Hi Bo,
I have used Lipos from Joen in Denmark. The oldest pack is now 4 years old and have about 200 cycles and still working fine. (Have not used them this season because of no time for flying). A 4600 pack is about 480 gram and with shornting the cable you might reduce the weight with about 10 grams or more.
Here is a link to his shop:
https://hobby4u.dk/shop/17-elektronik/283-5s-/