Battery compartment (again) and Sourcing parts

Since last time I have changed the banana contact on the lid to a smaller gold plated version.

lid_gold contacts

This removes all the plastic-plastic contact that could cause problems when gluing. Yes, I’ve changed my mind regarding gluing. It turns out that gluing high-end plastics is a really tricky business and plastic-plastic is harder than plastic-metal. I’ve changed to gold plated contact banana contacts, which aren’t much more expensive and inherently more robust.

Furthermore I just realised that the middle contact will not be a banana contact, because there is a need for three small pins for the charging of the batteries.

battery_loadingThis is due to the nature of batteries. The charge rate is a bit like tolerances, where they may charge at different speeds. The charger can monitor and compensate this by additional pins between total voltage, as seen in the picture above (click on it for a larger version). So V1, V2, V3, V4 should be the same, but aren’t. The only thing we know is that they sum up to Vtot. Just blindly charging them over Vtot will decrease the lifespan of the batteries greatly. So obviously more on the way to solve the charging a bit later.

I have also checked out what cable (Ölflex PUR S27 3×0.75) and cable glands (Skintop BS-M) to use and have generously gotten a some free samples from Miltronic, thanks! The Skintop is a bit bigger than I would like and the model (AGRO 1007.52) that I have previously looked at is still a work in progress in regards to if I am able to procure a small number of them. The Ölflex is 6.1 mm in diameter and the AGRO model has that as a maximum size, which would give a nice snug fit. The model which is perfect in this sense however has the rather weird TR thread, that I had previously never heard of. I may need to buy a tap for this, ugh. I would probably use the Skintop in that case, as it comes with M-threads.

Lastly, in earlier posts I talked about wanting to be able have two power-settings, one that was programmable and one that was adjustable. Finally, after sifting through the different models, have found the switch (NKK on-on-(on)) and hood that I want to use. This is also the reason for choosing three conductors, two for the power and one for the signalling.

I’ve also, together with Mikael, looked at electric components such as MCU, driver and dc-dc converter. When everything  is settled I will make a post on the subject.

Update (30 aug): Vanpee and Agro has generously donated a couple of Agro 1007.52 cable glands! Huge props for them being so nice! I was also told that these have been tested by Agro at 10 bar for four hours, this is great info as the IP 69K standard is more of a spraying type of test.

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