Thanks, I was wondering if lithium might be the answer. Are there genetic chargers that won't break the v wobbly bank?Looking at the datasheet, the original batteries are ~6kg.
If you were to swap them for some LiFePo 20Ah, some preliminary searching puts the weight between 2.3 and 3kg, and can be had for around £95 each, without any real hit on performance.
If you can point me towards the LiFePo battery that's be v helpful.