Batteries

My fishfinder says i should use a 12v battery.I have a battery from my bigger boat that says it's a group 24m marine battery 625 cranking amps .My question is does 24m group meen it is a 24 volt battery or is it just a good 12v battery .Thanks again for any help this site is fantastic.

it is a standard 12 volt battery.the group 24 is the size of the battery.the "m" stands for marine

Battery Size Codes
Batteries come in all different sizes. Many have "group" sizes, which is based upon the physical size and terminal placement. It is NOT a measure of battery capacity. Typical BCI codes are group U1, 24, 27, and 31. Industrial batteries are usually designated by a part number such as "FS" for floor sweeper, or "GC" for golf cart. Many batteries follow no particular code, and are just manufacturers part numbers. Other standard size codes are 4D & 8D, large industrial batteries, commonly used in solar electric systems.

Some common battery size codes used are: (ratings are approximate)
U1 34 to 40 Amp hours 12 volts
Group 24 70-85 Amp hours 12 volts
Group 27 85-105 Amp hours 12 volts
Group 31 95-125 Amp hours 12 volts
4-D 180-215 Amp hours 12 volts
8-D 225-255 Amp hours 12 volts
Golf Cart & T-105 180 to 225 Amp hours 6 volts
L-16, L16HC etc. 340 to 415 Amp hours 6 volts

here is a link to learn more about batteries


http://www.windsun.com/Batteries/Battery_FAQ.htm#Battery%20Size%20Codes