Have u tried swapping battery packs from a working to failed vent to confirm the packs themselves are the issue?
Yes. Swapping battery packs helped, sometimes. However, I think the battery contacts on the inside of the vent are also corroded in some cases, so it did not help all the time. Even if I swap battery packs, I only have the same number of battery packs as vents, so it just moves the problem to a different vent.
I'm dealing with a corroded battery pack where it ate through the bottom of the battery pack completely. I am going to perform a similar mod to what you did here but 3D print a replacement pack. I am fairly certain it's a JST1.25 2 pin connector, I have some being delivered tomorrow. Will report back my findings.
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I can confirm that a JST 1.25mm 2-pin connector fits.
I checked on the vents over the Christmas weekend (12/23-12/26/2023). I replaced all of the batteries around 12/3/2023. Much to my dismay, almost all of the batteries were in depleted states. Some NiMH measured 0V 0V 0V 0V (too low to measure using the Lacrosse battery tester I got recently). Other NiMH measured 0V 0V 1.3V 1.3V (meaning that the right two NiMH batteries were not used at all).
I replaced one set as non-rechargeable alkaline: that one set measured 0.95V 0.92V 0.96V 0.92V, meaning it was barely functioning but pretty much dead.
I replaced one battery pack with a somewhat generic purple color 18650 lithium battery (ASIN: B0B71R1VJ3). Originally it was fully charged and measured 4.2V. To my dismay, I found that battery measured 1.75V on 12/23/2023. The Keen Home Vent was still working (actually, it was the only one that was still working!) on 12/23/2023 but it stopped responding on 12/24/2023.
I chose three other vents that were measuring 0/0/1.3/1.3 to replace the battery packs with lithium batteries. I also recharged the original one that I worked on from 12/3/2023. Now, there are four lithium batteries installed: one purple battery (generic ASIN: B0B71R1VJ3), one yellow Victagen (ASIN: B0C4H138K6), and two lavender Samsung 35E 18650 3500mAh 8A battery (18650 battery store direct link).
I did not bring my soldering iron with me, so I just twisted the wires together and used heat shrink tubing to hold them together. They seem to work. I will try to bring my soldering iron for the remaining connections.
By the way, I accidentally connected red to red and black to black wires, which reversed the polarity, and plugged the JST connector into one of the vents. Within seconds the magic smoke started coming out of the Keen Home Smart Vent. 
I immediately disconnected and fixed the problem. Fortunately the vent still works. I am relaying this to tell you just in case you accidentally miswire your connections. 
I am going to observe the battery life of these vents again. The first purple 18650 battery test is very discouraging, but the battery is generic, which is why I am trialing other batteries. If the life of the vents on lithium batteries is less than 3 months, we will have to give up on Keen Home (and by extension, Hubitat as the controller).
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For what it's worth, here is a table of all the vents in the house, and the status of the batteries (all replaced around 12/3/2023, re-examined 12/23/2023, and replaced again 12/24-26/2023).
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Interesting. Because of the online reviews of the dismal battery life I am preparing a 4 pack of 18650s wired in parallel for a trial run.
I do also wonder if the integration(s) are being too aggressive in checking status but I don’t know much about how the protocol works or if this is a possibility. I will be running on Home Assistant and will be curious if that makes any difference.
How did this go?
I have been tracking and replacing the batteries on the Keen Home Smart Vents over the last three months. While I could post a bunch of pictures, summarizing seems like a better approach. Some vents last longer than others. Only a few of the 12 vents in this home have stayed up reliably. I used the following battery combinations:
- 4xAA Alkaline batteries (Energizer, Duracell): Some actually lasted several weeks, but these batteries are the worst for longevity.
- Li 1.5V AA PaleBlue: Works but dies somewhat quickly.
- Li 1.5V AA EBL: Works since 3/23/2024. Recommended if you do not want to change the battery case.
- 2xC Alkaline batteries (Energizer MAX): I thought this choice would last awhile since the capacity of an Energizer MAX C battery is supposed to be ~8000 mAh, which is drastically more than AA (or even Lithium-based battery types). I put battery packs into two vents on 3/23/2024. One vent stopped responding on the same day. The other kept on going for about a month (to-date).
- LiPO 18650: mixed bag. Some lasted 3+ months while others died after about 3-4 weeks.
- Tenergy NiMH: some vents are going strong; other vents died out quickly
- LiPO 21700: Too big! The battery and battery case case do not fit inside the Keen Home Smart Vent void space. Do not bother.
Overall, there is still not a consistent pattern to which vents and batteries die early and which last a long time. It just appears that some specific vents consume more power than others.
I think some of your inconsistency may be due to signal issues at individual vents. Have you tried putting zigbee repeaters in each location such as zigbee usb or zigbee dongles or checked rssi at each vent. Since i added one to my office i am going on 6 months on a set of batteries.
I get well over a year on the batteries in a vent in our master bath. It gets cycled twice a day. My bride shuts it to take a bath and then opens it when she is done. These are Amazon branded batteries.
I liked the idea of "smart" vents to limit where HVAC managed temperature. I installed my 17 vents in late 2016. Most of my vents had good battery life (9 months to a year). But I have had several lemons, and I have had to replace several of them. This was from two failure types - Zigbee radios completely failed - would not connect even after factory reset or would connect but not take commands.
I have also always had to limit open/close to 80%/20% because the motors would get stuck at 0%/100% and go to obstructed. This also happened on reboot (battery replacement) and if I didn't manually "help" the close/open swing on boot they would go red.
The biggest issue with the vents is the battery "boxes" are prone to corrosion and because Keen is long gone, there are no replacements available. The fact the batteries "live" in an area with dramatic temperature swings likely leads to the issue.
Last week I had to replace my entire HVAC (over 20 years old) and my new system is not HE compatible. Add the fact my HVAC "guy" has complained for years that the decreased airflow capacity caused by reduction of overall vent "size," I have finally pulled the plug and dumped all my Keen vents.
I have 11 vents and get a year or more out of the batteries. I get several changes an hour on each vent due to I use an ecobee and have all vents open every hour to circulate air. I believe very strongly in what @kahn-hubitat says in having plugin zigbee repeaters near each vent (i.e... 1 repeater in each room)
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I thought I would give an update on my Keen Home Smart Vents.
At my parents' house, the vents mostly went to pasture between April and September 2024. The vents all ran out of power, as reported by Hubitat, between 12/30/2023 (!), 3/23/2024 (!), 4/1/2024, 4/5/2024, 5/1/2024, 6/22/2024, 6/30/2024, and 7/1/2024. I.e., the longest-lasting batteries survived three months, April 1 - July 1, 2024 (approximately), but many did not stay connected after I refreshed the batteries at the end of March 2024 at all. For those that continued to communicate, several died within a month.
The vents and batteries that lasted the longest (according to Hubitat) were:
| Name | Last Activity | Batt Type | Batt Volt When Found |
|---|---|---|---|
| KHV Family Room | 7/1/2024 | NiMH Tenergy Green | 0V,0V,0V,0V |
| KHV Girls | 6/22/2024 | NiMH Tenergy Green | 0V,0V,0V,0V |
| KHV Living South | 6/30/2024 | LiPo Victagen Yellow | 3.12V |
| KHV Poolside | 7/1/2024 | EBL 4xAA | 1.08V,1.08V,0V,1.5V |
Interestingly, the LiPo "light purple" and "dark purple" batteries (which were Samsung 3000-3500mAh ones) pretty much died by 5/1/2024, just a month out.
I recharged and replaced the batteries at the beginning of September 2024, so we will see what happens.
I also checked the Keen Home Smart Vents at my rental property. The rental property uses SmartThings, not Hubitat. I cleaned the contacts with vinegar where there was visible corrosion, and switched out batteries in the first half of June 2024. Almost all batteries were switched to EBL Li-ion USB AA rechargeable batteries that are marketed as "3300 mWh". One or two vents were switched to 4xAA NiMH Tenergy Green batteries because I ran out of EBLs from my order (these things get expensive when you multiply by 10!). I did not do any LiPo mods.
By the beginning of September 2024, three vents died and the rest were still going after three months. Of the dead ones, one was NiMH Tenergy Green "Centura" (voltages went to 0V--SmartThings says it died August 17, which is 2 months), one was EBL (voltages went to 0 or ~1.0V--SmartThings says it died August 22, which is ~2.5 months), and one was EBL with strong readings (1.5V--the tenant reported that particular vent had not worked for a couple of months, despite swapping out the batteries).
I took apart the EBL-based one with strong readings and determined that corrosion on the battery terminals was pervasive, to the point that the corrosion went down the lead wires with green marks on the micro JST connector. Basically the entire battery compartment was hopeless from the beginning.
Overall, it seems that EBL Li-ion USB 4xAA batteries are the best--much better and more reliable than the 3.7V LiPo 18650 batteries. Why is this?
Let's look at the marketed capacity stats and extrapolate:
LiPo 18650 3.7V: 3500 mAh = 12950 mWh
EBL Li-ion USB AA 1.5V x 4: 3300 mWh per battery = 2200 mAh per battery = 8800 mAh total = 13200 mWh total
NiMH Tenergy Green AA 1.2V x 4: 2000 mAh per battery = 3000 mWh per battery = 8000 mAh total = 12000 mWh total
Duracell Alkaline C 1.5V x 2: 8000 mAh per battery = 12000 mWh per battery = 16000 mAh total = 24000 mWh total
PaleBlue Li-ion USB C 1.5V x 2: 3700 mAh per battery = 5550 mWh per battery = 7400 mAh total = 11100 mWh total
Perhaps surprisingly, the computed stats show that EBL 4xAA comes out on top--if the marketed stats are accurate and if we assume that the relationship between mWh and mAh is proportional to the nominal voltage. It's not actually directly propotional, because voltage decreases as the battery discharges, the nominal voltage is quoted differently for different battery chemistries, and the overall battery performance is affected by the rate of power consumption of the Keen Home Smart Vent as well as the ambient temperature.
Nevertheless, in my personal experience, the EBL 4xAA has worked out the best. (I also tried 4xAA Li-ion USB PaleBlue batteries in my parents' house, which fared poorly: the vent died on 4/1/2024. Note that the AA PaleBlue batteries are marketed as 1700 mAh / 2550 mWh @ 1.5V, which is substantially less than EBL AA, but not so much to explain the vast disparity in performance.)
My thoughts so far are that the Keen Home Smart Vents are designed for 3V alkaline so batteries that actually deliver close to 3V will behave the most predictably. The vent will continue to operate down to say 1.8V or 2V, but the vent was not designed to start at a "nominal" LiPo voltage of 3.7V. The actual starting voltage of 4.20V of a LiPo battery is just too high and out of design spec. The vent clearly works but may consume more power or may experience other problems (i.e., voltages stressing sensitive components) that would be a waste of time to diagnose. Furthermore, although the vent probably can and will tolerate a LiPo battery discharging down to 1.3V, "The usable voltage range for a standard lipo battery cell is 3.2v to 4.2v. Any lower than 3.2v and the battery may be permanently damaged." In my experience the LiPo depleted batteries were re-chargeable back to 4.2V but it took a very long time.
At this stage I would not recommend the 3.7V LiPo modification.
I tried to experiment with 2xC and 2xD batteries. First of all, 2xD is a non-starter because 2xD cannot fit in the smaller Keen Home vent compartments (4x10 vent size). 2xC fits but you cannot fit 4xC inside either.
2xC works, and capacities for alkaline batteries re excellent at 8000 mAh. Nevertheless I believe that 2xC is not tenable because of market failure. From some Googling and Amazon.com shopping, I determined that most C Li-ion USB batteries are marketed at 5000 mWh, or 3333 mAh. This is way less than a typical alkaline C battery which is 8000 mAh. As a result, you are actually better off with 4xAA EBL batteries than 2xC rechargeable batteries.
I did a quick check and determined that you can actually cram 8 AA batteries into the emptied Keen Home 4x10 vent compartment. Next I am going to acquire four 2xAA battery holders, wire them in parallel, and see how long the Keen Home will last in that configuration. In theory it ought to last twice as long as a Keen Home vent with 4xAA EBL batteries in the factory battery compartment (assuming that the factory battery compartment is pristine with no pre-existing corrosion).
I would suggest adding some zigbee plugs in each room or around the property that would act as repeaters and save the keen vent batteries. I get more than a year for all of my 11 vents.
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What batteries are you using?
Sam's Club batteries or Duracell from Costco. Nothing special.
FWIW I finally gave up on Keen and switched to Flair. Could not be happier. They just work.
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