*BLF LT1 Lantern Project) (updated Nov,17,2020)

Compared to the FW3A project, this one is moving at the speed of light. :sunglasses:

also interested, depending on price
will it be able to run on 1/2/3 18650?

Finally I have had the time to read the entire build progress and all I can think is that I love it, and can I please be put on the interest list…?

One thing I didn’t find was pricing ? Probably just missed it.

Thanks for all the hard work DBSAR and to your team as well.

@turbiny, yes, that is the advantage of using 4x18650s in parallel.

You can use 1-4x18650s in the light.

Just don’t put 1-3x fully charged cells with 1 partially discharged cell. Bad things could happen.

As far as price goes, nothing is settled but likely $30-$40 I believe.

Recent additions to the interest list include:
1066 T18
1067 mgracia85
1068 skroober
1069 skroober
1070 Mediocre99
1071 Kame Sennin
1072 asderferjerkel
1073 bmansc
1074 lachesis
1075 Cpeng
1076 bmengineer
1077 jdavis
1078 turbiny

Several more first time posters showing interest in this lantern, including asderferjerkel, Mediocre99, and skroober, as well as turbiny’s second post on BLF. Welcome to BLF :beer:

Note I somehow managed to skip 1066, so I put the last interested person, T18 there.

Master interest list can be accessed by most at the links below:

interest list sorted by entry number

interest list sorted by user names

were working on it, and waiting fro more info from the manufacturer and other team members.

I see this mentioned often but has anyone ever had an issue doing this? I’ve mixed fully charged cells with partially discharged cells and haven’t experience anything out of the ordinary.

Agreed, it is something like an urban myth.

Cells discharge, and re-charge curves are much the same. They will balance out, quite quickly.

It is probably not ideal to do this so fast, but I very much doubt that anything bad will happen.

there are a lot of factors as to it/how much trouble one could experience doing this. State of charge of the cells, internal resistance of the cells, the resistance of what is connecting them, the peak current capability of the cells, and others. It’s not a sure problem in every instance, but its also not a good practice to do routinely. Just like ideally you don’t charge cells on a pile of newspapers. Probably nothing happens, but if a cell did overheat, then you have lots of fuel to get your fire started. Especially the way BlueswordM created the scenario. Three charged cells trying to dump current into one discharged cells is definitely a bad practice.

Like I said, the discharged cell will only accept the charge at it’s own rate.

Basically all that is going on is that a cell is being connected to a low impedance voltage source of max. 4.2V.

Which, I don’t think is any danger at-all. Though it may not be good for the cells, long term.

It could be pushed in a lot harder.

These are not the fragile delicate dangerous scary things that some seem to think.

Otherwise you’d never dare to connect your EV to a supercharger and put in 80% energy in 15 minutes.

I have a damaged Skyray King here which suggests the issue is more than an urban legend. The “balance out, quite quickly” thing can happen fast enough to melt springs.

That’s probably a problem with the springs, not the cells. Or overall safety. Or maybe something was put in backwards ?

Still a real issue though. And not ideal. But no obvious alternative, unless we only have cells in series, which is hardly a practical way forward for many devices, and introduces a load of other concerns.

I wouldn’t mix cells of varying voltages if you paid me. I’m from the RC drone world, a lot of us use balance boards to charge several 3-6s lipo packs at a time in parallel. These boards connect the main discharge leads in parallel, and the balance leads in parallel.

Rule of thumb is never connect packs with cells that are larger than 0.1v difference to each other, or balance current can melt wires/damage cells. I push that rule to 0.2v sometimes, but I make sure to connect the higher voltage pack to a bank of lower voltage packs, never the other way around. Why? Discharge current. These batteries don’t like being charge rapidly. They’ll take it, sure. But they don’t like it.

The packs I use are rated for 5c charging current. That’s basically mAh capacity converted to Ah capacity, and then charge at an amperage equal to the Ah rate. Have a 3,000mah pack? That’s 3Ah, so a 1c charge rate is 3 amps. 2c is 6amps, 3c is 9amps, etc.

Discharge current between two packs at 0.2v difference per cell can be 5 or 10 amps, sometimes more, at least briefly.

To connect two batteries, one full and one dead, together, is to essentially cause a dead short. You’re gonna pull a crap ton of current out of the full battery, and dump it into the low one.

This would be bad enough with my lipo’s, with their high charge rate capacity of 5c. But the cells we use usually have a max charge rate of 0.5 or maybe 1c. The 30q has a max charge rate of 1.3c, or about 4amps. But in my experience they get warm charging at 0.3c, or 1amp.

So to mix cells of large voltage difference, and generate that massive balance current? Melting springs? Yeah, no thanks. Maybe it won’t blow up in your face, in fact it probably won’t. But dang it if it isn’t really bad for the battery, and potentially your face. No thanks, I’ll pass.

Sorry for the rant, of course you’re welcome to do as you please. But I agree with TK, it’s not an urban legend. Even if it’s not as bad as I’ve made it out to be, it’s still not good. Please don’t do it.

No, that was the springs doing their job correctly. They’re supposed to act as fuses in case anything like this happens. I’m lucky it was only the springs which got damaged.

… and that was with weak old NCR18650A cells. I’d hate to see what happens with a set of mismatched high-amp cells with bypassed or low-resistance springs.

This was something we worried about when designing the Q8, and looked into fusible links etc. on the tail PCB.

I did some tests and found it was not too bad. In that implementation.

We decided not to bother with that and rely on people being grown-up and responsible for their own actions.

But of course a 4P arrangement like a Q8 or SRK has a multitude of opportunities for putting in the cells incorrectly.

I’m interested. When will it be up for sale.

Interested

Cant help but think of the sign in my local bar ……“Free Beer Tomorrow”

Any idea if this will need high drain batteries like the 30Q? Or will NCR18650GA work fine?

This is a low power regulated light, using NCR18650Bs, Samsung 26Fs, etc, are perfectly fine within the power constraints of the light.