My friend at work found these nice looking LiFePO4 batteries that could serve as starter batteries.
They are much much cheaper than the 30Ah battery I bought around 3 years ago and paid for around £850.
The 30Ah models from this company are only $280.
The tricky part is going to be how to import them, is there a ban on shipping lithium batteries?
https://www.bioennopower.com/collect...tteries?page=2