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Jerud here is what you are missing. A BMS cannot perform the initial Bulk Balance of any battery pack. A BMS can only make very small corrections. Example say you buy 200 AH LFP cells from a chi-com like CALB. When you receive them the SOC is all over the place. You can have as much a 10 to 20% difference in SOC values. In a 200 AH cell is 20 to 40 AH difference. A typical BMS Balance Current is 150 to 300 ma. So to use a balance charger do some simple math on the time it takes. 40 AH / 150 ma = 267 Hours to recharge or 11 days.
This is why if you buy cells the very first thing you do is connect all the cells in Parallel, and walk away for a day. Then you either Top or Bottom Balance with them in parallel. Then assemble them in series and you are ready to go. Balanced batteries stay in balance and only need very small minor corrections from time to time as they age and from parasitic losses. Example self discharge rate is NOT exactly equal in the cells. Example let them sit for a year, and you might have .05% difference in SOC.
When you buy a Lithium Battery pack, not cells, but say a 12 volt LFP for your car, or 48 volt pack for a golf cart or 360 volt pack for an EV or Solar System all the cells have already been matched in capacity and balanced for you already. The only charger they require is a very simple CC/CV charger with a fixed voltage of the appropriate current. Really any current less than 1C will work for most Lithium cells. As long as the charge current does not exceed the manufactures maximum charge limit is fine.
Right now today if you are foolish enough to pay $800 to $1100 you can buy a 12 volt battery for your car or truck. They are a drop in replacement for your Pb battery. No modifications are required to your vehicle. Today's automobiles have standardized the charge voltage to be 14.2 to 14.4 volts which is perfect for LFP, and Pb AGM batteries. So with the cells already balanced and the equipped BMS inside the battery make it a non issue for Joe Consumer. When you start the car engine all the cells reach 100% at roughly the same time. So even if the BMS only can bypass say 0.5 amps aka 500 ma is a matter of a few seconds. So if you were to measure charge current, initially you might see 50 amps for a few seconds, then drops to 0 amps almost instantly when the battery voltage equals the charger voltage and the battery is now 100% SOC.
Try it yourself with your PL8. Balance a set of batteries. Then discharge them down to say 50%. Now recharge at say C/2 and watch what happens. Example say they are 4S LFP 100 AH and you charge at 50 amps. The charger will pump 50 amps until the voltage reaches 14.4. As soon as they reach 14.4 volts, current will start to taper off. At 10 amps the charge will terminate and the Balance circuit likely never turned on, and if it did was only in the last minute or two.
With the exception of LiPo battery packs made for Hobby RC Planes, cars, quads, ect, all consumer Lithium batteries have built-in BMS in which the factory has matched the cells because they have 100's of thousands of cells to work with to match, and balance the packs at the factory. It is the only way you can make a commercial product work because Joe Public does not know how and it makes it a liability issue for the manufacture. Even with all that automation, lithium batteries still blow up. You hear it on the news all the time.
This is why if you buy cells the very first thing you do is connect all the cells in Parallel, and walk away for a day. Then you either Top or Bottom Balance with them in parallel. Then assemble them in series and you are ready to go. Balanced batteries stay in balance and only need very small minor corrections from time to time as they age and from parasitic losses. Example self discharge rate is NOT exactly equal in the cells. Example let them sit for a year, and you might have .05% difference in SOC.
When you buy a Lithium Battery pack, not cells, but say a 12 volt LFP for your car, or 48 volt pack for a golf cart or 360 volt pack for an EV or Solar System all the cells have already been matched in capacity and balanced for you already. The only charger they require is a very simple CC/CV charger with a fixed voltage of the appropriate current. Really any current less than 1C will work for most Lithium cells. As long as the charge current does not exceed the manufactures maximum charge limit is fine.
Right now today if you are foolish enough to pay $800 to $1100 you can buy a 12 volt battery for your car or truck. They are a drop in replacement for your Pb battery. No modifications are required to your vehicle. Today's automobiles have standardized the charge voltage to be 14.2 to 14.4 volts which is perfect for LFP, and Pb AGM batteries. So with the cells already balanced and the equipped BMS inside the battery make it a non issue for Joe Consumer. When you start the car engine all the cells reach 100% at roughly the same time. So even if the BMS only can bypass say 0.5 amps aka 500 ma is a matter of a few seconds. So if you were to measure charge current, initially you might see 50 amps for a few seconds, then drops to 0 amps almost instantly when the battery voltage equals the charger voltage and the battery is now 100% SOC.
Try it yourself with your PL8. Balance a set of batteries. Then discharge them down to say 50%. Now recharge at say C/2 and watch what happens. Example say they are 4S LFP 100 AH and you charge at 50 amps. The charger will pump 50 amps until the voltage reaches 14.4. As soon as they reach 14.4 volts, current will start to taper off. At 10 amps the charge will terminate and the Balance circuit likely never turned on, and if it did was only in the last minute or two.
With the exception of LiPo battery packs made for Hobby RC Planes, cars, quads, ect, all consumer Lithium batteries have built-in BMS in which the factory has matched the cells because they have 100's of thousands of cells to work with to match, and balance the packs at the factory. It is the only way you can make a commercial product work because Joe Public does not know how and it makes it a liability issue for the manufacture. Even with all that automation, lithium batteries still blow up. You hear it on the news all the time.
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