The Skyrc Mc3000 can do that. You can select the termination voltage. I have one program set to terminate at 3.8V for storage… Or it will discharge to a certain voltage… again for storage 3.8V. It is not cheap, but it offers lots of flexibility. I have lots of other chargers, but I don’t remember any others that allow adjustment of the termination voltage. That feature would be nice in something at ~$50.
It’s not 4V like you asked… but If you’ve a charger that does LiFePO4 cells, that setting can be used for a termination voltage of ~3.6V.
Edit: I remembered there was a post somewhere on here about someone changing the termination voltage one of those li-ion charging chips by changing a resistor… I can’t find it now, if anyone knows what the mod was, I’d be interested, I’ve some unused chips and 18650 holders, could be a nice project to make a standalone, cheap, 4v charger.
If it makes it any easier to take, mine is over 12 years old. I use it pretty much everyday.
If you amortize the ~$100 over 12 years (about $8.33 per year), it is not that bad . Do I sound like an appliance salesman ??
Most no name Chinese brands will not give you this kind of longevity. I have been through multiple chargers.
That said i am a fan of paying for quality but you can’t know if you will get quality or money down the drain. Thus i assume any Chinese brand is sunk cost as soon as its spent.