HHKB Hybrid S battery voltage input tolerances

[babytexx]

Hey all!

I'm working on putting a LiPo in my Heavy Grail to use the BT functionality of the hybrid S. Do you think I need to use a buck converter to bump a LiPo down to 3.3v, or would it handle 4.2v without? Any advice is welcome.

[nevin]

if you want rechargeable, just get rechargeable AA batteries.
- AA batteries are 1.5v each, rechargeable batteries in the same form factor are 1.2v each (which both should be acceptable with the hybrid S)
- normal "running voltage of a lipo is 3.7v. they come off the charger at 4.2, and you usually don't want to drain them below 3.5v

what's the gain of switching it to lipo?
- you'd have to do a couple things other than change the voltage.
- you'd have to have a low battery cutoff & a charging circuit.
- lipos have a lot more charging/discharging/care requirements than other battery chemistries.

if you really want to do this, and do it safely, i would get hasu's alt hhkb controller. it's made to use a lipo.
https://geekhack.org/index.php?topic=71517.0

[babytexx]

The reason is this is a Heavy Grail, which doesn't have room for the AA batteries. I've done plenty of battery projects like this (as well as much bigger), so I'm not too concerned about safety.