Lithium battery - worth the expense?

[LDUBS]

I have what I consider an important question for those of us considering swapping over to a LiFEPO4 battery. My 12V TM recommends a 100Ah battery. Are the claims exaggerated or can I really expect a 50Ah LiFEPO4 battery to give me extended run time compared to my 105Ah AGM battery?

 

[Still Afloat]

I have what I consider an important question for those of us considering swapping over to a LiFEPO4 battery. My 12V TM recommends a 100Ah battery. Are the claims exaggerated or can I really expect a 50Ah LiFEPO4 battery to give me extended run time compared to my 105Ah AGM battery?

Two considerations:
1. The max discharge current of the battery
2. How long you are typically fishing, weight of boat, conditions, etc.

Edit: To clarify item one, I meant the max BMS current. For example, if you had a Terrova 80 with a recommended fuse or breaker size of 60A, a battery with a 50A BMS could shut down if you stalled the motor in weeds or something. MK specs this motor at 56 A max but, it’s probably more like 45A or less at full speed under normal conditions. Max current specs are commonly overrated from actual test conditions.

 

[Still Afloat]

I have what I consider an important question for those of us considering swapping over to a LiFEPO4 battery. My 12V TM recommends a 100Ah battery. Are the claims exaggerated or can I really expect a 50Ah LiFEPO4 battery to give me extended run time compared to my 105Ah AGM battery?

Also, that 105 A/hr AGM is roughly equivalent to a 65 A/hr LiFePO.

I’d go with 100 A/hr LiFePO for a larger boat and 50s for a smaller boat.

 

[Ray Clark]

I think the TM companies are making some assumptions about what their customer base will consider satisfactory performance, and so will recommend batteries that will provide that satisfactory performance. Still, you will find "squishy" terms like "extended run time" and "satisfactory performance". How long is "extended run time"? What is "satisfactory performance"?

What do you consider "extended run time"? Is it a longer continuous run at a given power setting? How long is that run?

My idea of satisfactory performance on the lakes I fish is the ability to have 8 hours on the water with no battery issues, and be able to use that motor to get back to the dock if my outboard craps out. But how do I use that battery during the fishing day? How does weather affect it? On many days, I only use the outboard to launch and get to my first fishing spot, then it's switched off until I'm ready to recover it onto the trailer. All the rest of that time is on my TM. Many of my fishing days only see 0.5 operating hours for the whole day on the outboard. The rest of the day's outing might be all on the TM.

If the power capacity ratings are correct as labeled, a 50Ah battery will deplete power of a fully charged battery in half the time of a 100Ah battery...under the exact same conditions.

But...that "if" is a "BIG IF." I've seen tests of batteries on YouTube that show wide variation among brands when it comes to meeting the labeled capacity on their batteries.

The max power draw for my TM is 50 Amps. If the stated capacity of my battery is true to the label (100Ah), then I have a maximum run time of 2 hours at full power -- in theory. I've never tried to deplete the battery under any controlled condition. I don't think I'd be happy with a lesser battery. I'd rather just use the larger battery than monitor use of a smaller unit so that I'm not caught short out on the water.

 

[thill]

@thill - well I picked up my first Timeusb this week based on your reviews. Ordered on the 7th and delivered on the 9th. Can't beat that. Was showing 13.2 when arrived. Put it on my little 2amp charger and after a few hours it's up to charge. I got the 50amp Pro for $135 (10% promotion). Decided to go lithium as this was for a new (to me) boat and I didn't have a core laying around. SLA group 24 would have been $100.

Congrats!

These batteries will probably run your TM longer than three or even four of those group 24 lead batteries. And they have a 10 year average life, so you will save money in the end. You are going to be happy with them. I waited until they hit the right price point, and I'm very, very glad I made the switch. No more worries that my batteries won't last the day fighting heavy current.

I recommend you charge and use the battery a couple of times before worrying about voltage. It takes them a couple of cycles to break in. The BMS will take care of everything. You are going to have some excellent run time. Remember to store them at 30-50% charge if you aren't going to use them for awhile. After a few cycles, the voltage will settle down and stay constant.

Wow, that must be a nice charger. I got $29 digital chargers from Amazon, and they have been excellent.

 

[LDUBS]

Two considerations:
1. The max discharge current of the battery
2. How long you are typically fishing, weight of boat, conditions, etc.

Edit: To clarify item one, I meant the max BMS current. For example, if you had a Terrova 80 with a recommended fuse or breaker size of 60A, a battery with a 50A BMS could shut down if you stalled the motor in weeds or something. MK specs this motor at 56 A max but, it’s probably more like 45A or less at full speed under normal conditions. Max current specs are commonly overrated from actual test conditions.

Also, that 105 A/hr AGM is roughly equivalent to a 65 A/hr LiFePO.

I’d go with 100 A/hr LiFePO for a larger boat and 50s for a smaller boat.

Thanks Still Afloat. I have a 55# 12V Powerdrive. Max amp draw is 50. Spec'd breaker is 60 amps. I never run it at full power. On the scale of 1 to 10, I'm 99% of the time at 2.5 to 3.5.

Again, I just don't understand how a LiFEPO battery with a lower AH rating can outrun one or even multiple batteries with higher AH ratings. Clearly battery tech is not in my wheelhouse. I guess my understanding why is less important than knowing if my current battery ever craps out, I might be able to consider a smaller capacity LiFEPO.

This thread has been incredibly helpful understanding these newer technology batteries.

 

[flatheadsteve]

Thanks Still Afloat. I have a 55# 12V Powerdrive. Max amp draw is 50. Spec'd breaker is 60 amps. I never run it at full power. On the scale of 1 to 10, I'm 99% of the time at 2.5 to 3.5.

Again, I just don't understand how a LiFEPO battery with a lower AH rating can outrun one or even multiple batteries with higher AH ratings. Clearly battery tech is not in my wheelhouse. I guess my understanding why is less important than knowing if my current battery ever craps out, I might be able to consider a smaller capacity LiFEPO.

This thread has been incredibly helpful understanding these newer technology batteries.

The potomac is flowing hard right now .I ran my 36v garmin for 4hrs not just anchoring but moving upriver as well at times using 70% throttle to make headway and at the end of the day the little 55ah 36v lifepo4 still had 80% juice.

 

[Still Afloat]

Thanks Still Afloat. I have a 55# 12V Powerdrive. Max amp draw is 50. Spec'd breaker is 60 amps. I never run it at full power. On the scale of 1 to 10, I'm 99% of the time at 2.5 to 3.5.

Again, I just don't understand how a LiFEPO battery with a lower AH rating can outrun one or even multiple batteries with higher AH ratings. Clearly battery tech is not in my wheelhouse. I guess my understanding why is less important than knowing if my current battery ever craps out, I might be able to consider a smaller capacity LiFEPO.

This thread has been incredibly helpful understanding these newer technology batteries.

Hi LD,
It really boils down to the discharge curve. The lead acid chemistry batteries start losing voltage as soon as a load is placed on them. The longer you use them, the lower the voltage. They typically reach their minimum allowable voltage well before the rated capacity. Also, the higher the load, the faster the discharge. It’s not linear, doubling the load will reduce the running time by more than half.

The LiFePO4 has a very flat discharge curve. The voltage remains almost constant until the battery is near full discharge. So basically you’re getting more useable voltage for a larger portion of the capacity. However, when the LiFePO4 voltage drops, it does so very quickly. The BMS should shut down the battery at or before full discharge but, common sense should tell you to remove the load when you finally do see that voltage drop.

 

[MDCrappie]

If the power capacity ratings are correct as labeled, a 50Ah battery will deplete power of a fully charged battery in half the time of a 100Ah battery...under the exact same conditions.

But...that "if" is a "BIG IF." I've seen tests of batteries on YouTube that show wide variation among brands when it comes to meeting the labeled capacity on their batteries.

I was basically only looking at what I consider the "better" cheap batteries (Weize, Timeusb and Litime) but it seemed like an overwhelming amout were actually over the rated capacity. Heck even the 95AH TimeUsb one that uses "used" cells was over the capacity.

Congrats!

These batteries will probably run your TM longer than three or even four of those group 24 lead batteries. And they have a 10 year average life, so you will save money in the end. You are going to be happy with them. I waited until they hit the right price point, and I'm very, very glad I made the switch. No more worries that my batteries won't last the day fighting heavy current.

I recommend you charge and use the battery a couple of times before worrying about voltage. It takes them a couple of cycles to break in. The BMS will take care of everything. You are going to have some excellent run time. Remember to store them at 30-50% charge if you aren't going to use them for awhile. After a few cycles, the voltage will settle down and stay constant.

Wow, that must be a nice charger. I got $29 digital chargers from Amazon, and they have been excellent.

This is the charger I ordered with the battery. Got 20% off too. I saw the one you got but only had 33 reviews and I'm a bit leery getting one with so few reviews, but it's probably the same darn guts inside.
https://www.amazon.com/dp/B09DCK7XG1?psc=1&ref=ppx_yo2ov_dt_b_product_details

 

[FuzzyGrub]

Just started the third season with LA G27 on our MG Xi3. Still strong after a full day of fishing high water. Not time to switch yet. Maybe next year.

 

[-CN-]

I have what I consider an important question for those of us considering swapping over to a LiFEPO4 battery. My 12V TM recommends a 100Ah battery. Are the claims exaggerated or can I really expect a 50Ah LiFEPO4 battery to give me extended run time compared to my 105Ah AGM battery?

My experience with this would tell me to answer your question "yes". Your motor manufacturer is producing their recommendation based off of "safe" assumptions regarding typical lead batteries, where your amperage is quickly depleted. A 50ah LiFEPO4 battery should power a 12V TM all day for at least a day.

 

[-CN-]

I do believe that I will be able to do that with my "Cheap Amazon Batteries" should the need arise based on my research. If for some reason I cannot I guess you will feel good saying "I told you so"? If I am though will you believe that you got ripped off paying almost 3 times the amount?

I wouldn't feel good buying a product that a company apparently knows of a problem but hasn't corrected it yet. Better read your "11" year warranty thoroughly though if you actually think you are getting 11 years.

Nowhere in my post did I call you out, undermine any of your choices, and imply that I make better decisions than you. Nor did I even quote you. Calm down your tone. If you think I'm going to have any desire or care to follow your particular battery story so that I can say "I told you so" if unfortunately anything were to happen to your purchase, then that is not a positive judgement on your part of a fellow boater. And after months of research before finally investing in one of these, why would I make the decision to buy something that would be a "rip off"?
The problem with the dozens of brands that use the cheap cells is they likely won't even exist as the same branded name in even a few years from now. Look at the top-selling cheap brands on Amazon, they are only a year or two old. Professionals who have been using a testing these batteries for longer than these companies have been around have noted the constant "brand name" changes as one design gets scrapped for another and they are rebranded. You can't get warranty replacements for items that don't exist anymore. They will ALL likely last 5-10 years or more if used and maintained properly. But it takes a reputable company who is in the business of making and promoting battery technology in order to be able to honor their stated warranty, not just an "assembler" putting chinese cells into a box as a one-off product that they can sell on Amazon.
And all of the warranties on these items are pretty much listed the same way. Yes, I've read them. The 11-year stated warranty, if I mentioned it, is simply a statement of the manufacturer's claims, similarly to any stated 10-year and 12-year warranties (and others depending on what their claim is). Of course there are standard prorated details in all of them. I am not obligated to break down the warranty claim into fine details in order to be able to mention it.

 

[MDCrappie]

Nowhere in my post did I call you out, undermine any of your choices, and imply that I make better decisions than you. Nor did I even quote you. Calm down your tone. If you think I'm going to have any desire or care to follow your particular battery story so that I can say "I told you so" if unfortunately anything were to happen to your purchase, then that is not a positive judgement on your part of a fellow boater. And after months of research before finally investing in one of these, why would I make the decision to buy something that would be a "rip off"?
The problem with the dozens of brands that use the cheap cells is they likely won't even exist as the same branded name in even a few years from now. Look at the top-selling cheap brands on Amazon, they are only a year or two old. Professionals who have been using a testing these batteries for longer than these companies have been around have noted the constant "brand name" changes as one design gets scrapped for another and they are rebranded. You can't get warranty replacements for items that don't exist anymore. They will ALL likely last 5-10 years or more if used and maintained properly. But it takes a reputable company who is in the business of making and promoting battery technology in order to be able to honor their stated warranty, not just an "assembler" putting chinese cells into a box as a one-off product that they can sell on Amazon.
And all of the warranties on these items are pretty much listed the same way. Yes, I've read them. The 11-year stated warranty, if I mentioned it, is simply a statement of the manufacturer's claims, similarly to any stated 10-year and 12-year warranties (and others depending on what their claim is). Of course there are standard prorated details in all of them. I am not obligated to break down the warranty claim into fine details in order to be able to mention it.

Did you forget about posting this question? Right after I posted that I had just purchased a "Cheap Amazon Battery". I was just answering your question, and providing my reasoning for my purchase.

I would ask - do you believe you can do that with your cheap Amazon batteries?

 

[Still Afloat]

Guys, take a break. Go fishing or something….

 

[-CN-]

Did you forget about posting this question? Right after I posted that I had just purchased a "Cheap Amazon Battery". I was just answering your question, and providing my reasoning for my purchase.

There was LOTS of talk about cheap Amazon batteries. I made a general statement. I never directed any questions at you.

Gone fishing for the rest of the day.

 

[MDCrappie]

There was LOTS of talk about cheap Amazon batteries. I made a general statement. I never directed any questions at you.

Gone fishing for the rest of the day.

Just got back from fishing and you did NOT just make a statement, you asked a QUESTION. May not have been directly towards me, but directed towards buyers of "Cheap Amazon Batteries".........which I was one of.
You even prefaced it with "I would ask".

Now stop or Dad's going to chime in again........

 

[LDUBS]

Two considerations:
1. The max discharge current of the battery
2. How long you are typically fishing, weight of boat, conditions, etc.

Edit: To clarify item one, I meant the max BMS current. For example, if you had a Terrova 80 with a recommended fuse or breaker size of 60A, a battery with a 50A BMS could shut down if you stalled the motor in weeds or something. MK specs this motor at 56 A max but, it’s probably more like 45A or less at full speed under normal conditions. Max current specs are commonly overrated from actual test conditions.

I was going over this thread again from the start and saw your discharge chart comparison in post #31. It makes more sense to me now.

 

[Still Afloat]

I was going over this thread again from the start and saw your discharge chart comparison in post #31. It makes more sense to me now.

Happy to help.

 

[muskyhunter1978]

I think Lithium batteries are the way to go these days if you're replacing older batteries. The weight savings is significant, they should last longer, and they give full power until their run dead. I'm still rocking lead acid's in my boat but as soon as they kick, I'll be going with Lithium. Also, the prices have come down significantly to the point where they're attainable for most folks.

 

[Still Afloat]

That’s a good plan. All my new projects use lithium batteries but, my Crestliner still has a couple hundred pounds or more of lead acid.