LifePo4 50ah batteries for dual batt setup in a Jeep TJ

[WSS]

Hello, I have two 50ah batteries that are new drop in replacements for cars. They are light, compact and have a BCM for under/over charging.

Can these be used with a in my TJ to replace my current single battery? I'm worried about discharge rate, my Warn XD9000i can pull 300+amps.

I here these are "miracle" batteries, so I'm hoping these will do the job. They are light on specs, for instance my TJ says a 500cca batt is the minimum. Does anyone know how to get these specs? here is a pic of the battery:

Here is my old optima setup in my CJ, it worked good for a long time:

 

[john61ct]

First off I personally doubt any batts touted as drop-ins are as good as a system based on high-reputation prismatic cells.

Then if there is internal circuitry, that can cripple C rates, far below what the chemistry can handle.

Here I assume as if bare cells, bypassing BMS limits.

For best longevity, do not exceed .5C or so, .3C even better.

If 12V 100Ah, that is only 30-50A.

If 24V 50A, half that.

Staying within that guideline, a 300A load requires a 600-1000Ah bank.

Especially if that load is supposed to last more than a minute or two.

Which would quickly flatten the bank anyway, easy maths there.

Very big fat robustly crimped wiring and CP is a must as well, also proportional to how long those amps are flowing between cool-down resting periods.

 

[john61ct]

Of course if the alt is putting out a decent proportion of those 300A, then the load on the bank is reduced.

But that would need to be actually measured with an ammeter, not guessed at using nameplate numbers.

 

[WSS]

I believe the winch would burn up after a minute of full load. My optima yellow tops are 55ah, they do a great job of handling my winch needs. Full load is seldom achieved on most winches for more than a few seconds.

Anyway, does anyone know if these new lifepo4 batteries with bms will do what a odyssey, optima or even a lead acid battery will do?

 

[jonyjoe101]

The specs I found on ebay, the ewt 50ah lifepo4 maxes out at 50 amps continuous discharge. I could not find if it had a pulse discharge limit. From the description it said they are for wind solar storage applications. On youtube someone took one apart its a 4s 15p made up of 26650 cells. The cells didnt look like the a123 26650 cells which are extremely powerful, 4 of those cells can jump start a v8.


You can find the specs for the bms on alibaba (100A Li-ion/Lifepo4 battery BMS/PCM 4S Bluetooth bms) it says the over current is 150 amps. This is the bms located inside the battery that was taken apart. Its a large bms with a huge heatsink and looks like it can handle high amps at least in short bursts. At worst it will shut down before it damages the cells.


But on the notes I see the max temperature to store it is 140 degrees. Inside the engine compartment it probably gets hotter then that, that might be the weak point. Lifepo4 don't like it too hot or cold.

 

[john61ct]

Varies enormously by what market you're in.

I avoid drop-ins myself.

Victrons may be worth looking at, but lead is so cheap here stateside, anything good is 10x the price per AH.

 

[SameGuy]

Also understand that LFP (LIFEPO4) batteries cannot be charged below freezing, not to say that they won't charge, but they will be damaged. Not a worry if you live in Florida but won't survive a Colorado winter. I would say LFP is not the best replacement for a starting battery or even second battery if its going to live under the hood.