a4988 adjusting current

Hello,

So I have a 28byj-48 (5 volts) stepper motor converted to bipolar with this guide

http://www.electronicsmayhem.com/?p=13

1. After converting to bipolar am I right to use 10-12v dc ?
2. How I can calculate the current to adjust on A4988 driver ?

Here is the 28byj-48 unipolar characteristics

Model : 28BYJ-48
Rated voltage : 5VDC
Number of Phase : 4
Speed Variation Ratio : 1/64
Stride Angle : 5.625° /64
Frequency : 100Hz
DC resistance : 50Ω±7%(25℃)
Idle In-traction Frequency : > 600Hz
Idle Out-traction Frequency : > 1000Hz
In-traction Torque >34.3mN.m(120Hz)
Self-positioning Torque >34.3mN.m
Friction torque : 600-1200 gf.cm
Pull in torque : 300 gf.cm
Insulated resistance >10MΩ(500V)
Insulated electricity power :600VAC/1mA/1s
Insulation grade :A
Rise in Temperature <40K(120Hz)
Noise <35dB(120Hz,No load,10cm)

Thank you

Actually ~7V (5 x sqrt(2)), since the power dissipation is the limiting factor normally, so V^2/R should remain the same
and you've doubled R. Note that will give sqrt(2) times more torque.

Measure the original current, divide by sqrt(2)...