Replacing Li-Ion Batteries

[Umibuta]

I need some advice regarding replacing the 3s2p Li-ion batteries in the 24W Darkbuster torch. However, they come its dedicated charger. Is it safe to just replace them with any protected Li-ion batteries and continue using the same charger? The charger has an output of 12.8V at 1A.

Thanks

 

[Umibuta]

As above, I am trying to replace the batteries for the 21/24W HID Darkbuster. I also noticed that the batteries have only 2 cables. Does this mean that the batteries are not charged balanced? Is there any hazard concern if not balanced charged?

Would be helpful if someone could chime in some advice on this and also if I can just replace the batteries with any protected Li-ion batteries in the same 2p3s layout.:shrug:

Cheers

 

[Umibuta]

If anyone could help me. Thanks :candle:

I am helping a friend to replace the batteries of the 21W Darkbuster and need some help understanding Li-ion batteries. I noticed that there is an accompanying circuit which I guess is to prevent over charge/discharge and possibly to balance charge the 3S2P 18650 pack.

I would like to replace the batteries and my questions are:
1) Can I simply replaced the batteries and connect to the same circuit as previously?

2) The originals are 2600mAh, and I have 2800mAh. Will these pose a problem for the original charger besides longer charge time?

3) What will happen if I have protected batteries and the circuit also have protection. Will this double redundancy cause any possible problems?

Attached are some pictures of the batteries.

Accompanying Circuit

 

[alpg88]

replace with unprotected cells, your circuit already has protection, and balance (may be), anyway adding any kind of circuit will not be a good idea. wire them exactly the same way as it was before.
get cells with tabs, don't solder or heat up the cells, you will damage them. solder tabs, and try to do it quick.

 

[Umibuta]

replace with unprotected cells, your circuit already has protection

Thank you for replying :wave: My only worry is that what if the circuit has no protection all this while. Honestly I am not sure what the circuit does and I am only guessing it is for protection and balancing.:shrug:

anyway adding any kind of circuit will not be a good idea

If there is protection, what are the possible problems with another redundant protection. Sorry about being anal here. But after reading about exploding Li-ions I am quite worried :duck:

 

[Quension]

From the pictures, the current wiring has the taps (green and white wires) necessary for balance charging and monitoring. The power cable goes to the board, not the batteries directly, so chances are the circuitry is in full control of charging. The manufacturer's info for that pack (2B0500042) claims it's protected (overcharge/overdischarge/overcurrent/reverse input/short).

alpg88 is right -- do not use protected batteries or otherwise add circuitry to that pack. Without a full understanding of the design and behavior of the existing circuitry, you cannot predict what will happen when adding more.

The PCBs on protected batteries work by looking for a specific set of conditions and then breaking the circuit when they detect something they don't like. (Note that "what they don't like" is external -- protection won't stop a bad battery from internally shorting and bursting into flame, it will just stop the load from pulling more current than it's supposed to, or the charger from trying to charge too long, etc.) When added to a pack like that, the PCB triggers may not match the load characteristics needed for normal use of the pack, and trip when they're not supposed to.

When one of the protected batteries trips, suddenly one of the two parallel cells goes "missing", leaving the remaining cell to take the full load or charge. At minimum, this will increase stress on that cell, and the sudden change in state at that tap may cause the pack's board to behave strangely. The behavior of a tripped protection circuit on an individual cell does not match what happens when the cell is wearing out, which is the situation the pack's board is designed to handle. Also, once protection trips on a battery's PCB, it needs to be reset to use it again -- but you may have a hard time doing that while it's part of a pack.

And that's without considering what might happen when one of the protection PCBs fails in some strange way...

If properly designed into the entire system, redundant protection would be fine, but it's not something that can just be added to an existing design after the fact.

One thing you should do to maximize safety is use high-quality cells as replacements (and make sure they match or exceed the charge and drain ratings of the current ones, of course). One of the most important things in a pack is that all of its cells behave as consistently as possible, and with the very cheap cells there's a greater concern of variation.

 

[LuxLuthor]

I have a battery pack spot welder, and have done things like this for myself and know what is involved. With some of your posts, as a matter of safety, I am concerned about your knowledge of Lithium cells. While the "use tabbed cells" is your only option, you still need to have cells that are matched to the PCB.

For an underwater application especially, I would strongly recommend that you just 'bite the bullet' and get a new replacement pack.

 

[Umibuta]

Thank you for all the advice. I think I might have to replace with a non-protected Li-ion and carefully see if it balance and control the discharge and charge voltages

Apart from replacing the batteries for the Darkbuster, I am also looking at the possibility of building my own battery pack for a LCD monitor for video. Incidentally, it also requires between 12-9V hence the 11.1v battery pack fits my requirement perfectly as well.

Lux, thanks for the link. I have also been sourcing for similar battery packs that i could replace like this. Unfortunately, they do not ship outside US and Canada. I would have gotten this if not for the shipping and the additional taxes that the US imposes for Li-Ion battery shipments.

Until I find a battery pack that I can buy here in Japan i might have to resort to building my own. I have read about spot welding the battery terminals and as you have said I might not be experienced enough for this. So my question is are there other methods to connecting the terminals without spot welding, i.e adhesives etc?

Thanks

 

[alpg88]

So my question is are there other methods to connecting the terminals without spot welding, i.e adhesives etc?

Thanks

don't use glue.
you can put them in a holder, battery space sells 18650 holders with protection circuit build in.
you could use small neodymium magnets, stick them to the battery, than use a wire with a small piece of steel soldered, it will stick to the magnet, than tape the whole thing.
i also used fishing split weight few times when i had to wire few cells, just put it on a stripped wire end, squeeze it with pliers, and tape it, stretch the tape as much as you can before it brakes so it pushes lead ends tight to the battery.

but the best way is to buy tabed cells.

 

[Umibuta]

Those are very good information. I did not know that they have holders with PCB. This would be good for my LCD monitor. But i guess the tabed cells will be good for the Darkbuster. Honestly, this is my first time hearing about tabed cells. Do I solder directly on to the tab. Hence, reducing the possibility of heating and damaging the cells? I supposed the cells are tab on both ends I found these tabed cells and they look good.

 

[alpg88]

i,ve used tenergy nimh cells, they work fine, not 1 or 2 but all of nimh tenergy cells i have, but i can't say if li ion made by tenergy are any good, never used them.
i mostly use cells from oem laptop packs, mostly they are made with good quality cells made in japan or korea, replacement aftermarket laptop batteries almost always use no name made in china cells, that aren't as good, in my personal experience, they don't last half as long, and drop V more under load.
good cells usually but not always are in red wrapper with little to no marking on them. also i had some green wrapped Panasonic and blue samsung cells. those had a lot of text, mostly in Japanese, or Korean.
i can't read either, but i can tell if it is Japanese or Korean or Chinese letters.

i just realised you are in japan, and looking to buy cells made in china???? lol.

normally cells are with no tabs, but places that sell them do offer service of welding tabs, if they do it in us, i don't see why companies in japan wont. i assume you have online sellers in japan that sell batteries?

 

[LuxLuthor]

Honestly, this is my first time hearing about tabed cells. Do I solder directly on to the tab? Hence, reducing the possibility of heating and damaging the cells? I supposed the cells are tab on both ends.

Yes. Yes. Yes. No idea on the quality of those Tenergy cells.