Today I want to share my experience in repairing the Li-Pol smart battery in my HP iPAQ 1930. See my previous post on it.. My battery was marked with HP H1910 string on its paper box. The problem with it is if you'll leave device without even a single charge cycle for several weeks, it will discharge to a level from which it is impossible to initiate further recharging. If nominal voltage is 3.7 Volts, and you have allowed to discharge to about 3 V, this is the situation considered. A small piece of electronics, consisting of charge controller IC (integrated circuit), and a couple of power field (MOSFET) transistor keys, is placed between actual Li-Ion (or Li-Pol) battery and the outer contacts. Charge controller IC monitors voltage levels at the battery itself and outer contacts, opens necessary power key transistors, and communicate with host device via SMBus or other protocol to allow it to know state of the battery. Problem with discharging of a battery below certain level is that this controller IC stops working, so it is impossible to recharge the battery, since power key transistor have become permanently closed. But in many cases it is still possible to reanimate the smart battery.
To do this, cut off small pieces of plastic from both sides of the battery, to open access to the inner contacts of Li-Ion (Li-Pol) battery. You should see and have access to two metal stripes after this operation. Get laboratory DC power supply unit, with both constant current and constant voltage, modes of operating. I use SHENZHEN MASTECH HY3005D-3. Constant current mode is indicated by "C.C." red round LED at the front panel, while constant voltage -- by the nearby LED named "C.V.". My battery has capacity of 950mAh. The usual current for charging Li-Ion batteries is calculated as capacity x 0.2 (in the appropriate units, in my case, it would be 950 x 0.2 = 190 mA). Since we want to bypass control electronics, and will not monitor temperature of the battery, it would be safer to decrease this value, I think, two times will be enough, so I assumed charge current of 100 mA. I shortened outputs of one channel of SHENZHEN MASTECH HY3005D-3 power supply unit, and set short-circuit output current to this level. (Be aware also that maximum allowable current that USB port should be capable of providing by its spec, is 500mA. So if your device is charged through USB, do not exceed this value under any conditions. Even safer would be to use half of that value, that is, about 250 mA, as an upper threshold for charging current.) Then I set output voltage to nominal voltage of the battery, 3.7Volts in my case. After this, I connected output of power supply to inner batteries contacts. Initial current will be 100 mA, equal to short-circuit, and "Constant Current" LED should be active. During a few hours, the battery will be charging, after which voltage should rise to its nominal value (3.7 Volts in my case), current drops to near zero, and power supply switch to "Constant Voltage" mode. That's it. Now you can power off power supply, disconnected wires from battery, place it into your handheld device, and continue using it, without having to buy a new battery.
WARNING 1: Do not try to repeat the process without power supply with both "Constant Current" and "Constant Voltage" output mode, and without proper and carefully checked set-up values.
WARNING 2: Li-Ion batteries might fire and explode. It is safer to put the battery into the metal or other solid case during the process to avoid possible harmful accidents.
