Lithiums on MK 24V/80/60...NO Speeds Higher than 85% for Prolonged Times?

[Tin Man]

Just installed my new MK Terrova 24V/80#/60".

Reading through battery connection portion of manual this section has me concerned:

"Minn Kota trolling motors can run on Lithium-Ion batteries. However, they are specifically designed to run on traditional lead acid
batteries (flooded, AGM or GEL). Lithium-Ion batteries maintain higher voltages for longer periods of time than lead-acid. Therefore,
running a Minn Kota trolling motor at speeds higher than 85% for a prolonged period could cause permanent damage to the motor."

Can someone with experience please explain what this means when using Lithium batteries?
I was considering two 12V/100amp lithiums, but I wonder if I should just stick to two group 27 deep cycle wet batteries.

Thoughts?

 

[LDUBS]

Just installed my new MK Terrova 24V/80#/60".

Reading through battery connection portion of manual this section has me concerned:

"Minn Kota trolling motors can run on Lithium-Ion batteries. However, they are specifically designed to run on traditional lead acid
batteries (flooded, AGM or GEL). Lithium-Ion batteries maintain higher voltages for longer periods of time than lead-acid. Therefore,
running a Minn Kota trolling motor at speeds higher than 85% for a prolonged period could cause permanent damage to the motor."

Can someone with experience please explain what this means when using Lithium batteries?
I was considering two 12V/100amp lithiums, but I wonder if I should just stick to two group 27 deep cycle wet batteries.

Thoughts?

I don't have experience with that, but what they are saying is, for example, if your speed range is 0 to 10, don't run it over 8.5 for long. I guess that is kinda obvious and you already know that. I bet the issue is overheating. Too bad they don't define "prolonged" use.

There are a ton of TM's out there running off Lithium batteries. I suspect this might be corporate risk management at work with an abundance of caution. But, I would heed the advice nevertheless -- especially during the warranty period. When I buy a new battery for my old PowerDrive, it will be Lithium. In reality, I usually am at 25% to 35% power in actual use. Only time I've been above 8.5 was when I wanted to see what full power was like.

 

[Azdesert]

I don't have experience with this...yet, but I will as that will be my set up soon. Reading this same topic on another boating site, couple guys say they run em on max a lot for over 2 years without issue. I think it is possible that with lead acids drop in voltage as they discharge, the Lithium stays at the same voltage causing the motor to run at a slightly higher RPM. How this results in an issue is bit beyond me?

 

[FuzzyGrub]

Outside of a main motor break-down, don't think you will be using full power for extended times. Myself, wouldn't worry about it. If the MK has a battery status indicator, that will not report correctly.

 

[jethro]

That would be a concern for me, but I agree with LDUBS, it's likely a CYA statement by Minn Kota. I am almost always trolling with auto pilot and cruise control on and if I change heading into the wind, maybe my enclosure is up and I'm trolling 8 lines, I gotta lot of stuff going on- it absolutely could be at max on the trolling motor to maintain whatever speed I'm trying to keep. I try to keep an eye on the remote to see what the prop is spinning and crank up my kicker to compensate, but sometimes it's controlled chaos I'm dealing with. That's the whole idea of an I-Pilot equipped motor for me, so I don't have to drive and can fish and help others catch fish. Also, I fish offshore quite a bit and if I'm spot locked in 20mph winds in an oncoming sea, absolutely could see max on the trolling motor for extended times, because I'm not using the kicker on spot lock. If the ground fishing is seriously hot and heavy I don't pay any attention to the motor but even with my 36v, 112# motor it can be at speed 10 for sure. But to be fair my boat is 21' feet long and well over 3k lbs, maybe over 4k with 4 big guys in it so that's a consideration.

I wonder if their new brushless motor is completely Li-Ion compatible? That would be a big reason to buy it if so.

 

[thill]

You probably don't have Lithium-Ion batteries, for what it's worth, but maybe you do.

LiFeP04 are what are currently the most popular.

I somehow doubt that an extra volt will hurt your TM, but I guess it doesn't hurt to be careful.

 

[Still Afloat]

LiFePO cells produce 3.2 while lead acid is 2V per cell.

A 12V lead acid has six cells: 6 x 2V = 12V
The closest match with LiFe Po is four cells: 4 x 3.2 = 12.8V

So two LiFePO batteries in a series configuration is 25.6V rather than 24V. A 6.6% over voltage (or even 10%) will not affect properly designed electronics.

In the real world a freshly 100% charged lead acid battery has a similar voltage as the LiFePO with the resting voltage of the LiFePO being a bit higher. The difference is that lead acid battery voltage gradually drops as the battery is discharged. The LifePO battery holds a fairly constant discharge curve until the usable charge is almost fully depleted.

MK probably designed the duty cycle of their motors and speed controllers around lead acid batteries where isn’t possible to run at full voltage for extended periods. They are now concerned about heat build up.

It’s good to know that MK is imposing a duty cycle for motors powered by LiFePO batteries but, I would not loose any sleep over this. How often do you troll at 100% for extended periods?

 

[Still Afloat]

Just installed my new MK Terrova 24V/80#/60".

Reading through battery connection portion of manual this section has me concerned:

"Minn Kota trolling motors can run on Lithium-Ion batteries. However, they are specifically designed to run on traditional lead acid
batteries (flooded, AGM or GEL). Lithium-Ion batteries maintain higher voltages for longer periods of time than lead-acid. Therefore,
running a Minn Kota trolling motor at speeds higher than 85% for a prolonged period could cause permanent damage to the motor."

Can someone with experience please explain what this means when using Lithium batteries?
I was considering two 12V/100amp lithiums, but I wonder if I should just stick to two group 27 deep cycle wet batteries.

Thoughts?

I suppose if you need the ballast from extra weight of lead acid it would make sense. LiFePO will provide better performance and a longer lifetime. They cost a little more up front and your charger might need upgrading but, your money ahead in the long run.

One concern is charging LiFePO batteries at or below freezing temperatures. If this is potential issue then you would want to get a battery with low temperature charge protection. Or just charge them in a warm place.

 

[Tin Man]

LiFePO cells produce 3.2 while lead acid is 2V per cell.

A 12V lead acid has six cells: 6 x 2V = 12V
The closest match with LiFe Po is four cells: 4 x 3.2 = 12.8V

So two LiFePO batteries in a series configuration is 25.6V rather than 24V. A 6.6% over voltage (or even 10%) will not affect properly designed electronics.

In the real world a freshly 100% charged lead acid battery has a similar voltage as the LiFePO with the resting voltage of the LiFePO being a bit higher. The difference is that lead acid battery voltage gradually drops as the battery is discharged. The LifePO battery holds a fairly constant discharge curve until the usable charge is almost fully depleted.

MK probably designed the duty cycle of their motors and speed controllers around lead acid batteries where isn’t possible to run at full voltage for extended periods. They are now concerned about heat build up.

It’s good to know that MK is imposing a duty cycle for motors powered by LiFePO batteries but, I would not loose any sleep over this. How often do you troll at 100% for extended periods?

Thanks for the specifics about both types of batteries. After speaking with local MK dealer where I purchased, they said that keeping motor foot pedal seeting at #8 would aid in keeping motor from reaching full max thrust. Setting 8 I assume would be close to the 85% stated in install manual.

Curious to know those that have 24V Terrova brushed motors with LifePo batteries, how they regularly use their motors.

As far as ballast, the TM weight (approx. 60#) plus two wet group 31batts (approx. 120#), plus my weight of 285#...that's 465#!!! The 12V/100amp LifePO batts are 23# each....reducing my bow weight by 74#.

I did read that MK recommends 110ah 12V batts....most 12V wet batts I have found, ex Interstate, have only 98ah.

 

[Still Afloat]

It‘s not straight forward to compare the rated A/hr capacity of lead acid and LifePO because the latter can use more of that capacity.

Some LifePO manufactures are comparing the capacity of their 100 A/hr batteries to 200 A/hr lead acid. That might be a slight exaggeration and it might vary from brand to brand but, LiFe PO batteries will give you considerably longer run times.

I bought into LifePO about 12 years ago with a 60 A/hr for my Ocean Kayak Torque which came from the factory with a 45 ft pound MK trolling motor and an electronic speed control. I ran it for a few weeks on 45 or 50 Amp/hr lead acid battery. It did well but, the battery was heavy and I usually paddled home a on day trips after the battery ran low.

LiFePO was the new thing and still quite expensive but, I spent $650 bucks on a 60 A/hr battery and another $200 or so for the charger, shipping and tax. That was (and still is) a lot of coins but, I got every penny out of it. Fishing time went from 1/2 day or little better to all weekend long. The lighter battery was easier to handle and yak performed like a had freshly charged lead acid battery in it at all times.

FYI, I still use that 12 year old LifePO battery. The capacity is down a little but, it‘s still going strong. It has actually out lasted me as I’m getting too old to comfortably kayak.

Here’s a link to short Torque review for anyone that’s interested.

 

[MrGiggles]

I have pretty much never ran mine at 100% for any period of time, even when I have broken down and used it to get to the ramp.

There's definitely a sweet spot, the difference between 80 and 100% on my Terrova 80 is about 15 amps in terms of current draw, 25 vs 40. The speed difference is .5mph or less, you're not really going anywhere faster, just sucking the batteries down a lot quicker.

Lithiums are well worth the upgrade in weight savings alone, plus they have a way longer lifespan, more stable voltage, etc. Really no downside at this point with how cheap they've gotten.

 

[thill]

I very rarely run my TM at 100% for more than a minute or two. Sometimes, when fish are popping up randomly, I'll hit the rabbit button to get over there before they go down.

As stated above, a fully charged, new lead battery has similar voltage as a lithium. Not even a slight issue in my mind. If you tend to run at 100%, you might need to go up in motor thrust.

 

[Tin Man]

Never ran a 24V in this boat so I do not know how much thrust will be needed, with 1-3 aboard and gear, to troll at 2-3mph, as I do troll 2-3mph for several hours (Striper hunting!). I also Bass fish which is not much trolling. I will also will use the rabbit function the same way as thill described.

I'm not sure where that speed (2-3mph) will equate to on the motors % scale under mostly calm conditions with less than 10mph winds? I know there many variables involved when determining TM thrust needed for a set mph and battery usage. The pedal (yet to purchase) has a dial of numbers (I believe 1-10). Motor came with the new style remote. Perhaps I will seldom be using settings 8-10 and the MK statement will not be an issue.

I guess I just need to take the plunge and give thew LifePO batts a try!

 

[beagle]

They're talking about Li-Ion , lithim ion, not LiFePo4 or lithium iron phosphate battery chemistry.... a top charged Li Ion cell is 4.1 or 4.2v, with a 3.7 or 3.6 nominal voltage compared to a Li Fe Po4 at tops 3.6-3.65 ish per cell with 3.2 nominal volts.

4 Lithium ion cells could be 16.8 volts when fully charged.
4 Lithium iron phospate cells could be 14.4 when fully charged
AGM if I remember likes around 13v when fully charged but that's up to the charger or regulator, it can be higher than that.

It's about whatever chemistry you use and the charger being used for it. Their motor is built to be able to stay running cool for X amount of watts. You can math it all out but it doens't mean much unless it all gets measured under use. LiFePO4 at full charge shouldn't really be a problem. Li Ion at full charge _really_ shouldn't be either - but they may have seen overheating in house and are compelled to make the statements. Could just be design paramaters and some engineer being a nanny for the lawyers. I'd think it would run cooler at higher voltage and lower amps than lower voltage and higher amps for the same amount of watts but we're talking 25% swing in potential voltage, and engineers get funky about that kind of slop.

Anyway, in theory, it should be fine with a LiFePO4 battery, they're in the same ballpark as AGM or SLA lead batteries for voltage, just a ton lighter ( and a ton better IMHO). What they are sweating in the paperwork is Li Ion, and I honestly wouldn't want a big Li-ION battery in my boat. They are different animals and require more attention. Thermal runaway is no joke. I have not seen anything but LiFePO4 batteries for golf carts or marine use in quite a while now, just something to be aware of when buying your battery.

 

[Still Afloat]

They're talking about Li-Ion , lithim ion, not LiFePo4 or lithium iron phosphate battery chemistry.... a top charged Li Ion cell is 4.1 or 4.2v, with a 3.7 or 3.6 nominal voltage compared to a Li Fe Po4 at tops 3.6-3.65 ish per cell with 3.2 nominal volts.

4 Lithium ion cells could be 16.8 volts when fully charged.
4 Lithium iron phospate cells could be 14.4 when fully charged
AGM if I remember likes around 13v when fully charged but that's up to the charger or regulator, it can be higher than that.

It's about whatever chemistry you use and the charger being used for it. Their motor is built to be able to stay running cool for X amount of watts. You can math it all out but it doens't mean much unless it all gets measured under use. LiFePO4 at full charge shouldn't really be a problem. Li Ion at full charge _really_ shouldn't be either - but they may have seen overheating in house and are compelled to make the statements. Could just be design paramaters and some engineer being a nanny for the lawyers. I'd think it would run cooler at higher voltage and lower amps than lower voltage and higher amps for the same amount of watts but we're talking 25% swing in potential voltage, and engineers get funky about that kind of slop.

Anyway, in theory, it should be fine with a LiFePO4 battery, they're in the same ballpark as AGM or SLA lead batteries for voltage, just a ton lighter ( and a ton better IMHO). What they are sweating in the paperwork is Li Ion, and I honestly wouldn't want a big Li-ION battery in my boat. They are different animals and require more attention. Thermal runaway is no joke. I have not seen anything but LiFePO4 batteries for golf carts or marine use in quite a while now, just something to be aware of when buying your battery.

You are right about Li-ION voltages but, these batteries aren’t that common for our application. With LiFePO available at prices similar to lead acid battery prices, LiFePO is dominating the “deep cycle” battery market. Or it soon will be.

It seems odd that MK would make a statement about Li-ION. A lot of people get mixed up when talking about Lithium ION and Lithium Iron.

 

[beagle]

You are right about Li-ION voltages but, these batteries aren’t that common for our application. With LiFePO available at prices similar to lead acid battery prices, LiFePO is dominating the “deep cycle” battery market. Or it soon will be.

It seems odd that MK would make a statement about Li-ION. A lot of people get mixed up when talking about Lithium ION and Lithium Iron.

Exactly - and why I was being a wind bag about it. lol. It applies, but not really, because the technology has already changed favorites for a less dangerous chemistry with significantly different performance. From the original post:

"Minn Kota trolling motors can run on Lithium-Ion batteries. However, they are specifically designed to run on traditional lead acid
batteries (flooded, AGM or GEL). Lithium-Ion batteries maintain higher voltages for longer periods of time than lead-acid. Therefore,
running a Minn Kota trolling motor at speeds higher than 85% for a prolonged period could cause permanent damage to the motor."

I guess technically, they are all Lithium Ion batteries, but the cathode material makes a huge difference in what you get out of it and how it behaves. The LFP batteries are not as hot rod performance as the LNMC batteries but they are more tolerant (safer) when mistreated, and a lot closer to lead acid voltages. Like you point out, and I agree, the batteries "they" are talking about are not the same batteries that are typically for sale these days. They should really be more specific in their wording, it creates confusion.