Monthly Archives: March 2015

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This week was a very slow week again, mostly seeing me on the keyboard trying to teach my AVRs to communicate with each other. Before I really start I want to have a serial monitor, so I can see what is going on on the bus between all the different devices. Nothing to show so far, so instead I have done something on the marketing front.

No project can be started without a proper anchor, in this case a logo and a tag line.

Because I don’t have a vehicle shape, I decided to go with a technical symbol with some nice colouring: turn on the EV!


And what better line than to be on the move. So voila, a new logo and tagline and all of it as a custom header logo for this blog.

Let’s get moving. eHaflinger: On the Move


Controlling Electrons continued 1

Controlling the Electrons

After last weeks message, I was busy (kind of) to try to tame the batteries.

This week (and the following), I will assemble the PCBs I have just received.


There are three boards, one having the flyback converters, one with all the logic, piggy-backed to the power board. Those two boards are stackable. For cost reasons, I start to test with one half string, that is, it will be a string of 36V thus a 3,6kW pack.

The rest is self explanatory, just watch the pics:

DSCN1049DSCN1050DSCN1051 DSCN1052

… baking electronics 🙂

How to Contain Electrons

Hopefully, the next weeks will keep me busy building my BMS. Hey, what is a BMS. Probably everyone understands different things under that synonym. Wikipedia gives a good overview.

My BMS will be a modular one. I will have several stacks of cells distributed through the vehicle. Each stack will be controlled by a BMS handling the following tasks:

  • monitoring the cells in the stack
  • balancing the cells in the stack
  • communicating with the vehicle
  • operating the contactor

maybe, if time permits, I will also implement a health check, a charge control and a charge counter.

This week I got the most important things for the BMS, the containers for the electrons also called batteries 🙂

They were used in another project (not mine) and sitting in storage to be used again.


To be used again, they needed to be unpacked:


Each energy block was assembled into 4 cells in parallel, giving a total capacity of 400Ah.

My requirements are slightly different, so they were taken further apart


until I have 12 cells. This is the number I need for a half stack. My full stack will have 72V. My half stack already has a beefy 3.6kWh of stored energy (My ZERO S electric motorbike has 4kWh).

To be honest, I am blown away by the size of the half stack, I probably will have to reconsider my range specifications, because I might not be able to integrate 6 full stacks into my small vehicle…