While this overall topic was discussed over pages of threads, there are two things I could not find after hours of reading:
What is the max. acceptable voltage? I’m planning to use 4-6pcs of 20700 batteries in parallel.
This will give me 19-28Ah with a nominal voltage of 3.7V (max. 106Wh).
After charging, these Li-Ion batteries peak at about 4.1-4.2V. I’d like to use them connected directly to the SKY, so I can see how the voltage drops and at which time a recharge is required.
Can the SKY accept this voltage without problems?
Any voltage-regulator would output a rather constant voltage which makes it impossible to see how the battery empties.
In order to bring the power into the SKY, I’d like to use the bottom-connectors with some 3D-printed adapter. I could start to measure and with some trial & error, but - is there a chance to get a 3D model / shape from WF?
A drawing would be good too, whatever
I can use Autodesk-Inventor files (IPT) as well as STEP, SAT, IGES, DXF, DWG etc.
Once I finish my pack (which is not even started yet due to the information above is missing), I’ll publish a manual for you guys.
Hi @matthiasginster . We would strongly recommend opting for the new Solar Power Accessory for SKY which has a built in charge controller and a 1000mAh LiFePo4 battery. We just received a batch of 1000+ units this week and will be emailing all existing smart weather stations owners with a %off coupon to purchase via shop.weatherflow.com in the next few days.
To answer your question, the max operating voltage for SKY is 3.8. Anything above that will probably break the unit. We would recommend using a buck converter or a LiFePo4 battery if you really want to supply external power.
How is a buck converter going to perform with the tiny power draw that the Sky needs? Maybe I’m going crazy, but I am under the impression that DC-DC buck converters like to be run under a harder load or bad things happen…
There are very good low power buck converters on the market now. TI makes the TPS62808 which is around 90% efficient at 1mA. Unfortunately, it’s a chip BGA package, so it’s very difficult to hand solder.
Actually, it would be no big issue with the taxes. The import rate for the EU is either for Luxemburg (17%) or Gemany(19%) the lowest. In both cases for an order of more then 3 SOL an additional fee of 2,7% would be applied.
One has to calculate and discuss with WF-Team if a group order of Gernany located or even EU located customers would be possible.
