I will be using a Rec-Active 12v BMS on my 1240ah 12v system. It has a 2 amp active balancer built in. However I figure with a bank that size I'd like to have another battery balancer to go with it just in case. I did some research on inductive balancers as that's what REC uses and opted to go with one of those. I think the Haltec new unit is also inductive but I found this inexpensive Sunkko unit that comes in either 5 amp or 8 amp. I went with the 8 amp version:
The unit has an on/off switch on the right and a force start button on the left. Press the on button and it will always be on until a delta of around 10mv (testing that now). The force start button will force the unit to turn on for 1 hour then turn off.
I plugged the unit in right away with the cells pretty evenly balanced and it started balancing around around .3amp. I did some basic testing by taking an 80% SOC battery and charged a single cell to 3.65v while the other cells were around 3.34v. I was now getting around 3 amps out of the highest voltage cell going into the other cells:
That's a far cry from 8 amps but honestly that's how I could see the battery pack being if there is a large imbalance so even three amps plus the 2 amps from the rec should be fine as this battery is going to live at the top end of the charge curve. I did replace the small gauge wire with comically fat silicon 14awg at this point.
I figure that most of these rated current figures are at the WAY extreme ends: one cell fully depleted and one cell fully charged. So that's what I did. I started at one cell at 2.8v and the other at 3.6v. The test started at 2:56pm. I turned on the balancer and BAM 8 amps right away. By the time I got my camera out the delta had already dropped to around 730mv and the current was at 7.17 amps:
3:13pm the delta was at 140mv and the current had dropped to 1.07 amps:
3:47pm the delta was now 92mv with a current of .74amps:
6:31pm the delta was now 46mv and a current of .26amps:
The plan for me is to turn this on via the REC-BMS once a single cell hits 3.42v so it probably won't get used that often.
The unit has an on/off switch on the right and a force start button on the left. Press the on button and it will always be on until a delta of around 10mv (testing that now). The force start button will force the unit to turn on for 1 hour then turn off.
I plugged the unit in right away with the cells pretty evenly balanced and it started balancing around around .3amp. I did some basic testing by taking an 80% SOC battery and charged a single cell to 3.65v while the other cells were around 3.34v. I was now getting around 3 amps out of the highest voltage cell going into the other cells:
That's a far cry from 8 amps but honestly that's how I could see the battery pack being if there is a large imbalance so even three amps plus the 2 amps from the rec should be fine as this battery is going to live at the top end of the charge curve. I did replace the small gauge wire with comically fat silicon 14awg at this point.
I figure that most of these rated current figures are at the WAY extreme ends: one cell fully depleted and one cell fully charged. So that's what I did. I started at one cell at 2.8v and the other at 3.6v. The test started at 2:56pm. I turned on the balancer and BAM 8 amps right away. By the time I got my camera out the delta had already dropped to around 730mv and the current was at 7.17 amps:
3:13pm the delta was at 140mv and the current had dropped to 1.07 amps:
3:47pm the delta was now 92mv with a current of .74amps:
6:31pm the delta was now 46mv and a current of .26amps:
The plan for me is to turn this on via the REC-BMS once a single cell hits 3.42v so it probably won't get used that often.
