# Battery life without a charging system



## bikerider (Apr 19, 2019)

I have a deep cycle battery that runs my fish finder and trolling motor in a 12 ft semi v. I have a gas outboard that does not have a charging system. I am curious, for those that have a similar setup, how long do you get out of your battery?


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## JNG (Apr 19, 2019)

Are you referring to how long the battery will power your stuff before a recharge? If so what matters is the amp hour/reserve capacity in minutes capacity of your deep cycle. Fish finders generally don't draw enough amperage to matter. As a real rough general rule of thumb you can assume your trolling motor draws the same number of amps as the thrust rating at its highest speed setting if the trolling motor is 12 volts. This does not apply to 24 or 36 volt systems. For example a 36# thrust TM draws roughly 34 to 36 amps at its highest speed. A 55# thrust draws some 52 to 55 amps. Etc etc. This amp draw varies from model to model and from Motorguide to MinnKota. Remember this only applies to 12 volt motors. Then look up the specs for your battery. It may even say on the battery. If it says 105 amp hours and your motor is a 40# thrust model, divide 105 by 40. You get 2.625 hours at high speed setting before the battery is completely discharged. TMs use far less amps at lower speeds so you may need to think about how you use the TM before estimating total possible run time. Note, you should never run a battery all the way down as it shortens it's lifespan dramatically.


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## bikerider (Apr 19, 2019)

JNG said:


> Are you referring to how long the battery will power your stuff before a recharge? If so what matters is the amp hour/reserve capacity in minutes capacity of your deep cycle. Fish finders generally don't draw enough amperage to matter. As a real rough general rule of thumb you can assume your trolling motor draws the same number of amps as the thrust rating at its highest speed setting if the trolling motor is 12 volts. This does not apply to 24 or 36 volt systems. For example a 36# thrust TM draws roughly 34 to 36 amps at its highest speed. A 55# thrust draws some 52 to 55 amps. Etc etc. This amp draw varies from model to model and from Motorguide to MinnKota. Remember this only applies to 12 volt motors. Then look up the specs for your battery. It may even say on the battery. If it says 105 amp hours and your motor is a 40# thrust model, divide 105 by 40. You get 2.625 hours at high speed setting before the battery is completely discharged. TMs use far less amps at lower speeds so you may need to think about how you use the TM before estimating total possible run time. Note, you should never run a battery all the way down as it shortens it's lifespan dramatically.



Yes, that is what I was referring to. I guess I have some calculation to do. I have a 27 lb thrust minn kota 12v. In years past I would power the boat with just that motor. So it was me, my buddy and our gear with the battery being used by the minn kota and the fish finder. I could get between 2-3 hours out of it with us mostly fishing in different spots around the lake and a little bit of trolling, having the fish finder on the whole time. I wanted to go a bit faster and not have to rely on just battery power. That's why I added a gas outboard.


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## JNG (Apr 20, 2019)

So your TM would draw somewhere between 25 and 30 amps. Just go with 27 amps it will be close enough. If you post what your battery is I can look up the specs for you. For example Autozone 29dp-dl or Interstate srm-27. Sometimes the company selling the battery hides the amps hour info from consumers. I have access to battery info through my job that most folks don't have.


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## Scott F (Apr 20, 2019)

2-3 hours with a 27lb trolling motor tells me your battery was not charged or was going bad. I used to have a 55lb thrust motor with 2 depth finders on A 17 foot glass boat and could run all day and the battery wasn’t used up. The batteries usually last 4-5 years. What kind of charger are you using and how long did you charge your battery.


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## bikerider (Apr 20, 2019)

Scott F said:


> 2-3 hours with a 27lb trolling motor tells me your battery was not charged or was going bad. I used to have a 55lb thrust motor with 2 depth finders on A 17 foot glass boat and could run all day and the battery wasn’t used up. The batteries usually last 4-5 years. What kind of charger are you using and how long did you charge your battery.



I keep the trickle charger on it whenever it's not in use. It's been that way since I bought it, but it is a budget battery deep cycle so perhaps that's the problem. Come to think of it, my buddy had an old wondertroll trolling motor on a small boat and we never once ran his battery completely out.


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## JNG (Apr 20, 2019)

Ahhhhhh........

The ole trickle charger. They do NOT properly charge a deep cycle battery. Period. Buy a 12 volt charger that inputs 10-15 amps. It can be an automatic charger or a manual.


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## bikerider (Apr 20, 2019)

JNG said:


> Ahhhhhh........
> 
> The ole trickle charger. They do NOT properly charge a deep cycle battery. Period. Buy a 12 volt charger that inputs 10-15 amps. It can be an automatic charger or a manual.



That's news to me. I will put the regular charger on it today. Thanks for the tip.


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## gnappi (Apr 20, 2019)

JNG said:


> Ahhhhhh........
> 
> The ole trickle charger. They do NOT properly charge a deep cycle battery. Period. Buy a 12 volt charger that inputs 10-15 amps. It can be an automatic charger or a manual.



I guess it depends on the charger, and the battery technology because I've been using a two bank "Battery Tender" 1.25 Amp charger / maintainer for three years to charge and maintain my deep cycle AGM batteries without any issues. I recently went to a NoCo Genius Gen3 12A (4A per bank) because I got tired of juggling / connecting my third house battery to the two bank battery tender. 

To the OP, you may find that when you goose your TM to full power your DF shuts off momentarily and resets because the TM may for a while drop your DC to where electronics will not run. A small lawnmower or wheelchair "house" battery for electronics will fix that if it becomes annoying.


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## JNG (Apr 20, 2019)

12 volt lead acid flooded cell deep cycle or dual purpose batteries are best charged via a charger that has an output of 10-15 amps. These batts need an input of 10-15 amps for the best life span and proper charging. This is straight from Johnson Controls recently and Interstate told me basically the same info over 20 years ago. Interstate even suggested running the charger on manual setting for 30-45 minutes after the automatic setting kicked off. It was their opinion that the automatic chargers kicked off too soon in the name of safety first, proper charge was a secondary consideration.


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## jethro (Apr 22, 2019)

Scott F said:


> 2-3 hours with a 27lb trolling motor tells me your battery was not charged or was going bad. I used to have a 55lb thrust motor with 2 depth finders on A 17 foot glass boat and could run all day and the battery wasn’t used up. The batteries usually last 4-5 years. What kind of charger are you using and how long did you charge your battery.



I agree. I have a Minn Kota Powerdrive 50 on my 14' Starcraft and power a Humminbird Helix 5. I have a single group 29 Interstate Deep Cycle that I use to power it all and I can run it as hard as I like for 6 to 8 hours solid before I am even starting to feel some loss of performance. And even then I think I could run for another few hours easily. 

My outboard has a charging system but that is inconsequential because the gas motor is run usually no more than 5 minutes in a typical 8 hour day of fishing. I charge with a Minn Kota portable charger that float charges at 10 amps.

JNG, I wish I still had my old Sears charger that was not automatic, so I could force a little more juice in on the initial charge. Deep cycle batteries really benefit from that initial burst of high power, then tapering off to a lower amp trickle charge.


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## bikerider (Apr 22, 2019)

Wow, I guess I do have the wrong battery. I've never done more than 6 hours on the water in one day. For now I will put the regular battery charger on the battery I have and put buying a better battery on the to do list.


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## gnappi (Apr 22, 2019)

JNG said:


> 12 volt lead acid flooded cell deep cycle or dual purpose batteries are best charged via a charger that has an output of 10-15 amps. These batts need an input of 10-15 amps for the best life span and proper charging. This is straight from Johnson Controls recently and Interstate told me basically the same info over 20 years ago. Interstate even suggested running the charger on manual setting for 30-45 minutes after the automatic setting kicked off. It was their opinion that the automatic chargers kicked off too soon in the name of safety first, proper charge was a secondary consideration.




In the 70's I worked in a place where we designed and made battery chargers and everything you said is contrary to the "low and slow" method we recommended to our clients who often ignored our advice and melted our chargers and their expensive batteries.

But your claiming that Interstate suggested high charge rates made me quote your comments to them and ask for clarification...

FW: Web Form Request - Support Page

Customer Service
Togarynappi
Apr 22 at 11:54 AM
5 attachments
Thank you for contacting us.

Our recommendation is to charge the batteries on the lowest possible setting for the slowest period. The maximum setting you can use is 10% of the amp hours of the battery. Without knowing the model of the battery, I could not speak specifically on the amp hours but our highest amp hour setting would be charged at 9.8 amps.



Debbie

Consumer Services

O: 888-772-3600

F: 972-587-3290



Interstate Batteries

4301 121st Street. Urbandale, IA 50323


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## JNG (Apr 22, 2019)

I have no reason to lie. That's what Interstate told me in reference to their brand of deep cycle marine battery I was using back then. Johnson Controls told me that in reference to the deep cycles I use to back up the fire alarm controls at my place of work. While each battery is smaller than the typical trolling motor battery, they are still deep cycles. I have been using Interstates advice for more than 20 years for boat batteries and have not had any problems with batteries (of any brand) or chargers.


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## JNG (Apr 22, 2019)

Further more I just remembered that when I was planning the layout for the new Jon boat, I went to the local Interstate battery store with wiring diagram in hand. The counter guy I got seemed to be more knowledgeable than the typical dumb counter jockey that seems to get that job. I explained what I was wanting to do with the two 6 volt deep cycle golf cart batteries I wanted to buy and had a question or two. One of which was the best way to recharge the battery bank. I explained that I could charge each battery individually at 2 amps or 15 amps. Or charge the bank as a large 12 volt at 2amp, 10 amp or 15 amp. This was with the chargers I already have on hand. He suggested charging the bank as a 12 volt at 10 or 15 amps. Preferably 15 amp. This is what I have doing with no problems (although everything is new so no long term evaluation can be done at this point). I guess we will agree to disagree. I have no interest in arguing online with anyone. No one ends up winning and it creates hard feelings.


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## gnappi (Apr 22, 2019)

No hard feelings come from dialogue, hard feelings come from beligerance, neither you nor I have been there. 

But I would take the opinion of the home offices of a huge battery maker before a retailer any day, if your experiences and advice has worked for you super, I will categorically say it will not for most.


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## bikerider (Jun 25, 2019)

JNG said:


> Then look up the specs for your battery. It may even say on the battery. If it says 105 amp hours and your motor is a 40# thrust model, divide 105 by 40. You get 2.625 hours at high speed setting before the battery is completely discharged. TMs use far less amps at lower speeds so you may need to think about how you use the TM before estimating total possible run time.



The battery I'm using has 70 ah. (https://www.homedepot.com/p/Nautilus-24-Dual-Purpose-Marine-Battery-24MDP/205309648) My trolling motor is a 27 lb thrust. Doing the calculations puts me at just over 2.5 hrs run time on full blast. This puts things into perspective for me and now I can determine what battery will work best for my setup. Thanks JNG, your info was quite helpful.


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## Jake2250 (Jun 25, 2019)

So, I will throw some numbers of what I am doing! 
First off, this is my back up fishing rig, Its an 8 foot pontoon boat, 30lb trolling motor and a depth/fish finder.
I bought a 35 Amp Hour AGM deep cell battery solely for the TM.
I also run a 5 Amp Hour AGM battery to power fish finder! 
I can get six hours of on and off use of the trolling motor to get me to my fishing spots and back with out having to break out the Oars! 
I get on and off about five hours or more out of the fish finder! 
Look on Ebay for wheel chair batteries, I have seen them higher than 35 AH but they are heavier. 
As far as the difference in vessels,, yours is a bit bigger and you are taking along a buddy, maybe maybe not. 
When I go out on my own on Flat water (lakes) I take the pontoon, but rivers and very large lakes I take the tin boat (15 ft Gregor), but it has a 35 HP main and a 55 lb trolling motor. I run the starting main motor on a group 29 lead acid battery and power trolling motor off of that one also. 
I run the two fish finders front and rear off of a 10 AH AGM. I can get about five hours out of the AGM for the fish finders,, the main battery is charged by the motor.

After every trip I charge the AGM's completely for the next trip! 

I have had really good luck with the deep cell wheel chair or powered cart batteries, they will hold a good charge and are truly deep cycle!

One thing to point out is, My 30 lb trolling motor is a 5 speed, I try to never go past 3rd and get like I said about six hours on and off use! 
Its rare I spend the six hours siting in the toon, I will find a nice spot and bank fish for a while and stretch my legs!


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## bikerider (Jun 27, 2019)

Jake2250, that's interesting. I never considered a battery just for the fish finder. You mention that you use the fish finder off and on and get 5+ hours out of it. Does that mean that you turn it off once you get to a spot where you will be fishing for a while? I will check out the wheelchair batteries. I think you also hit the nail on the head when you said you try not to go past 3 on the trolling motor. The last time I was on the lake I was trolling with the minn kota all the way up at level 5. We were catching fish like crazy but I doubt I needed to go that fast. We were on the water from 9-2 with a few breaks and some still fishing and the battery was completely depleted by the time we got back to the ramp.


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## Wallyc (Jul 1, 2019)

I run electric only lakes. I have been for 30 plus years . I have had from a 12 ft rivited jon to what I have now. 1648 welded grizzly. I keep four group 31 batteries in my boat.
2 for my 80 lb terrova. One for my 55 lb minn Kota on the transom. One for the electrical load of the boat I.e helix10,helix9, 360,radio, etc..
I know this sounds like overkill but I can fish 10 -12 hours with no fear of taking 1/2 the rating from the better . One thing no one brought up is life span for your battery bank. The more you take the shorter the life span . I’m on my third year of my batteries and they are still strong. . I charge with a 3.bank 5 amps per bank charge and a single 5 amp . I have to add very little water to the batteries because I’m not boiling the electrolyte out of the batteries with a high amp charger. The most important thing I quit doing is running the motor on high for extended amounts of time. Big power robber.
Even in a 12 ft riveted Jon boat I can get at least six hours out of a 55 pound troller
And a group 31. Running it at 1/2 power.


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