There are numerous web sites which explain these batteries can fall into a sleep mode if left uncharged, but can be revived. However, lithium batteries are made with very reactive materials and if mishandled can explode and burn vigorously, emitting toxic gas. So I was reluctant to try charging the battery with other than the supplied charger. Ryobi Corded Leaf Blower & Vacuum, at Salvos Stores Leichhardt, for $50, which the couple were very happy with. But I thought I might as well get the cordless unit to work.
To provide the 40 volts needed to charge the battery, I connected three computer power supplies in series. The Ryobi batteries are sold in Australia as being 36 Volt, but in North America as 40 Volt. The supplies could produce a maximum of 1 Amp, thus limiting the power to the battery.voltmeter. I connected these to the 40 volt power supply, but read only a few microamps charge. There are two other terminals on the battery marked T1 and T2, which I assumed were for temperature monitoring. When I checked with the voltmeter between the + and one of the T terminals, the current suddenly jumped to 700 mA for a few seconds, then dropped to zero, then jumped again, while the lowest of the charge indicator lights on the battery flashed. After a half an hour the battery had enough charge to work in the regular charger.
I dropped the unit off at the Bower Reuse and Repair Centre,. I noticed they had a few other blowers and leaf mulchers second hand as well.
Please note that this is not an repair recommended for the inexperienced. Do not leave the battery charging unattended.