Safety of inline battery pack LiIon in under-cabinet LED light

I purchased several of these:

https://www.amazon.com/dp/B071S1W87G/?tag=cpf0b6-20

LED lights, which use a "1500 mAh" LiIon battery pack. I can only see the butt end, and it's roughly the thickness of a AAA. Googling suggests there are 3 batteries in-series.

From reading this forum, I'm under the impression that that could be hazardous. I couldn't even get a straight answer from the vendor whether the batteries would stop charging when full... (An LED turns from blue to red when charged).

I really like the sticks, so don't just want to throw them away...

Thanks for any input.

skid00skid00 said:

I purchased several of these:

https://www.amazon.com/dp/B071S1W87G/?tag=cpf0b6-20

LED lights, which use a "1500 mAh" LiIon battery pack. I can only see the butt end, and it's roughly the thickness of a AAA. Googling suggests there are 3 batteries in-series.

From reading this forum, I'm under the impression that that could be hazardous. I couldn't even get a straight answer from the vendor whether the batteries would stop charging when full... (An LED turns from blue to red when charged).

I really like the sticks, so don't just want to throw them away...

Thanks for any input.

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Do you have a pic of the battery? How does it connect to the light, is it a wire connector or does it insert into some contacts? If you can take a pic of the battery and how it connects then might be able to give more input.

If the battery pack is the thickness of a AAA which is 10mm. The LiIon cell of equal size to a AAA is a 10440. The only way to get 1500mAh out of 10440's would be to connect 4 of them in parallel. 350mAh is a typical rating for a good 10440. You would need 375mAh x 4 for 1500mAh so its close, 1500mAh is a little optimistic IMHO. I would not leave it unattended while charging and periodically I would check it for excessive heat while charging.

Frank

The batt is encased in aluminum extrusion. I can only see the butt end. There are wires going into the extrusion.

I'm guessing I need to discharge shallow, and recharge often?

Thanks for your replies!

I agree the in that the battery pack is parallel cells or perhaps a single flat type battery as the charging is USB (5v). I always think any new product that has unknown components should be monitored when charging the first few times but they can make good charging circuitry easily these days that will properly charge lithium ion batteries personally I would be tempted to take it apart and charge it till full and check the final voltage of the battery pack as these cheap charging circuits can vary on the final stop voltage being below 4.2 is fine but much above 4.2v can overcharge and reduce battery life and if extreme can be possibly hazardous.
With decent lithium ion batteries and chargers there is no need to vary discharge, usage, and recharging patterns. I typically recommend charging related to usage if you know you will need the light for long periods of on time then you may want to recharge when it hits half discharged or less if the usage is shorts then allowing deeper discharge to perhaps 1/3 to 1/4 left is fine in that it reduces how often you have to recharge it saving you some hassle and time.

skid00skid00 said:

[...] From reading this forum, I'm under the impression that that could be hazardous [...]

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Certainly it could be hazardous if it is not properly designed, or if it uses poor quality cells. But is is impossible to say based on the little information provided. Did you do a teardown? If so, please post photos.

Gauss163 said:

Certainly it could be hazardous if it is not properly designed, or if it uses poor quality cells. But is is impossible to say based on the little information provided. Did you do a teardown? If so, please post photos.

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I've not tried to pull the batteries out of the extrusion. On first look, it seemed to be difficult to avoid damage to components.

Basically, if it's properly designed, it should be safe. There's no way for us to tell anything more than that without more info. It is worth keeping in mind that there are some chinese lithium ion powered things all over amazon and elsewhere now that are not really properly designed, but it's probably OK. If it's only 1500mAh, then there's not all that much energy there so even if it's bad it's probably fine.

Jon-LiionWholesale;5201393 [... said:

If it's only 1500mAh, then there's not all that much energy there so even if it's bad it's probably fine.

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Au contraire, that's plenty of energy to do serious damage. Even tiny button cells with 10x less energy can do serious damage, e.g. see this youtube video [start at time 37s to see the big blast]

.

Further, it is not only the energy that matters but also the flammability of the electrolyte, chemistry, etc, e.g. the button cell is primary Lithium which is more volatile than most secondary Li-ion chemistries. Nonetheless it demonstrates nicely how little energy is needed to produce powerful blasts.

Gauss163 said:

Au contraire, that's plenty of energy to do serious damage. Even tiny button cells with 10x less energy can do serious damage, e.g. see this youtube video [start at time 37s to see the big blast]

.

Further, it is not only the energy that matters but also the flammability of the electrolyte, chemistry, etc, e.g. the button cell is primary Lithium which is more volatile than most secondary Li-ion chemistries. Nonetheless it demonstrates nicely how little energy is needed to produce powerful blasts.

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That's a primary lithium battery. As you mentioned, secondary lithium ion is very different and 1500mAh is not very much for a secondary li-ion. Is it possible to be dangerous? Yes. Is it unlikely? Yes, even if you short circuit it from fully charged, it's unlikely to be able to heat up enough to go into thermal runaway. You would have to do something truly abusive to it.

Putting a Lit Torch to a battery is NOT a realistic and good example of what would happen during REAL life use. ;-)

Jon-LiionWholesale said:

That's a primary lithium battery. As you mentioned, secondary lithium ion is very different and 1500mAh is not very much for a secondary li-ion. Is it possible to be dangerous? Yes. Is it unlikely? Yes, even if you short circuit it from fully charged, it's unlikely to be able to heat up enough to go into thermal runaway. You would have to do something truly abusive to it.

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A 1500mAh Li-ion has almost 10x the energy of that Lithium button cell. In the OP's case it is tightly enclosed in a metal LED light case, so if it goes into thermal runaway it could behave like a small pipe bomb. Or the cell could shoot out the light tube like a bullet (check the smoke and fire subforum for examples where this happened with flashlights). Not to mention that if it vents and ignites some combustible material either in the light or nearby, then it matters little how much energy the cell has. Further, it's not true that the user "would have to do something truly abusive to it", e.g. thermal runaway could be caused by an internal short from impurities in manufacturing, or from overcharging due to a faulty protection circuit, etc, none of which are due to user abuse.

The odds of such failures are very low if the light is competently designed using high-quality components and cells. But generally there is no way for the end user to verify that.

IlluminationDomination said:

Putting a Lit Torch to a battery is NOT a realistic and good example of what would happen during REAL life use. ;-)

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Sure it is - it's simply a quick and easy way to induce thermal runaway.

skid00skid00 said:

I purchased several of these:

https://www.amazon.com/dp/B071S1W87G/?tag=cpf0b6-20

LED lights, which use a "1500 mAh" LiIon battery pack. I can only see the butt end, and it's roughly the thickness of a AAA. Googling suggests there are 3 batteries in-series.

From reading this forum, I'm under the impression that that could be hazardous. I couldn't even get a straight answer from the vendor whether the batteries would stop charging when full... (An LED turns from blue to red when charged).

I really like the sticks, so don't just want to throw them away...

Thanks for any input.

Click to expand...

Given the USB charger and the goal to make these as cheap as possible, I would lean towards 3 in parallel to achieve the absolute lowest cost.