Ive had that happen to me before. Usually a rule of thumb is any time a battery gets below 50% of the full capacity is when to replace it. I got almost 8 years out of my original one, and I changed it when it made around 210 cca. Try checking the terminals to see if they are tight on the battery posts

 

300 CCA should be fine but you may have a parasitic current draw overnight. May as well inspect the cables at the battery and at the starter as mentioned above

 

Do you buy batteries from the dealer or after market ones?

 

I bought mine aftermarket from Canadian Tire. One thing I will tell you is most Hyundai batteries are “custom sized” I bought a group 121 battery and its smaller than the original. So the original battery heat shield is too big. Depending on price, if I had to buy another battery, Id get an original OEM battery, or upgrade to an AGM.

 

Some are, but at least on our car the OEM battery is bigger in terms of dimensions. I see youre from Canada too, if you go into Canadian Tire the product number of the one I have is 010-1210

It also has a larger capacity of 550cca vs the 410cca of the factory one. I've never had an issue with it, apart from my heatshield rattling under certain rpm. I think though that has more to do with my intake/exhaust noise over the engine