Rapidrob
New Member
About a year ago I assembled a 12 volt battery pack for my Ham Radio. It has worked very well giving me several hours of operating time at 100 Watts out of the radio.
There are two 4-cell 38120S batteries running in parallel out to one power plug.
I'm using an "Air-8" charger for the pack. During charging, both BMS's are bypassed by the cables (2 ) of the Air-8. Each pack is wired directly to the + and - of the pack, not the BMS. I found trying to charge with the BMS's in line ( with one fuse removed allowing voltage to only go to one pack at a time ) the AIR-8 charger errors out instantly and shows " abnormal battery voltage" Both BMS's will do this if their are inline with the charger.
When charging the pack, each group of 4-cells are charged separately. One 4-cell pack charges to over 6,700 mAH, the other about 900 mAH. ( each cell has been tested by itself with no issues and very high current output. Voltage drop is the same under load)
Each pack of four has its own BMS of the same type and maker. The output Negatives of the BMS's are tied together at a terminal block, then out to the load.
The two Positives go to a 2- Fuse Holder, then out to the terminal block, and then to the load.
It appears that the 1st pack is doing all of the work, and the second which is still almost fully charged and providing almost no current to the load.
Is this unbalanced charging caused by a problem with the 2nd battery pack's BMS? Is there a conflict between the two BMS's under load of the radio and one is taking over depleting the 1st pack down much more than the 2nd pack? And when the voltage drops to a certain level the 2nd BMS takes over and sends more current out of the nearly fully charged pack? I can't see how the software of the BMS is that smart but I'm stumped as to what is going on?
Please help/advise.
Thank you.
There are two 4-cell 38120S batteries running in parallel out to one power plug.
I'm using an "Air-8" charger for the pack. During charging, both BMS's are bypassed by the cables (2 ) of the Air-8. Each pack is wired directly to the + and - of the pack, not the BMS. I found trying to charge with the BMS's in line ( with one fuse removed allowing voltage to only go to one pack at a time ) the AIR-8 charger errors out instantly and shows " abnormal battery voltage" Both BMS's will do this if their are inline with the charger.
When charging the pack, each group of 4-cells are charged separately. One 4-cell pack charges to over 6,700 mAH, the other about 900 mAH. ( each cell has been tested by itself with no issues and very high current output. Voltage drop is the same under load)
Each pack of four has its own BMS of the same type and maker. The output Negatives of the BMS's are tied together at a terminal block, then out to the load.
The two Positives go to a 2- Fuse Holder, then out to the terminal block, and then to the load.
It appears that the 1st pack is doing all of the work, and the second which is still almost fully charged and providing almost no current to the load.
Is this unbalanced charging caused by a problem with the 2nd battery pack's BMS? Is there a conflict between the two BMS's under load of the radio and one is taking over depleting the 1st pack down much more than the 2nd pack? And when the voltage drops to a certain level the 2nd BMS takes over and sends more current out of the nearly fully charged pack? I can't see how the software of the BMS is that smart but I'm stumped as to what is going on?
Please help/advise.
Thank you.
