Trolling Motor Battery Life

[amateurfishing]

Just had my boat out for 2nd time this year, has brand new interstate trolling motor battery. First timeout, everything was great and after 3 hours use, came home to recharge and charger said still 80% full. Thought that was very good. Got home @ noon today after 51/2 hours on water & charger showed @ 80% again, my only slight concern is motor seemed a little sluggish last 30-45 min on water even though it did not show speed decrease on fish finder.

1. shouldn't i have used more juice in battery this am with more than 2 hours on water from previous time? .....and

2. how long should a trolling motor generally last out on water any given time? If i was on water for 5 hours using it this am and charger says only 20% used, does that equate to working for 25 hours straight? very unlikely, right?

[BobT]

How much power your trolling motor will use depends on the load you are demanding from the motor. The faster you run the motor the more power it will use in a specified time period. I use a Minn Kota 40P Powerdrive. If I use it at about 40% power I can run nearly all day on a single charge of my 105AH deep cycle. If I run it at 100% it will maybe last me about 2-1/2 hours if I'm lucky.

It's in the math. A motor drawing 10A on a 105AH battery will run for approximately 10.5 hours steady before the battery voltage begins to drop below certain specifications. 10Amp X 10.5Hrs = 105Amp-Hrs. A motor drawing 40A will only last about 2.5 hours. 105AH / 40A = 2.625Hrs. There are other factors that may influence this but this gives you the idea.

[amateurfishing]

i know it will depend on overall load and speed setting used. i bought a ditigal reader so i can occasional check battery while out on water, im just suprised that 2 times on water with a 2 1/2 hour difference yielded same results on battery tester and charger yet felt slightly sluggish at end of 5 1/h hours on water. Honestly, in the 2 years i have had a trolling motor, my tester has never shown below 2/3 full, i generally am just putzing around on slowest speeds anyway, i would assume my battery charger & digital tester would not show false readings, right? So after on water for 5 plus hours, get home to recharge and charger reads still 80% full, do i interpret that as could possibly continue on water with same charge for up to 25 hours at same low speed? How would i know what amps my trolling motor is running on at different settings?

[MuskieJunkie]

I don't think those gauges are that acurate. Also, your charger is probably supposed to be unplugged to use that gauge, might want to check that.

[amateurfishing]

i never have the charger connected when using the digital reader

[amateurfishing]

my batteries marine cranking amps is 690 with motor using 33 amps at "nominal thrust" says owners manual. this is all the info i have from owners manual and battery which is interstate srm 24, cannot find anything regarding ah or am hours

[amateurfishing]

Interstate Deep Cycle/Cranking - 12 Volt BCI Grp # Interstate Type CCA

MCA

RC

(Min.) 25A Warranty

(Mo.) Hrs. at Ampere Load Dimensions (in.)

L | W | H Weight

(lbs) Terminal

5 15 25

24M SRM-24 550 690 140 30 16.4 4.6 2.3 11

6-7/8 9-1/2 46 Auto/Stud posts

i found this info drawing 5 amps=16.4 hours, 15 amps=4.6 hours, & 25 amps=2.3 hours. so if my trolling motor draws 33 amps according to owners manual, battery should not last over 2 hours? but yet i have been on water for 3 & 5 1/2 hours respectively, & when using digital tester (if any good) always says 2/3 full, and battery charger always said still 80% full when hooking up to recharge. Just trying to make sense of it all. Is my digital battery tester worthless and battery charger indicator just off?

[311Hemi]

What trolling motor do you have? If it is a Minn Kota with digital maximizer the power you are drawing is proportional to the setting your on. A Minn Kota powerdrive 65 draws around 40 amps at full throttle (setting of 10), 20a at half throttle (setting of 5), 10a at 25% throttle (settings of 2.5)...it's a fairly linear line. So, at a setting of 2.5 you could see 8-9 + hours with that battery and a PD65 trolling motor. A lower powered trolling motor may draw less than that...

I would also check the battery voltage with a good multimeter after the battery has rested for a few hours after use.

[amateurfishing]

its a 1984 mercury thruster. owners manual says it draws 33 amps at nominal thrust. so is my digital battery tester/reader and the reading off my battery charger junk?

[311Hemi]

If it says Dura Amp on it then I believe it's draw is variable like the digital maximizer that Minn Kota has, although I don't know the amps your aprticular motor draws at the different rates.

I am not familiar with the digital battery testers and their accuracy, but a good multimeter would be best. With a multimeter you can check the actual voltage.

[amateurfishing]

call me stupid, what am i reading here, i have a 12 volt battery 690 amps and owners manual says motor runs on bout 33 amps

[walleyemaniac]

Just a shot in the dark here. Your charger is reading 80%, and that's probably what's left in the battery's "overall" charge. Your trolling motor needs 12v to run efficiently, when volts start dropping below 12 your going to start noticing it in the motors performance. Your tester is showing you whats left in "over all" battery life not whats left of the 12 volts. Make sense.

The figures that have been posted thust far for battery life at X amount of amp draw are pretty close. Seems like you just didn't understand what your tester was telling you.

[SpecialK]

One other thing to think about and I am not totally sure this is the case but batteries will regain *some* charge after the load has been removed. If you have ever run a cordless drill down to nothing, let it sit for a few minutes, then hit the trigger it will turn the motor again.

Could that possibly be what you are seeing when you check the charge after you get it home?

[amateurfishing]

while i understand what walleye & special k r saying regarding equipment, how is it that after 1 3hour trip & 1 5 1/2 hour trip my charger still reads 80% full, should there not be a difference and .........

if true that the charger reads 80% full after 5 1/2 hour trip, does that equal working for 25 hours, i just dont buy that. I have googled my battery and it says 2 1/2 hours @ 25 amps. my motor is about 33 amps so does that equate to only 2 hours at a time?....which is impossible cause i have already used it more than that at once. dont understand why i cant find the amp hours for this battery.

[amateurfishing]

while i understand what walleye & special k r saying regarding equipment, how is it that after 1 3hour trip & 1 5 1/2 hour trip my charger still reads 80% full, should there not be a difference and .........

if true that the charger reads 80% full after 5 1/2 hour trip, does that equal working for 25 hours, i just dont buy that. I have googled my battery and it says 2 1/2 hours @ 25 amps. my motor is about 33 amps so does that equate to only 2 hours at a time?....which is impossible cause i have already used it more than that at once. dont understand why i cant find the amp hours for this battery.

[amateurfishing]

so it looks like the manufacturer specs are 140 min @ 25 amps, so how can i be on the water for 3 & 5 1/2 hours with this and why does my charger still say 80% full when hooking up to recharge? any ideas?

[amateurfishing]

more info that i found wast to take rc (140) x .4=56 AH, 56/33 (amp motor)= 1.7 hours. this may be true but again makes no sense with how long i have used it or my charger & digital reader always telling me its still 80% full.

[walleyemaniac]

Is it 33amp max? If that's the case then yah about 2-2 1/2hrs. (according to what specs you found for your battery) But if your not running it maxed out ALL the time it will last alot longer.

Your 8 1/2hr run time is doing good if your not running hard. Your 80% is total battery charge and your motor is going to feal like it's puking out when volts start dropping below 12. (I don't know at what percentage of charge a battery will start falling off 12v)

To many variables on any given day of fishing to really narrow it down. Most guys will tell ya when in dought go one size bigger. Better to have to much then not enough!!

On a windy day I'll burn up my batteries fast especially with the auto-pilot on, but when it's calm and I'm barely running it I might go 2 days fishing before the trolling motor starts to lag.

To your 25hr question, probably not. Your battery will probably still show a little bit of a charge even when it won't turn the prop on the motor just because that motor needs more power then what's left in the battery to run. You could still hook up a little light bulb to that same battery and get it to glow because it doesn't need as much juice to run. Hope this helps a little more.

Just remember your digital meter is telling you what's left in the battery till 0 volts.

[311Hemi]

dont understand why i cant find the amp hours for this battery.

You have the specs for the battery and already posted them, your not missing anything.

The question you need to answer is does your trolling motor pull 33 amps at all speeds or not?

Some trolling motors draw the same amps at all speeds (older minn kota without the digital maximizer, usually have a selection of 5 different speeds), and some have a variable draw depending on how fast you are running the trolling motor. If yours has a variable draw then that answers your question on why it is lasting 5 1/2 hours.

The battery you have should read 10.5 volts after running 25 amps for 140 minutes. You may be running them longer than you should, and could decrease the longevity of the battery in doing so. Go borrow a multimeter from a friend and figure out if your "battery testers" are reading true. I don't see how it would be possible to run 5 1/2 hours at 33 amp draw with that battery.

[amateurfishing]

the owners manual says 33 amps at nominal thrust, my foot pedal has 5 settings, so i would expect that to mean on low, not high.

[amateurfishing]

but cant i run the trolling motor until it no longer runs or is that not the appropriate usage of the battery, if thats the case, i think i need a bigger battery or should get an emergency backup. Is there any way to check whats left of the battery charge when on the water? the reason i am so concerned is this is my only motor right now till i can get my big one fixed and dont want to be left stranded.

[311Hemi]

the owners manual says 33 amps at nominal thrust, my foot pedal has 5 settings, so i would expect that to mean on low, not high.

Unless you know for sure how your particular trolling motor operates your just guessing.

Older Minn Kota trolling motors (with the 5 speed switch) draw the same amps at all speeds, so the battery will pretty much last as long at speed setting of 1 as it will at a speed setting of 5.

What is the actual model # on your trolling motor?

[311Hemi]

but cant i run the trolling motor until it no longer runs or is that not the appropriate usage of the battery, if thats the case, i think i need a bigger battery or should get an emergency backup. Is there any way to check whats left of the battery charge when on the water? the reason i am so concerned is this is my only motor right now till i can get my big one fixed and dont want to be left stranded.

To get the most life out of the battery you only want to run it down to 50%-80% depth of discharge (leaving 20% or more charge left on the battery). You can probably get an idea on the water if you have a multimeter and check the voltage after letting the battery sit for a 20-30min without use. It's best to let them sit a good amount of time (hours) to find what the actual voltage currently is. So, check the battery with a multimeter 4 hours after you leave the lake and see what the voltage is. That will give you an idea of how far down you are draining the batteries.

[amateurfishing]

K, so based on my numbers from above, the battery most likey is good for 1 1/2 to 2 1/2 hours yet would make sense that I was out for over 5.

1. why is it reommended to only use 75% of battery

2. what happens if i drain it all the way down other than shelf life

3. what does everyone else out there do to keep tabs on trolling battery status

4. do i need to get a second trolling battery, i really enjoy this larger boat we have and it is tough to get off water, 2 hours does not seem very long to m e.

[311Hemi]

1. why is it reommended to only use 75% of battery

The lower you discharge the battery, the less recharge cycles you will get out the battery. Typically draining a normal wet cell battery to 50% gets the most bang for your buck. This table is just an general idea what I am referring to, but is not for standard wet cell batteries.

2. what happens if i drain it all the way down other than shelf life

Basically the battery wont last as long...costs you more money to replace.

3. what does everyone else out there do to keep tabs on trolling battery status

Not sure on everyone else, but I may occasionally check mine with a multimeter a few hours to a day after using them to get an idea of how far they have been drained down. I typically don't worry about draining them down that much as I bought the biggest I could to begin with....so not much I can do about it. I also usually plug them in every night if possible after use. Knowing what your trolling motor draws for power and what you have had it set on all day also helps out a lot!

Typically, you will buy a battery based on how much power you think you need (amp draw from trolling motor) and size the battery so you don't drain it down past 50-80% discharge most of the time.

4. do i need to get a second trolling battery, i really enjoy this larger boat we have and it is tough to get off water, 2 hours does not seem very long to m e.

It would not hurt....although what would really help is to know what your motor is actually drawing for power. I know you say 33amp at nominal power, but what does that mean on a setting of 1, or a setting of 5? Maybe upgrading to a newer trolling motor with digital maximizer might help, that is if your old one does not have that type of technology in it. What is the actual model/serial number on your motor?