12 volt LiFePO4 50 amp battery build.

[Waynemarlow]

Looking through the forum, I can't seem to find much on building a LiFePO4 12 volt replacement leisure battery of about 50 - 60 amps. Anyone built one and why so few as they would seem pretty much an ideal replacement if a B2B charger is used off an alternator or even say a 200W panel over the day.

 

[ZeroEm]

The main reason is that most here want power density and light weight. Everyone agrees LiFePO4 are great and long lasting it's the weight. I would like one for my car but just bought a deep cycle agm. it was $700 vs $250. The AGM should last the life of my traction battery the LiFePO4 would be around for many more years. If the traction battery is replaced I would also replace the 12V then.

Go to this link LiFePO4

 

[Waynemarlow]

But there are LiFePO4 batteries appearing but are they expensive or what for the number of cells you know are in them.

The reason I want this type of cell are for a number of reasons, principally weight and the ability to leave them over extended periods without having to worry about trickle charging them.

 

[john61ct]

With A123 26650 you could use the spotwding, adapt the layouts no problem all laid out

4 in series of course, just parallel x2.5Ah to get the capacity you want.

But prismatics would be much easier both to build and to monitor / repair if you got a bad cell.

Winston, CALB, GBS, Sinopoly and CATL are all top notch.

LFP in general is not as popular with eBike / EV crowd have gone more to the 3.6-3.7V chemistries for even higher energy density, but IMO too short lived and fire risky for a mobile living solar storage use case

LFP or maybe LTO best for that.

Figure $600-800 all up for 50-60Ah @12V

 

[LeftieBiker]

The reason I want this type of cell are for a number of reasons, principally weight and the ability to leave them over extended periods without having to worry about trickle charging them.

If there is no 'vampire drain' then an AGM battery will be fine for months with no charging. If there IS a vampire drain then unless it's tiny it will threaten even a lithium battery over a few months if it decides to increase a bit.

 

[jonyjoe303]

I have used the a123 26650 cells to build a 4s lifepo4 pack, because of their limited capacity I only use as a jump pack. Like someone mentioned they take alot of space for the amount of power they produce. I was also going to build a 30 ah lifepo4 battery pack with a123 cells but it was taking up too much space, the project is on hold.

My house battery is a 220ah lifepo4 battery, 2x 110 ah packs connected in parallel. They are made up of x160 5500mah lifepo4 cells. The method to build is the same as li-ion. On the larger cells you need a tab welder, I couldnt get them to solder.

lifepo4 4s6p 10 amp hour versus li-ion 3s16p 31 amp hour. They are both about the same physical size and weight. The lighter higher capacity 3s li-ion pack runs all my 12 volt devices, no real good reason to use lifepo4.

 

[Waynemarlow]

I should perhaps add in the nugget that I already build EBike batteries for my own use and have access to a tab welder, also I'm just in the process of converting over a VW T5 into a weekend style camper van hence my interest in the technology. Having some 450WH batteries sitting on my bench also makes me think can I convert the 52 volts down to 12 volts for the weekend but can find no real B2B chargers that could recharge them easily ( although I've not really researched this )

I'm surprised with the low A/hrs of the LiFePO4 battery pack shown. Has battery technology moved on a bit since that pack was built ? If we take https://eu.nkon.nl/jgne-26650-3600mah-10-2a-lifepo4.html then all I would need is 4S15P to get about the 50amps I'm looking for. Cost at Euro 3.25 a cell if I went full monty at 100 cells is still way below a comparable built up battery. Is there a temperature controlled BMS with bluetooth on that anyone could recommend and how much are they in cost.

Oh lots of questions. Thanks all.