Repeated Battery Failures - Causes?

I keep replacing top line batteries which last only 2 years. A Month ago I put a new battery in and today I had it tested and it already is rated Marginal.The battery is rated 670 CCA and now measures only 516 CCA.

I don not know how to interpret this. Does this mean that the battery is not being charged correctly or that the battery cannot hold the charge.

Any suggestions about how to proceed?

Thank you.

May be a weak alternator. Also may not be driving it enough to charge the battery. If you're only putting 1-2000 miles on it a year, the battery won't get charged enough.

I keep replacing top line batteries which last only 2 years. A Month ago I put a new battery in and today I had it tested and it already is rated Marginal.The battery is rated 670 CCA and now measures only 516 CCA.

I don not know how to interpret this. Does this mean that the battery is not being charged correctly or that the battery cannot hold the charge.

Any suggestions about how to proceed?

Thank you.

I use solar panel to keep batteries in peak condition, I get 2-3 years out of batteries and they are just junk batteries somebody trades in for new ones!
I also always run two batteries space permitting.