A short while ago I gave a presentation on marne battery and charging systems to a group at a local marina. One item that we discussed was battery groups and sizes and to that end I compiled a chart of the sizes most common to marine applications. I have since been asked to post that information here.
Batteries Size Codes
Group 24 60-85AH 11X7X10” 50-55 lbs
Group 27 85-100AH 13X7X10” 60-65 lbs
Group 29 100-110AH 13X7X10” 65-70 lbs
Group 31 105-115AH 13X7X10” 70-75 lbs
4D 210-225AH 21X9X9” 135-140lbs
8-D 225-255AH 21X11X10” 160-175 lbs
6 Volt GC 200-240AH 10X7X11.5” 60-70 lbs
I would like to add that this information is averaged and that may be accurate to within about 6mm (1/4″) or so on size and that the capacity may be more or less 10%.
Battery size codes Eg: Group 27, 4D etc. refer to the physical size of the battery only and it is not indicitive of the capacity.
You will also note that Groups 29-31 are all listed at the same size. Again some may be slight larger and some slightly smaller.
At the bottom the 6 volt battery is labelled GC. This stands for Golf Cart and being 6 volt, 2 batteries must be wired together in series in order to produce the 12 volts that is commonly required for marine applications. When you compare a 6 volt battery’s space requirements as apposed to their current capacity the advantage becomes very clear. Another note about 6 volt batteries, that is if you’re considering going this route is that while they have a slightly smaller size foot print and they are taller than their 12 volt counterparts and this needs to be considered in the planning.