This is the OEM battery. Basic soldering skills and electronic assembly required
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Great post. This should help some people.
Where did you source it?
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This was purchased from batteryspace.com
Before I replaced the existing battery i checked the voltage and it was 0. I took a strong searchlight and shined it on the solar cells and the voltage came up. I then replaced the battery and the station came to life! I reinstalled it outside and it was operating fine for about a day and then stopped updating data..its been a few days now and getting plenty of sun but hasnāt updated since. The last battery voltage reading was 2.56. I will take the unit down and check to see if i can find out what went wrong.
If anyone has any suggestions please post your thoughts. I donāt want to give up easily, but my electronic troubleshooting skills are limited.
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18650 batteries are pretty universal and you can find pages and pages of then listed on Amazon as well as online retailers that specialize in flashlights.
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Sorry but I donāt get a single one of LTO 1865 with pins like a capacitor on Amazon.
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Not all batteries meeting the the same volt & mah specs are the same size. The Tempest has an internal opening that can only fit the battery part number I posted in a previous post.
This is the correct dimensions: 18.7mm(0.7") x 65.3 mm(2.6")
From Batteryspace.com (LTO-18650-1300)
Not on Amazon..
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Did you ever find out what was wrong? Iād read in another thread that the two ribbon connectors can be fussy to reconnect.
I think my battery is on the way out, as the Tempest went offline overnight and the last battery voltage reported was 2.11. (There was a sharp dropoff within the final two hours before going offline.) Looking at the chart, it usually lives happily between 2.6 and 2.8 volts but since July it rarely gets above 2.6v. Weāve had a couple of days of cloudy weather, but we have entire months of very infrequent sun during half the year (yay Michigan 
) and the Tempest has done OK throughout those stretches.
Once the sun hit it this morning it came back online, but is in ECO mode as itās recharging. (It came back online around 2.19v and is at 2.29v and climbing.) Iāll be watching it throughout the day. It should get full sun for most of the day, so Iāll see where weāre at.
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Hi Rudy, I hated the thought of trashing such a useful instrument so I gave it another try. This time I disconnected the plugs going to the solar panels and added an external power supply in parallel with the internal battery and It has been working on the bench for days. When I disconnect the external power supply, the instrument remained powered from the internal battery overnight without any significant drain. Now that I am confident the unit is able to function, I will add a solar panel. The solar panel has an onboard regulator to keep the output at 5V to the USB jack. Here are the Amazon ASINās: B0DF7PZ4TT, B0F9XGF24D
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Interesting project! I was actually considering tinkering around with a battery project on a larger scaleāI have one of those 1056Wh power stations that run off of a LiFePO4 battery, and the expansion battery (same size) actually costs more than the power station. But this can charge from solar, and itās really nothing to hook up an external 36V 100Ah LiFePO4 battery and a charger to keep the power station charged way longer than the official expansion battery (total capacity would be 4,656Wh vs. 2112Wh, and the cost would only maybe 30% more).
In my case, I just want to replace the battery in the Tempest. I had it replaced onceāmy first Tempest was from the IndieGoGo campaign, so a really early model, and it seemed to get a complete battery failure back in 2021. Under warranty, they quickly shipped a new one out, and I sent back the defective on. So the replacement has been going for four years now.
I always thought the battery would have a specific lifespan, but couldnāt find any information on life expectancy.
Looking at the graph again, since the outage and recovery, the battery has drifted between 2.40V and 2.49V, across three partly sunny days. So itās still not right, but at least itās working in ECO mode until I replace the battery.
Iāve also considered adding the official Power Booster accessory. Itās a bit pricey, but itās one less thing I have to tinker with, and since power outages are not that frequent here, at least I know it would remain powered up.
It looks like my solar battery finally failed in my sky unit. The unit is about 5 years old. Iāll hopefully take it down soon and check it out. I noticed your post, and saw that you purchased a Lithium Titanate (TLO) 18650 battery, this battery has a significantly different voltage (2.4V vs 3.2V) and charge algorithm as compared to what I think the original lifepo4 battery chemistry is/was. Iām not surprised it failed. Iām not sure if Iāll be able to find a replacement radial leaded lifepo4 battery or not. Do you have any pictures you can share of the original battery and how it was installed?
I actually had to fix the solar unit one time already, back in 2020, it doesnāt charge in the very cold with its original design. I removed some temperature sensing resistor at that point so it would charge regardless of the temperature. They said at the time they had life concerns with this, but I didnāt find that concern warranted. My sky unit would die in the winter with the original design, once I modified it, it would run all winter. Iām an electrical engineer by trade, so I should be able to find a solution eventually.
I actually had to fix the solar unit one time already, back in 2020, it doesnāt charge in the very cold with its original design. I removed some temperature sensing resistor at one point so it would charge regardless of the temperature. They said at the time they had life concerns with this, but I didnāt find that concern warranted. Iām an electrical engineer by trade, so I should be able to find a solution eventually.
Hi Bryan, unless yours is different from mine, the picture of the replacement battery is shown with the installed original battery in the background. (See thread for pictures).The replacement I purchased from batteryspace.com is the exact replacement, However, it did not solve the problem. I decided to unplug the solar panels from the main board and connect a power supply in parallel with the new internal battery and this worked. I am now working on adding an outboard solar panel to charge the battery. Your electronic knowledge is obviously greater than mine so I appreciate your input. Thanks
oooohhhh - if somebody could figure out how to put an inexpensive outboard panel on the old Sky that would really help a lot. I was a SPA beta tester and had multiple failures back then, and my production one failed right away so I gave up.
Iād love to find a way to get the Sky working simply on the Air+Sky station that I gifted to a family member on the other coast. He gave up feeding expensive AA to the monster way too often. We didnāt even try the SPA on the Sky as I knew before the fact that it didnāt work at all.
His original product Air still is running just fine on batteries at least 2 years old now.
I am still running two Skys using the production spa (solar power accessory). I have replaced the rechargeable cells in one spa once. Also when I do run them on AA cells I use alkaline to save money as my minimum temp is well above freezing.
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I wonder if this would get around the need for a battery, or, if itās only for charging the battery:
Having it plugged in and operating off of stable DC power would be preferable for me. I can still replace the LTO 1865 battery.
Not worried about keeping it going during power outages, as thatās the least of my worries.
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I have the battery back up and it works well plugged in. I also have a whole house generator that keeps our sanity intact during stormsš The battery back is great during those extended cloudy days in the winter.
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We have both a generator and a battery power station to get through power outages, but I donāt power the detached garage where the weather station is mounted. I agreeākeeping the house functioning does help preserve some of our sanity. 
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Thatās for sure. I call our generator our āSanity Saverā 
Weāve had it for about 5 years. It powered by propane with 4 125 gallon tanks. Itās a Generac rated at 21KW. I used to have a portable one that lived a hard life but I maintained it and got 700 hours out of it until the stator burnt out. I sold it for parts. I always kept about 30 gallons of treated gasoline on hand and would rotate it out every 6 months. So looking for fuel was never an issue. Those days are now behind me, thank God!
Anyway, back to the weather. Good luck with your Tempest. Iāve had mine for almost 5 years and itās been bullet proof.