12 January, 2017

Extending the range and power of the bike by adding two cells in the luggage carrier

Before this project, the battery of my bike consisted of 8 cells in series of 6 batteries LiFePo4 A123 in parallel each, and I realized that I could have some more top speed and range by adding two cells with the previously left over LiFePO4 A123 batteries, and changing the BMS for the one I found of 10S and 60A (much better than the previous 15Ah only):

BMS / Control LiFePo4 charging battery cells 10 and 60A  maximum.
I will not cease repeating that if ye ride yourselves a Lithium Ion battery, you must put always a BMS, as this is essential prottection for the battery, cutting the flow of current in both overload and over - discharge in any of the cells.
One important note: This only works if you use the SAME type and state of cells for the additional cells (or you will get an unballanced battery fast, or worse, damaged cells that can't cope with the current).

On the other hand, increasing only 6V maximum load, I can still use the configuration of the motor control for 24V (having automatic cut if they drop too low voltage with the BAC-281P ebike controller, we cut prematurely the current if we use 33V battery with a 36V configuration). 

Features of BMS 10S LifePo4 60A load balancing ref. BMS-10SQZ6060LF375 :

Important data:
  • 10 Cells LiFe 3.6V, 36V full.
  • Maximum peak current: 90A
  • Constant current approx. without sink: 30A
  • Standby power consumption: 0.1 mAh (100 microamperes / hour).
  • For the rolling is effective with only 70mAh per cell balancing, the load should be as slow as possible (depending on the difference of load cells), recommended < 500 mAh.
As  I noted, the 12 could fit on a damaged old hard drive enclosure aluminum made. 

There remained some slack, but could solve it with adhesive foam rubber to absorb shock well:

So I put hands to work. To have to go put them in groups of four , with the remaining in the center spread two to one side and two to another , so we must be careful not to make mistakes and connect, helping 2.5 mm cable. at least in the connection of the plants with the right poles of the other sides.

What first is to unite the end , positive with positive to put the four parallel welding the pole with copper strip wide enough to support the planned amperage (these batteries are the 2007 second hand, and no longer give more 7Ah instant by high internal resistance each, but still retain between 1900 and 2000 mAh its original 2300 mAh):

The plates got in his day the old drill batteries; you just have to sand them a little so that the tin (with internal flux) adheres well; for this I used the multi-tool Proxxon :

And as I explained in this video, I soldered cells:

Thus so are the two sides packs:

I put tape kapton high temperature where it could, heat, short-circuit one another
We must come to this; that is, a pack of 6 batteries in parallel connected in series with the other pack, but placing them in four 4:

Important protect high temperature Kapton tape all areas in contact with the wires

For this  I joined the two packs with the center , leaving loose union of the 4 with the next 2 to be folded power as in the following image:

 (Notice that the center joins only the positive side to the negative to the series)
This way you can fold, but lack join the other side by wiring:

Be very careful to protect both sides where the poles change and corresponding to the other cell, or will be guaranteed short , as shown in the figure below, where I soldered the cable between the two central positive to positive end of the 4:

A lack of support I helped legs;)

And finally I soldered two wires of 2.5 mm or more to positive and negative (positive blue) plus one green that is just fine for the BMS controls the voltage of the first cell, and wrapped in plastic tape, I used adhesive PVC:

Before putting them in place, also isolated the top of the box with wide PVC tape , so that the friction of the vibrations do not short with aluminum insulation descastarse time:

And and we put in place was very fair, but luckily the other side had ample space and was well adjusted:

And only the tops are placed, with a hole for cables and glued together with silicone:

And voila, we have a powerful battery with 10Ah LiFePo4 33V !, 0,33kW stored at 4 kg! And more than 1000W of peak power outputs What! (I add a video soon).

This is the former BMS , which was tied to the top (only used it to charge so, if I clueless, too discharged battery, partially damaging it ):

And the  wiring diagram of the new BMS  with rolling is as follows:

To connect, we need to have cables each connected cell and identified:

I have glued PVC tape that holds well behind:

And then silicone (enduring high temperatures) I have stuck in the central cavity of battery:

In this case, when 60A peak control and how rarely climb 30A consumption,  control, after rising cost of 10% of 300 mt barely been heated, so I see no need to add heat sinks  or attach to the top to dissipate excess heat:

And I have finished covering everything with masking tape (adhesive paper), which insulates enough, adheres better than the Kapton tape and also endures high temperatures:

No comments :

Post a Comment