Makita 21700 Battery 18V

thingiverse

Hi all, since Makita did not release a 21700 Battery yet, have made my own. (That batteries you can get e.g. from BOSCH or Milwaukee and maybe other brands, too) It is a little hard to print, especially the tool connector and you need a lot of support I made it with ABS and would avoid PLA since that does "not feel right" and the batteries might get pretty hot, too. PETG should also work fine Additionally, you need the 21700 cells. 5 for the one row version, and 10 for the two-row version. I used the Molicel INR21700-P42A and got 4AH respectively 8AH battery packs. https://eu.nkon.nl/molicel-21700a-4200mah-30a.html Unfortunately, I do not have the possibility to weld that, so I needed to solder them together where I used a 2,5mm² copper wire of a normal NYM cable. (see pictures) (A very powerful soldering iron is needed (60W+)) The battery compartment is designed to accommodate these wires, if you use thinner wires or even headframes than you get a very loose fit which needs to be compensated to avoid the cells from moving in the housing. Right now, only the "cheap" aftermarket PCBs can be used which is also used in the inexpensive aftermarket batteries. Maybe I try to fit a better one some time https://de.aliexpress.com/item/4000307047095.html?spm=a2g0o.productlist.0.0.3927e1c0GRDLsw&algo_pvid=2ef9150a-6acc-489b-a5aa-57147ffc443a&algo_expid=2ef9150a-6acc-489b-a5aa-57147ffc443a-55&btsid=0ab6f81615917285504455507e4bd6&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_ These small PCBs do not have a connection to all of the cells, so it is not possible to detect voltage deviations nor to balance the cells... (I am not sure if the original Makita batteries being balanced, but a significant voltage deviation within the cells could be detected since all of the cells are connected separately, BOSCH once said that they are not balancing the cells but detect the voltage differences and don't charge anymore if the voltage deviation is to high...) You need is a small spring with ~17mm length and ~10mm outer diameter and ~8mm inner diameter which should not be too strong. For the screwing I used 4 x M310 screws with adequate threaded inserts. I have used some from Ruthex which are pretty good. (M35,7) But I am not sure if they are globally available. (Do not use the cheap ones made for molded parts, they do not work properly. Especially not in blind holes) https://www.amazon.de/dp/B07YSRGZ9N/ref=emc_b_5_i I made some iteration loops and still the design is not 100% perfect. The fit to the tool is a little to tight so you need a little force to put them in and out (The original ones are a little bit more convenient) The air guidance for cooling at charging is of course not optimized and the effectiveness is questionable. But I did not get any issues with that and the batteries are not getting warm at all Still, these batteries are my favourite right now and I would not buy any other anymore. Price advantage is only minor with ~30€ for the 4AH battery and ~55€ for the 8AH battery. I attached the STEP file for reference and modification. Feel free to adapt that if you want.A 12AH version should also be possible. Please keep in mind that not all Makita “tools” are suitable for these wider batteries. I have ~15 Makita tools and most of them are fine with these batteries. But I do not get them (without modification) in: - Coffee Maker DCM501 - Radio DMR 112 (It does fit somehow but you cannot close the lid anymore) - Some tools with the belt clips attached. (E.g. at the DDF481) Since I do not use the belt clip I just removed it. The last point is probably the reason why Makita does not release a 21700 version of the batteries in the near future (or at all?) But if you are fine with the restrictions (as I am) than it can be a good solution for you. The weights: 21700 4Ah: 470g (=118g/Ah) 21700 8Ah: 880g (=110g/Ah) 18650 5Ah: 636g (Makita original) (=127g/Ah) So, they are only a bit lighter compared to the original. If the 4Ah battery can deliver more power (up to 45A) than the Makita one … that I do not know. In the end there is only a small benefit with the 4Ah battery - Less height - A little better weight/capacity ratio - A wider stand (maybe also better for some tools) - Some cost savings? ~60€ for the 5ah Makita battery =12€/Ah vs 7-7,5 €/Ah self-made (I do not compare the clones you can get because they have very cheap cells used which sometimes do not even have the capacity they are sold with, at least the ones that I have bought a couple of years ago…) The 8Ah battery does have a lot more capacity and could deliver up to ~1600W (Maybe there are some tools which could benefit from that, too. My circular saw already destroyed some batteries due to the high current consumption) But in the end, it is more or less just a “fun project” without the necessity to be better or useful edit: I have uploaded a 3-row compartment as well (as requested) I only scaled the two-row version since my parameterized model was done in beginner mode ^^ (did not do its job at all…) To use the 3-row version one would need a second “separator”. But I did not try that version at all in reality. So please be aware that if you are using that, you are alpha testing!