15:00 There are diodes parallel to mosfets 1 and 2, oriented up or pointing up (or whatever the term used). To transfer charge from V1 to V2 (ie, V1 > V2) MOS1 is turned on, it draws current away from V1 and into the inductor and into V2. Then MOS1 is turned off, the voltage at Vb drops to a low point such that the diode across mos2 will complete the circuit and charge V2. Buck charging. To transfer charge from V2 to V1 (ie V2 > V1) Mos2 is turned on. It draws current away from V2 and into the inductor and into V1. Then Mos2 is turned off, the voltage at Vb spikes up to a high point such that the diode across mos1 will complete the circuit and charge V1. Boost Charging. Rinse repeat using PWM to regulate the amp. The problem with this balancing is: It transfers charges between adjacent cells; it cannot transfer cells from C1 into C3 directly. And if you have 20 cells, you will have to ripple the charge across all cells. There is another inductor balancer using Transformer, which I believe is more superior than this Buck/Boost as it can balance on multiple cells and into multiple cells.
I've tried to simulate this on SPICE but unfortunately I had no luck. Starting from the top mosfet that keeps conducting to the duty cycle to properly regulate the charge. The idea was to create and Arduino version of the ETA3000.
If you set your PWM to 50% and the two cell voltages to the same value you should see no net DC in the middle balancer connection. If you then change one of the cell voltages a bit you should see that one cell has a net negative current and the other has a net positive current, this is the balancer at work :)
Hi, Thank you for this Video. What I do not understand, why is the charger connected? This principle should work always (during discharge, charge or even without both). Or am I wrong?
You’re absolutely correct, the IC works whenever there is a voltage imbalance. I used charging for the illustration because that’s usually when it matters most, trying to top balance a pack. If you are discharging with a very low current then it may also help eek out the last few joules of energy but most applications are faster discharge than the balancer could handle.
I think you have it wrong. Keep in mind, that when an inductor is charged, it reverses current when the power is cut off. So assume the top battery has less voltage than the bottom battery. To get the charge in balance, the bottom MOSFET turns on, and charges the inductor to + on left side and - on right side, using the voltage from the bottom (higher charge) battery. Then the bottom mosfet turns off and the inductor reverses charge, - on left side and + on the right side, then the top mosfet turns on and charges the top battery from the energy that came from the bottom battery. This constant checking and rebalancing utilizing the energy from the battery with the highest voltage to transfer energy to the lower battery using the inductor. The process is reversed if the bottom battery has less voltage. where the top mosfet charges the inductor, - on left side + on right side, then shuts off, inductor charge reverses + on left - on right, bottom mosfet turns on and charge that came from the top battery, goes into bottom battery.
Hi Mike, thanks for the comment. Your description of the circuit action sounds correct but your comment about the inductor seems wrong. An inductor does not like the current flowing to suddenly change, it will present whatever voltage to the circuit is necessary to keep the current flowing in the same direction. Thus it is the voltage that reverses, not the current. This forced continuation of current, resulting from the stored energy in the magnetic field, is what allows energy to be transferred from one cell to the other.
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15:00 There are diodes parallel to mosfets 1 and 2, oriented up or pointing up (or whatever the term used).
To transfer charge from V1 to V2 (ie, V1 > V2)
MOS1 is turned on, it draws current away from V1 and into the inductor and into V2.
Then MOS1 is turned off, the voltage at Vb drops to a low point such that the diode across mos2 will complete the circuit and charge V2.
Buck charging.
To transfer charge from V2 to V1 (ie V2 > V1)
Mos2 is turned on. It draws current away from V2 and into the inductor and into V1.
Then Mos2 is turned off, the voltage at Vb spikes up to a high point such that the diode across mos1 will complete the circuit and charge V1.
Boost Charging.
Rinse repeat using PWM to regulate the amp. The problem with this balancing is: It transfers charges between adjacent cells; it cannot transfer cells from C1 into C3 directly. And if you have 20 cells, you will have to ripple the charge across all cells.
There is another inductor balancer using Transformer, which I believe is more superior than this Buck/Boost as it can balance on multiple cells and into multiple cells.
I've tried to simulate this on SPICE but unfortunately I had no luck. Starting from the top mosfet that keeps conducting to the duty cycle to properly regulate the charge.
The idea was to create and Arduino version of the ETA3000.
If you set your PWM to 50% and the two cell voltages to the same value you should see no net DC in the middle balancer connection. If you then change one of the cell voltages a bit you should see that one cell has a net negative current and the other has a net positive current, this is the balancer at work :)
Good overview, thanks!
Hi,
Thank you for this Video. What I do not understand, why is the charger connected? This principle should work always (during discharge, charge or even without both). Or am I wrong?
You’re absolutely correct, the IC works whenever there is a voltage imbalance. I used charging for the illustration because that’s usually when it matters most, trying to top balance a pack. If you are discharging with a very low current then it may also help eek out the last few joules of energy but most applications are faster discharge than the balancer could handle.
I think you have it wrong. Keep in mind, that when an inductor is charged, it reverses current when the power is cut off. So assume the top battery has less voltage than the bottom battery. To get the charge in balance, the bottom MOSFET turns on, and charges the inductor to + on left side and - on right side, using the voltage from the bottom (higher charge) battery. Then the bottom mosfet turns off and the inductor reverses charge, - on left side and + on the right side, then the top mosfet turns on and charges the top battery from the energy that came from the bottom battery. This constant checking and rebalancing utilizing the energy from the battery with the highest voltage to transfer energy to the lower battery using the inductor. The process is reversed if the bottom battery has less voltage. where the top mosfet charges the inductor, - on left side + on right side, then shuts off, inductor charge reverses + on left - on right, bottom mosfet turns on and charge that came from the top battery, goes into bottom battery.
Hi Mike, thanks for the comment. Your description of the circuit action sounds correct but your comment about the inductor seems wrong. An inductor does not like the current flowing to suddenly change, it will present whatever voltage to the circuit is necessary to keep the current flowing in the same direction. Thus it is the voltage that reverses, not the current. This forced continuation of current, resulting from the stored energy in the magnetic field, is what allows energy to be transferred from one cell to the other.
@@Eclectronicschannel You are right. I meant to say, reverses voltage, not current. oood catch.
you are good but please slow down and use a clear permanent pin
This type of balancer can actually ruin a perfect Top Balance.