Lipo 18650 to 5xLR20 battery adapter

[briefer]

Hello

 

I would like to share this desing I have created to adapt 3x18650 lipo batteries to a keyboard that uses 5xLR20 batteries. It uses a buck converter to adapt the voltage from 11.4v to 7.5v

 

https://www.printables.com/es/model/706416-lipo-18650-to-lr20-battery-adapter

 

 

I splitted it to make it possible to be printed with a regular 3d printer, and also to make it easier to put it in inside the keyboard battery bay.

 

cheers

 

[Jokeyman123]

This is a good idea (I have 12 18650s I keep for various uses) but what specifically will this fit into although I know some devices use a 6-battery configuration inline for D cells and 9V?

 

For example-I couldn't use this in my XW -P1 which takes 6 LR-20 "D" cells since it fits 3 in 2 side-to side columns, as do some other instruments. And what would you use to charge a pack like this? Would have to be some type of charger-specifically for this voltage configuration. I am guessing the IC board is a balance charged circuit since these 18650's must be very carefully regulated to balance charge the cells. Or is this the buck converter?

 

I have a few laptop-style power supplies that have switchable voltage steps-from 12v to 19V that terminate in a variety of barrel plug adapters, could possibly used as a charging source for your pack if you haven't come up with one yet.

 

I don't think a typical 5V USB power pack would be sufficient to charge anything that draws more than 5V-and unless these is some kind of fail-safe shutdown in an IC board, could be very dangerous to undercharge a group of 18650s. Some of my RC radio-control stuff has this type of circuit-shuts off the battery if it falls below a specific voltage-but there are companies that are already selling these types-a "universal" outboard pack but would have to be, like your pack specific for a certain voltage.

 

Since most portable keyboards I've owned or played use standard 9V or 12V, including many of my tone modules and "danceboxes", these are the voltages for the portable packs I have, which are populated with 18650s or the smaller 14650's which are also 3.7V, and these just use a standard "wall-wart" type of charger with a barrel plug since (I hope) these portable packs must have a balance-charged circuit inside. If they don't, I'm playing with a potential hand-grenade, I'm not kidding. so far these portable packs have been OK, but I usually only use 18650/450 packs for short term, I am very nervous about overheating these, since this will create "thermal runaway" and bam, you're toast. But I'm sure you know all that already. Keep it up, good idea.

[briefer]

I would charge the batteries by removing them and using a charger like this one:

 

 

As an alternative, you could also add a charge circuit to the package:

 

and charge them with a USB charger, but that would make the connection more complex, as you should take cell balance into account.

 

cheers