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Battery & Smoke Alarm Products

Hall of Shame

Last update: September 2020

Amazon pays me a if you buy any of the stuff I link to.  At the end of the month I pile up all the money on the bed and roll around in it.


Various manufacturers:  Batteries don't have anywhere near their rated capacity

Lots of NiMH battery makers make batteries that don't have anywhere near their listed capacity.  A battery labeled 3000 mAh might actually have only ~500 mAh of capacity, as I discovered in my testing.  The bad batteries are usually obscure brands you've never heard of, or are completely unbranded (no label).  You're unlikely to see them in stores, but if you're shopping Amazon or eBay for batteries, they're everywhere.  I buy all kinds of things on eBay all the time, but rechargeable batteries isn't one of them.  For NiMH batteries, it's best to buy well-reviewed brands on Amazon.

Rayovac:  Tries to pass off NiMH as Lithium

The packaging for the "Rayovac 4.0" batteries doesn't even bother to tell you what kind of batteries they are.  But it's happy to mislead you.  In small type it says "Compare to" and "Ready to use like", and then in big bold type it screams "LITHIUM".  So maybe you'd think that these are, you know, lithium batteries.

But they're not.  They're actually plain NiMH batteries.  You wouldn't know that from the packaging, because the packaging doesn't say.  It also doesn't reveal the battery voltage or capacity, for that matter.

Incidentally, NLee bought some of these and after a while they dropped to about half of their original capacity (even after refreshing more than 12 times in a Lacrosse BC-900 charger), and so he no longer recommends them.

But for the misleading and incomplete product packaging alone, shame on Rayovac.

Kidde:  Useless customer service

Don't expect a helpful answer if you write to Kidde.  I noticed that the manual for their i9030 smoke alarm curiously says not to use lithium batteries.  Of course the manual fails to say why.  Batteries are batteries, so why are lithium batteries not okay for that alarm?  I wrote to Kidde to ask, and expecting a B.S. reply, I tried to preempt that by wording my query like this:

"The manual for the i9030 says not to use lithium batteries, but fails to say why. Why, SPECIFICALLY, are lithium batteries contraindicated for this and similar models? If you don't have the answer handy, please escalate to Engineering rather than sending a form letter or other reply that does not specifically answer my question."

Unfortunately my attempt at preempting a useless reply didn't work.  Here's the B.S. answer I got from Kathy Alberti in Consumer Product Support:

"The alarms were designed for use with Alkaline batteries and their associated properties, because of this we cannot recommend use of Lithium batteries in our products."

That's so breathtakingly stupid there's just really nothing more to say.

Smoke alarm manufacturers like Kidde, First Alert, and BRK:  Incompatible connectors

Various alarm manufacturers use differently-shaped connectors, so if you replace an alarm with a different brand, you're probably gonna have to wire in a new connector.  Most homeowners probably don't feel confident screwing around with their home's electrical wiring, and even if they do, it's still a hassle.  Possibly manufacturers use proprietary connectors in order to prevent you from switching brands when you replace your old alarm, but if so that's still a jerk move.  They could at least include adapters in the box, but they don't.

I found this out the hard way when I had a Kidde alarm that failed, and bought a BRK/First Alert alarm to replace it, finding after it arrived that I was gonna have to re-do the wiring.

While I'm at it, the BRK/First Alert alarm requires wedging a screwdriver between the connector and the alarm in order to remove the connector, and it's not easy.  I had a hard enough time with the alarm on my lap; I can't imagine how hard it would be when the alarm is installed on the ceiling.  There's no excuse for this, they could have easily used a squeezable quick-release connector.

Shame on smoke alarm manufacturers.

Tenergy & EBL:  Hides the true voltage of their 9V-size rechargeables

When "9V" (nine-volt) size batteries are the rechargeable flavor, they're not exactly nine volts.  They're either 7.2V, 7.7, 8.4V, or 9.6V.  As you might expect, the higher, the better.  9.6V is best, 8.4V is usually adequate, and 7.2V is often just asking for trouble.  So before you buy, of course you'd like to know the true voltage of the battery that you're buying.

Except in the case of Tenergy and EBL, they won't tell you.  It's not on their website, it's not in the product description they send to their merchants, it's not on the packaging, and it's not even on the battery itself.  When I called Tenergy to inquire about it they never called back.  I have never seen any other consumer-size battery that didn't have the true voltage printed on it.  Shame on Tenergy and EBL.

(By the way, I bought some so I could measure the voltage, and found that Tenergy's 200mAh NIMH is 8.4V, their Li-Ion 500mAh is only 7.2V, and EBL's Li-Ion is 8.4.  You won't hear that from Tenergy or EBL, but you'll hear it from me.)  Feb. 2013 & Mar. 2015 

Duracell:  Ambiguous guarantee, horrible customer service

Alkalines are more prone to leaking than any other kind of battery.  That's a great reason to use NiMH instead.  (That, plus the fact that alkalines can't be recharged.)

If you must use alkaline batteries, you'd hope that their guarantee would cover damage caused by their batteries leaking.  Well, dream on.  The first problem is that in the case of Duracell, their wording is so ambiguous there's no telling what they cover.  Here's how the guarantees are worded:

  • Energizer: "We will repair or replace, at our option, any device damaged by these Energizer® batteries.... Contact 1-800-383-7323.
  • Rayovac: "Guarantee on all batteries*. We will replace or repair at our option, any device damaged by this battery if sent with batteries prepaid to the address below."
  • Duracell: "Should any device be damaged due to a battery defect, we will repair or replace it at our option if it is sent with the batteries, postage paid to [the address below]."
I emailed Duracell and asked whether leaking alkalines were covered under the "damaged due to a battery defect" clause.  They responded with a generic form letter about their replacement policy which said absolutely nothing about leaking alkalines.  I wrote back, pointing out that they didn't answer my question, and asking again whether leaking alkalines were covered?  They responded with the same useless form letter!  I wrote a third time, asking them to answer my question rather than sending me useless form letters, but they never replied.

So now you're thinking you should buy Energizer and Rayovac instead.  But one reader's experience is that Energizer doesn't honor their guarantee (see next entry), and Rayovac is already in the Hall of Shame for misleading customers, so I wouldn't trust them on their guarantee, either.

Energizer:  Doesn't honor their warranty

Energizer's warranty says they'll "repair or replace...any device damaged by...Energizer batteries".  Getting them to actually honor that warranty is another story.  A reader who I trust writes, "I had an expensive flashlight that I used every day fail due to leaking Energizer batteries.  I called, I e-mailed, I sent then pictures as they requested, I talked to them a long time.  Every reply I got looked like a form letter.  I didn't even get replacement batteries or a coupon, much less a new flashlight."  July 2020 

PowerGenix:  Doesn't tell you that their batteries can ruin your devices

[Update: PowerGenix no longer makes NiZn batteries, but I'm keeping the below for historical purposes.]

As I write this, PowerGenix is the sole name-brand manufacturer of NiZn batteries and chargers.  NiZn's claim to fame is its high voltage of 1.6V, compared to 1.5V for alkaline and 1.2V for NiMH.  The extra voltage means that digital cameras and CD players can run longer, and flashlights can burn brighter.

But the voltage can be as high as 1.8V fresh out of the charger, and voltage that hot means that NiZn batteries can ruin your device, burning out the bulbs in your flashlights or frying your electronics.  (Some devices tolerate the extra voltage okay, some don't.)  Though that's not what gets PowerGenix into the Hall of Shame.  What gets them here is that they're not up front about how potentially dangerous their batteries are.  Every time their website has an opportunity to warn about the extra voltage, they ignore it.  Here's an example from their FAQ:

Will PowerGenix Batteries work with all devices?
The manufacturer does not guarantee compatibility and functionality of Nickel Zinc batteries with any device. Prior to use, please read user manual of each device to determine if restrictions exist as to which battery types may be used.

Nice CYA-wording!  They could bother to mention that the extra voltage could kill your device, but they don't.

And then the very next item in the FAQ:

Devices like digital cameras are referred to as “high drain rate applications”, meaning that they use a lot of battery power to function optimally. For these types of devices, it’s important to have a more powerful battery, and PowerGenix is ideal for this kind of application.

Sure they're ideal, unless they destroy your device completely.  Again, PowerGenix doesn't mention that possibility at all.

But this entry just takes the cake:

What does a higher voltage mean for my electronics?
In a nutshell, higher voltage means more power and better performance from your electronic devices. This is especially important in digital photography, when rapid flash performance can make the difference in getting the perfect shot. PowerGenix’s NiZn batteries have a voltage of 1.6 Volts, which is higher than NiMH and NiCd at 1.2 volts. With a higher cell voltage, the NiZn technology delivers energy quicker and this is why it can outperform other technologies in rapid flash applications: 65% faster compared to NiMH, 115% faster than consumer AA consumer lithium, and 150% compared to fresh alkaline batteries.

And that, my friends, is just criminal.  Literally.  The attorney general should be prosecuting them over this.  The question specifically asks what the higher voltage means to the consumer, and PowerGenix never once mentions what the higher voltage could REALLY mean—a destroyed device.

PowerGenix withholds that crucial information all over the site and in their product packaging, but the fact that they omit it in the very FAQ question that specifically asks what the higher voltage means for the consumer, is simply unforgivable.  Shame on PowerGenix.

Battery Xtender charger:  Barely charges batteries at all

Runtime of AAA after charging with each charger

AccuManager 20
Battery Xtender

Radio Shack NiMH (four different pieces)


Lenmar NiMH (three different pieces)


Sony NiMH  (two different pieces)



Very Good
Very Crap
The Battery Xtender charger is absolute crap.  It purports to be an all-in-one charger, charging both rechargeable and nonrechargeable (alkaline) batteries.  The reality is that this thing can't even fill up standard rechargeable batteries.  I ran some tests to see how much runtime I could get out of AAA batteries after charging them with the Battery Xtender vs. a real charger, and my results are shown at right.  Each battery was tested at least three times in each charger.

In 19% of my tests, the runtime on a battery charged with the Battery Xtender was less than one minute! The battery ran out almost immediately. But even if you tossed out all those cases, the average runtime from the Battery Manager is still woefully low, typically less than an hour.

As for its supposed ability to charge alkalines, I have a whole page on why that's not a good idea.  But alkalines aside, this charger can't even charge NiMH batteries correctly.

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