Moderator advice to all readers:
Cheez posts consistently dangerously incorrect information and advice that could lead to fire and death (in regards to batteries, etc).
Other information is simply incorrect and could lead to wasted money and severe dissatisfaction.
Do not follow any of their advice or information.
Original complete post below:
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There has been massive disinformation about needing for BMS for building battery packs for decades across the whole world.
I want to bring let you guys know that the BMS doesn't work as you believe the way they work.
First thing you need to know, is that you can't measure the voltage of any parallel group cells in a battery pack, except for the very first parallel group (+) and the very last parallel group (-). The BMS can't measure the voltage through these balancing wires connected on the positive side of the parallel groups. It will give incorrect/invalid voltage reading and will trigger the BMS to attempt to discharge and re-charge. The reason why you can't measure the voltage in any of the inner parallel groups of cells is because the positive end you are connecting the wire with is not really positive nor negative because all the groups of cells are interconnected to form a one large single cell. If you pay attention the positive side of the cell is connected to the negative side of the neighboring cell. You are connecting the wrong terminal points to measure the voltage. The only place you can measure the voltage is connecting your wire (or your multimeter probe) to the first parallel group of the cells (+) and the last parallel group of the cells (-). And that is to get the total voltage. You cannot get voltages from each parallel groups because they are all connected to form a one large cell.
Another thing you need to know is that the electricity doesn't travel from one point to another as it doesn't have a direction. They appear instantly when the positive and negative ends are connected. The electricity doesn't travel slowly from positive end of the cell to the negative side of the neighboring cell hoping/assuming your balance wire will "catch" it before it passes to the next cell. Because the electricity doesn't have a direction and appear instantaneously, the voltage cannot be measured. It is like you are attempting to connect the wrong points of the body of a battery cell. The only place you can connect is the very positive end and negative end of the battery pack.
The only time the BMS can "work" is to separate each parallel groups of cells from each other to create their own individual circuit, independent from each other. If you have 4 inner parallel groups you have to create 4 separate circuits. Run the BMS balance wires to those 4 groups of cells and you will be able to measure the voltage on each group, and balance them if needed.
You can also do so by separating those parallel groups of cells and create a sheet of pre-defined conductive metal to place on top of a battery pack and another one for the bottom side of the battery pack to "connect" those parallel groups of cells in series. Fasten these sheets (or board) of metals with screws/bolts and nuts. If you want to measure the voltage of each parallel group cells just lift/disengage the sheets of the metal connectors from the battery. If you re-attach them, you won't be able to measure the voltages on these parallel groups. It is the similar way how the Tesla electric cars are designed for charging their batteries. They have multiple groups of smaller battery packs in their vehicle, has a mechanism to attach or disengage these connections of the battery packs. When charging, they are disconnected from each other, to allow charging. Re-engage for Drive. But balancing the battery packs during charging wasn't the reason for the design of this mechanism but to "safely" charge each and every group of the smaller battery packs with lower voltages and current, as voltage needed to charge one large battery is too much for the battery. They knew that the batteries quickly deteriorate from high voltage stress. They also know the fact that the battery cells connected in parallel and serial in a pack self-balance charge anyway, eliminating the need of BMS or balance charging. The only time the battery cells don't self-balance is when they are run in serial connection-only, but when they are combined with parallel connections they all get self-balanced. Ask Elon Musk about this and he will tell you, which is why he designed the batteries for these cars in such way to charge them without getting batteries get damaged from stress.
So don't just sorely rely on the engineers who made these little BMSs (and any other balance chargers) for e-bikes and scooters because they don't really know how the electricity works in respect to batteries and charging. The only time the BMS/Balance chargers come to use is when you charge the battery cells individually. You can control how much you want drained or charged.
.
Cheez posts consistently dangerously incorrect information and advice that could lead to fire and death (in regards to batteries, etc).
Other information is simply incorrect and could lead to wasted money and severe dissatisfaction.
Do not follow any of their advice or information.
Original complete post below:
____________________
There has been massive disinformation about needing for BMS for building battery packs for decades across the whole world.
I want to bring let you guys know that the BMS doesn't work as you believe the way they work.
First thing you need to know, is that you can't measure the voltage of any parallel group cells in a battery pack, except for the very first parallel group (+) and the very last parallel group (-). The BMS can't measure the voltage through these balancing wires connected on the positive side of the parallel groups. It will give incorrect/invalid voltage reading and will trigger the BMS to attempt to discharge and re-charge. The reason why you can't measure the voltage in any of the inner parallel groups of cells is because the positive end you are connecting the wire with is not really positive nor negative because all the groups of cells are interconnected to form a one large single cell. If you pay attention the positive side of the cell is connected to the negative side of the neighboring cell. You are connecting the wrong terminal points to measure the voltage. The only place you can measure the voltage is connecting your wire (or your multimeter probe) to the first parallel group of the cells (+) and the last parallel group of the cells (-). And that is to get the total voltage. You cannot get voltages from each parallel groups because they are all connected to form a one large cell.
Another thing you need to know is that the electricity doesn't travel from one point to another as it doesn't have a direction. They appear instantly when the positive and negative ends are connected. The electricity doesn't travel slowly from positive end of the cell to the negative side of the neighboring cell hoping/assuming your balance wire will "catch" it before it passes to the next cell. Because the electricity doesn't have a direction and appear instantaneously, the voltage cannot be measured. It is like you are attempting to connect the wrong points of the body of a battery cell. The only place you can connect is the very positive end and negative end of the battery pack.
The only time the BMS can "work" is to separate each parallel groups of cells from each other to create their own individual circuit, independent from each other. If you have 4 inner parallel groups you have to create 4 separate circuits. Run the BMS balance wires to those 4 groups of cells and you will be able to measure the voltage on each group, and balance them if needed.
You can also do so by separating those parallel groups of cells and create a sheet of pre-defined conductive metal to place on top of a battery pack and another one for the bottom side of the battery pack to "connect" those parallel groups of cells in series. Fasten these sheets (or board) of metals with screws/bolts and nuts. If you want to measure the voltage of each parallel group cells just lift/disengage the sheets of the metal connectors from the battery. If you re-attach them, you won't be able to measure the voltages on these parallel groups. It is the similar way how the Tesla electric cars are designed for charging their batteries. They have multiple groups of smaller battery packs in their vehicle, has a mechanism to attach or disengage these connections of the battery packs. When charging, they are disconnected from each other, to allow charging. Re-engage for Drive. But balancing the battery packs during charging wasn't the reason for the design of this mechanism but to "safely" charge each and every group of the smaller battery packs with lower voltages and current, as voltage needed to charge one large battery is too much for the battery. They knew that the batteries quickly deteriorate from high voltage stress. They also know the fact that the battery cells connected in parallel and serial in a pack self-balance charge anyway, eliminating the need of BMS or balance charging. The only time the battery cells don't self-balance is when they are run in serial connection-only, but when they are combined with parallel connections they all get self-balanced. Ask Elon Musk about this and he will tell you, which is why he designed the batteries for these cars in such way to charge them without getting batteries get damaged from stress.
So don't just sorely rely on the engineers who made these little BMSs (and any other balance chargers) for e-bikes and scooters because they don't really know how the electricity works in respect to batteries and charging. The only time the BMS/Balance chargers come to use is when you charge the battery cells individually. You can control how much you want drained or charged.
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. In order to maintain that tolerance the Charger needs to stay on for several hours after the GREEN light comes on ... say every month depending on condition of the cells.
