Blackburn System X battery.

[Cubist]

I have a pair of Blackburn System X8 SL lights, but as is so common the battery pack no longer charges. It isn't covered by warranty, so I split it to examine the contents and discovered it contains three pink coloured batteries wired in series. I can't find any technical data to tell me what voltage these are, but they are marked up with a letter C, then KH8FJ22 and underneath that what appears to be a string of numbers, 028729, on another is 028730 and the other is obscured by the protection strip. Googling these doesn't help.

The charger kicks out 12.4 volts.

So, if I wanted to wire myself a new pack, which cells should I use? If the pack contains three pink cells to make 12 volts, does that mean I have to find 4 volt Li-Ions, or would four 3 volters do it?

 

[Cubist]

 

[fossyant]

They look like 18650 batteries.

Readily available from DX, but you'd need to re-attach the circuit board and protection circuit to them. They are 3.7v each, so that's the 12v (almost)

Link to similar

DX Batteries

 

[Cubist]

Thanks Fossy, I've ordered some cells, let's see how long they take to get here!!

 

[fossyant]

I recon you should be able to tape/glue the existing connectors on - wouldn't fancy soldering myself.

 

[gbb]

They do look like 18650s. I have made battery packs from a recycled laptop battery. They can be soldered but i don't know whether it's advisable, the cells can be unstable in some circumstances (they can go with a big bang if the inners come into contact with water IIRC)
That tab with some numbers on maybe an overload protection, i'd retain that. Mine has no protection circuit, that made me slightly nervous once i realised, but they've been fine.
But solderable they are, with care. I'd do some research re soldering first. just because i managed, it still may not be recommended...but then it may be.

 

[gbb]

I have a pair of Blackburn System X8 SL lights, but as is so common the battery pack no longer charges. It isn't covered by warranty, so I split it to examine the contents and discovered it contains three pink coloured batteries wired in series. I can't find any technical data to tell me what voltage these are, but they are marked up with a letter C, then KH8FJ22 and underneath that what appears to be a string of numbers, 028729, on another is 028730 and the other is obscured by the protection strip. Googling these doesn't help.

The charger kicks out 12.4 volts.

So, if I wanted to wire myself a new pack, which cells should I use? If the pack contains three pink cells to make 12 volts, does that mean I have to find 4 volt Li-Ions, or would four 3 volters do it?

IIRC 18650's are 3.75volt each. All batteries with that number will be the same voltage, you just have to consider or find out how many mA each battery is rated to. If you buy them too small, you'll lose some of the life between charges.

 

[Cubist]

They do look like 18650s. I have made battery packs from a recycled laptop battery. They can be soldered but i don't know whether it's advisable, the cells can be unstable in some circumstances (they can go with a big bang if the inners come into contact with water IIRC)
That tab with some numbers on maybe an overload protection, i'd retain that. Mine has no protection circuit, that made me slightly nervous once i realised, but they've been fine.
But solderable they are, with care. I'd do some research re soldering first. just because i managed, it still may not be recommended...but then it may be.

Yep, I got a bit cautious about soldering the batteries direct, but there are plenty of advice videos showing it can be done safely. The original nickel joining strips/conductors appear to be spot-welded.



However, and to save myself an awful lot of buggering about, I have ordered batteries with solder tabs attached. That way all I have to do is copy the series linking. That is indeed an overload circuit protector, and will be wired in with the finished article. All I'll be doing is swapping out the batteries themselves, everything else can stay more or less as it is. I'll even be sealing everything back into the original housing, as the charger jack and output jacks are still attached to it together with the main circuit board.

The importers reckon I'll be waiting a couple of weeks for the batteries. Shopping around I found some for less than a tenner all in, which is a fair bit cheaper than Blackburn's own replacements, at 75 quid for the soft pack and 90 for the whole powerpack.

The lights themselves are woefully dim compared with 30 quid DX bargains, but look smart on the commuter. They're certainly adequate for street use. I use MS 816 off road, and used to use the Blackburn as a helmet spot, but that will be replaced with a newly ordered T6 1200 lumen (claimed) beauty.

 

[Wobblers]

They're 18650 lithium ion cells, a standard size you'll find in most laptop battery packs. That tab with numbers on it is a resettable thermal cutout - it'll disconnect the battery pack if it gets too hot or too much current flows. The circuit board contains the protection circuitry.

They can be replaced, but first the obligatory safety warning....

Lithium ion cells can explode (the official euphemism is "vent with flame") when abused. And if that doesn't get you, the clouds of toxic hydrogen fluoride smoke probably will... Do not short circuit, overheat or overcharge. Cells that have been overdischarged have most likely been damaged and should be discarded.

Now that's out the way....

I'd check the voltage of each of those cells first. Any cell with a voltage of less than 3 V is dead - throw it away! If all cells have a healthy 3.6 V or more, that would suggest that they are fine, and the problem is elsewhere. In this case, check that resettable cutout for continuity: if its open circuit - there's your problem. You can probably get away with simply removing it, though it's better to have it.

If the thermal cutout and cells are fine, then probably its the protection circuit itself. In which place, all you can do is check for dry solder joints (unless you've got access to the full suite of test instruments and the time and knowledge to troubleshoot it... ).

If it is the batteries, I'd recommend replacing with quality cells: Sony, Panasonic, LG or Samsung cells. Since you're discharging three cells in series, it's best that they be matched so that they all reach their end of discharge at the same time - it makes for a safer, more reliable and longer lasting battery. The cells sold by DX tend to be more... shall we say variable in performance. If you can, get cells with solder tags on the terminals - it makes life so much easier and you can avoid heating the cells when you solder them (heat is a Bad Thing for Li-ion batteries).