LED Flameless Candles and Batteries

[Oriane]

Hello everyone. I was not sure where to post this, but the LED forum seems as likely a forum as any.

I recently invested in quite a few LED flameless candles that run on AA batteries, and I am about to purchase a large quantity of batteries to power them. My question is will they be able to handle Lithium AA batteries? I have been using a few alkaline batteries in them, but I need a lot more batteries. I began looking at batteries on Amazon, and there are so many brands and types out there that it gave me a headache after awhile. The Energizer Lithium batteries are suppose to be long lasting, which is important, and they are supposed to be leak proof, which is even more important to me. My question is will they be too strong for these LED battery powdered candles?? I read that some battery operated items cannot handle Lithium batteries. Unfortunately, none of the LED candle makers say whether or not one can use Lithium batteries or not. They just say to use high quality AA batteries. I normally buy either Duracell and Energizer alkaline batteries, but I worry about their longevity and most of all their potential for leaking.

If the LED candles can handle the Lithium batteries, I would opt for those because they are far less likely to leak.

Thanks to anyone who can help answer my question.

 

[nbp]

Should not cause a problem, but I think most here would agree that rechargeable NiMH cells like Eneloops would be the best option if you plan to use these lights for a while. Earth friendly, virtually leak-proof, and pay for themselves quickly.

 

[Dave_H]

I've collected a number of small battery-powered LED candles, many run on 3xAAA and I wish more ran on AAs as it will be more economical and hold up longer.

Lithium AA start out at 1.8v and at 1.6v are pretty much used up. They are expensive in small quantity, have not priced larger volume as I use them very selectively.

If the AA candles use 3 cells, I'd have a minor concern that the electronics is being stressed by the extra voltage (0.6v), unlikely to do damage. If 2 cells, probably OK, but might run a bit brighter, depending on the design.

Using NiMH would be most economical. Voltage is more constant than alkaline though they might run a bit less bright initially. But, alkalines can work down to as low as 1v per cell, so they would dim out towards the end with some designs.

I suggest trying a small number of NiMH is your various candles, before investing too much. Even cheaper ones should do a reasonable job. Of course you will need a good charger, a small overhead.

As for Lithium-ion in theory you could rig up a cell to run a 3xAAA candle but would need to disconnect and charge, and also assure that it does not get over-discharged in a circuit that is likely not meant for it. There may be a few products out there which run on Li-ion.


Dave

 

[xxo]

Definitely avoid alkalines, sooner of later, they will leak. Energizer ultimate lithiums should work fine, Voltage is not a problem since they drop to 1.5-1.4V under load, though current might be a problem if the lights have poor regulation. Before investing in a ton of batteries, compare the brightness level to another light running on brand new/fresh alkalines if the light running on ultimate lithiums looks significantly brighter, let it run for an hour and see if the LED is getting too hot to touch. If, it doesn't get too hot. you're fine. If you want rechargeables, Japanese made eneloops or fujitsu cells are the way to go, though, again test them against alkalines to make sure they don't over heat the LEDs.

 

[Dave_H]

Alkalines can leak, however I believe the risk/danger is sometimes overstated; especially with low-cost devices, and cells regularly cycled i.e. not left idle for long periods. But that's a topic for a different thread.

Lithium AA's are also primary cells which require energy/effort to recycle or otherwise end up in landfill. Fresh cells under light load should not drop to 1.5v or below. I checked nearly-new cells in a 2xAA candle, under load dropped from 1.8v to 1.76v. Large drop means heavy load, and/or cell well along in its life. A lot of these candles draw in the 10's of milliamps.

That's why NiMH are overall best; or even good NiCds if convenient, but with much less capacity and run-time. Cost per cycle will work out much lower than the other two.

I also doubt LEDs with a bit higher battery are likely to get more than slightly warm; if anything the current regulation circuit will take most of the brunt.

Dave

 

[Lynx_Arc]

It would depend on how often you are going to use the candles and how much a "candle" costs to replace as to what I would recommend. Alkaleaks are a risk for sure but in super cheap lights that you can easily access the contacts to clean up after a leak it makes a lot less sense to spend about $2 a battery ($1.25 or so in bulk from some places) for Energizer Lithium primaries and makes even less sense in spending money on rechargeables in super cheap lights that run for 100s of hours off the batteries in them.
If these candles run a super long time then I would consider not investing in a huge amount of batteries for them but enough to more than outlast an outage common to your area.
I have several single D cell lawn lanterns Energizer made long ago that run something like 200 hours off a battery. I have adapters to use AA or C cells in them too. These lanterns have sit for over 15 years never being used enough to replace the batteries in them I so rarely use them. With todays 18650 lights you can run a candle mode output on them and outlast alkaleaks easily and recharge the batteries later.

 

[roostre]

My wife has lots of decorative string light arrangements and fake candles with many set to automatically light up for 6 to 8 hours each evening. They all use either two or three AA sized batteries configured in series with no low voltage protection.

We are using NiMH rechargeable batteries and when the lights stop working (besides having very low voltages) usually one of the batteries in series from the "three-battery" lights has also temporarily reversed its voltage. It would be better to re-charge the NiMH batteries before they completely discharge, but with ~50 batteries normally in use and >100 during the holiday season, keeping track of each light's runtime would be a chore.

I have recharged these NiMH batteries about thirty times already without any visually noticeable adverse issues so it has saved us money over using non-rechargeable Alkaline batteries which unfortunately also occasionally leaked. The ambiance from the decorative string lights and candles is quite pleasant compared to our normal house lighting.

I charge the ~2000 mAh NiMH batteries at 600 mA which is a 0.3C charge rate and so far the batteries internal resistance as reported by my analyzing charger after being fully charged has not changed much from when they were new. I am using four different battery brands and are curious to see how long the various NiMH battery types will ultimately last under these conditions.

DISCLAIMER: I am not a Battery Expert (Just a Frequent User) so please let me know if there are any safety issues that I may not be aware of from recharging NiMH batteries that are always fully discharged with some having reversed their voltage.

IMPORTANT NOTE: I would never do this with re-chargeable unprotected Li-ion batteries.

 

[alpg88]

the only sure way would be to try with 1. most likely there wont be any issues,

if you need to store batteries for years, or in places with high and/or low temp. lithium are the best,

but if you regularly use those lights, rechargeable are way to go.

 

[Lynx_Arc]

I would consider using 18650s instead of nimh it would take some doing but you wouldn't have the issue of reversing a battery. Power banks could also be used with buck circuits to drop 5v to 3v and direct drive for 3 cells even.

 

[roostre]

For me it's easier to just use AA-sized NiMH batteries in devices designed for AA rather than trying to convert them to Li-ion. Some of our string lights are USB plug-powered which is convenient since I can use either a 120 Volt AC USB wall charger or Li-ion battery USB power bank.

I should clarify that for the NiMH batteries in series, when one of them would reverse voltage, that it would only have a slightly negative voltage (just below zero) when I first took it out of a string light or fake candle where the switch was left in the ON position allowing the batteries to become and remain fully discharged. In less than an hour after removing the battery, the voltage would become positive again. Sometimes the voltage would not rise enough to allow the battery to start charging in my analyzing charger so I would initially charge it with a dumb timer-based slow charger to raise the voltage before transferring it back to the analyzing charger.

I keep and use the same batteries together as sets of two or three batteries and do not mix them with batteries from other sets (even though it probably does not make much of a difference for NiMH batteries installed in series and abused the way I use them) but I am not concerned as to which battery position they end up in when installed in the device. I make an additional mark with a Sharpie Permanent Marker on a battery's wrapper each time it reverses voltage to keep track of how many times this occurs for each battery. So far it has always been the same battery of a set that reverses voltage, which is probably protecting the other batteries in series with it and I'm assuming I will eventually need to replace this battery first, but so far none have failed and amazingly the batteries in my sets all take almost the same amount of mAh to fully charge, even after some of them have reversed voltage multiple times.

I have many devices that use Li-ion batteries but prefer NiMH batteries (even though they are so much less powerful) for some applications, due to their safety and the amount of abuse they can take. I have a few AA and AAA devices (mostly remote controls) that do not work well with 1.2 volt NiMH batteries and require 1.5 volt primary batteries and this is unfortunate.

 

[Dave_H]

Candles with yellow/orange LEDs can get away with two 1.25v/1.5v cells; RGB needs three cells. An exception I have is a Christmas tree ball ornament using RGB (and remote controlled too!) using 1xAA with internal boost.

Yes, series cell mismatch can creep in over time especially with more than two in series. It's important to start with matched cells: same brand/type/capacity and use state, keeping sets together, and using same charger.

An additional thought, a good use for older NiMH's which no longer hold up in heavy load devices such as cameras, flashlights, toys etc. and are usually perfectly good for candles; and may come free as discards or hand-me-downs. Often, fast chargers stop charging them, but slower chargers work OK. Many people already have a charger,which reduces overhead.

Eneloops may be nice but any good-quality cells should do. Low-self-discharge is good but not a necessity.

For that matter I even use up zinc-carbons I have on hand (but never buy them) in several LED devices.

Something makes me doubt the OP (and many others) want to deal with connecting Li-ion cells, converters or booster battery packs to a bunch of these candles.

Dave

 

[Dave_H]

Interesting candle-like device is designed to sit on top of a fence post. I've picked up several at second-hand stores for typically a dollar each. It has a square 4x4" base and short translucent pyramid. Inside are two amber LEDs which flicker. These run from 2xAA, down to just above 2v, but are not solar. I use them indoors with great results.

Perhaps someone else knows of these. No packaging/instructions came with them, don't know the manufacturer.

To activate, there is a bottom on/off switch and small switch in a slot facing up. You need to press down in slot with small weight such as a nickel or quarter. Reason they were so cheap, people sorting in the stores probably didn't figure this out and just threw them into bags.

I managed to open one without damage. Inside is a 10-pin IC which looks like a micro-controller. Imagine that, a little computer chip telling two LEDs to go on and off.

Dave

 

[Dave_H]

Not exactly a candle, I have a table-top solar light which flickers. It's warm white, not yellow or amber, but has a nice effect. Being a one-of from second-hand store, I don't know the vendor/product. It uses 1xAAA NiCd or NiMH.

Opening up (as is usual case) to see what's inside I found a 4-pin IC marked YX806. Its description and Chinese datasheet confirm that the flicker effect is intentional. As many battery or line-powered LED devices use control chips not marked and traceable to a datasheet, I pass this along for anyone interested in playing around with this. For example, LED current/brightness can be changed using a different inductor, with impact on battery run-time of course. LED colour could be changed but I don't plan to do this; but have done for ac nightlights.

Dave

 

[Dave_H]

I have a 3AA COB lantern with simulated flame effect using amber LEDs plus steady white mode. It was sold in Canada by Dollarama under the Voltax brand, though not the past couple of years. I don't suppose anyone else has seen these, or has something similar?

Here is something nearly if not identical (disclaimer: not endorsing specific company or product):

https://diamond-visions.com/product/?Mini-Pop-Up-COB-LED-Lantern-with-Flickering-Flame-Effect-3938

Battery life is quite good, runs down to 1v/cell, and can use rechargeables.

I like the effect though it can be distracting at times; a response to being alert for actual flames from a real fire. You can tell looking directly at it that it's not real, but not always out of the the corner of your eye.

This gives me an idea though. A round base sitting under, possibly attached to, candle or lantern could be wired for an 18650 cell holder, and into the bottom of the device. Could be a large plastic cap, tube, or a small can with snap-on lid.


Dave

 

[Dave_H]

Interesting what's inside of some of these low-cost flickering-flame solar lights coming out recently.

I've opened up a couple, finding the light module is a long thin PCB strip with 5-6 orange SMT LEDs on each side. These are sequenced in a pattern which simulates a flame. Visual effect is pretty good. It could be used indoors also, by wiring to an external cell.

It's getting later in the season, finding lots of deals OTC. One of these flickering stake lights was priced only $5, now discounted as low as half price; not a lot of money! Minor issue the with one I have, it runs on 2/3 AAA 100mAh NiMH which is not the most common cell to replace for increased run time. They could have easily designed it to take a full-size AAA, maybe even AA.

Dave