Johnolar
Electric Yacht powered by LFP
Finally some progress with my build that's worth writing about
All the batteries - 17 cells -were delivered slow but ok. I had 5 boxes, 4 came together and the 5th a week later.
The packaging was done really well, all cells were placed in individual foam casings then placed in carton boxes which had the wall doubled on the inside with more foam sheets. On the outside the corners were reinforced with plastic.
Through transport the cartons incurred some damage but nothing made it all the way through the cells.
The cells measured ok, almost identical to the measurements from the video they sent before shipping. They were quite balanced, still I've put them in parallel and started the top balancing process on the 19/09. After the first 48 hours I started to see an quite obvious difference in the cell voltages: higher at the ends and lower in the middle (3,4x vs 3,3x). I was getting concerned that I would actually imbalance them, so for the following 24 hours I was changing the position of the lead from one end to another and to the middle, every 8 hours.
On the 22/09, after reading some more about the process and it's length especially if done with a low current power supply - 5A - I've decided to build the 48V bank - 16 in series - with the BMS and give it a good full charge with the 48V charger. By this stage, the cells voltage was 3,45 on average.
In 10 minutes the BMS cut off the charger as the battery was fully charged - reached 3,65V.
To my calculations, it should have taken much longer to reach full charge, but then i have no idea what was the actual SOC when delivered - suspect it was quite high... Anyway, I'm not that much concerned as I've tested one random cell for it's capacity, after the top balance, and it was exactly 280A (test conditions: avg temp 12 deg Celsius and current draw 10A - I was aiming for 20A but the cables supplied with the tester were warming up and I wasn't comfortable to let it off my sight like that, so I reduced the load).
Anyway, overall, so far, very happy with my purchase from Dongguan Lightning through Rain Zeng.
One thing I would change in hindsight: order more bus bars and bolts, as I got the exact number for a 17 cell in series bank...I had to be inventive to be able to parallel them for balancing which is not a bad thing but just added more variables and potential failing points in the play.
All the batteries - 17 cells -were delivered slow but ok. I had 5 boxes, 4 came together and the 5th a week later.
The packaging was done really well, all cells were placed in individual foam casings then placed in carton boxes which had the wall doubled on the inside with more foam sheets. On the outside the corners were reinforced with plastic.
Through transport the cartons incurred some damage but nothing made it all the way through the cells.
The cells measured ok, almost identical to the measurements from the video they sent before shipping. They were quite balanced, still I've put them in parallel and started the top balancing process on the 19/09. After the first 48 hours I started to see an quite obvious difference in the cell voltages: higher at the ends and lower in the middle (3,4x vs 3,3x). I was getting concerned that I would actually imbalance them, so for the following 24 hours I was changing the position of the lead from one end to another and to the middle, every 8 hours.
On the 22/09, after reading some more about the process and it's length especially if done with a low current power supply - 5A - I've decided to build the 48V bank - 16 in series - with the BMS and give it a good full charge with the 48V charger. By this stage, the cells voltage was 3,45 on average.
In 10 minutes the BMS cut off the charger as the battery was fully charged - reached 3,65V.
To my calculations, it should have taken much longer to reach full charge, but then i have no idea what was the actual SOC when delivered - suspect it was quite high... Anyway, I'm not that much concerned as I've tested one random cell for it's capacity, after the top balance, and it was exactly 280A (test conditions: avg temp 12 deg Celsius and current draw 10A - I was aiming for 20A but the cables supplied with the tester were warming up and I wasn't comfortable to let it off my sight like that, so I reduced the load).
Anyway, overall, so far, very happy with my purchase from Dongguan Lightning through Rain Zeng.
One thing I would change in hindsight: order more bus bars and bolts, as I got the exact number for a 17 cell in series bank...I had to be inventive to be able to parallel them for balancing which is not a bad thing but just added more variables and potential failing points in the play.