Dual-Purpose Battery recommendations?

[dtag31]

Hi All, 

I am completely overwhelmed with options and would appreciate some advice. Looking for a dual purpose that will start my 20hp motor and push my 55# Motorguide X3 for an 8 hour day of fishing. Electronics are run on a different battery. 

 

I rather spend $300-400 and have a strong battery for the next few years than $150 and have issues next year (that's what happened to me now). 

 

Thoughts? I know lithium is out of the question at that price range, what about AGM? I thought Optima blue top was the gold standard, but I only saw 75Ah for a group 31 which seems extremely low? I do a lot of off-shore structure fishing in 10+mph wind, so there are lots of times I am working the trolling motor to stay on a spot, I call it manual spot lock  

https://www.optimabatteries.com/products/bluetop-d31m

 

Thanks!

[TnRiver46]

I’d spend $79.99 and not have any issues 

[Jig Man]

First trolling motor and engine on the same battery is not the best  option.  Trolling motor on one battery and engine and electronics on the other one is a better option.

 

If you have a Sams club in your area,  they have some good group 31 agm batteries.  There are a lot of better choices than Optima.  Reserve capacity is what keeps your trolling motor going.

[GaryH]

3 hours ago, dtag31 said:

Hi All, 

I am completely overwhelmed with options and would appreciate some advice. Looking for a dual purpose that will start my 20hp motor and push my 55# Motorguide X3 for an 8 hour day of fishing. Electronics are run on a different battery. 

 

I rather spend $300-400 and have a strong battery for the next few years than $150 and have issues next year (that's what happened to me now). 

 

Thoughts? I know lithium is out of the question at that price range, what about AGM? I thought Optima blue top was the gold standard, but I only saw 75Ah for a group 31 which seems extremely low? I do a lot of off-shore structure fishing in 10+mph wind, so there are lots of times I am working the trolling motor to stay on a spot, I call it manual spot lock  

https://www.optimabatteries.com/products/bluetop-d31m

 

Thanks!

What is the battery that your using for your electronics? If it’s a good dual purpose Or cranking battery I would use that for your motor and electronics and purchase a deep cycle for the TM. A decent cracking battery will last all day for your electronics and still start your outboard.

2 minutes ago, Jig Man said:

First trolling motor and engine on the same battery is not the best  option.  Trolling motor on one battery and engine and electronics on the other one is a better option.

 

If you have a Sams club in your area,  they have some good group 31 agm batteries.  There are a lot of better choices than Optima.  Reserve capacity is what keeps your trolling motor going.

You type faster than me. ?

[WRB]

Recommend your use a marine cranking battery for your electronics and starting the engine. Your TM should have Gr 31 for the TM battery so voltage change as it draws down doesn’t affect the electronics. 20hp engine isn’t difficult to start manually if needed or doesn’t has a computer that affects starting. 

Dual purpose Optima 34M is a choice just not for me.

Tom

[Bankc]

It'll be cheaper in the long run to run two batteries.  Deep cycle batteries don't give up much cranking amps.  So even if they start off being able to start your engine, they probably won't keep that up for long.  And starter batteries don't like to be drained below around 80%.  So you'll drastically shorten the life of the battery by running a trolling motor off of it.  You can do both with the same battery, and they make batteries especially for that, but you'll likely get less than half their expected lifespan by doing so.  It has to do with their internal construction, and there's not really a way to make a single battery do both jobs well.  

 

So you'll get more service life from buying two $150 batteries (one starter and one deep cycle) than you will from buying one $400 battery to do both.  And you'll save $100 or so up front, plus another $400 down the line when that battery dies a premature death.     

[TnRiver46]

If you’re 20hp has a rip cord, one $75-80 dual purpose battery will be fine. It not, get two lead acid batteries for $150 instead of a single battery for $150. No reason on earth to have an expensive battery to start 20 horse engine