Hello all,
I recently bought a brand new 72v 50ah LifePo4 battery off aliexpress from X N technology that uses CATL cells. The thing seems to have the capacity more like a 25ah than a 50ah. My pooched 41.6ah li-ion battery has better range than this thing.
It never charges past 81-82v. always has one cell that is high (3.6v around there) which prevents charging the battery to it's full capacity (lifepo4 charges to 87, not just 84 like li-ion, right?).
My first test run on a 40km commute one way had me stranded at the last 7km due to the bms tripping and shutting everything off, and i mean everything...because a cell or two got too low in voltage (low voltage protect). But before it got close to that, it was running pretty good. Sag was decent, from 81 down to 76-78 on full throttle which for me is 70 line amps, 200 phase, 5kw nominal output, field weakening strong.
my 2nd test run I was more conservative with the throttle (another 40km). At the last KM or two, the battery died. it always does this thing where at around 70v, it will go down to 69, then 64, then eventually nothing and completely offline (my voltmeter on the handlebar). I knew it was going to die so i just pedaled the bike home then did a little test run around the house to see when the battery will actually die die.
Here are two videos, my settings on my xiaoxiang BMS and a screen recording of bms monitoring cells and so forth right before the battery dies.
What gives? Did i purchase a lemon, or is there a setting or two that I have wrong that is causing this?
Cutout video:
BMS settings video:
I recently bought a brand new 72v 50ah LifePo4 battery off aliexpress from X N technology that uses CATL cells. The thing seems to have the capacity more like a 25ah than a 50ah. My pooched 41.6ah li-ion battery has better range than this thing.
It never charges past 81-82v. always has one cell that is high (3.6v around there) which prevents charging the battery to it's full capacity (lifepo4 charges to 87, not just 84 like li-ion, right?).
My first test run on a 40km commute one way had me stranded at the last 7km due to the bms tripping and shutting everything off, and i mean everything...because a cell or two got too low in voltage (low voltage protect). But before it got close to that, it was running pretty good. Sag was decent, from 81 down to 76-78 on full throttle which for me is 70 line amps, 200 phase, 5kw nominal output, field weakening strong.
my 2nd test run I was more conservative with the throttle (another 40km). At the last KM or two, the battery died. it always does this thing where at around 70v, it will go down to 69, then 64, then eventually nothing and completely offline (my voltmeter on the handlebar). I knew it was going to die so i just pedaled the bike home then did a little test run around the house to see when the battery will actually die die.
Here are two videos, my settings on my xiaoxiang BMS and a screen recording of bms monitoring cells and so forth right before the battery dies.
What gives? Did i purchase a lemon, or is there a setting or two that I have wrong that is causing this?
Cutout video:
BMS settings video: