|Problem with HP 110+ / Portable Plus battery charging (+workaround)|
Message #1 Posted by John AS (UK) on 20 Apr 2010, 8:07 a.m.
I have a Portable Plus and have noticed the following problem with the way it charges the lead acid battery. Not sure if this is the same on other machines or just a fault with mine.
Problem occurred when the computer was left in a cupboard for several weeks and the battery voltage dropped very low, it would not then re-charge with the HP power unit, and the computer would not turn on.
Here's what I did to investigate & fix. I disconnected the battery from the computer, and it measured something like 2V (should be 6V or more). I then plugged the 8V AC power supply into the computer. The voltage across the computer leads for the battery measured 7.2V, and the computer would turn on. With the meter still connected to the computer I disconnected the power supply lead, the meter reading fell gradually to 0V. If the voltage fell below 10mV and I then connected the power supply, it would rise back to 7.2V again. If however I disconnected the supply, then when the voltage dropped to say 2V then reconnected the power supply, it would only go 2.3V and stay there. Obviously the computer would not turn on in this state.
So with a half-dead battery connected to the computer again, plugging in the power supply led to a charging voltage of only 2.3V so the computer would not turn on, and the battery did not get charged up.
I disconnected the battery and connected it to an external charger (I bought a trickle charger off eBay for 6V and 12V use, it was designed for motorbike batteries and cost about £8). Luckily the battery recovered and charged back up to 6V. I then reconnected the battery to the computer and it turned on, and when I connected the power supply the charge voltage is back to 7.2V.
The computer works fine and will work on battery power (I haven't tested it for many hours though!). The battery keeps enough charge to allow the computer to be turned off and put away for a day or so, but for long term storage I will remove the battery and recharge it from time to time.