Dual Battery Input Needed

[Rhardy]

Need some thoughts and input please. I currently have a 14’ jon boat running trolling motor only. I thought about a gas outboard but honestly the prices are holding me back. The last thing I want is to be out and have the battery give out on me before getting back. Really not interested in having to paddle my way back. 
 

What I am thinking is getting a second battery. I currently have a group 29 and considering buying a group 24. My thought is to head out using the group 24 and when it starts to get low switch to the 29 knowing I have to head back in for the day. 
 

Has anyone done something similar or have a reliable way to make sure to keep enough battery to get back? TIA.

 

Rex

[detroit1]

I have an outboard that sometimes doesn't work, so i carry a second t/m battery in case i need it. The lakes i fish are under 1000 acres, so i can always make it back to the ramp.  

[Scott F]

If you use two of the same size battery, in parallel, positive to positive, negative to negative, you will get twice as much run time without having to rewire your set up every time. 

[GaryH]

10 hours ago, Rhardy said:

Need some thoughts and input please. I currently have a 14’ jon boat running trolling motor only. I thought about a gas outboard but honestly the prices are holding me back. The last thing I want is to be out and have the battery give out on me before getting back. Really not interested in having to paddle my way back. 
 

What I am thinking is getting a second battery. I currently have a group 29 and considering buying a group 24. My thought is to head out using the group 24 and when it starts to get low switch to the 29 knowing I have to head back in for the day. 
 

Has anyone done something similar or have a reliable way to make sure to keep enough battery to get back? TIA.

 

Rex

If your going to buy a second battery and have it in your boat set it up in parallel so your not playing with it while out on the water. If finances allow buy 2 new batteries so there’s no issue with the older one draining the new one.

[Bankc]

Don't wire them together, in either series or parallel.  You can do this with two new batteries of the same type and size.  But you're mixing old and new batteries, and two different sizes of batteries.  The old battery draining the new battery will be a given.  But there's also a risk of one battery blowing up the other.  And you don't want a sudden explosion followed by being covered in hot, sulfuric acid while out on the water.  

 

What you can do instead, is hook up a switch to switch between the two batteries.  That way you don't have to rewire anything, but can just flip a switch.  It's okay to set up the switch so both of the negative terminals are connected all of the time.  So long as both of the positive terminals aren't connected at the same time as well, the circuit won't be able to drain from both batteries at once, which is what you want to avoid.  A simple SPDT switch, with the appropriate voltage and amperage rating (and probably a good idea to get a waterproof one in a waterproof container), connecting both of the positive terminals on the batteries to a single positive wire in your circuit will work.  

[WRB]

Before 24V DC trolling motors were available we used 2 ea 6V marine/golf cart deep cycle batteries in series. This doubled the amp hour run time. 

Today I would buy 1 new group 31 AGM marine trolling battery and use the older battery as a spare if needed. 

2 new group 29’s wired in parallel is more cost and weight but also doubles the amp hour run time.

Tom

PS, 50 amp marine Perko battery switch allows you to use 2 different size and age batteries separately.