Hi I have a 2009 Mazda 3 sport 2.0, the battery terminal posts are too small and whoever fitted the battery has put split pins on the posts and put the straps over them to make it fit, also the power seems too low for the size of car it’s 40ah and 400cca and sometimes there is not enough power to turn the engine over, can somebody tell me the size of battery that is supposed to be fitted, also this is the main battery and not the I-stop battery.
thanks

 

Welcome to the forum
Um your post does not make normal logical sense regarding the terminals for a 12 volt vehicle battery.
Unless by some weird chance you end up with a agricultural machinery 12 volt battery????

As for what battery there are several battery suppliers that have the exact listing for your Mazda on their website. I suggest that you go to them for the information about the correct battery to get.
Once you get the correct battery installed and all the connection at the battery starter and ground are clean and secured if you are still having starting issue for low power, we can list a few things at that point that may need checking!

First get a new correct battery for your application.

To save time and trouble before you walk out of the store with your new battery, or have it installed request that it be first load tested. DO NOT take the word from the salesperson or service "mechanic" that it is a new battery and is charged and ready to go. HAVE IT LOAD TESTED!!!!