So I need to replace some batteries in my dozer, and was wondering what the advantage is of the big battery. By big I mean physical size not cranking amps. Because the ones I was looking at are about the same price and the same cca. Does the bigger battery just not run down so fast if you have to crank on it for vey long. Hope I explained my question good enough.
Don't look at size IMO. Look at Amp-hour capacity and cold cranking amps (CCA) based on the actual size & specification of your original battery. You can go higher on capacity and CCA within the same size of battery. The downside of going physically larger, even if the battery box will accept the larger batteries, is nobody ever seems to modify the hold-downs so as a result the batteries bang around the box and so don't last 5 minutes. This is especially true of a dozer application. Buy good quality batteries - "buy cheap, buy twice" is especially true of batteries. Large physical size batteries have more reserve capacity to run an electrical system (not necessarily the starter motor) for longer if the charging source disappears. Take a 4D-size battery for example. For the same physical size (525mm x 275mm x 250mm) you can get a range of capacities from 140 to 210 amp-hours, and CCA from 1000 to 1500. If you're starting a lot in really cold conditions I'd suggest going up in both capacity & CCA from your original.