Okay but at $100 though. A MK is what? $300 bucks? Will last about 5 years if you take care.
MK? If you dont use it, leave it on standby float you get 10 years.
I used to get 9 months.
If you discharge it in an even smooth way, charge CORRECTLY and completely (16 hours) and never below the 80% discharge point you can get the caimed 500 cycles. Or 18 months.
However... If you use it in the real world, discharge in heavy pulses as we do, charge with crappy mobility chargers, and use it normally you get anything from 6 months to 2 years.
If you dont discharge it deeply, dont have mental heavy duty programming, and charge CORRECTLY you can get about 2 to 5 years.
If its hot where you live you kill it fast whatever you do.
A 100Ah LifePo4 in 10 years will have 80Ah capacity,
I have 3 old packs here that were used daily for 10 to 15 years, still as good as new, only 3% capacity lost.
Because I charge correctly, dont take too much current, and dont over discharge them. The exact opposite that happens with a too small lead brick replacement LiFePO4.
If you charge and balance each cell to 3.550V and never discharge at high current, use a battery that is large enough capacity so that you pull low current per Ah and so never get much past 30 to 70 percent used, charge every few days to a week, then I suspect 30 years is quite possible. Even if a battery ever deteriorates by 20% so that say a 244Ah pack, has only 80% remaining, it will STILL go 80 miles instead of 100.... Like you will care!
On the other hand, things that LiFepo4 hates...
1. High discharge currents. Its proportional to lifespan. So a small battery suffers WAY more than a large one here. This on lithium is the No 1 killer.
2. Charging it at, an elevated voltage above the 100% full point causes damage. Makes cells gas and swell, and go high resistance.
3. HOLDING the full cells at this elevated voltage while a weedy balancer balances the pack during charge. So BMS directly cause damage here. Because they pulse, balance, pulse, balance over and over...
4. remaining on charge (i) after all cells are charged too long at this elevated voltage, and (ii) cutting off too early during charge before all cells are balanced...
5. heat
6. chrging daily (eats up cycle life, and lithium hates being full!) because small pack.
7. discharging by a lot daily. Big pack? You cant. Maybe charge every 3 days? So the battery spends most of its time between 30 and 80% full where it likes to be.
So with a BMS that cant control the charger termination time, cell balance time, etc and with small cells, you will see much more rapid degradation.
which is still better than a brand new MK. Let's say BMS dies after 3 years. You can buy a new one and still cheaper than a MK. If you're savy enough, you can simply cut the battery open and replace the BMS.
No one should buy a lead in 2025 IMO.
If the BMS is the problem. The real issue is that a too small cells, that are heavily used will not last long and a BMS makes that worse.
Also, They make 100C lifepo4 now that can crank a V8 engine. Surely they can make a 3C group 24. Demand isn't there, probably.
Several things here.
They used to make higher C rate LiFePO4 commonly in the beginning. But heres how it works. If a cell (or say a complete drop in GRP 24 battery) has a fixed maximum size then in order to fit 100Ah into that case you need low C cells. Why? Because high C ones require a thicker heavier aluminium foils internally or thy cannot take the current....
I have been using lipo batts since 98 in hobby stuff. On my shelf I have a lot of 6S liPo packs. Some are 10C and used for low powered low current power in powered gliders. We use the LOW C on purpose here because for a given battery volume and weight we get more Ah. Same thing in a quadcopter. Low C ratings = longer flight times. In stuff that eats power such as a 3D heli, where we want the same tiny batt volume/weight battery to cope with 100A or more we use 70C or 100C or 130C packs. But these neccassarily have LESS AH in the same volume.
So to make a GRP24 size LiFePO4 pack thats only 260mm long 168mm wide and 210mm tall, AND fit a BMS inside of that plastic casing requires low C cells. If you wanted to make that with 3C cells, or 10C cells, they will not fit into that casing! And so you end up with a smaller capacity. Lets say they can only fit 70Ah if its 2C or 50Ah if its 3C and of course now they need a bulkier BMS as well... And so to sell batteries they fit 100Ah ones... Then a BMS that allows 300A for a few seconds. Now the battery sufferes and that 10 years is just a dream... Might get a week or a year.
