Lithium Battery Question - 50AH LiFeP04 for a 55# thrust Minn Kota?

[thill]

My Group 29 lead acid trolling motor battery is starting to slow down. For the last few years, I could fish a long day with no problem. Now, it's getting weak by the afternoon. It's time to replace, and I'm considering lithium.

I've heard that you get double the useable charge from lithium. So a 50A lithium will run your motor as long as a 100A lead acid battery, in theory.

Questions
1. Is this true about double the runtime per rated amps?
2. Do any of you run a 50AH battery for your TM?
3. If so, how long does it last for you? Happy with it?

Please let me know what you think. Trying to figure out whether the extra cost is worth it. I'm also thinking that if I eventually buy two 50 AH, I can use them for my 24V motor on my other boat. Thanks!

 

[Lost But Happy]

Interested in this question as well...

 

[Ray Clark]

My Group 29 lead acid trolling motor battery is starting to slow down. For the last few years, I could fish a long day with no problem. Now, it's getting weak by the afternoon. It's time to replace, and I'm considering lithium.

I've heard that you get double the useable charge from lithium. So a 50A lithium will run your motor as long as a 100A lead acid battery, in theory.

Questions
1. Is this true about double the runtime per rated amps?
2. Do any of you run a 50AH battery for your TM?
3. If so, how long does it last for you? Happy with it?

Please let me know what you think. Trying to figure out whether the extra cost is worth it. I'm also thinking that if I eventually buy two 50 AH, I can use them for my 24V motor on my other boat. Thanks!

I have a 100Ah LiFePO4 running my 55# thrust Minn Kota Powerdrive.

Regarding your comment that "I've heard that you get double the useable charge from lithium. So a 50A lithium will run your motor as long as a 100A lead acid battery, in theory." I don't think it works as cleanly as that. Real world results vary greatly with actual conditions. However, I think it's true that there is MUCH more available energy in a LiFePO4 than there is in the traditional lead acid batteries. Dakota Lithium's web site touts "2X the Power." OK, but is it twice as much stored energy, or is it because more of the stored energy in a LiFePO4 is available for use compared to a traditional lead acid? The energy in a LiFePO4 is dispensed at differing rates over time from the discharge curve of a lead acid battery. This is beginning to make my head hurt...

My 100Ah LiFePO4 is a cheap brand I bought on Amazon. I paid $349 for it a year ago. That same battery is now $310. A 50Ah LiFePO4 of the same brand is now $198. Cost per amp hour decreases as a bigger battery is bought, at least with that brand. I checked Dakota Lithium pricing and cost per amp hour stayed the same for 50Ah battery versus the 100Ah.

My experience, which is limited, results in me being happy so far with my 100Ah battery. I don't have a shunt on the battery that tells me how much of the battery's capacity I've used. I'll typically fish for 4-6 hours, and the troller is what I use for anchoring, making short runs between fishing spots, and adjusting positioning. It's probably not very taxing on the battery. But that battery does more than power the TM. It powers two fishfinders (not a large draw) and is also hooked to the bilge pump and nav lights (both rarely used).

If it was me, and I wanted to run my TM all day, I think I'd take the recommendation to size the battery at the TM manufacturer's recommendation. For my Minn Kota, that's 100Ah.

One final aspect....and it regards moving your battery between boats to team it with another like battery for a 24V setup...how will you make sure that your setup is balanced when you hook those two batteries together? It's something you have to think about.

 

[thill]

Thank you for sharing. Sounds pretty good.

My theoretical plan is to buy (2) 50AH batteries. Run either one or both in parallel for the 12V 55# motor in my aluminum boat, and both in series for the 24V 70# motor on my big boat.

I don't understand the question about them being balanced. Do you mean making sure both are charged to the same level? Or is there something else? Does it require something electronic to balance the load between them?

 

[Ray Clark]

Thank you for sharing. Sounds pretty good.

My theoretical plan is to buy (2) 50AH batteries. Run either one or both in parallel for the 12V 55# motor in my aluminum boat, and both in series for the 24V 70# motor on my big boat.

I don't understand the question about them being balanced. Do you mean making sure both are charged to the same level? Or is there something else? Does it require something electronic to balance the load between them?

I was meaning charged to the same level.

I think I'll withdraw the concern for that, as long as your hooking together batteries of the same voltage and capacity in series.

I'm still in the "buy one bigger capacity battery camp."

 

[CRS]

I guess I'll add my opinion.
A hundred amp hour battery has 100 amp hours charged fully, regardless of the type. The difference is if you run any lead acid type past 50% capacity it is damaged. Continue doing this and your battery will fail prematurely. Lithium type batteries can be run down 80%-90% capacity without damage. Some say 100% but I prefer caution and limit mine to planned 80%. In different terms lead acid you have 50amp hours available, Lithium you have 80 amp hours available.
Paring the batteries is a little more than just the full charge on each, as was mentioned as batteries get older they do not function the same as new. If an old battery is paired with a new battery both will function as the weaker older battery. By running the two batteries together all the time either parallel or series keeps them the same "age" thus paired.
The run time is impossible to predict as a rule covering thing. A digital clamp meter will allow anyone to estimate run time. Simply place the meter around the negative cable, it will read the amps being drawn. Then run the motor at different settings and record the amp usage. Example if the motor is drawing 25amps at a certain setting, a lead acid will be good for 2 hours with a100 amp battery while a lithium will be good for 3.2 hours for an 80% discharge. Unless my motors are a fluke, you will find you can go much farther going slowly then faster. So in an emergency slow down to get back to the ramp.
My set up is as follows:
2 48 volt 96 amp hour parallel for the electric outboard.
2 12 volt 100 amp hour series for the trolling motor
2 12 volt 18 amp hour parallel for the electronics on board
All are Dakota lithium
Apart from the obvious, the reason for having 2 18's is if one of my 100's expires. My trolling motor is an MK Ulterra and with out current the motor cannot easily be stowed. While the 18's would not run it very long they would be able to get it out of the water.
Hopefully this post will help.

 

[MrGiggles]

I'm in the same boat, but I already pulled the trigger and am still testing them out.

I have a 24V Terrova and two 40ah lithiums. I read the same things you did, that you can essentially go with lithiums that are half the size because you get 100% of available capacity, versus 50-80% with SLA. I had thought this was at least part bullcrap fed to you by someone trying to sell you a battery. What I could never find out was if SLA batteries were rated with that taken into consideration (only discharged to 50%), or if you really only got 50AH out of a 100AH battery.

I have not ran the 40s dead yet, although I typically don't run the electric motor at higher speeds for very long. I have installed a hall type battery monitor but have not yet gotten it calibrated, as you have to drain the batteries completely to do so. When it is setup properly, it should track charge and discharge rates over time, showing you how much battery capacity is left. When lithiums are dead, they're dead, so I feel like it would be a very handy thing to have.

I purchased two more of those 40ah batteries so I can double the capacity if I needed to, but at this point I'm not sure if I will need to.

 

[Robert Smith]

My Group 29 lead acid trolling motor battery is starting to slow down. For the last few years, I could fish a long day with no problem. Now, it's getting weak by the afternoon. It's time to replace, and I'm considering lithium.

I've heard that you get double the useable charge from lithium. So a 50A lithium will run your motor as long as a 100A lead acid battery, in theory.

Questions
1. Is this true about double the runtime per rated amps?
2. Do any of you run a 50AH battery for your TM?
3. If so, how long does it last for you? Happy with it?

Please let me know what you think. Trying to figure out whether the extra cost is worth it. I'm also thinking that if I eventually buy two 50 AH, I can use them for my 24V motor on my other boat. Thanks!

AC DELCO 31 series deepcycle trolling battery, BEST BATTERY DOLLAR FOR DOLLAR THAT CAN BE HAD, I've installed these for customers for YEARS and NEVER any issues ever and they cost half the money and last just as long, BUT you have to LEARN how to take care of your Batts, will never use lipos,

 

[AlanT]

Approximately twice the storage capacity assuming a lead acid Depth of Discharge (DOD) is 50% and LifePO4 lithium DOD is 100%. But as mentioned there are other factors. Lead acid will deliver less power (voltage and current) as it discharges. And I wouldn't run a lithium to 100% discharge despite the specs. A claim of twice the power may be some marketing "puffery".

One thing to consider is matching your TM max amperage to the battery you select. For example, a 12V 40ah lithium may have a maximum discharge current of 40 amps. It may be higher for short bursts (5 to 30 seconds). Some Minn Kota 55# thrust TMs will draw 50 amps at wide open throttle. Over drawing your lithium battery could result in damage to the battery or TM, so match the specs. The world gets more complicated every day. Good luck and have fun.

 

[airshot]

AC DELCO 31 series deepcycle trolling battery, BEST BATTERY DOLLAR FOR DOLLAR THAT CAN BE HAD, I've installed these for customers for YEARS and NEVER any issues ever and they cost half the money and last just as long, BUT you have to LEARN how to take care of your Batts, will never use lipos,

Having years of experience with lipo batteries, I would never use one in a boat !!! Now...the LifePO4 is a different battery and much safer to use...however all instructions must be followed to the letter to make them work well. When my 31's die off I will ve upgrading to LifePO4 batteries !!

 

[sonny.barile]

If you read the battery literature itself you will see that most list cycles as the life of the battery. It’s not totally apples to apples but you can kind of view a cycle as a use and recharge. (Duty cycle)

AGM batteries will be listed as 400/500 cycles typically.
That cycle is at 30 percent discharge at 10a draw. There is an industry standard used for the numbers.
If you do anything different with your use it has an affect on the life……..reduced cycles. Lead acid batteries like to be fully charged all the time. So even after a little use you should top them off. Any prolonged period of non-use while not fully charged shortens the life.

Lithium Iron Phosphate (Lifepo4) also list life cycles. It’s 5000/8000 cycles at 50 percent drain and 10a draw. Some of the marketing literature goes a little deeper and state lower life for more drain or higher draw. Most of the batteries have onboard management systems that cut you off at About 2 amps capacity because it won’t take a charge if you completely kill it. So you can technically get the majority of the stated power.

Voltage drop on lead acid will stop your 12 v trolling motor from working at the higher speeds when the voltage hits low 11’s. That will happen when you have about 40 percent left. Most Lifepo4 batteries will supply enough voltage until just about dead.

Now does that mean you should drain a lithium down to 10/20 percent? Probably not……but even if you do that regularly, it will still have 5/10 times the cycle life of a lead acid battery.

 

[sonny.barile]

Having years of experience with lipo batteries, I would never use one in a boat !!! Now...the LifePO4 is a different battery and much safer to use...however all instructions must be followed to the letter to make them work well. When my 31's die off I will ve upgrading to LifePO4 batteries !!

It’s the same here. I use them in other places but not on my boat. My starting battery is AGM and hooked up to my outboard for charging. My TM battery is an AGM 92 amp and for that I have an onboard Minn Kota single bank charger. All are getting long in the tooth though……My TM battery is 64 lbs…….I could probably get away with a 65 amp Lifepo4 battery……..they are only 15 lbs.

 

[thill]

Good information, everyone. I need to think it out first before buying.

I'm very curious how the two 40 AH batteries work for you, Mr Giggles. Please report back how it works, as that is the same setup I'm considering.

 

[thill]

I was meaning charged to the same level.

I think I'll withdraw the concern for that, as long as your hooking together batteries of the same voltage and capacity in series.

I'm still in the "buy one bigger capacity battery camp."

I'm considering getting a single 100A battery to start with, and then buy a second one later, but am still unsure. If the two 50's work, that would be more flexible, but if they die too quickly, it may be false economy.

 

[Cuttem Jack]

I have three 50 amp ionics for my Tm. Trolling motor is 36 volt minn kota. I can fish all day and still have 70 percent power left. I don’t have spot lock but it wouldn’t worry me if I did. Best thing I did for my needs.

 

[airshot]

My question is why two 50's instead of one 100 ah battery for a 12 v TM ??? I am looking at these lifepo4 in the future...so what do I need to know??

 

[CRS]

My question is why two 50's instead of one 100 ah battery for a 12 v TM ??? I am looking at these lifepo4 in the future...so what do I need to know??

1 reason for 2 50's instead of 1 100 would be for a back up. If one battery fails you still can get back to the ramp. Of course this is if electric is your only means of propulsion. Another would be weight, lifting a 50 is much easier than a hundred.

 

[Buster]

I've been using a 100Ah Amped Outdoors LiFePo4 to run my 12V Terrova for two years. I have a SmartShunt attached so I can monitor current draw and capacity real time. At full throttle it draws about 38 Amps and pulls my ancient 14ft Lund at 3.2-3.6 mph. At a mile an hour it pulls about 3 amps. Recently spent two weeks up north fishing 5-8 hours a day and after three days was still at 45% capacity and I was trying to use as much batter as I could so I'd often hop between spots with the electric instead of firing up the outboard.
Unless you use high throttle settings a lot, like fighting a current, 50Ah is more than enough for most people. I could have saved some money and weight but what did I know at the time?
Is anybody interested in speed setting vs current draw data? I can run a quick test next time I'm up and then pull the data off the SmartShunt. It could be useful for anyone looking at a 12V, 55lb MinnKota. Of course, your data will vary based on how big and heavy your boat is, but this would be a good start.

 

[Lost But Happy]

I've been using a 100Ah Amped Outdoors LiFePo4 to run my 12V Terrova for two years. I have a SmartShunt attached so I can monitor current draw and capacity real time. At full throttle it draws about 38 Amps and pulls my ancient 14ft Lund at 3.2-3.6 mph. At a mile an hour it pulls about 3 amps. Recently spent two weeks up north fishing 5-8 hours a day and after three days was still at 45% capacity and I was trying to use as much batter as I could so I'd often hop between spots with the electric instead of firing up the outboard.
Unless you use high throttle settings a lot, like fighting a current, 50Ah is more than enough for most people. I could have saved some money and weight but what did I know at the time?
Is anybody interested in speed setting vs current draw data? I can run a quick test next time I'm up and then pull the data off the SmartShunt. It could be useful for anyone looking at a 12V, 55lb MinnKota. Of course, your data will vary based on how big and heavy your boat is, but this would be a good start.

Great post!

Your post has now tilted me into getting 2 50amp LifePo4 batteries instead of 1 100amp.

If you would be so kind to run the test and post it here, I would much appreciate it!

 

[Buster]

Great post!

Your post has now tilted me into getting 2 50amp LifePo4 batteries instead of 1 100amp.

If you would be so kind to run the test and post it here, I would much appreciate it!

I won't be on the water again for a couple weeks, but I will run the test and post it when I am.