Changing My Battery Set Up

[plenty of fish]

Okay I am going to make the change. Take the bad 8D out of the starter position and replace it with the good 8D house battery. Then I will replace the house bank with 4 6v golf cart batteries. In my area Sam's is giving me the best price. Here are the specks on the batteries:

20 amp hour rate:215
5 amp hour rate:157
6 amp hour rate:156
Battery Electrolyte Composition:Acid
Battery End Type:Top Post
Battery Purposeeep Cycle
BCI Group Size:GC2
Contents:ONE EACH
Freight Class:65
Minutes at 25 amps:395
Minutes at 75 amps:105
Terminal TypeIN
Volts:6

With these hooked up as two twelve volt batteries and wired together to make one large twelve volt battery and my max draw is 6.5 amps, how long should I be able to go before I need to charge the batteries?

 

[alldodge]

Try this out
Google battery amp hour calculation. Then select the link at Battery Stuff

 

[Silvertip]

The wise man charges batteries immediately after use. Doesn't matter how long they've been used.

 

[jhebert]

...Here are the specks [sic] on the batteries...6 amp hour rate:156 [Ampere-hours]

With these hooked up as two twelve volt batteries and wired together to make one large twelve volt battery and my max draw is 6.5 amps, how long should I be able to go before I need to charge the batteries?

If you have four 6-Volt batteries of 156-Ampere-hour rating (at a 6-Ampere drain), and you connect them in a series-parallel arrangement to create a 12-Volt battery bank, the Ampere-hour rating of the 12-Volt battery bank will be 2 x 156-Ampere-hour or 312-Ampere hours (for a 6-Ampere discharge rate). On that basis, if you begin with all batteries at completely full charge, and drain all batteries to complete discharge, you should be able to sustain your 6.5-Ampere load for approximately 315/6.5 = 48-hours.

If you want your investment in all those batteries to produce good service life, you should avoid such deep discharging of the battery bank. In particular, with batteries wired in series and parallel it will be difficult to have all four batteries discharge at precisely the same rate, so you are likely to drain one of the batteries in the bank to complete discharge before the others. Very deep discharge of batteries to complete loss of charge causes a reduction in their service life.