Need more battery power for TM

[Tatsu Dave]

Use a 45lb thrust foot controlled minn kota wired straight to a 27 group deep cycle battery. It has always worked great and charge lasted for a fishing trip 6 hours, bought a weedless prop to replace the standard power prop. It is larger and heavier than the original but works great in the weeds. Problem is turning a larger prop seems to take more battery and it goes out on us after 3-4 hours of intermitent use. Should I get a bigger series 12 volt battery, or should I hook a second 24 group battery in and run two? We use standard deep cycles from Walmart, what am I looking for more amps? Thanks Dave

[Jig Man]

You need more reserve capacity.  If you have room a 31 series normally has the highest RC.

[MN Fisher]

I would get a second Group 27 to match the one you already have and wire them parallel. When parallel hooking two batteries, it's best to make them 'twins' - exact same.

[GaryH]

I would go with a 31. If you decide to go with a 27 then you should definitely buy 2. Hooking up a new battery in parallel with a older one is never a good idea.
 

[WRB]

If you are only running the TM, no sonar or OB starting, then reserve power is useless. You want a deep cycle marine battery group 31, if you have space, not a dual purpose cranking/ TM battery. 

Always keep your batteries the same age and size if wired in parallel or series.

Tom

[Jig Man]

1 hour ago, WRB said:

If you are only running the TM, no sonar or OB starting, then reserve power is useless. You want a deep cycle marine battery group 31, if you have space, not a dual purpose cranking/ TM battery. 

Always keep your batteries the same age and size if wired in parallel or series.

Tom

What do you mean by reserve power?  I’ve never heard of that.

[MN Fisher]

1 minute ago, Jig Man said:

What do you mean by reserve power?  I’ve never heard of that.

A starting or dual-purpose battery is rated in minutes of reserve. This is for a 25amp draw...so if your TM draws 50amps, divide the reserve time in half.

 

Note this is for fully charged battery.

[Tatsu Dave]

Thank you all for the info...........understand a bit better now, have to get 2 batteries and hook them together. I only run the troller w/front battery which has a circuit breaker inline as well. Back battery starts motor and runs depth finder, also charges off motor when running. Again thanks to all responding poster's.  Dave

[Jig Man]

12 hours ago, MN Fisher said:

A starting or dual-purpose battery is rated in minutes of reserve. This is for a 25amp draw...so if your TM draws 50amps, divide the reserve time in half.

 

Note this is for fully charged battery.

That is reserve capacity, isn’t it.

[WRB]

The reserve is reserved capacity to use a cranking power.

A TM Deep cycle battery doesn’t save reserve capacity it’s designed to drain down power fully and be recharged multiple times when drained down. 

Tom

[Way2slow]

If he's looking to go from three - four hours back to his original six hours, that's close to a 100% increase.  There is not a group 31 on this planet that's going to be double the capacity of a good group 27, at the most maybe 10 - 15%.  For that kind of an increase, a two battery setup is about his only practical choice.

Now, it might pay to have the group 27 tested to make it's reaching it's full capacity.  Of course, then you have to find someone that has enough smarts to do that.  I have very little faith in most understanding enough about testing one to do that.

 

One note.  Reserve minutes/capacity has nothing to do with cranking.  It's strictly based on how many minutes the battery will last with the current used to test it (usually 25 amps by most) before it's at a level considered fully discharged.  The Trojan ssc225, about the best flooded cell deep cycle battery there is gets its name from the fact is has 225 minutes reserved capacity.

[Tatsu Dave]

15 minutes ago, Way2slow said:

Now, it might pay to have the group 27 tested to make it's reaching it's full capacity.  Of course, then you have to find someone that has enough smarts to do that.  I have very little faith in most understanding enough about testing one to do that.

This was the problem, the battery had a bad cell and wasn't taking a full charge. Bought a new one and removed and replaced, will find out tomorrow if things are back to normal or If I need to get another and hook them together. Even two will not be that bad $ wise, it's a small alum. boat and another can replace the back battery, than hook the two together. I want the run time and will do whatever it takes to accomplish this. Thanks to all who took the time to answer....I should have had it tested right off but never considered that possibility.   Dave

[WRB]

Used Trojan SSC 225’s for deep cycle marine use for years, best wet cell battery available. The problem is maintenance with wet cells, I used a watering system that helped.

There are a few high end AGM’s that are worth the extra $$, NorthStar is good. I had VMax Tank MR137-120 in my last boat over 10 years, very good AGM for the cost.

My guess is the OP battery is tired. Gr 31 vs 27 will provide extra run time but not all are batteries equal is size, weight or performance.

Reserve is rated at 25 amps in minutes. 

Not a fan of running TM batteries in front of the drivers seat, should be located behind.

Have the battery tested.

Tom

 

 

 

[Tatsu Dave]

They did test it and said had a bad cell. It was four years old and I replaced it. Will take out tomorrow and test to see if I'm back in business with new one.