improving inexpensive cell holders

It is not easy to come up with decent aa and 18650 cell holders for applications such as diy chargers, etc. I’ve purchased a number of these in the past and although they are inexpensive they have some major failings.

!!

The wires are very thin, they are too short for protected cells and if a cell fits the holder it is darn difficult to remove.

!!

The first modification is to remove one pair or both pairs of “wings” along the top edge of the holder. I’ve found they aren’t really needed. A quick application of a sharp knife and they are gone. (in the photo below I’ve removed one pair although later I’ve removed both).

!!

The next mod helps with those following. Take a sharp knife, hacksaw or bandsaw and cut the holder in half (across the middle). There is a hole in the centre that makes this very easy.

!!

Referring to the photo above you can see I have modified both ends to allow for lower resistance contacts. On the positive end, after cutting the holder in half, I drilled out the rivet type of contact. The rivet spun on the end of the drill and it pulled out of the plastic. I found a small round head bolt and a couple of matching nuts (in this case they were 10-32 which was all I could find in my stock). A matching drill bit was used to enlarge the hole. The blue wiring connector is all I could locate in the right size - note that it would be a good idea to cover the blue with red shrink wrap to prevent mistakes in polarity.

On the negative end I’ve soldered a piece of braided copper solder wick - a piece of moderately heavy guage wire could also be used. In order to keep the heat from melting the plastic holder (and it does have a low melting point) place a damp cloth between the spring coils near the negative end of the holder and wrap the damp cloth around the end of the holder. This keeps the plastic cool enough to prevent damage. I did not remove the existing black wire - it can be used together with the copper braid as the lead from that end. Use heat shrink tubing to reduce the amount of bare copper leading away from the battery.

Space the two pieces apart on a base (alumium, plywood etc) and epoxy them in place. Scuff the base of the holders with course sandpaper so the epoxy grabs. Wrapping an appropriate cell in shrink wrap plastic and putting it in the holder will serve to keep the ends lined up while the epoxy hardens. Use tape or clamp(s) to hold things in place.

I didn’t polish the end of the 10-32 bolt however that is a good idea. It would be easy to do in a hand held drill.

Unfortunately I did not think to measure resistance before and after the mod. If someone does this perhaps they can contribute the results. I don’t have another “virgin” 18650 holder on hand or I would do that.

John.

Good post.
I got some of those single 18650 and twin series battery holders as well as these .I had to heat and cut off the reinforcing gussets and cut off one whole side of each single cell holder.The open sides are on the outside.I haven’t done the wiring yet.The double cell holders only need one side removing.They all need the ends trimming lower to fit in the waterproof boxes.There is no rattle :slight_smile: .I am planning to use this as the battery bag.I’ve got 4 boxes in the bags so two 2p2s battery packs,and still room for my sandwiches :wink: And they are so cheap.

Thanks for the ideas for connections,I may well follow you and braid the tail springs.

Billy X - I tried to come up with some off the shelf solution for bike light batteries a couple of years ago but was using nimh (eneloop aa’s) and didn’t yet have 18650’s. Ended up using plastic water pipe with some fittings but never felt it was satisfactory. I needed at least 4 aa’s in series and it ended up being a long tube. Looks like your solution should work as long as the bags are waterproof.

I would still like to come up with something elegant and well made that can be made with a minimum of tools and off the shelf items from the hardware store. In the meantime these can be made to work fairly well. I’ve used them with the little tp usb charger boards - rather than using magnets on the leads. Don’t think I’d use them on bike lights however.

John.

Good explanations of both the shortcomings and solutions/workarounds of these. I've got some also and when I first tried to remove a battery I was like: What concussed retard developed this piece of &#%¤

Did you try a pvc weatherproof box? They are available at most hardwares that sell conduit and they work well as project boxes.

adnj

I haven’t seen those before - they look good and it appears they come in various sizes. I’ll take a look next time I’m in the hardware area.

I’ve also thought about making a battery holder with plastic pipe of suitable id, cutting it in half lengthwise and glueing two caps, one one each end. It would be trivial to install a good spring in one end soldered to 18 guage or so wire and installing a good contact in the other end. If I do this I’ll post the results. It is surprising that there isn’t a decent one on the market - something similar to the system used in the nitecore i chargers with the moveable track.

Thanks,

John.

Urgh, I’m about to start hacking my battery carriers up as well.
Those crappy steel springs and awful wiring are such a pain the ass, more hassle than they’re worth in stock form really.
Think I’ll do something similar, thanks for sharing.

Yes actually, it is rather easy.

One of the common approaches to ease charging woes is to solder wires to nickle plated magnets to make magnetic charging leads. There’s a lot of info in this thread. Personally I like to get the high temperature NS grade Neodymium magnets from K&J for this, available HERE. I tend to buy the D42SH’s. The high temp magnets will be more forgiving if you end up putting a lot of heat into them during the soldering process. I have never had an issue with these magnets. You may want to use a freeze spray to cool them quickly after the procedure. You can also simply stick the magnets to some alligator clips and pinch the clips onto bare leads. No need to even solder them in this case.

For parallel charging cradles, I like to use the square battery holders that have flat contacts and bare leads coming out of the bottom or sides. The flat contacts are beefy and don’t have resistance issues like the coil spring type. Solder your own wires of heavy gauge. FYI, it is not recommended to charge NIMH cells in parallel. Charge them in series. For NIMH cells you can just use magnet leads and put a bare magnet between each of the cells in the series. Maybe cut a piece of plastic pipe in half and set them in it to keep them in line… or some similar approach.

Look in the “Battery Products” > “Battery Holders, Clips, Contacts” section and of the Memory Protection Devices brand at digikey. They are also sold by the other brands too such as Keystone Electronics.

Here some examples. 1x AA holder from digikey. (There are also larger versions: 2s, 3s, etc.)

(this image credit digikey.com)

I bought two of the 3 cell 18650 holders and made a 6P charging cradle. All I had to do is solder stripped charge lead cable wires to each of the contacts and then glue it to a wood block. I milled slots in the block but of course a wood chisel would make easy work of it as well. Alternatively the solder tabs can be bent out 90 degrees and flush mounted for simplicity.

Hoop:

Thanks for the additional info. I’ve made and used magnetic charge leads but found that fixed holders just worked better. Granted, the magnetic leads are quite adaptable for various battery configurations. My needs are for eneloop aa’s, unprotected 14500’s and protected and unprotected 18650’s so quite limited compared to others who may have a greater number of rechargeable cells.

I do like holders with springs on the negative end as they can be adapted to fit various lengths of cells - eg. protected vs. unprotected and the like.

Would it be possible for you to give us the range of lengths that the mpd/digikey aa and 18650 holders will take? That would certainly be of interest.

Thanks,

John.

Those digikey holders look miles better than the ones from china.