bait tank battery

[tateman]

would the cranking battery be best? after fishing all day and not so much running up the lake my tank pulls the cranking battery down pretty bad? thought about putting it over on the trolling motor batteries but not sure being that I have a 36 volt trolling motor, how it would do if I depleted one more than the other two? just not wanting to carry 5 batteries on the boat. how is everybody else connected, do y'all leave the tank running all day?

[striperseeker]

You could run it off the three trolling motor batteries at the same time by going positive to positive to positive and negative to negative to negative. It would hold the voltage the same but up your amps. It would take equal amounts of electricity out of each of the three trolling motor batteries. Given that they are deep cycle batteries, it would hardly effect them at all. Just be sure to use some fuses in the circuit.

[mwardncsu]

Striperseeker - are you suggesting having the three TM batteries connected both in series AND in parallel - pulling the TM off the series connection (+ to - to + to - to + to TM) and the bait tank connected off the TM batteries connected in parallel?

I'm trying to get my head around this and in drawing it out, I'm not so sure..... I should be able to get my head around this having started off college as a EE, but I guess the years in sales and marketing have taken hold and I'm just not sure about the voltage differentials that get setup in that configuration once both loads (TM and pump) are connected. It may be OK, just never seen a setup in parallel AND series with loads being pulled off each way.

Some folks will hook up a load to one 12V battery when connected in series, but Tateman this is not good practice as it will pull one battery down more than the others.

What size cranking battery do you have now? I have a Grp 26 that I used to run all the electronics and tank off of, but last year I put in a dedicated "house" battery - a Grp 29 (would have gone 31 but could not fit it) that powers all electronics and the tank pump. If you have a light electronics load, then you might just consider a dedicated deep cycle battery for the pump - could probably do a Grp 26 as the 500 gph Rule only pull about 3 amps. Always better to have constant loads on a deep cycle as you can discharge them further and they will bounce back - discharge a cranking batter too far and its toast..... they are meant for large current supply in short burst - not long, sustained draw.

[striperseeker]

Hi Mward!!!

I just drew it out. You are right it will not work. Now of course, if you did not use the batteries for the trolling motor and just used them to run the bait tank it would be OK.
I wonder if you put a diode in the circuit, only allowing the electricity to leave the batteries it would work. I just don't know enough about diodes. I just drew that out and that will not work either since the series will increase the voltage through the batteries.

So its your way of the highway.

[mwardncsu]

I was thinking the same re: the diodes - but they would have to be pretty heavy duty diodes to handle the 100+ amp draw from the TM, and then by the time you fuse it properly and such you'd be better off just buying a dedicated deep cycle batt for the bait tank.....

I will say that before all my electronics and tank pulled off my Grp 26 cranking battery and there were a few times when after fishing a long morning in one spot and we went to move the motor would not turn over and I had to switch over to the 2nd / backup cranking battery. Now that I've rewired, I have one dedicated cranking battery with nothing on it but the backup power for the bilge pump, and then a dedicated Grp 29 deep cycle for all the electronics and bait tank and I've not had an issue yet.... fished some long days without issue, but I do have the batteries wired up in a manner with a switch so that if needed I can connect the batts and fire up and get home.

[striperseeker]

I was having the same issue but my solution was to buy a much bigger cranking battery. So far the excess capacity of the battery has solved the problem. But I do like the solution of a separate battery. It is such a nice clean simple solution. A small battery would do.

Yes the diodes would cost a fortune. But you still have the problem that the voltage running across the plates inside of the batteries goes up when you connect them in series. Maybe a combination of diodes with transformers (to bring the charge across the plates back to twelve volts) could make it work. Of course, by the time you buy all of that you could afford another boat to follow you around with a battery in it to run the bait tank. ;D

[mwardncsu]

K.I.S.S - buy a bigger, or separate battery ;D

[tateman]

thanks, for the advice, separate battery it is

[CorneliaGale]

For my 2 cents worth, the starting battery needs to be separate, you don't want to take a chance on having it low when something goes wrong and you need to start up and get out of the way. I always have my lights and bait tanks, electronics on a different battery. Towed in a bunch of boats in the morning that had been out there all night because they drained the starting motor battery where it would not start the boat.

[mytoyzfishing]

Seprate battery. My setup is as such- Cranking battery for the outboard, lighting, and main FF.
2 batteries dedicated to the TM. A battery that strickly runs my bait tank and a small FF up front that I only use for looking for bait. I have run my 50gal tank 24+ hours on the dedicated battery without issue and still going stong. I think most of the rule pumps that gets used in the bait tanks draw 5 ah

[leeb]

you can not run a parallel and series circuit with the same batteries unless you like to see the magic black smoke.

You can run three batteries in series for 36v and three pumps, one on each battery. This will give you three separate 12v circuits to pull the batteries down evenly.

I would recommend just running 5 batteries. You could also look at finding a battery with a larger reserve capacity that still meets your cranking amp requirements.