Li Ion 1.5V AA Rechargeable -not good for AM reception

Cabral954 · 2019-09-04T01:45:11.000Z

I’m sure many people on this forum have used Li Ion AA 1.5V rechargeable batteries. I purchased some on eBay from Blackube & some from Sorbo. The Blackube have a micro USB connector to charge the batteries using a standard USB cable & the Sorbo have a USB-A male which is part of the battery assembly and plugs directly into an AC charging adapter - thereby eliminating the need for a USB cable.

Both work great in small AA/14500 Flashlights.

My reason for this post is to inform readers that when/if you insert these batteries in a portable Radio the FM band works fine BUT the AM band is all static for the entire band. The internal DC/DC converter which steps the 3.8-4.2 Li Ion voltage to 1.5 volts uses a buck type architecture switching converter & the square wave/switching frequency radiates from the battery & overloads the front end of the AM receiver.

I wrote to both companies & from their responses it’s apparent they never tested these batteries in a portable radio. They asked me to send them videos/audio of this problem & the model numbers of the 3 radios I tried. FM works fine since it’s less susceptible to noise. AM on the other hand is sensitive to noise which makes the batteries useless for AM reception.

Just FYI if you ever want to use AA Li Ion 1.5V batteries in an AM radio.

JoeRodge · 2019-09-04T02:09:50.000Z

Are these any better than NiMh? It sounds like an expensive scam. But maybe I’m missing. Something? Won’t there be a lot less capacity?

Is the big advantage that they can hold their voltage under load?

roguesoul · 2019-09-04T02:19:04.000Z

JoeRodge:

Are these any better than NiMh? It sounds like an expensive scam. But maybe I’m missing. Something? Won’t there be a lot less capacity?

Is the big advantage that they can hold their voltage under load?

Remarkably enough not all electronics will function using the lower voltage of NiMH. Like my electric tooth brush among other things as well. Fenix has one of these 1.5v lions I wonder if it causes rf interference.

Cabral954 · 2019-09-04T02:19:44.000Z

Both are rated at 1200 –1250 mah so I’m assuming they are better than NiMh. Also they output a constant 1.5 VDC similar to a standard non-rechargeable AA battery.

I don’t know how to post pictures but if someone can tell me I’ll post pictures of these batteries.

Again they work great with AA flashlights but not so good (if at all) with a portable radio tuned to AM.

Cabral954 · 2019-09-04T02:23:41.000Z

My GF tried these with her toothbrush & they worked fine. Like I mentioned a DC/DC converter uses switching type architecture & square waves are rich in odd frequency harmonics which contributes to the overloading of the AM front end.

I still have not heard from either company on their testing or redesign.

roguesoul · 2019-09-04T02:44:49.000Z

Although I’m not a listener of radio, thanks for posting this. I had not thought about looking for another brand besides Fenix.

As for the energy comparison between these and AA NiMH. It’s almost a given the marketing is way overstating what their actual mAh rating is. Since 14500 batteries have been released with 1000mA but the space needed for the buck converter no doubt reduces this by x. And NiMH Eneloop Pro are 2550mA. So 3.06 watts Eneloop vs < 3.00 LiIon watts.

Cabral954 · 2019-09-04T02:52:23.000Z

Thanks - very good response. I’m not familiar with the Fenix AA rechargeable 1.5 V Li Ion but if someone out there has a few of them try them in an AM/FM radio & report back. Maybe Fenix has adequate shielding of their buck converter circuit as compared to the brands I tried.

Lightbringer · 2019-09-04T05:36:49.000Z

They are not 1.5V cells, but regular Li cells that have a step-down circuit to provide 1.5V for whatever stuff takes that. And anything that needs bursts of high-current won’t work with them (they even warn you about that).

That step-down circuit is likely what’s hosing AM reception.

{Bah, I hit [save] instead of [preview]…)

Anyhoo, they’re not filtered in any way, so all those big fat juicy harmonics will sweep the entire AM band, like you mentioned. Even the output likely has huge ripple currents that can sneak its way through into the radio’s supply. Umm, forget “sneak through”, it’ll use a ram and barge its way into the radio’s supply.

They’re great for things like electric toothbrushes, small lights, anything that’s not critical, but anything that depends on a nice clean supply, forget it.

EDCba · 2019-09-04T12:09:09.000Z

And I heard the 9V versions do the same to wireless mics.

flydiver · 2019-09-04T14:44:08.000Z

HJK has done a review of the Kenti: Test of Kentli AA 2800mWh (Blue)
This is one of several.

I’m trying out a brand called Tenavolt. On sale they are about $2.50/each. The ‘charger’ is simply a USB box that distributes 5.0v to all batteries. All charge/discharge control is in the battery.
You cannot effectively use a normal NiMh or Li charger. Won’t work right, though some people try and have had….some….success. The feedback loop for the charger is compromised and it won’t charge properly.

They have a narrow range of good uses, but for the proper application they seem great. Never tried them in a radio. Not good for high drain, and not as effective for very low drain as more appropriate LSD NiMh or alk.
I like ’em, have a dozen now, and I already have a LOT of good NiMh.

snakebite · 2019-12-24T12:29:55.000Z

the 9v with 1 cell and boost do this to radios too.
2 cell and no problem.
the designer probably asked how many users are going to use these in am or sw radios?
not enough for us to care about them.

hank · 2019-12-23T22:35:11.000Z

Would you test the distance over which this AM interferanceis a problem?
Does it only affect the radio in which the battery is used, or does it affect other AM radios at some distance away?

snakebite · 2019-12-24T12:35:16.000Z

i doubt it would carry far.
but its going to be tough to suppress the rfi well enough for use inside a radio.at least in a cheap product with very limited space.

hank · 2019-12-24T17:01:36.000Z

Well, as a ham radio operator, I’m always interested in identifying sources of RFI.
It would not surprise me if this battery charger noise can be picked up some distance away.