I think that is the problem. By not shorting it, the device thinks it is very cold, so won’t charge. Short it out and see if it works.
While you are officially correct, @eric, this specific situation outlined in the original post did get a, “didn’t think of using AA sized LFP cells like that. That should work fine” comment from the appropriate engineer.
@w_strassburg, this might also be the issue. Short the thermistor and test. If you still have issues, disconnect the battery in the SPA, to rule that out as the culprit.
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I cut out the internal battery and used the 4 lifopo4 batteries. Works for a while and then plummets.
Suggestions?
A few questions:
- Did you disable the temperature compensation circuit?
- Have you had plenty of sun lately?
- What is the link to your station so I can look at its data?
I have a SKY which suddenly started using more energy than it did originally and the SPA isn’t able to keep up with it. I have to periodically swap out the SPA and manually charge it and the internal LFP batteries. I have some extra SPAs since all my previous SKYs have died. 
There is the possibility that there is an issue with the charging circuit and/or solar panel.
I have not messed with the temp compensation circuit. It’s been pretty warm, so wasn’t sure if that contributes.
Yes, quite sunny.
It’s offline, need to charge again. But only lasted a few days so not going to work out easily if there isn’t a fix.
My next thought was to remove the solar and leave the rechargeable batteries (fully charged) and see how long it lasts.
I’d buy 8 lithium non rechargeable batteries, but if they don’t have a chance I’d rather not spend.
That really looks like it has done what mine, and a few others have. They seem to get something stuck where it keeps draining the battery really fast. It looks like it only made it from March 3-7 before draining things flat. If you used the batteries I referenced above that would be over double the capacity of what comes in the SPA. The SKY used to be able to run for much longer than that on the SPA with no solar input. I think something might be wrong with your SKY sensor.
The only replacement option is a Tempest. It will work with your existing hub but the old hubs are unable to process Tempest firmware updates. If you get a new hub, your AIR device will work with the new hub, too. I have a station with a Tempest and 3 AIR devices. Two of them are indoors, one in my shop and one in my pump room.
@gizmoev my SPA finally failed on my Sky. I figured it was the internal battery of the SPA, but when I go to measure the pogo pins there is no voltage coming across them at all. I tried to see if I could get any electrical signal to pass between the two battery leads and was dead as well.
So I removed the batteries and tested them and they were at 3.0v each and seemed ok. Measuring the solar panel contacts shows that they are putting out around 130millivolts when the panel is in some sunlight so the panel seems fine.
It seems to me that the failure was not so much the batteries but perhaps the circuit board the solar panel connects to.
The question is whether there is anything I can do to modify this to get the SPA to still charge the LiFePO4 cells if I put them into the SKY as recommended in your modification?
I just took down my SPA as it wasn’t holding a charge for very long. When I measured the solar panel output just by itself it was putting out around 4V in full sun. I would suspect if yours is only putting out 130mv it seems the solar panel is bad.
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Does anyone have the specs for the solar panel used? I’m only getting 1.7v from mine.
Thanks.
In my SPA it used a TP5000 charge controller IC. I looked up the datasheet for this IC, and it has an input range of 4-9 volts, so at minimum the solar panel should put out 4v in order for this charge controller to charge the lifepo4 batteries.
I couldn’t find any replacement battery packs for mine, so I made one out of two individual lifepo4 batteries and one of their protection PCBs. It was a fun little project.
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