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Discussion Starter · #1 ·
Just about to buy some holders from DX so I can do higher voltage packs (sold my only 14.4V pack with the light it came with) for my 7-up light and some other projects I have in mind. I have 4 of the Trustfire whatevers that were very popular here still kicking around (new!) and may take apart one or two of my Geoman packs and just use the cells in a holder. Anyhoo, just curious what you guys are using, what holders, and where you buy them.
 

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MPD holders from Digikey. Keystone ones look good too. In my opinion, the DX ones are cr!p: thin wires, non-positive contact for flat-tops (like some AWs), and grabby unless you shave bits off them. (Other people here -- names escape memory -- don't share this opinion, so ymmv.)
 

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Discussion Starter · #5 ·

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Yup, those are them. They've got little tabs on the back that you solder to, so you can choose whatever configuration you want. I've knocked off the sharp corners and drilled a hole (about 1") in the back to make it easier to push the batteries out. (Gosh, that makes me sound like a bit of a hypocrite after I slagged the DX ones, eh?)
 

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I also use the Digikey holders, though I use the singles. I mount them with a couple small screws to a piece of Lexan. The singles have tabs that really retain the cells well.

BK-18650-PC2 MPD (Memory Protection Devices) | BK-18650-PC2-ND | DigiKey

I cut grooves in the Lexan for the wires and also attach a strain relief for the cable. I have used them for 3 years now with no issues.
 

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I've used a variety of those Digikey holders and they're really nice to work with. The singles I find hold onto the cells a bit well for me, so I shaved the side tabs back a bit.

If you're building 2-4 cell packs, you can't go wrong with Panasonic NCR18650A at ~$9 per cell in the US, although the NCR18650B are awesome at higher current drains which might be relevant if you're boosting. For larger packs, unless you're swimming in cash, there are a variety of Samsung and LG 2600mAh batteries floating around for $5-6 which would be a good bet. You'll give up a bit of capacity, but you'll save quite a bit if you're building big packs.

I'd avoid anything with *fire on the label if you're going to be drawing lots of current. Some cope fine, others sag into their shoes.
 

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I've used over 100 of those Digikey single holders and like Matt said they are very nice to work with. The trick that I learned on the single holders is to wrap the battery with a small piece of tape and LEAVE a small tab sticking out so that you can pull the tab to remove the battery easily.

I have a bunch of the single holders and a roll of GITD tape that is the perfect width for making the pull tabs. I also have some new Keepower 2900mah 18650's. If anybody wants to order a "kit" so to speak, just let me know
 

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I'm currently using a batteryspace 2S1P protected holder, and I've been having problems with the low-voltage cutoff. Namely, it's a little over-zealous, and it's getting worse. I've been using it for about four months now, and taking out the cells to charge them individually. Almost every time I put the cells in, the low-voltage cutoff has tripped, because the holder had no voltage when the cells were removed. The fix for this is to put > 7.2 V across the plug for the holder for about 30 seconds, then the cutoff resets and the pack works fine.

Lately, the cutoff has been tripping if there's even a very short break in the connection between one of the cells and the holder. What this means is, if I go over a bump hard enough to jostle the pack, sometimes it causes the cells to shift for a moment, breaking the connection for that moment, which causes the cutoff to trip, and my lights to go out. Which is not good on a night ride...I've tried bending the contacts to make a more secure connection with the cells, but it hasn't fixed the problem.

Since I haven't heard other riders complaining about the batteryspace holders, I may just have a defective unit.
 

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I had one of those with a bad connection in the protection circuit, which I re-soldered.
Worth checking the soldering job.

Right now my plan for my next pack is for unprotected 3400mAh Panasonics, DigiKey holders, with PCBs from Ktronik that I solder in myself. Most complex way to build them, but should have the best power and protection.

I'm currently using a batteryspace 2S1P protected holder, and I've been having problems with the low-voltage cutoff. Namely, it's a little over-zealous, and it's getting worse. I've been using it for about four months now, and taking out the cells to charge them individually. Almost every time I put the cells in, the low-voltage cutoff has tripped, because the holder had no voltage when the cells were removed. The fix for this is to put > 7.2 V across the plug for the holder for about 30 seconds, then the cutoff resets and the pack works fine.

Lately, the cutoff has been tripping if there's even a very short break in the connection between one of the cells and the holder. What this means is, if I go over a bump hard enough to jostle the pack, sometimes it causes the cells to shift for a moment, breaking the connection for that moment, which causes the cutoff to trip, and my lights to go out. Which is not good on a night ride...I've tried bending the contacts to make a more secure connection with the cells, but it hasn't fixed the problem.

Since I haven't heard other riders complaining about the batteryspace holders, I may just have a defective unit.
 

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Discussion Starter · #13 ·
I had one of those with a bad connection in the protection circuit, which I re-soldered.
Worth checking the soldering job.

Right now my plan for my next pack is for unprotected 3400mAh Panasonics, DigiKey holders, with PCBs from Ktronik that I solder in myself. Most complex way to build them, but should have the best power and protection.
Maybe a dumb question, but would it even matter about protection if I never run the batteries down too far?
 

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Maybe a dumb question, but would it even matter about protection if I never run the batteries down too far?
I doubt protection would matter if you charge with an intelligent hobby charger, and run them with a TaskLED driver. Some of my friends have cheapo chargers, so I add protection just in case.
 

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The problem with just using a TaskLED driver to monitor voltage is that it only monitors total pack voltage, which means that you could have a cell drop below a safe voltage while the pack is still above your cutoff voltage. It's not likely if you're balance charging and keeping your cells matched, but it is possible.
 
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