LiMn battery choice

[abies]

Hello,

I have done extensive search but I can not figure exactly which LiMn batteries I should buy. I am considering changing LED, driver and battery pack from an old (dive) light. I would use four 26650 in 4S1P configuration.
LiFePO4: I am not considering them because voltage would be too close of the forward voltage of the LEDs (w/ buck driver)
Li-Ion, Li-Po, LiCo: despite a lot of the debates on CPF, since it would be used underwater, safety first! (good quality batteries and PCB should be safe but I can not use batteries that could possibly 'reject' explosive gazes in a closed canister)

That leaves me with LiMn2​O4​ (called LiMnNi as a short form?) and LiNiMnCoO2​ (short name LiMnNiCo).
What would you recommend me? (first criteria is safety and then density power)

I have only found LiMnNi batteries on batteryspace: any way to buy somewhere else? (ideally in Europe)
By the way, LiMnNiCo are said superior in density power but the only 26650 cells I have found:
- LiMnNi: 3,7 V - 4000 mAh
- LiMnNiCo : 3,6 V - 3600 mAh

Thanks,

abies

 

[SilverFox]

Hello Abies,

Welcome to CPF.

The question you need to consider is how well developed is the LiMn chemistry. Is it still being developed and considered on the leading edge? If so you may find more issues regarding cycle life, balancing, and matching a set of cells for use.

Li-Ion and Li-Po are well developed and have a proven track record. Lithium primary cells may have a higher potential of problems when soaked in water for an extended period of time, but in actual use they work fine. Li-Ion is not sensitive to water so there should be fewer problems.

On the other hand if you want to study LiMn batteries and further their cause, then jump in and get some cells and give it a try.

On a side note I noticed a warning against getting the LiMn battery wet. It seems its protection circuit can become damaged with water exposure.

Tom

 

[abies]

Thanks for your reply!

I am certainly biased for not considering Li-Ion/LiCo/Li-Po mainly because:
- to mention two of best diving light manufacturers, Tillytec and Hartenberger chose respectively LiNiMnCo and LiMn and both of them insist that Li-Ion is not the most appropriate for underwater use (see links). And Mangrove chose LiMn and LiNiMnCo depending of the products (and Li-Ion for low power lamp - with only one 18650 cell).
- on my chemistry studies, I still remember Li (and Na) reaction with water (actually, you can not forget it). Since Li-Ion is basically less stable than LiFePO4 (for example), even if engineers have made it much more safer with protected cells, I prefer avoiding it. Of course other types of batteries generates gazes, but at least, they do not explode (as far as I know).

By the way, on CPF, I saw yesterday the thread of an old man where his flashlight exploded and he almost lose his hands. They are VERY rare but still, I think you have my point ;)

 

[SilverFox]

Hello Abies,

You can always fall back to NiMh. It is well proven and has less possible issues... except for the production of H gas in extreme conditions. It is more forgiving in water though.

Tom

 

[RetroTechie]

- on my chemistry studies, I still remember Li (and Na) reaction with water

Afaik Li-ion batteries don't contain lithium metal, only lithium salts or otherwise bonded chemically (where the compound isn't one that reacts violently with water). In case you don't believe me: check the material safety datasheet for a typical Li-ion battery. Perhaps you were confusing with lithium primaries?

 

[abies]

Right, I only know from Lithium metal (I read on Li-Ion not to submerge, but this recommendation is the same for all technologies). I am using Li-Ion underwater for one or two 18650 cells, I just would like to avoid high power battery pack with Li-Ion underwater.

NiMh have a slow power density :(
Li-Mn have been use for more than 10 years, but it seems it is not in the 'consumer' hobbies. Anyway, if someone has advice with LiMn, that would be greatly appreciated :)