One or two people on other forums have been recommending li-ion batteries,so I thought I would give one a try.
First problem not all chinese ebay sellers will ship to France,but I did find one seller who would ship to France and he supplied me with a 12v 9800mAh.
As per recommendations I taped up the supply male plug and just use the charging socket for supply and recharging.
The battery was charged when it arrived(12vs) so I attached it to a Aristocraft lil-critter with a trail truck to carry the battery.
Having no speed controller fitted and the speed of the critter being a tad quick for my liking,I also attached seven tank cars.