replacement charger required?

Somebody else said that a DRAPER 18V CHARGER FOR 77604 also fits this model (but I haven't checked!); for sale at http://www.toolshopdirect.co.uk/item.php/site/froogle/sn/72865

I assume you mean the connector from the adaptor that goes into the charger:
I have a trimmer Challenge sh-18v400 and couldn't find a 23V adaptor either. In the end I decided to buy a 24V adaptor (lots of them available on eBay) and try it. This works fine for me.
Make sure that:
1. the adaptor is at least 400mA (I bought one that was 1A=1000mA)
2. you don't overcharge. My batterypack states 1200mAh which means that with 400mA it takes 3 hours; so I don't charge the batterypack for longer than 3 hours. Otherwise this will likely effect the charge the batterypack is able to hold and could cause an explosion.
I hope this works for you too.

Steppefox
October 2010