forum threadDesertGardener | Staff posted Dec 08, 2025 05:13 PM
Item 1 of 7
Item 1 of 7
forum threadDesertGardener | Staff posted Dec 08, 2025 05:13 PM
4-Pack HW 9 Volt 1400mAh Rechargeable Lithium Batteries w/ USB-C Fast Charging Cable $14.39 + Free Shipping w/ Prime
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It would be nice if these lasts a lot longer than typical alkaline while costing less than single use lithium 9v.
My concern is that these packs may use an internal boost converter to keep the voltage at 9v right up to the point where it is fully drained causing the smoke detector to miss the low battery chirp.
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It would be nice if these lasts a lot longer than typical alkaline while costing less than single use lithium 9v.
My concern is that these packs may use an internal boost converter to keep the voltage at 9v right up to the point where it is fully drained causing the smoke detector to miss the low battery chirp.
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I have used both 9V EBL Li-ion and 9V Tenergy Centura Ni-Mh rechargeables.
The Tenergy Centura have 7 Ni-Mh cells, so nominal voltage is 7 x 1.2 = 8.4V. Right after you charge them, they will measure 9.8V but within weeks that drops to under 9V and eventually settles at around 7 x 1.2 = 8.4V. Between the low 200mAh capacity and the inherent voltage drop over time, after about 6 months my smoke detectors start beeping (loudly), usually in the middle of the night when temperature is lower. I have to remember to charge in December to avoid being woken up at night.
The EBLs have a different problem. They use 2 Li-ion cells, but nominal is only 3.6V each. They charge up to 2 x 4.2V = 8.4V, so already well under the 9V needed. They have higher capacity, but again over time voltage drops to 3.6 x 2 = 7.2V. Again in my experience they will last 7-9 months before smoke detector starts beeping.
For these HW batteries, the seller claims they have a circuit that keeps voltage constant at 9V (similar to AA/AAA Li-ion rechargeables that are kept at 1.5V constant). A reviewer measured their real capacity at about 400mAh. As mentioned above, will try them when they arrive.
It would be nice if these lasts a lot longer than typical alkaline while costing less than single use lithium 9v.
My concern is that these packs may use an internal boost converter to keep the voltage at 9v right up to the point where it is fully drained causing the smoke detector to miss the low battery chirp.
It would be nice if these lasts a lot longer than typical alkaline while costing less than single use lithium 9v.
My concern is that these packs may use an internal boost converter to keep the voltage at 9v right up to the point where it is fully drained causing the smoke detector to miss the low battery chirp.
I used SMARTOOOLS "brand" from aliexpress for lithium 9V with a similar plug. Works well and lasts longer in my smoke detector and voltmeter than the cheap shit 9V batteries they send me though the mail.
I'm not sure about this brand though...
Bah, Humbug. The bigger the lie, the worse the product.
I have what I think is some of the best 9v Lithium (ipowerus) [ipowerus.com]. You have to get them through a commercial account. Mine are over 10 years old, still workiing, and have ~400-500mAh. There are 2xlipo sacks inside with voltage charge/discharge circuitry. So....4.2v fully charged x 2=8.4v. In reality it's usually ~8.2v, but they hold their charge a LONG time. I do use them in smoke detectors. They work fine for about 6 months.
NiMh 9v? Pitiful capacity, don't bother.
EBL lithium 9v? got 4 of those. Merely OK. lost ~200mAh in 4 years of use.
Nothing this size can do 1400mAh. I've not tested the current ipowerus 9v/800mAh but my suspicion would be that is absolutely the most you can get in a battery like this.
Marketing is easy, especially if you don't have scruples. Engineering and manufacturing is a tad harder.
https://lygte-info.dk/review/batt...arator.p
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