no charger for 3.7v li-on powered oscilloscope

[Bwad]

Hi i have a hand held oscilloscope but lost the charger.:D

I have opened it up and its a small 3.7v li-on battery inside. It is a fairly small female plug on the oscilloscope.
I would like to know what charger voltage it should get as im thinking of chaging the socket and maybe finding a laptop charger or something like for the job.:confused:
Any ideas would be good.:D

[McSteel]

That would depend on the charging circuitry. If the SoC (state-of-charge) and C/D (charge disruptor) are located in the charger itself (sometimes it's done to help with size/complexity reduction of the battery-powered device), then you have a real problem. If, however, the charger is simply a power supply, and nothing more, you could use a 5V DC adapter, or even cook up a USB-charging setup. Bear in mind that the absolute limit for a typical (3.7V) Li-ion battery are 4.2V (inter-cell voltage, not necessarily output voltage) and 1.5A charge current.

In order to strike a balance between maintaining capacity and at the same time keeping longevity of the battery, it's probably best to charge at 4V flat, and around 1.2A. First the battery needs the full amps until the cell(s) reach ~95% of the max voltage (4V in this example), then you charge it with constant voltage until the current drops to around 3% of the max (which is 1,2A in this example).

Most chargers stick to charging to/at 4.2V and 1500 mA. USB chargers, if using a single port for charging, naturally charge at less than that, since USB only provides up to 500 mA per port. Seeing how the max charging energy is 6.3W, and a USB port only gives out up to 2.5W, we arrive at around 600 mA charge current for the 4.2V case, assuming the charge circuitry is lossless (which it isn't).

A photo of the insides around the battery compartment and around the DC input jack could potentially help...