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Drop In LiFePo4 Batteries Round 2

4757 Views 30 Replies 6 Participants Last post by  colemj, 
Don L
I saw some to me unbelievable low priced 100Ah drop in LFP batteries on Amazon today (Amazon.com). At least low priced to me who got my last set of batteries only 2 years ago and was comparing costs of LFP to the FireFly batteries I got. Now I read Rod's article slowly this morning:

marinehowto.com

Drop-In LiFePo4- Be an Educated Consumer

Lead is Dead (almost) Warning: This article is long and detailed. It may require two reads so the nuances and detail are not missed. You may be wondering why I am saying lead is dead ?The answer to that is simple; lead acid battery makers dug their own graves
marinehowto.com

and chased down the full spec sheet attached.

To my reading this seems a good LFP battery spec compared to the items Rod's article

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Don L
flixed
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Don L
meanwhile my point is that drop in LFP are getting fairly inexpensive and the specs are looking pretty good

I could get 500Ah of LFP for what I spent 2 years ago on 481Ah FireFly batteries. And I could probably not have to made any changes other than controller programing.

of course I could get 440Ah of FLA for about 1/3 the price
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Don L
capta said:
I was thinking of using this on my LifePo batteries. Anbody see a problem? View attachment 145415
Click to expand...
why would there be a problem

I have had 1 of those on my start battery for 8 years
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Don L
So how do the max charge currents work when a BMS drops out a drop in battery? Lets say you have 3 batteries that can accept 50A each and your alternator + solar could do 120A. When the batteries are charged 1 of the batteries BMS drops it out and now there are only 2 50A acceptance batteries on line with a 120A supply. What if another battery drops out????
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Don L
Skipper Jer said:
For the case you stated the battery voltages track each other very closely within 10's of millivolts so the case of having 2 batteries charge completely then the entire 120 amps flows into the one battery won't happen because the current will decrease as the battery voltages rise. Which is way it is recommended NOT to mix old LiFePO4 with new ones.
Click to expand...
So users just ASSUME that is what will happen? All batteries will be so close that they all go off line at same time and therefore don't experience the over spec charge rate?
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Don L
I am not interested in "debate" really. What I read that as is it comes down to faith. My alternator would easily overcharge a single battery in my example since LFP acceptance resistance doesn't limit current.
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Don L
colemj said:
Your main concern would be burning up your alternator from running full blast continually.

Mark
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Well, I don't run my alternator at full blast now and have it belt reduced to 70% plus have a temp sensor.

This is all just "wondering"
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Don L
Don L said:
I saw some to me unbelievable low priced 100Ah drop in LFP batteries on Amazon today (Amazon.com). At least low priced to me who got my last set of batteries only 2 years ago and was comparing costs of LFP to the FireFly batteries I got. Now I read Rod's article slowly this morning:

marinehowto.com

Drop-In LiFePo4- Be an Educated Consumer

Lead is Dead (almost) Warning: This article is long and detailed. It may require two reads so the nuances and detail are not missed. You may be wondering why I am saying lead is dead ?The answer to that is simple; lead acid battery makers dug their own graves
marinehowto.com

and chased down the full spec sheet attached.

To my reading this seems a good LFP battery spec compared to the items Rod's article
Click to expand...
Looking at the price of the 3.6V individual cells I can't really believe the price of those drop in batteries.
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Don L
I want to bump this thread back into drop in replacement discussion. I was 99% close to installing LFP batteries 30 months ago (I had ordered but they hadn't shipped) and changed directions to FireFly batteries. These are looking to be a false promise and I could have saved $1500 with replacement T105s for batteries to last 2.5 years. So:

In post 1 I posted a drop in battery I found on Amazon (https://www.amazon.com/ECI-Power-Re...fos.765d4786-5719-48b9-b588-eab9385652d5&th=1).

You can get 400ah, 2-200AH batteries, for $1200. To me that seems just too good to believe after my research just 2.5 years ago. And it isn't uncommon. Yet there are other builders selling 100AH "drop in" LFP for $1000, These ECI batteries have good charge/discharge specs, meaning they are good match to my current charging system etc. It has built in BMS and even has bluetooth (cheap way to meet the new tech requirement). To me they tick off all the cautions in Marinesails warning article.

Am I missing something or am I headed down another sucked path?
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Don L
Well my battery voltage got low enough last night that my freezer turned off. The Firefly batteries should have been about 75% charged but the voltage was only 11.5V at a 5A load. So I can not take off to the boonies with these and this drop in LFP battery issue is now a must do decision. So choices:

  • some G31 batteries that will probably last 2-3 years $600
  • some LFP drop in batteries that whose knows how long they may last $1200
  • some more expensive LFP drop in LFP $2500+
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Don L
So I had to act. Watched some utube tear aparts and decided the $300-350 100aH drop ins overall all are pretty good. Funny boaters will get all hair splitting over LFP batteries considering the pretty much unknown construction of the batteries they have used for years.

In the end i ordered 4 100ah Power Queen batteries off Amazon for $1319 all in. That is what boaters have been paying for agm batteries in the past and is $700 less that i sucker paid for my FireFly batteries 2.5 years ago.
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Don L
colemj said:
What changed your mind about the ones in your previous link?

Mark
Click to expand...
The 2- 200aH ones didn't space fit as well as as 4-100aH ones. I watched some tear apart tests of both and they pretty much appear to be the same. I think I may even have gotten confused by the end and didn't really order the one I met too. I was going to order the ones that had a GA warehouse that I thought might be a fast delivery time for my in FL as they are shipping to daughter's house in Jacksonville and I am in West Palm Beach and have to drive up to get and hoped to do on the Christmas trip up.

They all just just became what smoke and mirrors to believe in really.
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Don L
Only been 1.5 days with the LFP, but the boat appears to like them a lot. The electric head really likes the extra 1v and sucks a bowl full right down. Feel I got the batteries fully charged yesterday as the 4 got to 14.4v and were only accepting 6.8A. Feels funny this morning getting up to batteries that are 75% SOC and 13.2+ V
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