Trying to make sure I don't fry my electronics... I have a 4 battery system (3 trolling and 1 starter). We fished Media bass this weekend and right before weigh-in our starter battery was dead and we had to scramble to get it started. Luckily we got in for weigh-in but I don't want to get caught like this again. I took the starter battery in and had it tested and it loaded tested ok. Only thing I can figure is the graphs are wired to the starter battery and ran it down. Is this normal or do you run them to another battery in the trolling motor series? Is it ok to put the graphs and accessories on the trolling motor batteries even though they are wired in a 36 volt series? Thanks in advance.

Yes it is normal to run them on the cranking battery. Need to set the alarm on them to let you know if it is getting to low. I run 24v trolling, 12v cranking and another 12v that runs my electronics. You don't want your FF on your trolling motor battery or you will likely have interference issues. Sounds like you might need a larger capacity battery for the electronics

I will make sure to set alarms(didn't know that was a feature but I am sure our Lowrance graphs have it). Thanks.

After doing a lot of searching on the net I believe the issue we have revolves around our live wells running all day (paired with the graphs running all day) off the cranking battery and that is what is draining them... I don't know why that would be such a large draw but I guess after 8 hours it takes its toll. Hope that helps anyone in the future if they encounter the same problem.

Your problem is most likely in your cranking battery. I do the about the same (power poles, live wells, 3 hds gps/sonar units, box fan, lights, etc) all on the cranker.

Get a 1000 CCA or larger not mca or reserve capacity.

I just installed a dual circuit battery on/off switch just for auspicious occasions such as a dead starting battery. I have two batteries in the trlling battery back and I connect the pos & neg from the battery that supplies 12V to the starting battery so if it does go dead, I can flip a switch and have cranking voltage. I hope I won't need it, but it's there at any rate.

Depends on how much time the big engine is running to recharge it.

I put in a type 29 deep cycle with 114 amp-hour rating. The Amp Hour or is what you need for electronics.

With my 114Ah battery in theory I can run an 11.4 amp load for 10 hours. I do turn off the console graphs when I'm on the trolling motor to save battery.

"An ampere hour (abbreviated Ah, or sometimes amp hour) is the amount of energy charge in a battery that will allow one ampere of current to flow for one hour."

http://whatis.techtarget.com/definition/ampere-hour-Ah-or-amp-hour

This is a good theory, except that on cranking cycle, or trim cycle on the outboard can "kill" the theory.
To the OP, the outboard (I didn't catch the size) will have certain "minimum battery requirements". You will need to size the battery so that after a days drain from electronics, pumps, etc. it can still deliver that requirement. This is why a lot of guys run AGMs for the cranking. They deliver the power as if they are fully charged, right up to the point that they are fully discharged.
John

The best cranker I ever had was a Sears PM-1 AGM but they don't carry it anymore. So now I run an Optima.

It's a 115 Yammi. I can pretty much jump start it off two 9v batteries in parallel.

I had a blue top die on me half way through a tournament and lost my graphs and worried about the big motor starting when I changed over to the 29. I always carry a set of jumper cables but in this case I was fishing Texoma on the windy bank on a windy day and a bit of panic set when the graphs died and I was unsure of where the boulders were. I was running Humminbird 798si, 998si, 1199si, 360 and livewell pumps with bubbler...now adding a Ultex so I can spot lock and not have to work the trolling motor as much. Would have been handy when the graphs died...but then again would spot lock continue to work with the graphs down? In the future I will turn off the console 798 and 998 to conserve battery.

PABrokers,

Even if your cranking battery tested fine, it is possible that it has a greatly diminished capacity. It could still have lots of CCA to start your engine when charged, but not the capacity to run your equipment all day. The only way to find out is to actually test the capacity by fully charge the battery and then applying a load on it for several hours, then checking the voltage. Do the same on a known good battery for a baseline. The electronic tester that most places hook up the battery to tell you if the batter is "good" or "bad" cannot determine a battery's capacity with a simple conductance test.

Also take the battery off a charger and see what the voltage is 48 hours later.

http://www.mmbalmainauto.com.au/PDF/State_of_charge_12_volt_batteries.pdf

From the TFF everything you want to know about batteries...

http://texasfishingforum.com/forums/ubbthreads.php/topics/7275000/1/everything_you_want_to_know_ab