box design - brainstorming

[mikelovic]

in this issue we want to discuss about possible design elements for the batteries and electric components. based on the V0.1 of the Libre Solar Box.

requirements:

• ecological materials, upcycling elements
• easy production
• moveable
• scalable

[case06]

some thoughts:

Ecological materials:
We can replace the cover-plates with wood-plates . I would recommend multiplex/plywood of 12mm. Question is how to fix them onto the frame.

upcycling

Hmm, in a project which should be easy reproducable by others a more crucial aspect is the overall availability of the components from regular sources and a BOM which list that sources clearly. But you can maybe upcycle/use any appropriate plate-materials for the cover plates.

easy production

Biggest prob is the availability of pcbs in small numbers eg. <= 10 pieces. Commercial production from watterott is an option starting with 50 pieces, but we need smaller quantities for prototypes and their testing.

Possible solutions:

1. Pick&Place-machine (a cheap one: https://www.liteplacer.com/shop20/index.php?route=product/product&product_id=64)
2. produce smaller batches manually (maybe as "production-workshop"-event at fabulous St.Pauli)

Btw., one thing which is even more important than "easy productions" is "easy maintainance".

moveable

I have added some nice handles to the upklib. See https://wiki.opensourceecology.de/images/8/80/Upk_handles.jpg and https://wiki.opensourceecology.de/images/6/64/Upk_handle2.jpg

scalable

Since the Mosfets are rated at 80A it is theoretically possible to drive it with up to 4 MPPT20s, what means up to 1.6 KWp PV-panels. In practice we maybe better go with 3 MPPT20s and 60A to stay comfortable under the Mosfets limits equal to 1.2KWp PV. Optimum loading is with 3/10C that means with 60A LiFePO4 cells with 200Ah fit perfectly, if you want to reach a lifetime of about 8000 full-cycles (~ 20 calender-years)

This means to construct a backplane for the MPPTs, which consists of the CAN-bus data-lines (blue) and two 12V-Power-lines (black and red) like in this diagramm: https://wiki.opensourceecology.de/images/e/e8/Bms12v_systemuebersicht.png

[mikelovic]

@case06
can you open the zip file and import it in FreeCAD. Somehow i can't import it correctly in my FreeCAD version (0.16).
thank you in advance

[mikelovic]

@FWdesign
Feedback:

• der gewichtsschwerpunkt sollte in der mitte liegen. die batterie sollten somit mittig in der box platziert sein.
• optional eine version ohne inverter (blaues modul). damit kann das ganze kleiner produziert werden. -> evtl zwei verschiedene version. oder modular erweiterbar um den inverter. anschluss an die box über DC anschluss.

[case06]

When i imported the .igs file into freecad 0.17 it became extremely slow ... like swapping.
Then i changed the view of the whole object into transparent and the performance was normal.

So i saved it into a freecad file

https://github.com/CollectiveOpenSourceHardware/LibreSolarBox/blob/master/design_proposal/Solarbox_Trommel_transparent.fcstd

with transparent view.

see

[mikelovic]

@FWdesign
weight of batteries. 1.9 kg per cell. So for the 4 cells it is round about 8kg ( exactly 7,6kg).
here you find the specs http://evwest.com/support/CAM72FI%20Final.pdf