mm busbars.
Later I’ll share other pictures.