I did get one of the Jaycar / Silicon_Chip kits a while back but wasn't that impressed with it.
I had better results using an ARC welder to zap a NICAD
pack in a cordless drill. That didn't cost anything and worked brilliantly.
Save your money and put it towards a gell-cell lead acid battery, like the Optima batteries, or the new lithium batteries, like this http://www.evworks.com.au/index.php?product=BAT-LP12V60AH
. Make sure it is the Lithium Ferous
Polymer (LiFePO), which don't burst into flames when abused and can be dropped straight in to replace a lead-acid provided you don't charge over the set voltage and don't let the voltage discharge below 3V per cell.
Then again doing that to a lead-acid battery will also cause damage, just not as bad.