Trolling battery life

[ameyers41]

I have an 80lbs Terrova with 2 24 series batteries. The last two times I've used the trolling motor, my battery has died the same day. I keep the onboard charger plugged in when not in use. Boat is a 94 Lund 1775 Pro V.

Does anyone know how long I should get out of a charge? Obviously, there's a lot of variables, but I'm just looking for approximations from those who troll all day, etc.

Sunday, I was on Mille Lacs mainly trolling. Used the motor from about 2-8pm. It was going most of the time; with the wind from about 3-6 speed and against the wind running on 8-10. Used the spot lock for an hour or so too. I know the GPS and the US2 draws power. I haven't pulled the batteries to do a load test yet, but they are new this year.

Just curious what I should expect. This is my 1st 24v setup. Used to use a 55lbs 12v.

[BobT]

It would be very difficult if not nearly impossible to calculate the amount of run time you would get under various conditions such as wind and speed settings. Also, without knowing what the motor current draw is at any one speed setting it's not possible to calculate that either.

If you think the run time has dropped in recent uses, then one thing I would suggest is that you check your batterys' electrolyte to be sure they are still within appropriate levels. This could certainly reduce your batterys' capacities.

[JohnMickish]

Probably the biggest thing is how big are your batteries? If you are using group 31 deep cycle batteries and they die, then it's probably bad batts, if you are using something small like a size 24 then you are probably just running them out of juice.

This is assuming that the batteries are healthy to begin with and that they are in fact recieving a full charge. You are using a two bank charger, right?

[TruthWalleyes]

I fish quite a bit, and to me an 8 hour day is a short day of fishing.

I've got a 55# and got sick of running out of batteries, so i keep two batteries in the boat just for trolling which ensures that i don't run out of juice on the lake! BTW, i'm using the 29 rated batteries. So my advice would be to guarantee that you don't run out of juice by putting another batt in the boat.

I'll be remodeling my boat this fall and will be putting a switch to change between the two batteries for a quicker changeover in the boat.

[delcecchi]

I think a group 24 battery is like 80 amp hours. A 80 lb terrova draws on the order of 50 amps wide open. So if you are running near wide open, a couple of hours or thereabouts is all you will get.

[Whoaru99]

Yup, sorta easier to think about it in terms of watt-hours.

One Group 24 battery with 80AH at 12V = 960 watt-hours. Add a second Group 24 in series now you have 1,920 watt-hours (24V x 80AH). If the trolling motor power use is (for example) average of 20A at 24V, that's 480 watt-hours, so run time is roughly 1,920/480 or 4 hours.

Now some of that math can be short cut if we know the system is 24V, so 80AH/20A = 4 hours but sometimes it's helpful to see the long math, so to speak.

[delcecchi]

Yup, and two in series is roughly equivalent to 160AH (24Vx80AH ~= 12Vx160AH), so if pulling 25-30A, give or take, on average using the motor (purely speculative numbers) then 5-6 hours is about right.

Sorry Charlie. Thanks for playing. If you put two 80 amp hour batteries in series you end up with a 24 volt 80 amp hour battery. The same current passes through both batteries.

If you put them in parallel you get 160 amp hours at 12 volts, but the terrova won't work hardly at all.

[Esox_Magnum]

I run 27's in my 17' deep v glass and have yet to see the charge drop below 3/4charge after 12 hours+. Granted I rarley run above 4 but it runs steady for those 12-14 hours...

[Whoaru99]

No, not really sorry Charle. I understand completely how series and parallel circuits work. The power (watts) in the end is the same (24Vx80 vs 12Vx160), but as you see I edited my post in the time of your quoting because I suspected this sort of confusion might occur the way it was initially written.

[ameyers41]

Thanks everyone. So, it's entirely possible that I'm simply draining the little size 24's running full or near full power for that long. I know, I know, always get the biggest motor, batteries, etc you can... Lesson learned!

I might still do a load test to ensure I didn't get a defective battery/batteries, but they were brand new this summer and I've only been out for about 5 days of fishing in the boat (which is a whole other sad story).

[Whoaru99]

Five days...lucky you. That's five days more than me. Last time my rig was on the water was last fall for winterization. I probably should just sell it...

[RangerJack]

I run 27's in my 17' deep v glass and have yet to see the charge drop below 3/4charge after 12 hours+. Granted I rarley run above 4 but it runs steady for those 12-14 hours...

I can run my batteries without charging on a week long trip to Rainy Lake. I just use it on the lowest power mode, and drift with socks. The wind has its advantages too!

[EBass]

How old are the batteries and what make? I had a similar situation and I was using Trojan 27's (2 for a 70lb Minnkota)and they would only last part of the day towards the end of the season. Every year I needed to replace both.

I then broke down and bought Optima's Blue Tops and I'm on the 4th year with them. They last longer than I do.

I have a dual bank onboard Minnkota charger to.

[Whoaru99]

In case it hasn't been mentioned yet, or not often enough, key to good battery longevity is charging the batteries as soon as you get home from fishing. Don't leave them sit in a state of partial discharge. Also, even though they're called "deep cycle" batteries doesn't mean they like to be run until they're dead.

[sheephead2]

I had issues with my batteries got new ones this spring.

1st charged them over night and ended up boiling them all night woke up went to garage and smelled like Sulfur. Unplugged charger figured the charger was shot. Bought new charger and still the charger would not stop charging meaning not go to maintenance mode. Exchanged batteries for new ones NOW new charger and new batteries. Still would not go to maintenance mode on charger. Exchanged the charger tried charging batteries still issues. Brought back batteries again thinking battery cells were bad . Had FF load test them found out load test was BAD on the Bolt side but was good on the POST side. He said they have been having issues with the threaded sides. He told me to get a post to wing nut conversion$2.65 and use only the post side.I have it on charger as I type hope it is the Cure

[herdog]

I understand the math but there must be some other explanation. My buddy runs his 80# minnkota for days without charging it & I can't do that. Are some motors or some model years more efficient?

[kg2]

All of the Minn Kota 80# thrust motors have a spec of 56 amps at high speed.