# Lifepo4



## Zum (Oct 10, 2021)

Anyone but the lifepo4 batteries through amazon?
They seem to be half the price of what i can find through other places. Canadian price of $550 ish, with the little searching ive done the mext lowest is $960 for a 100 aH 12V.
Do you think i would need a 100aH , for a 55lbs thrust trolling motor?


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## LDUBS (Oct 10, 2021)

I haven't bought them at all, so can't help you there. 

My 55 lb Minn Kota specifications say use a 100AH battery. But that is for a lead acid battery. I don't know how that might change with a lithium battery. Here is a blurb from Minn Kota about using lithium batt's. To be honest, I don't really even understand what they are saying, especially the part about the battery turning off. 

_"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. 

The LiFePO4 Lithium batteries can be used with our motor. LiFePO4 batteries that have a maximum continuous output current ratings need to be higher than the maximum current ratings of the trolling motor or the battery will turn off."_


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## LDUBS (Oct 10, 2021)

Saw this on another forum: 


_Renogy is offering their 100ah battery with Bluetooth for $499
https://www.renogy.com/12v-100ah-lit...y-w-bluetooth/


And their 200ah for $999
https://www.renogy.com/12v-200ah-lit...y-w-bluetooth/_


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## Jim (Oct 11, 2021)

Interested!

My 3 batteries are going on 6 years. At some point I’m going to have to make a purchase. 

Still a little more than I want to spend.


Sent from my iPhone using Tapatalk


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## onthewater102 (Oct 11, 2021)

I've been using the Ampere Time 50 amp-hour one from Amazon for a few months now. Amazing how lightweight it is. Time will tell if it holds up, but so far so good.

The 50lb weight reduction in my 12' made itself known the first time I fired up the outboard and went to make a run up the river.


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## Zum (Oct 11, 2021)

Its mostly the weight saving im looking for as well. I charge my batteries in the basement and lugging a group 31 around is getting old, just like me. Im also thinking of going to a 4 stroke, which is going to add some weight as well depemding on which hp i go with. I know i can move things around in the boat but the lithum battery would save 40+ lbs.
I was just thinking the amazon batteries are some sort of knockoffs. I was on a RV forum reading what they had to say and it could be hit or miss...they gave some names of a few to try and others that maybe i should avoid.


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## onthewater102 (Oct 11, 2021)

LDUBS said:


> ..._"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.
> 
> The LiFePO4 Lithium batteries can be used with our motor. LiFePO4 batteries that have a maximum continuous output current ratings need to be higher than the maximum current ratings of the trolling motor or the battery will turn off."_




Two things going on here:

1st - Wattage (work/power) = Voltage x Amperage. Their motors are designed to draw a fixed amount of amperage which the engineers based on the anticipated voltage drop experienced by lead acid batteries. Without this drop they still draw the same current, but receive it at a higher voltage and therefore generate more power. More power = more heat, so this is likely where you'll run into an issue running your motor on high for an extended period of time (too much heat buildup in the motor or circuitry)

2nd - Lithium batteries have a built in computer control called a battery management system (BMS) which controls many things, one of which being the maximum current that can be drawn on the battery to prevent damage to the cells in the battery. These batteries are rated both for an amp-hour capacity as well as the maximum amperage load that can be applied to them at any given moment. There is a safety built into the BMS which will internally disconnect the cells from the terminals in effect "turning off" the battery.


It is really differences in the BMS that seem to separate the quality of LiFePO4 batteries available from what I could tell. The BMS has to protect it from overcharging, charging when the battery is too cold or charging when it's too hot, to name a few other things. Lithium batteries should not be put on a trickle charger (as lead batteries need to maintain their charge), and you can damage them by using lead-acid chargers on them for this reason.

Great overview of LiFePO4 batteries can be found here:

https://marinehowto.com/lifepo4-batteries-on-boats/


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## LDUBS (Oct 11, 2021)

That is good stuff. Thanks OnTheWater. I learned something.


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## InSaneFisherMan (Oct 12, 2021)

Automobile and aircraft companies have and are having thermal runaway issues with lithium batteries.

It not just the BMS, but how they are built, put together, and charged.

I personally like lithium batteries, but, the reason they call it thermal runaway, is because lithium gas burns, heats the next cell, burns, and typically can only be extinguished by submerging the battery in a liquid that cools the cells enough to stop the runaway.

Boating industry needs to create a specification for boat batteries.

Buy a quality battery.


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## onthewater102 (Oct 15, 2021)

Generalizing "Lithium battery" is almost like walking into a hardware store and asking for a "screw", it's a greatly over-simplified reference.

Lithium battery chemistry varies significantly, some use cobalt or other metals to achieve better discharge or storage capacity parameters. These other chemistry types are the "lithium batteries" which are the subject of what you heard about issues on planes and with car companies testing various batteries for use in vehicles.

The LiFePO4 construction's claim to fame is safety, accepting several performance restrictions to achieve it, so unlike the others when they have issues with heat they shut down and fail to work but do not catch fire.

Decent summary article on battery chemistry can be found here:

https://owlcation.com/stem/Comparing-6-Lithium-ion-Battery-Types


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## InSaneFisherMan (Oct 15, 2021)

Lifepo4, may be safer, but does it meet ABYC TE-13 requirements for marine application?

TE-13, I think is still in draft, but will most likely be the standard for batteries lager than 600Wh.

So, before purchasing cheap/inexpensive or any lithium battery for marine applications , ask if it meets current TE-13 requirements or at least UN 38.3 standards.


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## onthewater102 (Nov 10, 2021)

InSaneFisherMan said:


> Lifepo4, may be safer, but does it meet ABYC TE-13 requirements for marine application?



While I found this on their site I couldn't find any batteries from a variety of sources (including the Tracker Marine branded ones sold by Bass Pro) which claimed to have been tested for compliance with it yet. UN 38.3 is just a shipping standard, at least as far as the Ampere Time batteries I bought they all came in packaging with a UN 38.3 marking.


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## MrGiggles (Nov 11, 2021)

100ah is a good match for any trolling motor. Just as a rule of thumb, 1 amp per lb of thrust in 12v motors, close to half that for 24v. That would give you roughly 2 hours of wide open run time,

Lithium manufacturers will tell you that a lithium will have more reserve capacity than a similarly rated lead acid, since you can discharge them 100% without damage. I was never totally sure if lead acids are rated with their maximum 50-80% discharge taken into account. If not, in theory a 50ah lithium will be equal in output to a 100ah lead acid, since you can only safely discharge the lead acid to ~50% capacity.


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## onthewater102 (Nov 11, 2021)

Speaking with Minn Kota's customer service they caution against using their trolling motors on more than 80% power with a lithium battery as they're designed around the voltage drop a lead battery would experience with that much current draw. 

I'd never heard mention of this before from any of the tournament guys plugging their lithium battery manufacturers.


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## InSaneFisherMan (Nov 11, 2021)

onthewater102 said:


> InSaneFisherMan said:
> 
> 
> > Lifepo4, may be safer, but does it meet ABYC TE-13 requirements for marine application?
> ...



Probably all imported batteries and cells are tested to this standard. The problem is when cells are assembled into a battery. 

The assembled battery may/may not meet UN 38.3, especially if it is not exported.

A battery that meets UN 38.3 may not meet TE-13 requirements, but is probably a better choice than meeting no standards.


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## InSaneFisherMan (Nov 11, 2021)

MrGiggles said:


> 100ah is a good match for any trolling motor. Just as a rule of thumb, 1 amp per lb of thrust in 12v motors, close to half that for 24v. That would give you roughly 2 hours of wide open run time,
> 
> Lithium manufacturers will tell you that a lithium will have more reserve capacity than a similarly rated lead acid, since you can discharge them 100% without damage. I was never totally sure if lead acids are rated with their maximum 50-80% discharge taken into account. If not, in theory a 50ah lithium will be equal in output to a 100ah lead acid, since you can only safely discharge the lead acid to ~50% capacity.



If lead acid batteries had a built in BMS that accounted for the 50% debt of discharge and rated like a lithium batteries, performance would be similar and cost analysis would be a lot different.

Hope the new mandates in CA don’t drive up cost on these batteries.


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## onthewater102 (Nov 30, 2021)

Limited number of uses to this point, but thus far I'm pleased. Trying to avoid my own confirmation bias, I did notice a few points about the Lithium that wouldn't have been possible with the lead acid.

Most immediately, the weight difference is the first thing I noticed. Running with all the same gear loadout as ever and a partner I now have to back off on my throttle a decent amount with 2 people in the boat as not to over-rev my motor using a 13P prop. Previously, I could open it up 100% with 2 people in the boat and be right at the top end of the range at 5,900/6,000 rpm. This is due to the fact that I'm only carrying the 1 LiFePO4 100amp battery, as opposed to 2 size 29 lead ones which would require swapping at some point (only room for 1 up front, so the 2nd rode in the back of the boat until needed.) This is exciting, as I've got a 15P stainless prop which in the past I had only used when fishing alone out of fear of over-lugging my motor when carrying the extra weight of a companion, but it pushes the top speed of the boat over 40 when the conditions will allow for it.

On a recent trip to Oneida we fished the morning from 8am until shortly before 1pm in very heavy winds with the 12v trolling motor working on 50% - 70% power setting the entire time we weren't using the gas motor with no noticeable loss of control over the boat towards the end of that time (from past experience I know the lead battery wouldn't have held up to this, but I cannot quantify a comparison.) What was exceptional about the lithium was when we put the boat on the trailer around 1 to grab lunch and change into a dry set of clothing we hooked the battery in to charge at the hotel (not long after 1pm), and it was fully recharged by the time we headed back out at 2:45 pm.

More recently, I fished for striped bass in the mouth of the Housatonic River which always taxed my motor to its limits, and in 7 hours on the water the 12v was still holding against the incoming tide as well as it had against the outgoing to start the outing. There was roughly an hour of time on the gas motor in the mix, as well as 2 hours of slack following the morning low tide, but all in all I know the lead battery would have needed to be swapped out somewhere in the later part of the trip, whereas this held its ground the whole time.

Everything else I've used it for is to a lesser extent where any differences between them are negated (other than the weight.)

That I'm only able to charge it when it's above freezing is proving to be more and more of an issue in NW CT as the season drags on, but this was to be expected. Onboard charging up north for the next month is not going to be an option, but it's much easier to move this in and out of the garage/basement than it ever was a lead battery before it.

This is a less-discussed limitation of this type of battery new owners need to be aware of ahead of time.


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## Jim (Dec 1, 2021)

Thanks for the real world experience with those types of batteries.


Sent from my iPhone using Tapatalk


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## onthewater102 (Dec 2, 2021)

Found this searching through the paperwork with the battery for a coupon code.


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## InSaneFisherMan (Dec 3, 2021)

Great, looks like very good quality batteries.

Does the BMS give you access to number of charge cycles or status of charge.


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## onthewater102 (Dec 3, 2021)

Not that I'm aware of, there isn't an interface for the BMS externally on the battery and it isn't a blue-tooth model.


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