I installed my SPA yesterday and have noticed since that during daylight hours my SKY battery voltage appears to follow a sawtooth pattern. I assume this is normal behaviour, and is the result of some sort of voltage regulator in the SPA that is ensuring the battery is not being overcharged?
Do you have taken out the AA batteries of the Sky?
Definitely! There was a big 
STOP notice that came with the SPA warning users to remove the batteries first.
Yes, I know but… you never know.
And I would have asked first, before this will cause the issue and damage either Sky or SOL or the batteries.
Sorry, it was a good question to ask. I didn’t mean to imply otherwise. Hopefully @dsj might be able to explain what is going on (and whether it is a bad thing), as I have had a look at some other stations and I can’t see the same behaviour.
It has continued all day like clockwork with some small variations in the peak and trough voltages.
Both my SPA’s do that too. I believe it is different charging/suppling states and their switch point levels.
This one has a bit more variation than yours, but still works fine.
That’s what I thought too. The fact that it doesn’t do it overnight when it is always in a supply state provides strong evidence.
I dont have that behavior i think only that charching stops by 3.6 V link is in my profile
I think this is something in the production units. David mentioned a change from the field test units that has to do with power.
I think you get it a little bit if you zoom in on your voltage curve, just nowhere near as pronounced as my production unit.
Indeed but i think this is normal behavior the voltage should be between 3.3 and 3.6 V
Mine is the same @peter - its the dodgy sun in the UK 
Mine does the same pattern. Whatever is doing it pretty much caps it at 3.6v
Just got a 2nd solar unit and attached it to my Air. Voltage stays pretty constant at around 3.3v day and night. My other solar unit rides up to about 3.5 daytime and 3.3 nighttime (got it during field testing last winter.)
Not worried about it, but just curious why the new solar is so constant with only little variation in full sun vs night. The connected Air seems to be working just fine tho. Station #3778.
Look at this thread: When is the solar panel charging
That sawtooth pattern looks appears to peak and trough in 30 minute intervals. Of course, it could be a coincidence.
Keep in mind that the voltage is read every 10 minutes.
