Considering BMS (or just monitoring) for LiFe cells

Hello,
I use 20Ah A123 prismatic cells on almost all my E-bikes.
I never used a BMS, since the cells are very similar to each other, and I do a check-up and an individual 3.6V top-charge every few months.
Recently I start to think over about the BMS thing as the cells start to age (6 years but still perform incredibly well), so I don't need to worry about one of them giving up and risking the entire battery with it.

So my options are:
1. Install a fully fledged BMS with LVC and HVC - Since the A123 pouch cells are practically unlimited with their current capabilities for E-bike usage, I assume a BMS for 24S (25S on my other bike as well), 150A discharge and 50A charge would be heavy, and expensive. If I am wrong, please correct me. I would like something which isn't expensive, yet can perform the task without being a Chinese BMS (Battery Murder Service). MiniBMS will be far too expensive for me...

2. A BMS that just bleeds the cells between each other and don't monitor LVC or HVC. I assume it would probably be much cheaper.

3. A voltage monitor/LED indicator for all 24S (and 25S on the other bike), that can warn me when a cell is dropping below 3V, or have reached already 3.5V. With LEDs it can be logical to have 24 (or 25) color changing LED's on the dashboard of the bike.
With a voltage display I assume all 24/25 can't be displayed at once.
So far I only found 6S voltage monitors (For LiPo's - or "Gun Powder"), and finding a bleeding BMS (and the fact that it's for LiFe) seems impossible.

4. Making my own 24/25 color changing LED monitor. I have started considering making my own circuit by using zener-diodes, but they have soft knees, and, good luck with finding one for the voltages I look for...
I tried searching for voltage regulators for 3.6V, but to no avail.

What is your take on this?

I have a 6 year old maybe 7 year old A123 20 ah 24s pack 1,389 cycles. Charge to 3.5 discharge to 2.9v at most . A couple times I've drained them to there was no power. This was the only times I balanced charged after bulk charging. After many problems with bms on my ping I gave of for now. Just don't loan your bike. Because you can't talk someone how no to deplete the battery. Especially your dad or your brother. Or all wives girlfriends and kids need a bms with lvc.

999zip999 said:

I have a 6 year old maybe 7 year old A123 20 ah 24s pack 1,389 cycles. Charge to 3.5 discharge to 2.9v at most . A couple times I've drained them to there was no power. This was the only times I balanced charged after bulk charging. After many problems with bms on my ping I gave of for now. Just don't loan your bike. Because you can't talk someone how no to deplete the battery. Especially your dad or your brother. Or all wives girlfriends and kids need a bms with lvc.

Click to expand...

This doesn't answer my question...
But anyhow, I also have A123 26650 cells, bought in 2011, experienced 20C discharge currents and 4C charge and were brutally abused with their cycles, and only lost 20% of their initial capacity. Amazing technology... It's sad they went bankrupt
The LVC and HVC is being performed for now using the Phase-Runner voltage limits and it works very well. So it's good also for novice users.
However, it's important to have individual cell voltage monitoring....

I just have 4-6s sense wires and monitor with a cellog. And use a una9 plus+ thru the sense wire balance charger if ever needed. Maybe 4 - 6 times. With my ping. One channel on the bms drain one cell to zero. Ouch bms no thanks. Sorry me no like bms. I can regen 1,000 watts how would a bms like that ?

999zip999 said:

I just have 4-6s sense wires and monitor with a cellog. And use a una9 plus+ thru the sense wire balance charger if ever needed. Maybe 4 - 6 times. With my ping. One channel on the bms drain one cell to zero. Ouch bms no thanks. Sorry me no like bms. I can regen 1,000 watts how would a bms like that ?

Click to expand...

That is what I do for now - Balance charge them occasionally with my up to 6S compact charger. But it's a chore (and I have lots of bikes), plus, a cell can always die at some point and risk his neighbors... (by inflating over them, physically)
The "cellog" is interesting. I thought about something like that.
The problem is that it requires me to have 4 units like this (at least), or to plug it 4 times to 4 different connectors.
I want a built-in monitor on the dashboard of the bike. That's why I thought of changing-color LED's, because it's more practical than reading 24 different numbers on the same screen...

having a safer chemestry do does mean you should not take less precautions. so just get a proper bms that you can program (see bluetooth bms thread) and be done with it.

I will move to 18650 and get a BT bms at that point. I just don't know which cell will last and not have mega voltage sag. A123 lifepo4 iis pretty flat discharge. And big and heavy.
How many amps at discharge and charge ?

999zip999 said:

I will move to 18650 and get a BT bms at that point. I just don't know which cell will last and not have mega voltage sag. A123 lifepo4 iis pretty flat discharge. And big and heavy.
How many amps at discharge and charge ?

Click to expand...

On the 25S E-bike, with two DD motors, the peak discharge current reaches 110A. That is more than 5C.
The max charge current during regen is about 40A which is around 2C.
Considering we talk about 25S which is 82.5V, note that we talk about +8KW and -3.5KW....