Can I return Xmas lights as faulty because they need fresh batteries every other day?

[BruceAndNosh]

I've had outdoor string lights round bushes at front of the house at Christmas for a few years. Battery operated and they last over 2 weeks before I need to put new fully charged batteries in them. These are 6 hour ones on a timer.
This year I bought some extra sets - stars for garage doors and starbursts for front window - and they are dim after two evenings of 6 hours on.

Would you think I can return them as faulty /not fit for purpose?
I've got a new battery charger with indicator light on it, so I'm sure I'm not putting duff batteries in them.
All three sets of lights are from same shop

Rechargable batteries don't last for ever. Maybe try some new ones first?

I did get 2 packs of new rechargeable batteries but I haven't a clue which set of lights they ended up in!

Try ordinary batteries in one string of lights and see if they last longer. I have found that rechargables aren't always as good.

I have also bought outdoor items that state in the instructions not to use rechargables. Might be worth checking that too.

If you actually want to keep them that is. It sounds as if you aren't able to work it out for yourself though.