I’m certainly no expert (although MANY years ago I studied to become an electrical engineer), but after reading about LiIon here on BLF (and other forums), I think the dangers of mishandling the cells shouldn’t be neglected. The biggest risk (apart from using rubbish cells and chargers) seems to be charging the cells in series (without individual cell monitoring).
As long as the charging is done separately (individually in a separate charger) and the cells are identical (and have been used together all the time, with the same number of cycles) it should be OK to use them in series during the discharge, at least until one of them gets worn out. So the cells individual condition needs to be monitored at all times.
Many of the accidents with burning hover-boards seems to be related to charging the LiIon cells in serial without individual monitoring of the cells.
Running cells only in parallel is of course always safer, but not without risks either.
Since higher voltage brings down all losses and makes everything more efficient, it’s a balancing act (as most things in life).
Texas Ace, thanks for posting that information,
I have been trying to figure out all that was just discussed and was leaning towards the 4S, mainly because I didn’t know anything about what I do know now thanks to your great explanations and all I was doing and thinking was, I have the M43 and all batteries are what I know now as 4S and when I test them are all in perfect sync discharge state, of course I did intentionally buy all my batteries at the same time as the light and use them only in that light and it works so perfectly for me, so that was all I was going by when trying to figure out which configuration to buy.
I had not seen before a 2S2P light and couldn’t understand why they would consider that as an option, but I sort of understand now, thanks again.
BG has these for sale and there is a coupon floating around by Martin that brings the 07 from $95 to $80 and the 03 from $129 to $109.99, leaves a little money for the HaikeLite suggested Sanyo GA 18650 or other semi-button top unprotected 18650s which RMM has a good price for the Sanyo’s GA’s unprotected.
I have also asked BG which version they are selling as it does not say on their site and it does make a difference as I’ve come to understand.
Still leaves me to wonder which light the MT03 or MT07, but at least I know it’s 4S preferably per explanations by and thanks to T-A… Thank You, I was very confused, and maybe still am…
You do need to follow basic lithium handling protocols naturally but even these are blown out of proportion IMHO. I have taken apart hundreds of Battery packs, many of them 10-20 years old with unknown hundreds of cycles on them. Virtually none of them with balance charging.
It always amazes me that even with all that use they are generally within .1v of each other in balance (minus bad call naturally).
On top of that the battery packs I have built with old, mismatched, virtually dead cells also maintain an amazing level of balance as a rule, even without balance charging them (which is why I use old nearly dead cells, I simply do not care enough about them to balance them).
Basically even int he worst possible conditions I have come to find that cells do not just randomly fall out of balance. There has to be some serious abuse for this to happen (or a bad cell naturally).
Even if the cells were mis-matched in a single discharge it is just about impossible for a set of the same cells, from the same batch to be come mismatched enough to over-discharge any single cell to the point of damage assuming you have LVP on the light.
I too am surprised by the relative scarcity of LiIon accidents. We’ve been using LiIon cells for 20 years and there are billions of devices using them out there.
So why so few accidents (relatively speaking)?
Could it be that quality used to be higher, since there was more money to go around (devices using LiIon used to be pretty expensive)?
Maybe today’s mass market production have gone one step too far in its penny pinching and we now will have more accidents?
Samsung Note 7 comes to mind…
The reason there are so few accidents is because lithium cells are actually quite stable. The difference is that when abused outside of the design parameters (which are pretty extreme in themselves) they have the ability to create flames instead of “just” leaking acid or dying.
As far as the ones you do hear about, first off you will notice the vast majority of those are in custom sized/made battery packs for things like cell phones, not standardized 18650’s.
The reason those tend to have more issues is simply space, they are trying to cram as much power as possible into the tinyiest space possible and with the least weight possible. This combo leads to sacrifices in other areas and those can lead to much larger issues.
It is really the technology race having long ago outpaced lithium technology but there being nothing better to replace it so they just keep pushing it further and further.
1) It is nevertheless ironic that you don’t hear any accidents with these *Fire 4x26650 (or 18650 with spacers), 16xXM-L T6 21000 Chinese lumen light for 89 Dollars or something, and these suckers just don’t explode…
2) You all know how long it takes to charge lithium ion right? Ever noticed how quickly your phone charges? Ever notice that your phone gets fairly warm during charging, but your cells in your xtar charger (or any other brand) don’t get that warm at all (0.5A)? Get the feeling they (phone producers) are pushing the boundaries…
Yep, the pressure to get a heads up on the competition with the already very tough smartphone market has force manufactures to push things WAY past what they should. This usually works out ok, sometimes you get a note 7.
I’m actually going to be seeking a little wisdom from you as far as buck drivers go. I have two lights that I’m going to mod and each light is going to need a buck since the battery carrier is set up 4S. I’ve never stepped into the 12v realm before…only 3v and 6v and only with fets. However, I’m getting away from fets on these particular mods because of the setup. I’m use to piggybacking on contact boards and other drivers but have come to the realization that the bucks are going to have some kind of heat displacement. Would covering the driver with silicone or another potting material suffice…if it’s being used as a piggyback? Also, where would I get a buck driver that would push 2.5 amps to a XHP35 with an eswitch setup? I’ve got another light with the same setup but it’ll have an XHP50…where would I get a buck driver for it to push it to it’s max? I’ve also already had my ambien so if none of this makes sense, lol, sorry :weary:
I knew as I logged off, I was thinking did I saw 4S or 4P…, Well I was certain of one thing, I will know the answer to that when I log back on, and yes it is 4P so Thank You and by the way no need to be sorry about confusing me, I am an expert at confusing me
One thing is for certain with me and that is if T-A says the 4S is the way to go, and I think Tom says the same, along with KB, so 4S it is and I will learn the rest as it goes.
Maybe I should just go read on parallel and series applications more, back to basics, fundamentals,
I sure am not short on info being I actually have Google on my computer, I think it came with it when I bought it… Sure is handy.
I’m kidding ya, I paid extra to have it installed… :laughing: … but I do want to know more about this issue and well just about everything else also, …
Thank you for clarifying my mistake, I do appreciate that…!!
Yes indeed, I counted what lights I have in plain site, phone rang and last I recall I was somewhere in the high 80’s, I could probably times that by three and come out short, it is insane.
It get even stranger when your going to go out in the evening and can’t decide which light to take with you…
