Sorry mate - misread the text and didn't see you referring to type 038 batteries
, my earlier reply refers to type 063 car batteries.
I have used type 038's previously and found you get about 5 miles from each of them. They are ideal for those that want to keep the original keyswitch assembly but don't have as good a range as a type 063.
The type 015 is a similar size and also accepts the Sinclair battery top, but is more powerful than a type 038. Hope this helps.