4 batteries 3 bank charger

So I am wondering what I should hook my 3rd bank To. I have a 24v setup so 2 banks are used there but I'm wondering if I should hook up to my deep cycle that runs graphs and electronics or if I should hook it up to my starting/auto bilge battery.i hear people say you can run everything as far as electronics go off of just your starting battery but my graphs seem to zap juice fast! What would you guys do?

I would say hook it to the battery that has no way of charging itself.

Tough situation. I run my electronics off the starting battery. Depending on how many start/stop episodes you have in a day, it is possible to run down your starting battery. Also, your dedicated electronics battery has no way to charge if you don't charge it.

In your current set up, you need a 4 bank charger. I would set it up to your TM and starting battery and get a separate single charger for your electronics battery so that you can have all 4 on a charger.

This way if you decide at some point to pull the extra battery, you won't have to rerun any battery wires.

Just buy a cheap battery tender type charger and hook it up to whatever battery is not connected to your 3 bank charger.

Great into guys, just to answer a couple of suggestions I have a stand alone charger that I use for my electronics battery right now and I run the boat a decent amount but not enough to put my electronics on without having it in the back of my mind. When I'm running autochart my batteries seem to give up on me about 8 hrs in. I guess my real question is do I have to worry as much about my starting battery since it charges itself. My gauge tells me it's full after being on the charger for like 5 minutes so I feel as if I'm wasting a bank.

You can parallel the starting battery and electronics battery to one bank of the charger, just remember two things....

1. It takes longer to fully charge both batteries when they share a bank
2. Remember to un-parallel the batteries after charging.

Or you could run two of the batteries in parallel. You'll have the same voltage but more capacity and then you could connect that charger to charge the two batteries as if they were one. I run 4 batteries, 2 for trolling motor, one for the starter and one for electronics for the same reason as you. Last week, I ran two of the batteries in parallel to test and see if their capacity was large enough to keep everything going and this way every time that I run the motor I will be putting a charge in both.

Now, I have 2 two bank chargers in the boat so I charge all separately but yours should just take a little longer to recharge if they are low. I was warned against it by someone because of the possibility of one battery going bad but if that happens, I can always disconnect them on the water and connect only the good battery.

Theoretically, your cranking battery should be charged and can get by without charging it every trip BUT, do you have anything that might draw current while it is stored? What if you accidentally bump a switch and turn something on while it is stored and you don't find out until you are at the lake? Could ruin a day of fishing.

Steez, I saw you answered while I was typing. Why does he need to un-parallel after charging?

The above is a viable option.

Here's what I installed,I have one battery for starting and one for the electronics,
https://smile.amazon.com/gp/product/B000RZNP5K/ref=oh_aui_detailpage_o00_s00?ie=UTF8&th=1

Using this the starting battery charges first and when fully charged the electronics battery is charged. You can combine both batteries in the event you need a boost. As I understand hooking them in parallel both batteries will discharge at the same rate and charge at the same rate...so if you discharge them below what is needed to start the motor both will be dead. It should take longer to discharge them, but it will also take longer to charge them using a single bank or charger with them hooked in parallel and if one battery is weak it will discharge the other...so there are some draw backs in hooking them in parallel .

Not Steez, but they should be disconnected in some type way -- my preference is with a battery selector switch. If connected, the lower of the two (they will not be at the same rate of charge) will become a load on the fully charged battery and draw it down trying to equalize. If one goes bad, it will drain the other as a load. If separated, then a bad or low battery will not drain the other.
John