Drop In LiFePo4 Batteries Round 2

That is a 4Ahr battery, which is probably the reason it looks relatively cheap compared to larger capacity ones.

Mark

flixed

Don't know anything about that battery, but the max charge current of 90A and discharge of 120A for a 200Ah battery sounds like it might have a fairly small BMS inside. On the other hand, those specs are probably higher than most would put on it.

Mark

Just bought 2 Ampere Time 200 AHr Plus LiFePO4 batteries from Amazon. When I purchased them on October 20th there were 742, now 690 each when buying a two pack. Wonder if I can get the difference back. I purchased those batteries mostly because of the good reviews and Will Prowes tear down on YouTube.

Are they drop in? NO! I have added a DC-DC from the alternator to the lifepo4, removed the AGM charger and replaced it with a inverter charger, added 3 160 panels and a MPPT charger.

Looking at the Ampere Time specs, those have max charge/discharge of 100A, so perhaps this 0.5C rating is common among dropins.

For comparison, the higher quality cells used to build batteries have 1C charge and 2C discharge ratings.

Mark

colemj said:

Looking at the Ampere Time specs, those have max charge/discharge of 100A, so perhaps this 0.5C rating is common among dropins.

For comparison, the higher quality cells used to build batteries have 1C charge and 2C discharge ratings.

Mark

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The 100 amp rating might be for the non plus model. We purchased the Plus model. From the plus model with the 200 amp BMS:
recommend charge current 40 amps
max continuous charge current 200 amps
max continuous discharge current 200 amps
max discharge current for 5 seconds 400 amps
cycle life 4000 times

What I don't like are the operating temps 0-50C charge -20 to 60C discharge and storage temps of -10C to 50C but that is due to the chemistry.

Skipper Jer said:

The 100 amp rating might be for the non plus model. We purchased the Plus model. From the plus model with the 200 amp BMS:
recommend charge current 40 amps
max continuous charge current 200 amps
max continuous discharge current 200 amps
max discharge current for 5 seconds 400 amps
cycle life 4000 times

What I don't like are the operating temps 0-50C charge -20 to 60C discharge and storage temps of -10C to 50C but that is due to the chemistry.

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Yes, those sound more usual. Likely they are the same battery cells with different BMS's. Those temps are just what is required of the chemistry like you say. If you need to charge in lower temps, make the battery warmer with heat pads. The upper temp shouldn't be a concern unless you need to put the batteries in a very hot compartment.

Mark

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

capta said:

I was thinking of using this on my LifePo batteries. Anbody see a problem? View attachment 145415

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why would there be a problem

I have had 1 of those on my start battery for 8 years

capta said:

I was thinking of using this on my LifePo batteries. Anbody see a problem? View attachment 145415

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No, those are common fuses used in LFP systems. The main fuse to the battery would be better to be a class-T fuse for interrupt current rating. Otherwise, those MRBF fuses are great branch circuit fuses.

Mark

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????

Don L said:

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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I'm assuming the batteries are wire in parallel. In our case the MPPT controller is limited to 40 amps, the DC to DC is limited to 20 amps (didn't want to overload the alternator) and the inverter charger can do 100 amps but is settable in 5 amp steps. So even if all three devices are pumping in amps the BMS limit is not reached in our application. The alternator is always connected to the lead acid battery so it is never unloaded.

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.

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.

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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?

Since the 3 batteries are wired together they are charged with the same voltage for the same amount of time. When the two batteries are fully charged the BMS doesn't disconnect because the charger voltage has not risen to the over voltage trip point. The third battery's voltage is so close to fully charge voltage the charger can not rise the voltage enough to push the 120 amps into the remaining battery, assuming all the equipment has been setup correctly and is functioning within manufactures specifications and all three batteries have been slowly charged so the BMS had time to equalize each cells voltage.

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.

Don L said:

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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In this case, I think not because the batteries BMS would shut the battery off from the alternator if it tried to deliver too much current. And the amount of current allowed is multiplied by the number of batteries in parallel (to an extent). Since you are looking at 5 of these, that would be a maximum of 450A of charging current allowed (nominally).

Even then, you couldn't overcharge a battery because the BMS would cut it off when the battery is full.

Your main concern would be burning up your alternator from running full blast continually.

Mark

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"

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:

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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Looking at the price of the 3.6V individual cells I can't really believe the price of those drop in batteries.