Conversion to LiFePo batteries

[FSH 210 Sport]

After having my boat for a second and full season, I found that can get about 10 miles out of my trolling motor battery, or about 6 hours of use at 1.8 mph, which is not enough for my average day of fishing which is 10-12 hours. So I was messing around with idea of replacing my trolling motor battery SLA batteries with lithium batteries, and possibly my house battery as well. I haven’t seen a thread detailing the math of LiFePo batteries, only that they are lighter, have more energy than SLA batteries, and most are super happy with them. Hopefully some of you will find the following numbers as enlightening as they were to me when I penciled this all out.

Coming from an electrical field (see what I did there) using KWh to determine a batteries capacity is easier and more accurate than going through a table on a battery manufacturer‘s website and trying to poke a needle into that voodoo doll of Ah discharge rates. Let’s face it, most of us are not going to turn things on or off based on discharge rates, we are going to use our devices as we wish and we will want to exploit the advantages the LiFePo batteries’ performance to offset their initial high cost. @Zeusmotorworks use of a single 36V 60 Ah LiFePo battery for his 112# thrust MinnKota Rip Tide troller is a testament to the high usable KWh of a LiFePo battery. https://jetboaters.net/threads/210-fsh-trolling-motor-mount-pics.24573/

I currently have three Deka SLA 12V 90 Ah batteries in series which yields 3.24 KWh of energy, 36 Volts X 90Amp hour rating of the battery, you only use the Ah of 90 because Ah is not additive in a series configuration. However the SLA battery can only be discharged 50% or damage occurs to the battery, so there is only 1.62 KWh of usable energy. Also, the voltage decay in a SLA battery may render the troller in operative even though there is energy left in the battery. I found this out last summer when I heard a double beep from my troller and the only thing it would do is stow itself since the battery voltage was too low. A good design feature for both not leaving too little power to stow the motor, and to prevent damage To the motor.

A single Dakota Lithium 36V LiFePo 63 Ah battery yields 2.26 KWh’s of energy, at a discharge of 95% that leaves 2.147 KWh of usable energy. That’s a 32.5% increase in capacity Over the SLA battery. A battery bank consisting of three Dakota lithium 12V 100 Ah LiFePo batteries will yield 3.6 KWh total, @95% thats 3.42 KWh of usable energy, an increase of 211% in usable energy Over the SLA battery.

Cost:

• 3-Deka SLA 90 Ah batteries=$488, or $301per KWh. ($488/1.62KWh)
• 3-DL 12V 100 Ah batteries= $2399, or $701 per kWh ($2399/ 3.42KWh)
• 1-DL 36V 63 Ah battery= $1699, or $791 per kWh ($1699 / 2.147 KWh)

Weight:

• 3-Deka SLA 90 Ah batteries=160.5#
• 3-DL 12V 100 Ah batteries= 95.7#, or 59.6% / 64.8# less weight than the SLA bank.
• 1-DL 36V 63 Ah battery=59#, or 63.3% / 101.5# less weight than the SLA bank.

Other advantages:

• Flat voltage curve during discharge
• Slightly smaller overall size
• No sulphuric acid in the storage / head compartment
• Charge in half the time of a SLA battery
• Up 4 times the service life
• LiFePo batteries are not damaged if left in partial state of discharge

Disadvantages:

• Higher up front cost
• Cannot charge if the battery is less than 32°F. I’ll have to install a heated battery blanket or pad during the shoulder seasons.
• At -35°F the battery will be damaged. So for those rare instances of temperatures in this range the battery (boat) will have to be in my heated shop.

 

[JetPowered]

I think one more thing to add to your pro category is longer serviceable life. This should reduce your price per kWh (increase ROI). Looks like lifespans in the 3-10 year range. Yes, your capacity will start to diminish with age and cycles, but nothing like lead acid based batteries.

 

[FSH 210 Sport]

I think one more thing to add to your pro category is longer serviceable life. This should reduce your price per kWh (increase ROI). Looks like lifespans in the 3-10 year range. Yes, your capacity will start to diminish with age and cycles, but nothing like lead acid based batteries.

Agreed!

If just the upfront cost for the SLA battery is adjusted to meet the same performance (+32.5%) of the single 36V lithium the cost per kWh goes up to $399 per kWh. When the SLA battery cost is adjusted for charging / discharge cycles, 4X the price goes to $1596 per kWh.

 

[mrcleanr6]

Most Li batteries have a max discharge of 80% not 95. I would rework the math there just so your comparison is apples to apples. The other big advantage of Li is that they can be charged at incredible rates. You can pretty much dump as much power as possible into them so be sure your charger is BIG and set up for Li.

 

[FSH 210 Sport]

Most Li batteries have a max discharge of 80% not 95. I would rework the math there just so your comparison is apples to apples. The other big advantage of Li is that they can be charged at incredible rates. You can pretty much dump as much power as possible into them so be sure your charger is BIG and set up for Li.

Thanks! According to the video’s linked on the DL site, the youtuber says 95%, but the DL site states 2000 cycles at 80%, so thanks for pointing that out! Still with 4X the cycles, dropped the price down to $175 per KWh if one wanted to look at it that way.

For me, it is the battery performance that is paramount, weight savings is next, not having any battery acid in the head compartment is also huge, and being able to use the battery over several days without charging will not damage the chemistry of the battery like would happen with a lead acid battery.

 

[mark_m]

Where are you sourcing the LiFePo batteries? I plan to upgrade for next season. My flooded lead acid batteries are done.

 

[FSH 210 Sport]

Where are you sourcing the LiFePo batteries? I plan to upgrade for next season. My flooded lead acid batteries are done.

Dakota Lithium at the moment…. They seem to have a whole section dedicated to trolling motor banks with wiring kits for the three battery banks, as well as single 36V batteries.

I’m looking at the single vs. three battery set ups with their pros and cons for what I want them to do.

 

[FSH 210 Sport]

Simplest:

https://dakotalithium.com/product/dakota-lithium-36v-63ah-deep-cycle-lithium-iron-phosphate-marine-single-battery/

LIghtest:

https://dakotalithium.com/product/dakota-lithium-36v-54ah-deep-cycle-marine-trolling-motor-battery/

Most KWh:

https://dakotalithium.com/product/dakota-lithium-36v-100ah-deep-cycle-marine-trolling-motor-battery/

Each one of those batteries has its pro’s and cons.

For full on capacity the 100Ah batteries give the most at 3.6KWh gross, roughly a 211% increase in capacity over my lead acid battery bank. 64.8# less weight.

For simplicity and a 32.5% increase in capacity the single 36 V battery is compact, 101# lighter than my lead acid battery bank. 2.26KWh energy gross

For the lightest weight the 60 Ah batteries would be 111# less weight than my current battery bank and 2.16KWh of energy gross. These batteries can also be used as a start battery, this one may make a good choice when replacing the start / house battery set up. Currently I have had a few times where I had to start the mains to recharge the house battery during long days while the live well was running all day.

My goal for doing this is primarily capacity increase, so at the moment I’m leaning towards the 3x100Ah bank. This would give me more than enough capacity for full 12-14 hour days of fishing, and or would provide the energy for multi day fishing trips where shore power was not available, and still pull 65# of weight off the boat in front of the center of gravity.

Next will be the house battery, and I think I have found a good battery in the lightest category.

 

[FSH 210 Sport]

Update:

@mrcleanr6 made some great points in another post regarding lithium batteries which led me to ask some pointed questions to Dakota Lithium. I will just say that based on DL’s responses, both verbiage and time wise, I began to look else where. I checked with Anti Gravity batteries since I have them in my dirt bikes and have been nothing but very pleased with their performance.

As it turns out, Anti Gravity recently came out with two group 31size deep cycle batteries. One is their top tier battery a V1 and the other a V2 has a few less goodies than the more expensive one, but both are 100Ah batteries with excellent performance. And according to the founder Scott, all of the 100ah batteries test out at 105 to 110 ah.

To name a few things that the AG batteries have that the DL’s don’t have.

• Bluetooth app that shows-battery voltage, amperes and watts in and out, 435 connectivity (if you use that), state of charge, internal battery temperature and a few others.
• BMS system that auto resets. The DL batteries have to be put on a charger to wake the batteries up after the BMS isolates the battery. THE FACT THE DL BATTERIES BMS DOES NOT AUTO RESET WHILE ON THE WATER MAKES THE DL BATTERY A NON STARTER FOR ME.
• BMS system that prevents charging if the batteries are too cold for charging to prevent damage. While this may not be an issue for most, for me during the shoulder seasons it can easily drop into the teens at night while being in the 30’s during the day. For me, this takes away something I would have had to deal with. With the AG batteries it is no longer something I’d have to worry about. The DL 60 Ah group 24 size has this cold charge lock out feature but the 100Ah batteries do not, and to the best of my knowledge neither do the other batteries including the 63 Ah single 36 volt battery.
• The AG batteries are 4.5# less weight than the DL’s, just an added bonus.
• The more expensive AG V 1 battery comes with two threaded attachment points per pole, this is one of the things that the less expensive V 2 battery does not have.
• The AG V1 comes with an integrated fuel gauge on top of the battery.
• The AG battery has 100 amp continuous discharge rate where the DL is 60 amps. My Ulterra trolling motor draws 62 amps at full throttle-this would be another way the DL BMS could cut off the trolling motor power while on the lake and not be able to reset it. The AG also has several much higher discharge rates that are far superior to the DL’s, not that I’m planning on using them at those rates, just a fact.
• The AG battery web page has links to the user manual where it talks about wiring set ups etc… where the DL site is, well, lacking in that aspect.
• The AG website has a tech on duty during the day so you can get real time answers to your question, the DL battery requires an email sent and “within two days” you‘ll get a response.

I sent the tech guy at AG a good size list of questions regarding the operation of the BMS system thanks @mrcleanr6 for making me aware to ask these questions, once I get all of those answers back I will update this thread again with a line by line comparison of the AG and DL batteries. As it stands now, and depending on the answers I get back from AG, my choice is going to be the AG batteries as they are far superior to the DL’s in functionality. Sure the V 1 is a bit more money, $80 per battery more but you are getting what you pay for in my opinion. Don’t want to pay the extra $80? Then the AG V2 battery is the same price as the DL battery. With the V2 you still get the bluetooth battery monitoring, there is only one threaded connection per pole, the 100 amp continuous discharge is the same.

Go to AG’s web site and check it out for yourself. DC-100-V1 Lithium Deep Cycle Battery

@mrcleanr6 I’d appreciate your feedback.

Thanks!

 

[mrcleanr6]

ahhh nice! its funny what you find out about these different batteries and the companies that make them once you start digging. almost everyone would just look at the price and the ah rating and figure it was all the same. there is definitely quite a difference from company to company. actually i think the battery in my ktm is an antigravity from the factory. curious if you compared the AG battery to the battleborn? would be interested to see the differences in the specs on those.

something i did find out concerning insurance. now this may not be true for all insurance companies and not sure how it applies to small boats like ours but atleast for larger boats and their systems, most insurance will not write a policy for a boat with lithium UNLESS A: the batteries are installed by an abyc certified marine electrician and B: the batteries have to be made in the usa and i believe ul listed or, there is another cert i cant remember off the top of my head...maybe ce, not sure. many of these people going the diy route on their boat with lithium are either uninsurable or the ins co drops them if they find out. if their is an accident, etc, the ins co can deny the claim. i have heard this same story and requirements from more than a half doz boat owners all with different insurance companies. again, bigger boats here. i dont think having a lithium battery on your boat for a trolling motor is going to make a bit of difference. these are more for boat with integrated house banks.

 

[HangOutdoors]

I figured if I went the with LiFePo4's that are in the majority of Bass Trackers and Rangers that the Pros beat the shit out of day in and day and swear by, I couldn't go wrong. Plus the price was right.

12V 80Ah Lithium Battery for Solar Power, RV, EV and Marine Applications | RELiON (relionbattery.com)

Tracker Marine Lithium Super High Output Lithium Deep Cycle Marine Battery | Bass Pro Shops

 

[FSH 210 Sport]

ahhh nice! its funny what you find out about these different batteries and the companies that make them once you start digging. almost everyone would just look at the price and the ah rating and figure it was all the same. there is definitely quite a difference from company to company. actually i think the battery in my ktm is an antigravity from the factory. curious if you compared the AG battery to the battleborn? would be interested to see the differences in the specs on those.

something i did find out concerning insurance. now this may not be true for all insurance companies and not sure how it applies to small boats like ours but atleast for larger boats and their systems, most insurance will not write a policy for a boat with lithium UNLESS A: the batteries are installed by an abyc certified marine electrician and B: the batteries have to be made in the usa and i believe ul listed or, there is another cert i cant remember off the top of my head...maybe ce, not sure. many of these people going the diy route on their boat with lithium are either uninsurable or the ins co drops them if they find out. if their is an accident, etc, the ins co can deny the claim. i have heard this same story and requirements from more than a half doz boat owners all with different insurance companies. again, bigger boats here. i dont think having a lithium battery on your boat for a trolling motor is going to make a bit of difference. these are more for boat with integrated house banks.

You are most correct sir! Fun fact, DL shows their home base if you will in Grand Rapids North Dakota. But, if you try and find DL in Grand Rapids there is no listing, only the WA address for “sales” is listed along with a 877 number for sales. AG has a So Cal area code and number, 310 which is used to be the 213 area code a very long time ago, in a galaxy far away…

I had forgotten about the insurance thing! I will definitely check with my insurer on that!

Another fun fact… after I finished my text / chat session with the Tech Chad, I got a transcript of that session sent to my email.

So point of interest here… when I get evasive answers to questions, it makes me suspicious and I dig deeper. To wit, I had asked Minnkota about any known problems with using LiFe batteries, the MK tech said that with the ulterra or auto deploying motors, they had several issues with the use of LiFe batteries mainly because the motor thinks it has encountered a obstruction and locks out. However the reasons that the MK tech gave me were diametrically opposing to electrically theory. When I told the MK tech what he said didn’t make any sense, E.G. voltage going up as well as amps-that’s not how it works folks, if the amperage goes up then voltage decreases, watts are watts, volts times amps. So, if the motor thinks there is an obstruction its because either the voltage has dropped, or the amperage has gone up, not both.

He also said that running the trolling motor at full speed with a LiFe battery would cause a thermal runaway condition. I said okay but that doesn’t happen when using a lead acid battery? And he said no, again, if the voltage stays high which is a characteristic of LiFe batteries, amperage, in a given power situation, stays the same, if the voltage was going down as with using a lead acid battery, the amps would increase along with heat, so what you are saying doesn’t make sense from an electrical theory stand point, nor from a thermodynamic stand point, because at max power with a LiFe battery the voltage will stay constant and amperage will increase along with the watts. So if anything with a LiFe battery the unit should run cooler. I don’t think he really liked that but that is a ”him” problem not a “me” problem, I don’t make the laws of physics, I just live within the laws. I then asked the MK tech which LiFe batteries were being used and he said he did not have that information

When I told DL’s tech rep about what MK said, using the LiFe batteries would cause deployment or over heat at high output the DL rep said I would have to talk with Minnkota. WTH? I just told you I talked with them and what they said, and on the DL website it says that DL works with MK trollers? It’s those types of questions, evasive, that turn the gain on the bs radar to full for me. I would have totally accepted, “ I don’t know because I’ve never had any reports of problems like that”. Unless you can’t say that because it would be a lie. Logic trap. I put those issues down to fringe issues as you never know what these people with issues were doing, was the boat moving too fast when they either deployed or retraced the motor causing the lock out? If it was a huge issue there would be tons of posts about it.

 

[FSH 210 Sport]

I figured if I went the with LiFePo4's that are in the majority of Bass Trackers and Rangers that the Pros beat the shit out of day in and day and swear by, I couldn't go wrong. Plus the price was right.

12V 80Ah Lithium Battery for Solar Power, RV, EV and Marine Applications | RELiON (relionbattery.com)

Tracker Marine Lithium Super High Output Lithium Deep Cycle Marine Battery | Bass Pro Shops

Right on… right in there with the other batteries pricing.. again, I would have never thought to ask the questions that I’m asking now if @mrcleanr6 had not suggested them. Before I drop $3000 on batteries I want to make sure I’m not going to have some kind of issues with them. I’m a go way away from people and utilities type of guy on my trips and I need to make sure to the best of my ability that when I’m 70-100 miles by water away from modern conveniences that something will not happen that I could have known about if I had just asked the correct questions.

I’m super glad that your set up is working without dramas! We need to see more fishing pics from you this year using your troller on the BIG lakes!

 

[FSH 210 Sport]

The best thing about threads like these is that we all learn something from them!

I also asked AG if they were going to be producing a group 24 size deep cycle in the future, and, if the group 24 size battery they have now in the 60Ah size would be suitable for deep cycle use. Crazy amount of CCA in the 24 size battery, 1500 CCA‘s.

 

[HangOutdoors]

If you look at the Tracker Lithium which are rebranded Relion's the price is 10-20% cheaper, same battery but they buy them in gross. If you hit it right at cabela's or Bass Pro, you can get the 100ah for $699 and the 80 ah for in the $500's, which is what i got. Could save you at least $1000 if my math is correct. Sign up for one of their credit cards and get up to $200 more off, when the special is running then just use it for the purchase.

Look at the specs on the Relion spec page as well, very interesting when I reviewed them next to Battleborn and Dakota Lithium. Although I am not into as deep as you are. What I found interesting was the charging temperatures and the discharge percentage with cycles.

 

[mrcleanr6]

@HangOutdoors just from word of mouth, relion's are supposed to be fairly decent. i have no hands on with them though or many of the other brands out there. lithionics only really.

please keep in mind, i dont claim to be any pro concerning lithium batteries. all i am doing is passing along what i have learned from my deep dive into this subject from building my new boat and getting info from people like marine electrical engineers and many people who have done the 80-$150k conversions from agm to lithium. while not everything transfers from the big systems to a 1-2 small battery system in yamahas, some of the basics do so i just try to make everyone aware so you can do your own research. im glad it helped out @FSH 210 Sport.

 

[HangOutdoors]

@HangOutdoors just from word of mouth, relion's are supposed to be fairly decent. i have no hands on with them though or many of the other brands out there. lithionics only really.

please keep in mind, i dont claim to be any pro concerning lithium batteries. all i am doing is passing along what i have learned from my deep dive into this subject from building my new boat and getting info from people like marine electrical engineers and many people who have done the 80-$150k conversions from agm to lithium. while not everything transfers from the big systems to a 1-2 small battery system in yamahas, some of the basics do so i just try to make everyone aware so you can do your own research. im glad it helped out @FSH 210 Sport.

For me the specs were Great if not better than the Dakota's and the price was right. I can go all day off and on without issues and haven't killed them yet. They should outlast me if I keep the boat for many years. I only know what I have read and have been told. I do wonder if I should of got the 100ah, but haven't needed it as of yet. I will probably revisit the LiFePo4 purchase if I change out the boat to a larger one. Hopefully the technology price comes down.

 

[FSH 210 Sport]

Quick update:

@HangOutdoors thanks for the tip about the tracker branded Relion batteries.. went to cabelas yesterday to put hands on a 12V 100 Ah, man those things are light. Was looking at Relions website this morning, I’m impressed so far. Lots o discharge and charge tables, comparison tables etc. as well as BMS disconnect levels with the tabular description sheets. That combined with the ability to take a bad battery back for exchange is very convenient. Going to call Relion in a while and see if they can answer my questions. So far I’ve not been able to actually talk with tech reps with the other battery companies-frustrating, that gives me pause when thinking about any issues going forward, if those other companies can’t answer me except within two days, what’s going to happen if I have an issue?

I do really like the AG batteries Bluetooth app to monitor battery specs though.. there was a tiny time stamp in the corner of the chat transcript I was sent, 8 hours ahead of my time zone, see attached screen shot of where that is. That time zone encompasses the DRC where 70%+ of the cobalt comes from for LiFePO4 construction…All of the companies are owned by the chinese. Just an observation .

Jury is still out…

 

[FSH 210 Sport]

Update #2 for today:

I called Relion office in South Carolina, what a concept an actual person answered on the second ring. I spoke with Karen a CSR for a good 40 min. While not the tech person I would talk to after her, she was very up to speed on her role within the company. When I told her that I was so impressed that an actual person answered the phone she remarked, “ I get that a lot”. When I mentioned supply chain logistical things she responded that Relion had shipped 17 containers to Cabela’s / Bass Pro shops in the last three months this is due to the fact that the ships coming from china where the batteries are made go through the Panama Canal and go to SC, the home base for Relion.

After talking with Karen, I was then handed off to Craig the supervisor for the Tech answer line. Craig as awesome as Karen was. I asked him every question that I could think of (big shout out to @mrcleanr6 !) and he answered them all.

• -Does the battery BMS system prevent charging in temps below 32*F. No it does not, but Relion sells a LT or low temperature version of the their 100Ah battery ($1350) that has an internal heating pad that is powered by ones battery charger. If the battery is at -4*F it will take approximatley 1.5 hours to bring the internal temp of the battery up high enough to start charging which the BMS will do automatIcally. This is important for me since the late afternoon / overnight lows in my area can drop into the teens during the shoulder seasons.
• Battery charger: My current (see what I did there?) Minnkota precision battery charger set on AGM is totally suitable for charging these batteries with its 10A per bank charging capability. I asked him twice whether or not I needed to upgrade my charger and he said no, that he was familiar with my charger and it would be totally fine.
• Under voltage protection: This aspect of the BMS is the only one where in the BMS would not automatically reset. This activates at 10 volts on an individual battery. If this was to activate, to get the BMS to reset, one would need to disconnect one leg from the battery so that the BMS see’s that there is nothing connected to the battery and then the BMS will re connect within a matter of micro seconds. @HangOutdoors this might be helpful to you in the future if you did not know that. In my case with a self deploying trolling motor, this could be very useful to know. If one were to let the batteries sit for a while after UVP disconnect the it is possible for there to be enough power to stow the motor upon reconnection of the BMS as mentioned above.
• BMS protection: The other aspects of the BMS protection whether it be high heat, high amperage etc. will reset once the offending thing has been removed. So if the battery went out on high heat it will reconnect as soon as the battery cools off.
• Bluetooth connectivity: The Relion battery does not have Bluetooth connectivity yet, Karen said she knew I was going to ask that question. Karen told me that Victronics sells a shunt style of Bluetooth capable monitor that I could hook up to keep an eye on the batteries. I believe it was Karen, could have been Craig, that said that functionality is coming in another year.

I went and looked for the Victron Energy bluetooth battery monitor and found it here:

https://www.amazon.com/Victron-SmartShunt-500AMP-Bluetooth-Battery/dp/B0856PHNLX/ref=sr_1_4?crid=2AFN07SL6NH0W&keywords=victron+battery+monitor&qid=1643320847&s=hi&sprefix=Vic+Tron+%2Ctools%2C176&sr=1-4

It will monitor State of Charge, Amp hours used, Watts, Voltage, and battery temperature and well as monitoring the voltage of an additional battery. Seems like a easy set up and this battery monitor could be replicated for all the batteries on your boat with additional units.

Finally heard back from Antigravity, the CSR said he was traveling for a trade show and sent a link to the user manual for their batteries. https://antigravitybatteries.com/downloads/AG-DC100-V1-Battery-User-Manual.pdf

So far Relion has taken a sizeable lead in my search… I think they are going to be the winners but have not made a final decision.

 

[HangOutdoors]

Respectfully, you may be over thinking it. Throw some trackers in, save some dough and you should be fine for many years to come. People I have spoken to, whom fish day in and day out, for a living, swear by them.