Lithium battery for trolling motor

Looking for some advice on lithium batteries for a boat trolling motor. I currently have two standard batteries powering a Minn Kota Riptide Terrova on a 23’ bay boat. The batteries are starting to go bad and require almost 24 hours of charging for a full charge. Considering a lithium replacement. I think I can replace the two standard with one lithium, I believe they are 2 12V in series that I could replace with a lithium 24V.

Would love to hear from anyone who’s done this themselves.

 

Don't. Li-ion don't like deep voltage draw downs.

Stick with the Deep Cycle batteries.

 

Can you be more specific? Are you saying if drawn close to capacity they fail, or don’t last as long as the standard deep-cycle equivalent?

Lithium batteries I’ve researched are designed to permit 100% capacity draw and have a 10-year warranty…

 

A lithium battery of the same amp hour rating will provide twice as much run time on the water, thousands more cycles and weigh 75% less. Only reason I have lead acid deep cycles is that they are $100 not $500.

 

Li-ion batteries can do 100% capacity but only up to a certain point. They'll be fine but the more you do 100% draw on a Li-Ion battery, they fewer cycles you'll get out of them. Granted, you'll still get upwards of like 2000 cycles from them when they're a bit more "damaged" which is more than a lifetime's worth.
The problem you might encounter is amperage draw. Li-ion batteries can do 1C discharges just fine but asking 1C consistently might be a bit much for it. Make sure you get the proper power rating. As well as one that has a good proper BMS.
Also, li-ion batteries don't like to be charged when it's cold. you'll actually permanently damage them if you charge them when it is close to freezing. a good, proper BMS should prevent charging. (this is the reason why many electric cars come with heaters to make sure the batteries don't get too cold)

I think you can do li-ion for a trolling motor. Might be uber expensive though depending on the power requirements.

 

It’s definitely expensive. I would estimate new standard batteries will put me back about $250, and the correct lithium version would be near a grand. But would last a lot longer, and weigh much less.

There’s much in your post that goes outside of my battery/electric knowledge wheelhouse (which is a very small room by the way), so at some point I just have to press the I Believe button.

 

haha. There's a lot of info out there on li-ion but not very centralized, I think. You coudl find all that info if you looked but it will require some knowledge of how to google things.
I still think a correct li-ion battery will work just fine though. price aside though. I'm a believer in li-ion...if implemented correctly.

 

I’m a highly qualified Googler, but I really wanted to hear from folks who are currently running a lithium battery with a trolling motor, see what their experience has been…

 

Example: Power tool Li-ion batteries have very sophisticated computer controlled circuit boards in both the battery and the charger. A deeply discharged Li-ion is unstable. It has a tendency to ignite into a self-sustaining fire. The control in the battery will "shut-off" the battery at a specific discharge level to prevent unwanted events. The same board will communicate with the charger to prevent charging below a specific battery temperature. The control in the charge will modify the charge rate depending on the battery state. These are just some of the tasks the control board perform.

If you are considering the Li-ion for a long life.
Think about...... How long did your current battery system last? What is the cost to replace the same system? Will the cost multiplier of the Li-ion result in a similar multiplier in life?

I suspect a 4X cost will not translate into 4X life. Even if it does.......that is break even. No gain.

FWIW, I'm not against Li-ion. Just offering another view point and things to consider. I worked in the power tool industry for 20+ years and saw the development of Li-ion batteries and many catastrophic events related to charging and discharging.

 

Those are important considerations and I appreciate it. Sounds like I need to contact Minn Kota and find out if there is compatibility with their charging bank.

It’s not just a cost/life comparison, the other factors would be weight, and battery life on a single charge. Also, charging time.

 

Li-ion don't have the the drop-off performance as "conventional" battery chemistry. It is a much flatter output....until it steps off a cliff and stops.

The conventional chemistry batteries give a "signal" of charge depletion with a degrading lower output. Li-ion do not exhibit this depletion "signal".

The risk is the Li-ion battery could deliver power to your motor, then suddenly quit, leaving you rowing back. Where a conventional battery would show a declining output with degrading motor response.

Good Luck with your decision.

 

When you’re talking about this performance cliff, are you talking about everyday drop off when the battery is depleted, or the point at which the battery fails completely and can no longer accept a charge?

I use the trolling motor for silent movement along shorelines to cast a large area, or for offshore spot anchoring. It’s never a primary means of propulsion. At most it moves the boat 2 MPH. So it’s ok if I don’t have prior warning it’s coming up on depletion for a single cycle.

 

Totally agree; weight is huge. Lugging the batteries from the truck to my boat is a huge PITA. I’d spend more to cut that weight down on my next setup.

 

It will cutout on the lake much more abruptly than the lead acid battery. Lead acids you'll notice the that instead of 1.3mph on setting 5 you have to go to setting 8 on the controller, or something similar. Lithiums tend to just go from providing power to cutting off for the day.

 

Gotcha, well, I’ll have to take that into consideration. If the lithium battery lasted just as long or longer, I guess it wouldn’t really be an issue. I typically don’t use a full charge on a trip.

 

Disagree.

There is a huge difference between lithium ion and lithium iron phosphate. Lithium Iron Phosphate is what you want. If you can afford it, it is a huuuuge improvement over lead acid.

Li-Fe phosphates are great trolling motors. You just have to keep them in a dry box. Their wrappings are somewhat permeable and they lose performance if they get wet. Other than that, they outperform lead acid by a country mile. About 50% of a lead marine deep cycle's capacity is useable. Repeated deep discharging of a marine battery can damage the plates as we all know.

OTOH, about 80-90% of a Li-Fe is useable.

I just converted my camper - 120 hours of marine batts to one 120Ah Li-Fe. It lightened the tongue by 65 pounds (bonus) and it seems I can run 4 days instead of 2 without having to break out the solar panels.

 

You'll get close to twice the run time with the same amp hour rating. If you have 50AH of lead acid and can run for five hours then 50AH of lithium will net you close to ten hours of run time. There are companies that make 24v lithium batteries so you can clean up the wiring required for two 12v batteries in series.

https://dakotalithium.com/product/d...rolling-motor-solar-energy-rv-single-battery/

 

A single 24V is exactly the direction I was considering, thanks for the link.

 

You need a battery monitor that estimates discharge by amp draw instead of volts. Fairly easy to install, and it keeps you from even approaching that cliff.

 

Well, I did find this regarding the Li-Fe composition:

https://www.minnkotamotors.com/supp...on-12v-batteries-my-minn-kota-digital-charger

interesting that it’s specific to 12V only though.

Edit: the digital charging bank is exactly what I have.